HELP ENGINE -C4 L98 Stock
Thread Starter
Le Mans Master
Joined: Aug 2003
Posts: 9,884
Likes: 3
From: Magnolia Mississippi
St. Jude '03-'04-'05-'06-'07
HELP ENGINE -C4 L98 Stock
Guys, Need some help here. (87/L98/Stock)
She starts right up, runs high idle, then slowly chokes out and dies. You can give her gas, and she will continue to run, with constant gas, but leave off the throttle and she chokes out and dies.
Pressure : 43psi @ rails and holds for 1hr+
Startup: Fires right up, no hesitation on startup
Battery: 12.2v costant
Codes: No error codes and no codes during scan while running.
Vacume Lines: all lines check and connected, no leaks, did leak testing
Any help would be appreciated.
thanks
vinnies87
She starts right up, runs high idle, then slowly chokes out and dies. You can give her gas, and she will continue to run, with constant gas, but leave off the throttle and she chokes out and dies.
Pressure : 43psi @ rails and holds for 1hr+
Startup: Fires right up, no hesitation on startup
Battery: 12.2v costant
Codes: No error codes and no codes during scan while running.
Vacume Lines: all lines check and connected, no leaks, did leak testing
Any help would be appreciated.
thanks
vinnies87
Pro
Joined: Nov 2002
Posts: 737
Likes: 11
From: Charlotte MI
Originally Posted by vinnies87
Guys, Need some help here. (87/L98/Stock)
She starts right up, runs high idle, then slowly chokes out and dies. You can give her gas, and she will continue to run, with constant gas, but leave off the throttle and she chokes out and dies.
Pressure : 43psi @ rails and holds for 1hr+
Startup: Fires right up, no hesitation on startup
Battery: 12.2v costant
Codes: No error codes and no codes during scan while running.
Vacume Lines: all lines check and connected, no leaks, did leak testing
Any help would be appreciated.
thanks
vinnies87
She starts right up, runs high idle, then slowly chokes out and dies. You can give her gas, and she will continue to run, with constant gas, but leave off the throttle and she chokes out and dies.
Pressure : 43psi @ rails and holds for 1hr+
Startup: Fires right up, no hesitation on startup
Battery: 12.2v costant
Codes: No error codes and no codes during scan while running.
Vacume Lines: all lines check and connected, no leaks, did leak testing
Any help would be appreciated.
thanks
vinnies87
Le Mans Master
Joined: Jun 2006
Posts: 5,642
Likes: 5
From: One day you're a Comet...the next day you're dust... Arkansas
I don't know if that battery reading is using a meter or off your dash display, but 12.2v at start-up is pretty low. If i remember correctly 12.9 is a fully charged battery. If it's the dash, mine reads about 14.2 at start-up and then drops back to 13.9 after running a while. I'm wondering if your alternator is going bad or there is a battery problem.
Thread Starter
Le Mans Master
Joined: Aug 2003
Posts: 9,884
Likes: 3
From: Magnolia Mississippi
St. Jude '03-'04-'05-'06-'07
Originally Posted by BADDUCK
I don't know if that battery reading is using a meter or off your dash display, but 12.2v at start-up is pretty low. If i remember correctly 12.9 is a fully charged battery. If it's the dash, mine reads about 14.2 at start-up and then drops back to 13.9 after running a while. I'm wondering if your alternator is going bad or there is a battery problem.
Le Mans Master
Joined: Oct 2003
Posts: 6,130
Likes: 2
From: seattle WA
As clean as you keep your vette, I suppose the fuel filter is OK? More than likely the IAC, and if it's carboned up it probably won't show on the scanner..
Last edited by rick lambert; Jul 16, 2006 at 12:48 PM.
Thread Starter
Le Mans Master
Joined: Aug 2003
Posts: 9,884
Likes: 3
From: Magnolia Mississippi
St. Jude '03-'04-'05-'06-'07
Originally Posted by rick lambert
As clean as you keep your vette, I suppose the fuel filter is OK? More than likely the IAC, and if it's carboned up it probably won't show on the scanner..
thanks, have a new iac here, and am just in the process of replacing and setting. Don't think its the filter or pump at this point. Gonna replace the IAC and set IAC & TPS again. TPS shows on the scanner @ 5.5, so it looks good. Thanks, for the words of support.
Race Director
Joined: Sep 2000
Posts: 17,298
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From: The Top of Utah
Originally Posted by rick lambert
As clean as you keep your vette, I suppose the fuel filter is OK? More than likely the IAC, and if it's carboned up it probably won't show on the scanner..
RACE ON!!!
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Le Mans Master
Joined: Oct 2003
Posts: 6,130
Likes: 2
From: seattle WA
Exactly what I'd do, it's probably pretty well carboned, just make sure you clean the passages. I don't know why guys just clean the pintle and passages and call it a day, these only cost about $30, new stepper, gasket etc. and replaces the 20+ yr. old part. Wifey says Hi, and says to say Hi to yours. 
That's probably a good point CFI-EFI, the normal steps are 1-40, so I think you could still have a carbon build up that just may be hard to see.
That's probably a good point CFI-EFI, the normal steps are 1-40, so I think you could still have a carbon build up that just may be hard to see.
Last edited by rick lambert; Jul 16, 2006 at 01:07 PM.
Race Director
Joined: Sep 2000
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From: The Top of Utah
Originally Posted by vinnies87
Rick:
thanks, have a new iac here, and am just in the process of replacing and setting.
thanks, have a new iac here, and am just in the process of replacing and setting.
Originally Posted by vinnies87
TPS shows on the scanner @ 5.5, so it looks good.
RACE ON!!!
Thread Starter
Le Mans Master
Joined: Aug 2003
Posts: 9,884
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From: Magnolia Mississippi
St. Jude '03-'04-'05-'06-'07
Originally Posted by CFI-EFI
If the IAC passages have a blockage, the scanner should show the IAC counts through the roof as the ECM attempts to get air in there to maintain an idle.
RACE ON!!!
RACE ON!!!
Going to try to reset IAC
Injector pulse @ 2.9ms
Throttle sensor .58
Fuel Rail pressure @ 42psi and holding
Per this test, ruff & var idle.
Thread Starter
Le Mans Master
Joined: Aug 2003
Posts: 9,884
Likes: 3
From: Magnolia Mississippi
St. Jude '03-'04-'05-'06-'07
IAC Setting and test:
1. Followed IAC procedure,
engine off - A/B Diag mode
Ign ON - 30 sec
Ign ON - disconnected iac connector
Remove Diag mode
Start engine (at this point she ran, had to keep idle up but she was running) - on to ops temp
Engine - off
Connected IAC
Restarted and she was still REAL RUFF and WOULD CHOKE OUT AND DIE.
Disconnected MAF and same results.
1. Followed IAC procedure,
engine off - A/B Diag mode
Ign ON - 30 sec
Ign ON - disconnected iac connector
Remove Diag mode
Start engine (at this point she ran, had to keep idle up but she was running) - on to ops temp
Engine - off
Connected IAC
Restarted and she was still REAL RUFF and WOULD CHOKE OUT AND DIE.
Disconnected MAF and same results.
Thread Starter
Le Mans Master
Joined: Aug 2003
Posts: 9,884
Likes: 3
From: Magnolia Mississippi
St. Jude '03-'04-'05-'06-'07
IAC Setting and test:
1. Followed IAC procedure,
engine off - A/B Diag mode
Ign ON - 30 sec
Ign ON - disconnected iac connector
Remove Diag mode
Start engine (at this point she ran, had to keep idle up but she was running) - on to ops temp
Engine - off
Connected IAC
Restarted and she was still REAL RUFF and WOULD CHOKE OUT AND DIE.
Disconnected MAF and same results.
1. Followed IAC procedure,
engine off - A/B Diag mode
Ign ON - 30 sec
Ign ON - disconnected iac connector
Remove Diag mode
Start engine (at this point she ran, had to keep idle up but she was running) - on to ops temp
Engine - off
Connected IAC
Restarted and she was still REAL RUFF and WOULD CHOKE OUT AND DIE.
Disconnected MAF and same results.
Race Director
Joined: Sep 2003
Posts: 16,839
Likes: 341
From: Database Error Indiana
Vin, have you looked at any spark plugs, I am sure you are doing all the right things. I am just throwing out suggestions. If it had been MAF it woud have improved when un plugged.
Thread Starter
Le Mans Master
Joined: Aug 2003
Posts: 9,884
Likes: 3
From: Magnolia Mississippi
St. Jude '03-'04-'05-'06-'07
Originally Posted by Spankyellow
Vin, have you looked at any spark plugs, I am sure you are doing all the right things. I am just throwing out suggestions. If it had been MAF it woud have improved when un plugged.
Le Mans Master
Joined: Oct 2003
Posts: 6,130
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From: seattle WA
Could be wrong, but I thought I read somewhere you had to disconnect the EST to set the IAC.
You know, something just occured to me, didn't you just put the new plenum and runners on? I know you're detail oriented, but I'd definetly check for vac. leaks. Just a thought.
You know, something just occured to me, didn't you just put the new plenum and runners on? I know you're detail oriented, but I'd definetly check for vac. leaks. Just a thought.
Last edited by rick lambert; Jul 16, 2006 at 02:28 PM.
Thread Starter
Le Mans Master
Joined: Aug 2003
Posts: 9,884
Likes: 3
From: Magnolia Mississippi
St. Jude '03-'04-'05-'06-'07
Originally Posted by rick lambert
Could be wrong, but I thought I read somewhere you had to disconnect the EST to set the IAC.
Thread Starter
Le Mans Master
Joined: Aug 2003
Posts: 9,884
Likes: 3
From: Magnolia Mississippi
St. Jude '03-'04-'05-'06-'07
Originally Posted by rick lambert
Vac leaks? also you may want to pull the hose from the EGR, plug it and see if that makes a difference.
So replaced ECM back, stock chip, reset it all again, just to make sure and she RUNS FINE. So, I'm thinking that maybe the ECM go locked in a state and until the chip was removed, reseated and powered down, she then reset herself.
Being a CIO, this was my last attempt before call one of the MGCC club members who owns a Corvette Speciality Shop and having it trailered down there.
What can you say... GREMLINS for sure