stumble
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Joined: Jul 2002
Posts: 54
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From: Clifton co
stumble
I have a stumble every time I take off. It runs fine at a stop.Once I step on the gas it stumbles. Once the rpms are up its fine. I have put in a new fuel pump-filter--injectors-plugs-wires-cap-maf-K&N and every thing else that would do this. So now I need help.
Burning Brakes
Joined: Jul 2002
Posts: 871
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From: Costa Mesa CA
Re: stumble (insanegt1)
Welcome to the C4 club.
I see this all the time here on the forum. I have that off-idle hesitation or stumble myself. I've tried everything as well. If you figure it out please let us all know.
BIG JIM
I see this all the time here on the forum. I have that off-idle hesitation or stumble myself. I've tried everything as well. If you figure it out please let us all know.
BIG JIM
Racer
Joined: Feb 2002
Posts: 455
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From: Fraser MI
Re: stumble (BIG JIM 54)
Welcome to the C4 club.
I see this all the time here on the forum. I have that off-idle hesitation or stumble myself. I've tried everything as well. If you figure it out please let us all know.
BIG JIM
I see this all the time here on the forum. I have that off-idle hesitation or stumble myself. I've tried everything as well. If you figure it out please let us all know.
BIG JIM
if someone knows what causes this i would REALLY love to know!!
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Joined: Jul 2002
Posts: 54
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From: Clifton co
Re: stumble (Black84)
For got to say what year the C/4 with the stumble. Its an 86. If this helps anyone I did notice that the stumble did go away when I made a mistake and put way to high of injectors in the first time around. It used one hell of a lot of gas so I installed #26lb injectors and the gas useage went way down and the stumble came back. So maybe it has something to do with fuel??
Instructor
Joined: Apr 2003
Posts: 205
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From: Saugus Ma
Stumble
I have a 86 also that stumbles. It's all tuned up recently.
My mechanic told me the EGR valve was possibly leaking but it was a pretty big job. Does anyone have any other solutions to the OFF IDLE HESITATION better know as STUMBLE? How about relacing a EGR valve is it really a big expensive job???
Thanks Jerry
My mechanic told me the EGR valve was possibly leaking but it was a pretty big job. Does anyone have any other solutions to the OFF IDLE HESITATION better know as STUMBLE? How about relacing a EGR valve is it really a big expensive job???
Thanks Jerry
Le Mans Master
Joined: Jan 2000
Posts: 6,595
Likes: 1
From: Thornton CO
It might be a bad O2 sensor. If it runs fine when you first start it up and then starts acting up after a few minutes it could be the O2 sensor. When it's in open loop it's reading from 1 set of tables and once it's in Closed Loop it's using the O2 sensors to base it's corrections off of and if the O2 sensor is faulty it can cause the car to run rich or lean (mine was running rich). Also, if it runs fine at wide open throttle that would also point to the O2 as it runs in Open loop at WOT.
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Instructor
Joined: Apr 2003
Posts: 205
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From: Saugus Ma
Please explain open and closed loop. I replaced the O2 sensor recently.
It is inconsistent, sometimes it hesitates sometimes it doesn't. I can't get the pattern yet. It may be the temperature. I just had installed a temp switch so now my fan kicks on at 195 instead of 228. This should help, I hope.
Thanks Jerry I'll check back tomorrow.
It is inconsistent, sometimes it hesitates sometimes it doesn't. I can't get the pattern yet. It may be the temperature. I just had installed a temp switch so now my fan kicks on at 195 instead of 228. This should help, I hope.
Thanks Jerry I'll check back tomorrow.
Le Mans Master
Joined: Jul 2004
Posts: 7,163
Likes: 61
From: NH
St. Jude Donor '14
I have the same thing. Hope we can diagnose this issue.
I have a brand new O2 sensor. I think its the injectors though, to be honest. I'm going with 30lb injectors when I can tune it / get a tune done. I'll let everyone know.
-Joe
I have a brand new O2 sensor. I think its the injectors though, to be honest. I'm going with 30lb injectors when I can tune it / get a tune done. I'll let everyone know.
-Joe
Racer
Joined: Apr 2001
Posts: 452
Likes: 0
From: Tulsa Ok, Racing the wind
I had the same problem, had to change out the ECM after many new parts. It was reading the TPS incorrectly, To test, get a scanner hooked up also hook up the VOM to the TPS. watch the voltage on the scanner at idle, should be around .54 same should show on the VOM. Slowly go to WOT watching the VOM match the Scanner reading for the TPS. My ECM would go up to 1.8 v then stop and the TPS on the VOM continued up to 4.89. Changed the ECM problem gone...
$70 at Autozone. It might be the probelm, but then again it may not, I searched for 2 years before I finally found my probelm.
$70 at Autozone. It might be the probelm, but then again it may not, I searched for 2 years before I finally found my probelm.
Le Mans Master
Joined: Oct 2003
Posts: 6,130
Likes: 2
From: seattle WA
Bet you guys aren't throwing any codes either-are you? Had a friend with a similar problem, turned out to be a faulty coolant temp and a faulty oil temp sensor. He said what happens is, the ecm tries to correct the problem without storing the fault. Therefore it corrects the problem before it reaches a fault code. Probably the same from 88-96. I know it's a B to try to locate an intemitent problem, and this may not solve everyones problem, but it's cheap fix if that is the problem.
Le Mans Master
Joined: Jul 2004
Posts: 7,163
Likes: 61
From: NH
St. Jude Donor '14
http://forums.corvetteforum.com/show...post1548270662
I might've solved my problem: ECU related, but if anyone has any imput for the resister I need for my stereo to close the loop, let me know!
I might've solved my problem: ECU related, but if anyone has any imput for the resister I need for my stereo to close the loop, let me know!
Advanced
Joined: Jun 2001
Posts: 60
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From: Rockton IL
Bigger injectors mean more fuel going in than is required, since, unless your chip is reprogrammed, your computer thinks it is working with about 22 lb injectors. Seems to me the larger injectors would create problems. The builder made sure that I didn't have the 30 lb injectors. I have 23 lb injectors on my significantly modified '90 and it does 368 hp at the crank and 434 ft lb torque. No stumble. This is after a major rebuild of the engine for other reasons, new wires(old wires caused miss), new fuel pressure regulator(old one defective), new O2 sensor(while you're at it), proper timing assured, calibrated TPS, engine dyno tuned custom performance chip.
As for injectors, I would make sure all have the right resistance of about .15 ohm, don't leak, and that the wiring is in perfect condition.
As for injectors, I would make sure all have the right resistance of about .15 ohm, don't leak, and that the wiring is in perfect condition.