engine miss

[Shimy87]

Finally got to put some miles on the kids car, about 100 miles. Most everything is good except it has a slight miss when under very light load. example when you go down hill or come up behind a car going 5 mph slower, so your still in the throttle but barely, then i can feel the miss. It goes away as soon as a load comes back on car or you give it more throttle. Have not been able to look at anything yet. Was going to start with plugs/wires but really not sure where to start??

also think the shift cable from throttle body needs adjustment, at 40-45 mph, very light throttle it hunts back and forth sometimes for what gear it wants....think I need to depress tab and pull cable back a couple clicks??

[Steve Wood]

what are the O2s doing when the car has the apparent light miss?

On the second problem, is the car shifting at the normal shift points mph-wise?

[Shimy87]

O2's seem to be jumping all over 

shifts at normal points, converter locks up normally also

[Steve Wood]

It should be in closed loop so the numbers would jump around, but, I was trying to see if it was going leaner than it normally is at the point of the light miss.  Seeing more low numbers than usual.....

It does not sound like a TV cable adjustment if it is shifting at the normal mphs

[Shimy87]

I think it is low when it happens but will double check.....I did notice when i completely lift off throttle I saw numbers less than 100 and that seemed like something I had never seen on my car

[Steve Wood]

that is too low.  Check your fuel pressure.  Add a little fuel to idle.  Of course, our old favorite..chec k for an air leak...

You can also put it on blms and see if they jump up when you let off

[Shimy87]

will do,  BLM was at 118, on the air leak..... now that I have a vacuum gauge in this car when let off at cruise it shows 21 lbs vacuum.....doe s that tell me anything?

[Steve Wood]

Sounds healthy.  Don't put a lot faith in your fp gauge. Those small cheap ones can be off 20%

[Steve Wood]

Wonder if a pcv that is not working right could let too much air back in when you let off?  

[Shimy87]

Used a good fp gauge and set it to 43 with hose off....it was actually at 49 with hose off

Pcv seems good, it rattles

Have not run with any boost yet, now that I have this fp gauge hooked up will check it at 5 then 10 lbs and make sure I get correct fp raise

Only have a bit over 100 miles put on, should I put more on before putting some boost at her

[Steve Wood]

try adding a little fuel to idle in the chip and see if that does the trick

[Shimy87]

I have a tt chip, I don't see where I can adjust idle fueling, just WOT adjustments in different gears?

[Steve Wood]

Oops, I forgot. My tt chips (SD) give you that ability.  Raise the fp 2 lbs and see if it changes. Or plug the PVC line and see if that changes it. Make sure the hoses between the mag and turbo are all well connected.

[Steve Wood]

Also, disconnect the battery memory wire and clear the ecm.  Then go drive the car and let the chip relearn.

[Steve Wood]

my best guess is reset the chip