Service Engine Soon, but no codes?
Thread Starter
Instructor
Joined: Jul 2005
Posts: 140
Likes: 2
From: RI
Service Engine Soon, but no codes?
Hello, I finally have my 1988 back on the road after some time without it. I replaced the ecm, injectors, regulator, pump, egr valve, mat sensor, coolant sensor, egr sensor, cold start sensor, oxygen sensor, throttle position sensor, iac sensor, and plugs.
My car starts right up no problems and idles about 1,200 rpm until it warms up and then it settles down to the usual 700, but it is taking longer to do this.
Upon starting the service engine soon light comes on. I proceed to drive on the highway and get it up to 2000 rpm, and it goes off. If I decrease speed it will come back on. At idle it is on. If I brake suddenly it comes back on.
Car drives fine for the most part. The idle is steady. There are no codes.
Does anyone have any idea what the problem is, and why the light only shuts off at highway speeds with rpms over 1900?
Thank you,
Chris
My car starts right up no problems and idles about 1,200 rpm until it warms up and then it settles down to the usual 700, but it is taking longer to do this.
Upon starting the service engine soon light comes on. I proceed to drive on the highway and get it up to 2000 rpm, and it goes off. If I decrease speed it will come back on. At idle it is on. If I brake suddenly it comes back on.
Car drives fine for the most part. The idle is steady. There are no codes.
Does anyone have any idea what the problem is, and why the light only shuts off at highway speeds with rpms over 1900?
Thank you,
Chris
Melting Slicks
Joined: Apr 2002
Posts: 2,118
Likes: 0
From: St. Charles, MO Route 66 Corvette Club
Chris: Consider posting this in the tech section as a lot of good people are there and may be able to help you. I do not have a clue what is going on with your car.....sorry!
Le Mans Master
Joined: Jun 2001
Posts: 6,694
Likes: 3
From: Less Talk, More WOT | Houston TX
Hello, I finally have my 1988 back on the road after some time without it. I replaced the ecm, injectors, regulator, pump, egr valve, mat sensor, coolant sensor, egr sensor, cold start sensor, oxygen sensor, throttle position sensor, iac sensor, and plugs.
My car starts right up no problems and idles about 1,200 rpm until it warms up and then it settles down to the usual 700, but it is taking longer to do this.
Upon starting the service engine soon light comes on. I proceed to drive on the highway and get it up to 2000 rpm, and it goes off. If I decrease speed it will come back on. At idle it is on. If I brake suddenly it comes back on.
Car drives fine for the most part. The idle is steady. There are no codes.
Does anyone have any idea what the problem is, and why the light only shuts off at highway speeds with rpms over 1900?
Thank you,
Chris
My car starts right up no problems and idles about 1,200 rpm until it warms up and then it settles down to the usual 700, but it is taking longer to do this.
Upon starting the service engine soon light comes on. I proceed to drive on the highway and get it up to 2000 rpm, and it goes off. If I decrease speed it will come back on. At idle it is on. If I brake suddenly it comes back on.
Car drives fine for the most part. The idle is steady. There are no codes.
Does anyone have any idea what the problem is, and why the light only shuts off at highway speeds with rpms over 1900?
Thank you,
Chris
Thread Starter
Instructor
Joined: Jul 2005
Posts: 140
Likes: 2
From: RI
As soon as I find out more, I will report back with my findings.
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Le Mans Master
Joined: Feb 2006
Posts: 8,753
Likes: 9
From: Louisiana
Drifting
Joined: May 1999
Posts: 1,478
Likes: 3
From: Sacramento, CA Money can't buy happiness - but it's more comfortable to cry in a Corvette than a Yugo.
Hello, I finally have my 1988 back on the road after some time without it. I replaced the ecm, injectors, regulator, pump, egr valve, mat sensor, coolant sensor, egr sensor, cold start sensor, oxygen sensor, throttle position sensor, iac sensor, and plugs.
My car starts right up no problems and idles about 1,200 rpm until it warms up and then it settles down to the usual 700, but it is taking longer to do this.
Upon starting the service engine soon light comes on. I proceed to drive on the highway and get it up to 2000 rpm, and it goes off. If I decrease speed it will come back on. At idle it is on. If I brake suddenly it comes back on.
Car drives fine for the most part. The idle is steady. There are no codes.
Does anyone have any idea what the problem is, and why the light only shuts off at highway speeds with rpms over 1900?
Thank you,
Chris
My car starts right up no problems and idles about 1,200 rpm until it warms up and then it settles down to the usual 700, but it is taking longer to do this.
Upon starting the service engine soon light comes on. I proceed to drive on the highway and get it up to 2000 rpm, and it goes off. If I decrease speed it will come back on. At idle it is on. If I brake suddenly it comes back on.
Car drives fine for the most part. The idle is steady. There are no codes.
Does anyone have any idea what the problem is, and why the light only shuts off at highway speeds with rpms over 1900?
Thank you,
Chris
This is a guess, but you might have an electrical problem that is due to poor power flow from the alternator, or power to the ECM. I would pull the ECM (pretty easy on the 88) and use some "quality" contact cleaner on all of the contacts. I suggest using some DeoxIT from Radio Shack. The DeoxIT ProGold kit has a spary cleaner and protectant. I'd also double check the cleanliness and tightness of the battery connections. Use some cleaner there as well. Check all connections to the alternator. Disconnect, clean and reconnect. All of this will take under 2 hours and cost less than $15. See if that helps.
