Engine light came on then went off
Thread Starter
Drifting
Joined: Jan 2011
Posts: 1,853
Likes: 81
From: Hamilton Virginia
Engine light came on then went off
1994 corvette. Driving home yesterday no issues. Stopped at the toll booth, then took off. I gave it about half throttle to open her up a little. She stumbled at about 4000 rpms, engine light came on. She seem to run ok except for at idle there was an erratic miss plus the cooling fan was on. I drove to the auto repair shop that I go to and asked if they could look at it and they said to come back Friday which was fine. I get back in the car and start it, then engine light went out and the miss was gone and she was running smooth again, drove the rest of the way home, no more engine light no more issues. I am still going back on Friday to have them check it. But I figured I would ask here to see if anyone had any ideas.
thanks,
thanks,
Le Mans Master
Joined: Feb 2000
Posts: 9,058
Likes: 214
From: Epping NH
Could be anything, like a temporary bad reading from a sensor, bad gas, etc., just pull the codes
https://tech.corvettecentral.com/201...trouble-codes/
https://tech.corvettecentral.com/201...trouble-codes/
Last edited by bac22; Jun 7, 2018 at 08:09 AM.
Safety Car
Joined: Aug 2013
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From: Minneapolis Mn
I had an issue with my 86 where start it up when it was cold out, after about 6-10 blocks it suddenly ran terrible and would barely idled. Get it home and shut it off and no codes found most times. In my case it appears it was a sticking IAC valve or connection. Got that working and hasn't happened again.
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If it did not log a code you will need a scanner to watch what's going in on the fly.
Team Owner
Joined: Sep 2003
Posts: 25,358
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After the move from ECM to PCM many 'drive-ability' codes will clear on the NEXT ignition cycle, many also won't set a MIL/SES/CEL either. If you're going to have them scan it ask that they pay attention to HISTORY in particular.
If it doesn't happen again before tomorrow and the shop is 'busy' maybe you wait it out for a re-occurrence.
You might call the shop in advance and mention it's a '94 OBD1 car with a 16-pin ALDL and a PCM. If they've used a scanner before on your car then it's certainly no issue.
If it's a 4L60E there's much more to what actually turn on MIL/SES/CEL regarding drive-ability.
If it doesn't happen again before tomorrow and the shop is 'busy' maybe you wait it out for a re-occurrence.
You might call the shop in advance and mention it's a '94 OBD1 car with a 16-pin ALDL and a PCM. If they've used a scanner before on your car then it's certainly no issue.
If it's a 4L60E there's much more to what actually turn on MIL/SES/CEL regarding drive-ability.
Zen Vet Master Level VII
Joined: Mar 2016
Posts: 5,214
Likes: 1,173
From: Southlake, TX
If the light was a quick flash then out your computer (probably) had a moment.Acceleration is the most stressful event for these ancient computers-- there are WAY too many readings crashing the system all at once. You ECM could have been overwhelmed for a split second and threw a light but not a code.
Think of pushing too many buttons on your cell phone too quickly. Sometimes they freeze for a moment and then regain full functionality once the internal computer has caught up.
I think you are good.
Thread Starter
Drifting
Joined: Jan 2011
Posts: 1,853
Likes: 81
From: Hamilton Virginia
After the move from ECM to PCM many 'drive-ability' codes will clear on the NEXT ignition cycle, many also won't set a MIL/SES/CEL either. If you're going to have them scan it ask that they pay attention to HISTORY in particular.
If it doesn't happen again before tomorrow and the shop is 'busy' maybe you wait it out for a re-occurrence.
You might call the shop in advance and mention it's a '94 OBD1 car with a 16-pin ALDL and a PCM. If they've used a scanner before on your car then it's certainly no issue.
If it's a 4L60E there's much more to what actually turn on MIL/SES/CEL regarding drive-ability.
If it doesn't happen again before tomorrow and the shop is 'busy' maybe you wait it out for a re-occurrence.
You might call the shop in advance and mention it's a '94 OBD1 car with a 16-pin ALDL and a PCM. If they've used a scanner before on your car then it's certainly no issue.
If it's a 4L60E there's much more to what actually turn on MIL/SES/CEL regarding drive-ability.
Funny thing is I was going there tomorrow anyways to have an alignment done tomorrow. I am going to tell them what you said. This is a pretty good shop, they have done work for me before. I do all my own work except when it comes to computer stuff, just do not have the tools. As others have said, it might have just been a hiccup in a sensor. The weird part is the engine cooling fan was on the whole time after the hiccup, then when I shut the car off, then re started it about 10 minutes later, the ses light went out, the car was running smooth again, and the fan didn't come on. I drove home about 10 miles with all being well.
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Thread Starter
Drifting
Joined: Jan 2011
Posts: 1,853
Likes: 81
From: Hamilton Virginia
If the light was a quick flash then out your computer (probably) had a moment.Acceleration is the most stressful event for these ancient computers-- there are WAY too many readings crashing the system all at once. You ECM could have been overwhelmed for a split second and threw a light but not a code.
Think of pushing too many buttons on your cell phone too quickly. Sometimes they freeze for a moment and then regain full functionality once the internal computer has caught up.
I think you are good.
Thread Starter
Drifting
Joined: Jan 2011
Posts: 1,853
Likes: 81
From: Hamilton Virginia
It sounds like it set one of the codes that when set turn on the fans by default. I know the ECT (Coolant temp) is one of these. I'm going to guess that the light DID set a code, and it will be in History.
I don't have any experience with 4L60e in Corvette, but in the trucks the OBD I 60e codes don't set the CEL. Trans codes set, but no light is associated with the code.
If you don't have a scanner, you should teach yourself how to use the onboard diagnostics that utilize the speedo readout and the fuel/range/etc buttons. At least you can find History codes, although real-time data is limited.
There's some ideas. Please report back when you have the shop's report. It's how we learn.
I don't have any experience with 4L60e in Corvette, but in the trucks the OBD I 60e codes don't set the CEL. Trans codes set, but no light is associated with the code.
If you don't have a scanner, you should teach yourself how to use the onboard diagnostics that utilize the speedo readout and the fuel/range/etc buttons. At least you can find History codes, although real-time data is limited.
There's some ideas. Please report back when you have the shop's report. It's how we learn.
Thread Starter
Drifting
Joined: Jan 2011
Posts: 1,853
Likes: 81
From: Hamilton Virginia
I drove her to work this morning, about 47 miles. no engine light came on and ran smooth as a babies bottom. We will see if the shop gets any information. Hopefully it was just a hiccup.
Will report back tonight.
Will report back tonight.
Thread Starter
Drifting
Joined: Jan 2011
Posts: 1,853
Likes: 81
From: Hamilton Virginia
Drove home from work another 47 miles and still no light and she ran great. I stopped by the shop and the owner/head mechanic took her for a spin. He came back and we talked about it. He said he could spend some time hooking it up and doing a scan but said the way she was running he doesn't think it would be worth it. He discussed a few things like plugs, or a fuel filter to change if I hadn't. He also mentioned possible the egr valve and how old was it. So I agreed, to wait and see if the light comes on again, bring it back and he will check it with the light on. I told him to do the Alignment that it needed, then call it a wrap.
I think I am going to read up on how to do the paperclip thing and see if I can pull anything up. Thanks everyone for your input and your preverbal ear.
I think I am going to read up on how to do the paperclip thing and see if I can pull anything up. Thanks everyone for your input and your preverbal ear.