Author Topic: Neighbors Corvette is kicking my rear...need some help.  (Read 265 times)

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Offline nocooler

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Neighbors Corvette is kicking my rear...need some help.
« on: July 17 2020, 04:30:18 PM »
So I've been helping the neighbor try to diagnose his issues.


The major glaring issue I see is TPS volts climb to 1.8v at WOT according to the scanner. New sensor didn't help, connector housing was cracked so I de-pinned it and used a new connector. I have 5v across the ground and reference at the sensor. I have like 4.8v checking across the reference and signal wire. All within spec
I've traced the wires from the TPS to the firewall and they look good. I tested the voltage at the computer and it sees 2.3v @ WOT at the connector, so within a half a volt of what the scanner shows. The harness looks untouched under the dash the pcm connectors were clean.
The wiring diagram (http://chevythunder.com/198689_f__y_body_1227165.htm) shows that the TPS shares a ground with the MAT and CLT sensors. If I test across the wires at the MAT is get 5v, at the coolant sensor 4v. The CLT wires look good to the firewall, the MAT I can't trace without pulling the plenum off. The scanner show logical temp numbers for the MAT and CLT sensors when plugged in and unplugged the scanner shows -31f or whatever the lowest value is.
Scanner doesn't show ecm voltage.
I am getting a code for the for the low TPS and the MAT sensor high air temps. Scanner shows CLT and MAT are reading right.
I'm thinking it's probably a ground issue - I can't get to the grounds at the back of the heads, but that is where I am leaning. Hopefully they are accessible from the bottom. The other possibility is when the exhaust shop welded the exhaust they didn't disconnect the battery and damaged the ecm - but that's more of a long shot imo.
Any other ideas? 
IhaveaV8

Offline nocooler

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Re: Neighbors Corvette is kicking my rear...need some help.
« Reply #1 on: July 17 2020, 05:08:38 PM »
This almost seems like what it was doing - http://www.gearhead-efi.com/Fuel-Injection/showthread.php?6793-165-ECM-weird-CTS-and-TPS-readings
Maybe I should have him pickup a used computer?
IhaveaV8

Offline Steve Wood

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Re: Neighbors Corvette is kicking my rear...need some help.
« Reply #2 on: July 17 2020, 05:31:54 PM »
My first thought was bad ground, but, after reading that link, I guess another ecm is within reason.  Hate to buy stuff so is there anywhere he could borrow one?
Steve Wood

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A lot of broken parts does not make you a racer; it makes you a slow learner.

Offline nocooler

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Re: Neighbors Corvette is kicking my rear...need some help.
« Reply #3 on: July 17 2020, 06:46:58 PM »
I hate to buy stuff too - I don't know anyone else that has one we could borrow.
https://www.autozone.com/engine-management/engine-control-computer/blue-streak-engine-control-computer-ecc7165/10450_50404_6207
This seems reasonably priced.
IhaveaV8

Offline Steve Wood

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Re: Neighbors Corvette is kicking my rear...need some help.
« Reply #4 on: July 17 2020, 06:50:17 PM »
Yes, it is.  Maybe you can take it back if it does not fix the problem?  Or, for $73, it could be a back up if I had to justify it.
Steve Wood

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A lot of broken parts does not make you a racer; it makes you a slow learner.

Offline nocooler

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Re: Neighbors Corvette is kicking my rear...need some help.
« Reply #5 on: July 17 2020, 08:59:52 PM »
Heís ordered one tonight - fingers crossed it fixes it
IhaveaV8

Offline nocooler

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Re: Neighbors Corvette is kicking my rear...need some help.
« Reply #6 on: August 01 2020, 05:37:45 PM »
I installed the computer today and it fixed the issues. I set the tps and told him to go rip it. He drove around for 30minutes enjoying the new found power it has. Itís funny it sound like a lame duck and now itís sounds almost healthy.
He says from a stop itíll just burn the tires and from a 10-15mph roll it hooks good.
It needs the IAC reset but all the vacuum lines need replaced so I figured thatíll all happen when itís a little cooler out. 
IhaveaV8

Offline Steve Wood

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Re: Neighbors Corvette is kicking my rear...need some help.
« Reply #7 on: August 01 2020, 05:45:46 PM »
Good newd
Steve Wood

http://www.vortexbuicks-etc.com

A lot of broken parts does not make you a racer; it makes you a slow learner.

Offline nocooler

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Re: Neighbors Corvette is kicking my rear...need some help.
« Reply #8 on: August 06 2020, 02:29:18 PM »
So while the new computer fixed the issues we were having, the car was having flooding issues. 
Ran the fuel pump by tripping the relay and it'd hold pressure fuel pressure
Turn on the key and it'd drop to zero - must be the injector drivers are bad.
Put the stock ecm back in and it stopped flooding itself with the key on but is back to running like a lame duck.
He was off to see if they could get him a different one.
IhaveaV8

Offline Steve Wood

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Re: Neighbors Corvette is kicking my rear...need some help.
« Reply #9 on: August 06 2020, 03:30:40 PM »
joys of buying a used electronic part
Steve Wood

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A lot of broken parts does not make you a racer; it makes you a slow learner.

Offline nocooler

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Re: Neighbors Corvette is kicking my rear...need some help.
« Reply #10 on: August 06 2020, 04:03:53 PM »
It was re-manufactured....heís going to exchange for another one.
IhaveaV8

Offline nocooler

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Re: Neighbors Corvette is kicking my rear...need some help.
« Reply #11 on: August 12 2020, 08:17:57 PM »
Swapped out the ecm today - and everything seems to be good with this one.
Started right up - warmed up went closed loop and it just purrs. 
IhaveaV8

Offline daveismissing

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Re: Neighbors Corvette is kicking my rear...need some help.
« Reply #12 on: August 12 2020, 09:13:49 PM »
Unhappy to hear the amount of effort they put into testing a reman unit.
-Drain plug by Earl Brown, custom oil pan by Rich's Auto

Offline nocooler

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Re: Neighbors Corvette is kicking my rear...need some help.
« Reply #13 on: August 12 2020, 10:22:55 PM »
1st one was a Blue Streak and the 2nd was cardone. He is very happy now.
IhaveaV8

Offline Steve Wood

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Re: Neighbors Corvette is kicking my rear...need some help.
« Reply #14 on: August 12 2020, 11:55:22 PM »
That's good news!
Steve Wood

http://www.vortexbuicks-etc.com

A lot of broken parts does not make you a racer; it makes you a slow learner.