IHADAV8.com - Turbo Buick Tech, and Nonsense
Tech Area => General Buick Tech => Topic started by: Recap on November 11 2011, 05:34:43 PM
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Hopefully someone on this forum can help me out. As stated in the subject, I have a sick GN. I have been trying to sort this out off and on for the last 2 months. Below is what I have done to date.
-replaced plugs (twice)
-checked full pressure
-replaced plug wires
-new O2 sensor
-new fuel filter
-checked resistance between engine and battery negative post
-checked exhaust manifold temps with infrared temp gun
-new Coil Pack (Accel)
-new ignition module (Standard LX338)
-checked compression and all within 5psi
-verified signal to injector 4 was present (node light)
-had injectors backflushed and flow checked (checked out OK when he received them)
-moved injector that came out of cylinder 4 to different cylinder, no. 4 still not firing
I am not sure where to go from here. Any and all suggestions welcome!
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have you verified spark....did you change coil pack because there was no spark or just because you wanted to
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Replaced coil pack due to checking header temps and having a cold cylinder. When that did not work, I replaced the ignition module. When that did not fix the issue is when I pulled the injectors and sent them off to be checked and serviced. Tried to put the list in chronological order as to what I have done since trying to diagnose the problem. Regarding checking spark, have ordered a little tester to do just that, so have not done so yet.
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As I suggested, pull that plug wire and put a plug in it while it is laying on the valve cover. Start the engine for a second while watching the plug gap to see if it is sparking properly.
Normally, a firing problem that is associated with the coil and/or module, will affect two plugs at the same time because we have a waste spark system so both plugs on an individual coil pack will fire, or both will not. So a single cylinder is usually a bad plug, or a bad wire.
As the noid lite was blinking, that would mean the injector harness was okay.
If the problem stayed on number four even after switching the injectors about, then that should eliminate the injectors.
Now, the only thing that could account for a truly cold cylinder would be a lack of compression and that would be most likely due to a valve train problem unless there is a big hole in the piston.
I hate to assume things, but, I hope you cranked the car up, let it warm up a bit, and then disconnected one injector lead at a time to demonstrate that the engine started to miss on each cylinder except for the number four cylinder which stayed the same. If you have anyone to help you, have them sit in the car, foot on the brake, car in drive, while bringing the rpms up against the converter to add a little load. This should make the miss worse and easier to discern. I am not disputing that number four is colder, but, I have been fooled a couple of times using that as my sole determiner. :)
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I was thinking valvetrain too/lack of compression.
Can you do a compression test on that cylinder? You seem to have cover most of the basics.
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he said he checked compression... but..on a cold/dead cylinder I would be surprised that reading was within 5psi of the others.
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I know you can ground the plug, but was warned by Red Armstrong about only firing one of the two paired cylinders as it can take out the module. So picked up one those gadgets that connects between the plug and plug wire with the internal light to test it with this weekend, hopefully. New 4 post lift arrived a week early while I was out of town so will be spending most of the weekend trying to put that together so I can get it off the drive. Will let you know what I find out.
I did check compression and all looked good. All cylinders were cold when the test was done as I was changing the plugs out at the time and thought I might as well check compression while I was at it. I am also planning to pull the valve cover and have a look at the valve train to see if there may be an issue there. Having said that, I can't see how this could be an issue from sitting but at least it will rule it out.
Thanks for the interest and the suggestions. Keep them coming! I will post the results as soon as I get the checks done.
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I just plug the the sparkplug into the wire and lay it on the valve cover...that makes the ground. It is very hard on the module to run the engine without all wires connected as he said altho many do it....I always wonder how much life they took from the module doing that, but?
Be sure you disconnect one injector connector at a time and "prove" #4 as the culprit. I have been fooled before, cold pipe or not. :)
Also be sure your egr valve plunger is not rusted partially open and that there is no leaks around its base.
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Does checking the EGR involve removing it? Have never had it off, so............
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crank the car up and let it idle. before it gets too hot, stick your fingers under the can on top of the egr that contains the diaphragm. There are holes in the lower side that allow you to put your fingers on the actual diaphragm. Lift up, the car should stumble badly...that means the plunger in the egr is at least moving...does not say for sure that it is completely closed, but...it's a start.
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Well I think I have figured out what is going on. Checked to see if all cylinders were firing with my new widget and to my surprise they all were. So started to pull off the passenger side valve cover. It's been 5 years so I forgot what a pain it is to remove. Any way, got all the bolts removed and tried to get it off. Forgot you need to remove the heater pipe running along the valve cover. As I was trying in to remove it with the heater pipe still installed I noticed a piece of blue anodized aluminum hiding in the from of the head! Looks like I had a rocker arm give up the ghost. Never would have guessed that one in a million years as the car has basically been siting for 5 years straight. So hopefully once I get the valve cover off I don't have too much of a mess. Thankfully I think T & D are just up the road from me about 15 miles. Thanks everyone for all the input. Will let you know the final out come once I get the valve cover off. My back had had enough for the night as I just got my 4 post lift assembled over the weekend and the GN was parked underneath it and the lift was just high enough to park the GN under it. Oh my aching back! Bad planning on my part.
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I love my four poster....
sounds like you are making progress....I was pretty sure it was firing, but, I figured you had to prove it to yourself. :)
I hope it is not too badly messed up.
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Drained the rad and removed the heater pipe so I could get the valve cover off and inspect damage. The rocker arm on cylinder 2 exhaust was the one that broke. The pushrod on intake 2 was bent so bad I had to pull it out with a pair of vise grips! As I am this far I think I will pull the intake off and make sure the lifters and cam are ok. The intake has been leaking from the back for years so I can kill 2 birds with one stone. I think cause of all of this is the splash shields on the valve springs. It looks like there is a clearance issue with the roller rockers and the bigger cam. I read in the GNTTYPE archives that .450 was as big as you can go without out having an issue. Need to check my cam card, but am pretty sure the lift is more. When the guy originally built the heads he did not put the splash shields on. He also installed PC seals on the intake valve and no seals on the exhaust. This made the car smoke like a fog machine at idle. So I re-installed the splash shields, which only marginally helped and the installed seals on the exhaust valves which ultimately solved the issue. So it looks like my fog fix caused the problem. I can see some minor marks on the underside of the other rocker arms, but it was barely enough to remove the blue anodize. Also better check all the other pushrods to make sure none of the others are bent. Will try and post some pictures of the damage tomorrow if I get a chance.
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Roller rockers often cause problems, but, you know what you are looking for so...Hopefully the cam is okay.
I am not so sure that the lift is the problem, but, I think it is more the rockers.
Strange that you had a smoking problem on the exhausts as they don't suck oil like the intakes that see vacuum. The seals should have fixed that problem unless the guides are worn out.
At any rate, looks like you are on the road to getting it fixed. Glad you figured it out. :)
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Did get the broken rocker replaces some time ago and while I was that far into it, decided to fix the intake manifold gasket that has been leaking oil down the back for my block for years! So all back together, start it up and it still runs like crap. So as it was still cold out, I was in no great hurry to drive it as there was snow on the ground, and the fact that I was totally pissed off at it, I have not looked at if for several months. So back at it again this weekend in hope of being able to drive it some time! About a week away from dragging it in somewhere and saying "fix it". So to outline again what I have done as best as I can recall
- New O2 Sensor
- Checked fuel pressure
- New sparkplugs X 2
- New Plug wires
- New Fuel Filter
- New Coil Pack
- New Ignition Module
- checked resistance between engine and battery to see if it was a grounding issue.
- Removed injectors and had them flushed and flow checked
- Compression check on all cylinders
- Checked injector harness with node light to make sure all injectors are pulsing
- Checked to make sure all plugs are firing.
- Replaced roller rockers with stock rockers as on #2 cylinder 1 rocker arm was broken and other valve had bent pushrod
- Checked cam position sensor, all good. Suspected maybe time chain was off for some unknown reason and thought this was the easiest way to check this.
- Rechecked compression on #2 and #4 cylinders.
Any suggestions any one? I am out of ideas. Thought I had this diagnosed when I found the broken rocker arm, but that was only part of the problem. Still runs like the timing is way off or it is not firing on a cylinder or 2. About the only things I have not replaced on the MAF and crank position sensor at this point.
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You replaced the roller rockers with stock rockers...so I assume you're using stock length pushrods...as the ones for the rollers mite not be stock length. Just checkin'.
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That's correct, changed out the pushrods as the roller rockers took a different length pushrod. Just did a bit of checking on my ignition timing and all looks good. Put a 1.5" piece of tape on the balancer on the advance side and looked like everything was ok. Was looking at my scanmaster 2 and the airflow does not seem to change much when the car is revved up. Took it up to 3K and not much of a change from idle. Could I have a soft fault on my MAF as it is not setting any codes? Did the tap test on it a while back and again today and it does not stumble when you tap it. Unplugged it and the car ran pretty much the same with it unpugged! All the above has been done in park sitting in the garage. So no load on the engine. Runs too bad to think about driving it.
Also swapped in another chip of unknown comodity. Think the guy I bought the 40# injectors from gave it to me. Says 108 on it so am assuming it is a race gas chip. A different chip made no difference to how it ran. Thought it was a stretch, but had a bag full of them sitting around. Wish I could remember what they all were! The chip I am running is one Jay Carter made for me about 10 years ago. But any way, does not appear to be the culprit.
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The maf numbers should be 4-6 at 750-800 rpm and should increase when the rpms go up. How much they go up will depend upon how much load is on the engine as well as the rpm. I would think your O2s would be dropping and the blms going up altho this will not be as dramatic when the car is not being driven. Darned sure will run like crap in this case.
Not sure why it is not throwing a code, but, it sounds like you have found a place to start. Is the check engine lite on when you turn the key to on?
Be sure to check the ecm connectors for lack of corrosion and a good connection on all pins...as well as the ones going to the maf.
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I assume you put fresh gas in and it's not 5 yrs old. Try and swap the injector from the dead cyl to another and see if the problem moves. May be just a clogged injector.
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Gas was changed out every year and stabilizer added. So I don't think it is a fuel issue. And the injectors have been removed and sent out to have them cleaned and flow checked. I think the issue with the dead cylinder was the broken rocker arm and bent pushrod. Neither valve was opening. I will check the ecm connection again, but did check them in past. No service engine light except when the key is first turned on before you start the car. Any idea what sort of air flow numbers I should see at higher rpms with no load. I can drive it if that would help, just runs real bad. If I do buy a new MAF, any suggestions as to where to get one or which ones to avoid as I know the remanufactured ones can be a bit hit or miss and really don't want to send the money on a translater at this point in time until I get the current issue sorted.
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Not sure numbers from my car would be meaningful, but, I would guess the maf should be close to 30 at 2000 rpm...
Maybe someone that is running a conventional set up will give us a better number from their car while in Park.
Rebuilt mafs are a turkeyshoot and none of them ever seem to be spot on, but, sometimes you get lucky and find one that is pretty close. I would stay away from Airtex/wells and Cardone, myself. I would rather try a Standard, or maybe an AC Delco altho I have heard of them being off as well
Now that you replaced the rockers, I am assuming the valves are going up and down normally and you are seeing normal compression of about 145/155 on those cylinders on a warm engine?
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Cylinder pressures are a little lower, around 135 but that was on a cold motor. Only did 2 and 4 as I wanted to make sure 2 was ok after that I found. After doing a lot of pondering regarding why the rocker broke in the first place, I think I have a reasonable explanation. Rocker arms were contacting the splash shields slightly as there are small witness marks underneath the rocker where it contacted the splash shield. I think when I set the lash the rocker arm was resting on the splash shield as opposed to top of the valve. My guess is that I had lash on a hydraulic cam and finally beat the rocker arm into submission. The reason I say this is that the stock rocker arms have a lot less valve train noise than the roller rockers did. I will give the standard MAF and try and see how I get on. I think I can get this through Autozone locally. Wish me luck!
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You did not mention how much the mafs were increasing?
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Well the new MAF arrived yesterday and I bolted it on and was greatly disappointed as this does not seem to be the issue. Did drive it around a little just to see if it would magically get better! Not. So about to give up and see if I can find someone around here that can work on them. Any other suggestions before I give up?
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As you have not given any scantool numbers, we are just guessing.
I am assuming you have not check engine light burning because I don't recall you mentioning that.
What was the fuel pressure when you checked it?
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someone did not put the cam sensor in 180 out, did they?
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As the car ran for several years in it's current state I don't think the cam sensor could be 180 out. I do have a scanmaster so I can give so data. That was why I thought my airflow numbers were out as I was getting the data from that.
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Fuel pressure was at 42 psi with vacuum line off.
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You never did give us the maf numbers at 2000 rpm before you spent the money...but, I guess it matters not now.
It sure sounds like a fueling problem. How long ago did you clean the injectors?
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Is #4 still dead? Are you sure it's OK mechanically? Do you have a bad lifter, that you bandaided with valve adjustment? If all Ok then you can swap ign wires, plugs, injectors to other cylinders to see if the problem moves. I know you said you cleaned the injectors, I would still swap with another cylinder. You also could have bought a bad MAF. The reman units are so so these days.
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Injectors were cleaned a couple of months ago. I am going to get after it again today so will post some numbers from the scanmaster later today. Plan to replace all the vacuum lines as they are all original equipment with the exception of the wastegate line, check electrical connections, and unplug injectors one at a time and see if I have a non-firing cylinder. I may also swap back on the old coil and ignition module just for grins as it has been known for new parts to be bad and that was all changed before I found the broken rocker arm. Also going to verify spark and fuel pressure again. Basically go back to the beginning and start over and see if I have missed something. So here goes!
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Make sure it is not leaking around the base of the egr valve as well-they run really badly when that happens, or the egr sticks in the open position
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Stuck my fingers underneath the EGR valve and was able to push the diaphram up. This made the car idle badly and would smooth out once I released it. So from this I am assuming it is not stuck of leaking.
Did replace some of the vacuum lines. Any idea how you get to the long one that seems to disappear into the drivers side fender. I assume this is for the cruise control and the module is located back in there.
Pulled the injector connector the infamous cylinder number 2 (same cylinder that had the bent pushrod on one valve and the broken rocker on the other valve) and idle did not change and car runs the same when you rev it. Checked for spark, that's good. Checked to see if the injector is getting a signal, that's good. Pulsed injector with fuel pressure gauge attached, pressure drops. Compression was checked the other day on 2 and 4 and they are the same.
So, looking for a little advice as to where to go from here. I was thinking maybe I have a bad lifter that is collapses under valve spring pressure and not letting either fuel/air in or exhaust out. Hate to have to pull the intake again, but thought I would ask for opinions in this before I headed down this path. Was thinking it might make sense to pull the valve cover and stick a dial indicator on there and see what sort of lift I was getting at the valves first.
Thanks again for all the input, hopefully I can get this thing running before the Hot Rod Power Tour. Was hoping to make the first part of that as it starts in Detroit which is only a couple of hours away from me.
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well, sure seems like that cylinder is not doing anything to contribute. Does the plug look like its firing? Is it fuel wet?
Believe you said you had used a noid lite to verify that it is getting an injector pulse? Seen plenty of bad harnesses the past few years.
If it has compression, one would think the lifter was working. Maybe do a crude leak down by blowing air into the plug hole and see if it leaks out the exhaust or intake when the valves are close-wondering about bent valves
Could also follow Ed's suggestion and swap the injectors about to see if the problem stays on that cylinder or follows the injector to completely eliminate the injector. Sure seems to be associated with the broken rocker and pushrod but????????????????
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When I pulled the injectors to have them cleaned I did not put them back in the exact same location. So don't think that is an issue. I have an air hose I can attach to the cylinder to add compressed air. Did this when I removed the splash shields back when I found the broken rocker arm. I did not notice a huge air leak then, so my thought is that bent valves are probably not my issue. Pulled the plug a few days ago when I checked the compression on numbers 2 and 4 and it is black, but so was the plug on number 4. Car is running pretty rich at the moment at idle. I'll go pull the plugs again and have another look.
Any thoughts on my suggestion to check lift at the valve?
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One other thing I forgot to mention. Early on I did a compression check and all checked out fine, even cylinder 2 in which neither valve was opening as the rocker arm and bent pushrod had not been found at that stage.
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I'm betting there's damage to the valves, guides or seats on number 2 cylinder.
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two and four have nothing in common electrically at the coil level. Think you said you had proven the plugs were firing which would eliminate wires and plugs??
Bit strange to have the same compression if the valves were not moving which sure sounds like bent or such
Really hard to check lift on a hydraulic lifter as they tend to bleed down under pressure when the engine is not running.
Best would be to pull those four lifters and examine the bases for erosion as well as look down the lifter bore with a good light at the lobes.
Be nice to have leakdown gauge on the cylinders to see if they hold air pressure at all
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oh, yeah, put air in two and see if it comes out four, and vice versa
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Not sure I understand what you mean by "put air in 4 and see if it comes out 2 and vice versa"?
Although I do no have a leak down checker, I could do the same thing rather crudely with my air hose, could I not. If I attach the air hose to the cylinder and set the pressure and then turn off the air to the regulator, which has a gauge on it and leave it for a period of time. Then check the pressure after that, wouldn't this at least give me so sort of indication. I could do no. 2 and another one just to get a comparison. What of you think?
Heading out of town for a few days tomorrow, so don't really want to rip it apart and then leave. Really don't want to take it apart again, but may have not choice. If I did pull it back apart again, and the cam looks ok, would it not make sense to throw a couple of new lifters in while I am there seeing as they are reasonably inexpensive and I am already there.
Almost forgot, pulled the plug in 2 and compared it with another cylinder and 2 looks like its wet.
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take the plugs out of two and four...pump air into one hole and see if air comes out the other
yes, if you gave a gauge in the line you can see if it holds the pressure or goes right back down
If you install new lifters, you have to go thru the break in procedure again....if the lifters are bad, I would think they would be noisy. Assuming the plungers are not jammed solid, I would think they are okay...
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Little confused. How can air from cylinder 2 escape to cylinder 4? Or are you looking for a blown head gasket? Had to think about that one for a second since we had been talking about valves, lifter, etc. Will try and get that done tonight as I am getting motivated again now that I seem to have a direction to head. Shooting in the dark gets a bit old after a while.
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I have seen them pop a gasket between cylinders and run like crap because they did not build combustion pressure but would build compression. After 25 years, virtually everything I have assumed has been proven wrong at least one time :)
Also run your hand between the head and the block on the bottom and see if you feel any air there...
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Hooked up compressed air on cylinder 2 with plug out of 4 and no air coming out of 4. Also did a crude leak down check on 1 and 2 from 120 psi to 80 psi. Number 2 took 24 seconds and number 1 took 31 seconds. Was going to check 4 as well, but compressor ran out of air and I ran out of gas!
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Also forgot to mention I sprayed starting fluid around base of the EGR valve with the car running and there does not appear to be any leaks.
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Any thoughts?????????????
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Finally got it sorted out. Ended up pulling the head to see if I had any bent valves as a result of the broken rocker arm and bent pushrod. Valves checked out good. Put new head gaskets on both sides while I was there. Fired it up Monday night and low and behold I have all 6 cylinders firing. So it looks like I had a blown head gasket, even though my compression checked good. Go figure.
A big thanks to all that chimed in, and especially to Steve Wood, who was a great help. I was ready to throw in the towel. Going to take her out for a spin tonight! Can't wait.
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Fortunately, you are the persistent kind! Enjoy it :)
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Fortunately, you are the persistent kind! Enjoy it :)
Funny how sometimes these cars & persistance go hand in hand!
Many have quit & sold the car but it's good to hear it's all good. All that work is gonna make the Smile on your face even bigger when your flying down the road! :atbeer:
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too late to help, but when you did your compression checks - did you remove just the plug for the cylinder you were working, or did you remove all 6? I wonder if pulling all 6 for the check might have isolated this sooner.
I posted a different question, so I figured I'd better keep things even try to help someone. So far, I can't. But since my car has sat as long as yours, a little empathy for your problem is as close as I can get.
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Premature celebartion. Started the car up a couple of days later to take it to a local cruise night and it is running like crap again. Go figure! Back to number 2 not firing but have spark, fuel and compression. Swapped injector leads between 2 and 4, swapped plug wires, swapped coil connections on 2 and 5. Still can pull connection at injector 2 while idling and it does not make a difference to the idle. I'm stumped! :x
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that was your bad rocker arm, right? Any chance something is still not right there and your exhaust valve isn't cycling in sequence?
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Ended up being a bad injector. Swapped the suspect injector in cylinder 2 and not 2 is firing. So replaced them all with a set of 42's and a TT chip and she is now running sweet as a nut. Have put over 600 miles on here since fixing the problem. A special thanks to Steve Wood for all his help! Wouldn't have got it fixed with out it.
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I told you that 4 pages ago :icon_eyes:
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Hope you had some fun on the tour...:) glad the fix stayed fixed!
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Read the entire thread was glad you found the issue... If possible can we get an admin add to the heading off topics that have been solved or fixed to have the word solved in parenthesis (SOLVED).
Or even better make a section of solved problems and move them into a solved problems section?
Something like this would help big time when dumpster dive searching threads for diagnosis... O0
Posted From Tapatalk
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Read the entire thread was glad you found the issue... If possible can we get an admin add to the heading off topics that have been solved or fixed to have the word solved in parenthesis (SOLVED).
Or even better make a section of solved problems and move them into a solved problems section?
Something like this would help big time when dumpster dive searching threads for diagnosis... O0
Posted From Tapatalk
Solved. :rofl:
I added it to the OP Subject line - will consider the other suggestions.
Thanks
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Ya, likely the seals on the exhaust side (which there should be NONE) certainly contributed to the problem. The stack up certainly would have bent a pushrod or more, especially at high lift and higher ratio than normal.
The exaust guides have to be cut down, and modified exhaust valves added to run seals on that side.