Hi Dan, not been around any of the meets as the Corvette is playing up at the moment. Some issues sorted but far from right at the moment. Of on holiday until early July but hope to solve problems and get it behaving when I get back. Might need some thoughts if there are any Corvette people out there. Regards John.
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Renegades working with Beaulieu to put on this show on 16th June 2024. Renegades meeting at Rownhams Services to leave at 8.00am to convoy down to Beaulieu.
https://www.solent-renegades.co.uk/threads/beaulieu-custom-and-american-show-16th-june-2024.55909/
C4 Corvette
- Thread starter John B
- Start date
AmericanThunder
Super Moderator
Share your Corvette woes, you never know what people will come up with.
Hi John, Dennis has a Corvette C4 in Portsmouth, just off the eastern road, a little further on from the Farmhouse, he is very knowledgable, and knows C4's inside and out.
Feel free to post on here, someone will surely have an idea for trouble shooting.
Feel free to post on here, someone will surely have an idea for trouble shooting.
Thanks for that guys. My problems as follows. The car had not missed a beat up to 10 to 12 weeks ago. I was going out for a spin. Drove about 1 mile and the engine lost power and was miss -firing badly. Felt like fuel starvation. Had fuel filter changed and fitted a new fuel pump. Car fired up and seemed fine. did about 20 miles with no hint of a problem. Took it out next day and the loss of power and miss-fires back. Checked fuel pressure on fuel rail, and all was fine. Came to the conclusion that it was probably a sensor issue.Fitted new ECM sensor and it ran fine. Took the car out a couple of days later and there were a few miss-fires, but seemed to clear. I had a new exhaust oxygen sensor which I got fitted. Car started up fine when I collected it, then service engine soon light came on and lack of power and miss-fires back again. Need to get it sorted when I get back from holiday in early July. Regards John.
AmericanThunder
Super Moderator
What year Vette?
saleen 192
Core Member
Know where you are going A/T. obd 1 or obd2 and scan it see what faults it brings up.
have you taken plugs out and looked at them? when was it last serviced?
vacum leak ?
have you taken plugs out and looked at them? when was it last serviced?
vacum leak ?
AmericanThunder
Super Moderator
Nope. The C4 had various engines over the year. The Crossfire, the L98 and the LT1.
So diagnosis starts there, especially if it's the LT1 engine as I'll be firmly pointing the finger at the opti-spark.
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AmericanThunder
Super Moderator
Ok, so that's the L98 engine.
When it misfires does it pop in the intake manifold or the exhaust?
Does it only happen only at WOT or across the range?
When it misfires does it pop in the intake manifold or the exhaust?
Does it only happen only at WOT or across the range?
Started the Corvette yesterday. Warmed up and ticked over at around 680 revs per minute. Took it out of drive and drove it to the end of the road, about 200 yards. Misfire started again. Just about enough power to take it around the block and get it up my sloping drive. I took off the bottom cover under the dash/steering column to test the ECM codes via ALDL, but couldn't find it. The car is not standard so possibly moved to another location.Perhaps I can see it if digital dash panel is removed. I am going to take out the fuel pump again(new one fitted recently) to fit a new fuel filter to it. I had to modify the old filter as it was damaged, by cutting it in half. Getting back to running the car, when started, all warning lights go off, but when misfire starts, yellow service engine soon came on. Also. digital dash average mpg dropped to 8 MPG and range also erratic .Will post again when in tank filter fitted and pump wiring renewed.Thanks to all showing interest in my problems.
saleen 192
Core Member
we like problems keep posting.
Right, took out fuel pump assembly today. Changed all wiring and fitted new in tank filter. Put it back together, re/connected battery and fired it up. No (service engine soon ) light. Set temperature controller to 100c and let it run in drive. When the fan cut in, held 1200 rpm for around 1 minute. Service engine soon light came on. Turned ignition off and restarted the engine. Revved engine from tick-over (680rpm) to around 2000 rpm and the light stayed off. Left car running for around 30 minutes, checked several times and the dash board stayed clear. I will take it out in the next couple of days and will see what happens. If any problems, I will remove instrument panel and look further for ALDL unit. Should this be fixed to steering column or is it loose behind instrument panel?.
saleen 192
Core Member
don't know this type of car's system as not work on one but would have thought it to be fixed and not floating hanging down as this put strain on wring and would expect it to be under dash?
service light shouldnt be effected by the fuel pump/filter??
you proberly looked here already ?
service engine soon light - CorvetteForum - Chevrolet Corvette Forum Discussion
Service Engine Soon light? - SmokinVette.com Forums
service light shouldnt be effected by the fuel pump/filter??
you proberly looked here already ?
service engine soon light - CorvetteForum - Chevrolet Corvette Forum Discussion
Service Engine Soon light? - SmokinVette.com Forums
Not sure what the diagnostics would be on that era of car. My '89 firebird i had to short two pins on a similar connector, and a code came up on the dash board n the form of a flashing light you had to count the flashes. One problem I had on the Firebird was simular sort of thing, fine on tick over, but stumbled when driving. I think the error was 3 flashes a gap then 4 flashes. Error code 34, which was a bad lamda sensor, this plays with all the fuel mixture. Could be fine on idle, but down on power when driving, all because of that sensor in the exhaust.
AmericanThunder
Super Moderator
Could also be the EGR. This is operated when a cruise condition is determined, i.e. Steady RPM's for a period of time, exactly like your test scenario. When the EGR opens it recirculates exhaust into the intake cycle. A 3rd gen Firebird that we used to own suffered with this issue as does the Fiero.
If it's electronic you might have to disconnect the connections but this also might trigger a code. If the EGR is vacuum operated you could just disconnect and plug the vacuum connection.
If it's electronic you might have to disconnect the connections but this also might trigger a code. If the EGR is vacuum operated you could just disconnect and plug the vacuum connection.
Been trying to get the C4 out for a couple of days. Some prize prick parked a car dead opposite my drive and left it for a couple of days. I left a note on it and it has suddenly moved elsewhere. I will try to get it out tomorrow if the idiot doesn't come back. Thanks guys for your thoughts.
OK, tank filter fitted and wiring replaced. Started car on drive, warmed up and ticked over at around 680 rpm as sweet as a nut. Took it out and drove it up the road, service engine soon light came on and misfiring started again. Limped back into our road and engine cut out. Started it and service engine soon light was off. Drove a couple of hundred yards and the service engine soon warning light came back on and misfiring started again. Limped back home and got the car back on the drive. Turned off ignition and restarted the engine. Warning light stayed off, and I revved the engine hard , pick up great and no misfires, left it running for 10 minutes or so with no warning light or misfires. It seems that the problem only occurs when the car is in gear and running. Auto box by the way if it has any bearing on the problem. I have got to find the ALDL and retrieve any fault codes. Will keep you posted, and as usual, any thoughts would be appreciated.PS, digital dash average mpg saying 99 and instant saying 0. Can the digital dash cause the sort of problems I am having?.
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AmericanThunder
Super Moderator
Are you using any gearbox oil? (Is the level dropping?)
