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Topic: 82 Corvette rough idle then dies out

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82 Corvette rough idle then dies out (1/9)
 6/9/21 6:15pm
benny65
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Joined: 8/16/2013
Posts: 8

My car starts and idles rough 400 rpm to 1500 rpm goes up and down and then dies out.

Check engine code, got 22 replaced TPS and adjusted to specs the old one was shot no changes when trying to adjust.

Car starts but does the same thing.  No 22 code after new TPS was installed.

A member suggested to change coolant temp sensor, Got a Delco newer style one, install and still have rough surging idle.

Check for codes, Only flashes 12 12 12 ETC..

I can hold the throttle to keep engine running.  TBI spraying a nice umbrella shape fuel pattern,

but once throttle is release TBI sprays very little fuel and engine dies out.

Vacuum for the headlights goes up and down without a hitch, trying to rule out vacuum leak.

Any other suggestions and advices is appreciated.  Thanks.  Trying to get the Corvette ready for the summer.



|UPDATED|6/9/2021 3:15:22 PM (AZT)|/UPDATED|
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Re: 82 Corvette rough idle then dies out (2/9)
 6/9/21 9:19pm
Adams' AppleLifetime Member
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Duncanville, TX - USA

Vette(s):
#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas


Joined: 11/8/2003
Posts: 19830

Without more info, or live engine data(from a scanner), I would suspect the Idle Air Control valve. The Crossfire set-up takes a special "tool" to plug the air intake passage while the AIC self adjusts. It could certainly be a vaccum issue also. Has the car done this for a while, or did it just start, and throw the 22 code for the TPS? You might try disconnecting the battery overnight, and then start it, and give it time to relearn the idle. I can look in the Factory Service Manual and see what the process is, but I won't be able to post it until tomorrow. As an owner of an '82, I would also highly suggest you get a Service Manual if you plan on doing the upkeep on it yourself....they can be quite cantankerous! 



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Joel Adams
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Re: 82 Corvette rough idle then dies out (3/9)
 6/10/21 2:47pm
73shark
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Overland Park, KS - USA

Vette(s):
1973 Orange Metallic Coupe (orig owner), L82, 4 spd (WR), PS, (A/C & PW (I installed from wrecked 73)), leather, AM/FM Stereo, ran with '65 FI unit earlier & will again some day.


Joined: 7/9/2003
Posts: 674

Sounds like how my 87 IROC Camaro did when the fuel pump was going out.  If you don't have one, get a fuel pressure gauge at Home Depot for about $25.



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1973 L-82 4 spd

Re: 82 Corvette rough idle then dies out (4/9)
 6/10/21 7:12pm
benny65
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It just started to happen, started it up last month and it ran fine, when I start it 2 weeks ago all this happen.  Where do I connect the pressure gauge to test fuel pressure?  Looking at the set up and can't figure it out.  Did a search, only see custom piping set up to test.  Any suggestion is appreciated.  Thanks.

Re: 82 Corvette rough idle then dies out (5/9)
 6/10/21 7:13pm
benny65
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Where do I connect the pressure gauge?  Thanks.

Re: 82 Corvette rough idle then dies out (6/9)
 6/10/21 8:58pm
73shark
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Overland Park, KS - USA

Vette(s):
1973 Orange Metallic Coupe (orig owner), L82, 4 spd (WR), PS, (A/C & PW (I installed from wrecked 73)), leather, AM/FM Stereo, ran with '65 FI unit earlier & will again some day.


Joined: 7/9/2003
Posts: 674

On my IROC, there was a Schrader fitting on the fuel rail.  Of course it was a TPI system whereby yours is dual TBI Cross-Fire setup.



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1973 L-82 4 spd

Re: 82 Corvette rough idle then dies out (7/9)
 6/11/21 6:13am
Adams' AppleLifetime Member
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Duncanville, TX - USA

Vette(s):
#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas


Joined: 11/8/2003
Posts: 19830

Checking fuel pressure requires a "special tool" that replaces the fuel line that connects the 2 throttle bodies, allowing a gauge to be installed. Attached is the chart for checking the IAC system. 



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Joel Adams
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Re: 82 Corvette rough idle then dies out (8/9)
 6/20/21 2:14pm
benny65
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Joined: 8/16/2013
Posts: 8

Thanks for the reference page.  Reading the 1st block idle engine and record RPM in park or neutral, RPM is erratic surges from 400 RPM to 1500 RPM and dies out.  Don't know how to go farther if I can get pass this 1st step.  

I have so much to learn and figure out.  I guess I should find some way to test the pressure first before moving ahead.

Thanks for the help.

 

Here is a video link to show what the car is doing...

https://youtu.be/cgBwKQ3AMqk

Thanks for the help



|UPDATED|6/20/2021 11:14:03 AM (AZT)|/UPDATED|
Re: 82 Corvette rough idle then dies out (9/9)
 6/21/21 2:01pm
F4Gary
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Grapevine, TX - USA

Vette(s):
1972 LT-1 convertible with factory air.


Joined: 8/26/2006
Posts: 1048

The guys in this thread may have some helpful information.  There is also a link there to a TBI specialist site.

 

https://www.corvetteforum.com/forums/c3-general/4538608-my-crossfire-16146299-ecm-odyssey.html



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