QuestionQUESTION: We have had this on-going for over a month. We've had to our mechanic who has workedd on the car as long as we have owned it. And we are stumped. When you start the car on occasion the Idle speed will be 12000 to 1400 rpms and as you give it gas to increase your speed it will hold an engine speed the same even though you let off the gas. This will go on for a period,(Very Dangerous)Then you shut it off and it will repeat the problem, then for no reason stop doing it and drive like the great car it has been for us for over 5 years. They have replaced a throttle sensor (i Bel.)to no avail have tried flashing the computer. It works ok for a short time then back to high speed again. I took it up to our mechanic, Mon. when I dropped it off it was running at 2200 rpms. When they went out to get it later in the day it was doing it for them previously they had a prob. with repeating the issue. They said they had a conversation with Cadillac about this and they said to replace the ECM. Which they did. They said it was running like differnt car. My wife went up picked it up ran to the store car running fine went in the store came out stated the car same problem, She pulled in the garage engine over3000 rpms HELP.!!
ANSWER: What size engine ?. 4.6L or 4.9L ?.
Exactly what throttle sensor did they replace ?. Was it the throttle positioning sensor (TPS) or the idle air control valve (IAC)?.
what other work has been performed on the car recently ?.
---------- FOLLOW-UP ----------
QUESTION: It is 4.6L 300 hp it was the IAC valve.
ANSWER: Ask whoever installed the IAC if they PRE-SET (ADJUSTED the IAC BEFORE they installed it in the engine.
This is VERY critical to know if they did or did not.
---------- FOLLOW-UP ----------
QUESTION: Yes, the IAC was pre-set. On the history of the car. The problem 1st happened on July 2nd on our way to Iowa to see our daughter and her husband. It happened in Beloit. I stopped turned the car off, turned it back on and it was fine. I t did it 1 more time on the way back same solution worked. The next time it happened to my wife as we were returning from me rec’ing a treatment for my M.S. So I was was sleeping then she woke me up. I told her what to do. And that straightened it out again. After we got home the following week it was doing this more often. So I said that we were at 99000 miles, sowe might as well let our Garage do the 100,00 mile tune-up. This was done (The owner of our Garage, father-inlaw also has a 97 Caddy, so he does know the car and he comes from a dealership experience as do his other mechanics, So I think I have the story pretty much covered. I do trust them as I said before they have the equipment I believe necessary to do the job. And this last time they had the car they checked for vacuum leaks, any thing they could think of. I just am wondering if you’ve evr ran across this I sure appreciate the quick response. Thanks So much From an Old “1971 to 73 Pontiac Garage Employee” Ha, long time ago and a lot of changes since then.
I just took the car back last night, the garage is just blocks from our house I never touched the gas pedal, just the brake, when i arrived went to shut it off it shot up to 3200 rpm's Boy they've checked and double checked. Thanks so much for any help. hope this isn't too much info.
ANSWER: Are there any diagnostic CODES from the computers ?.
---------- FOLLOW-UP ----------
QUESTION: No codes our 97 has all auto temp contol could get no codes to show, But Fri. P.M. after our mechanics played with various voltage checks computer hooked up to the car for 3 hrs the engine still racing, they Threw in the towel unhooked the equipment, turned the car off then back on again, and it was perfect Idle between 600 and 800 rpms They called the Cadillac dealership and basically made an appointment for me for this a.m. BUT The car has been running just fine since fri. I went to the dealership this morning and talked to them, and they said unless it is acting up they really can't do anything. I asked about updates to the computer and they said unless it is 2000 or newer there wouldn't be any propritary info for it. So I guess I wait and pray it is "fixed" They Did say if does it again bring it in right away, I said no appt? Service manager said not a problem, just do it. Interesting to say the least. Thank you for your tips I did pass them along and made sure they double checked it.
AnswerIt is possible that while testing voltage readings at the various components that you had an intermittent wire connection and when they manipulated the wiring harnesses the connection corrected itself.
Yes, Unless the symptoms are doing it at the time you take it in to any facility there is not much they can do.
Keep me posted and let me know.
