QuestionQUESTION: Tom,
I have a 1990 Cadillac Eldorado Biarritz 4.5L 74,000mi. This week the car started to accelerate abnormally without applying pressure to the gas pedal. Upon starting the engine it will race and then level out to a normal rpm. When placed in drive, the car will idle forward until around 7 mph and then the car will quickly pick up speed as if I had applied some pressure to the gas pedal. I have to ride the brake in idle once I’m on the road. Has clean air filter. No codes. Any advice would be greatly appreciated.
Bill
ANSWER: Sounds like the IDLE SPEED CONTROL MOTOR mounted on the drivers side of the throttle body is jammed due to internal plastic gear failure and will have to be replaced. However, Without seeing it, It is impossible to say that this is what is causing your problem.
---------- FOLLOW-UP ----------
QUESTION: The ECU finally threw E055 code for the THROTTLE POSITION SENSOR. I just wanted to follow up in case someone presents similar issues. I will keep your previous answer in mind if any future problems occur. Thanks.
ANSWER: If there is a fault as I described with the ISC motor it will cause a TPS code because the idle speed is to high and this causes the TPS voltage reading to also be to high thus triggering a TPS code.
There is a long procedure in testing and replacing the ISC motor and the TPS to see if the cause is the ISC or the TPS.
---------- FOLLOW-UP ----------
QUESTION: I read into the correlation between the two parts. I will replace and adjust both with new parts to try and avoid any duplication of work in the future. I will be using the specifications listed in the Haynes repair manual. Thanks for the info!
AnswerThe Hayes manual is the biggest book of miss-information that I have ever seen besides the Chiltons manual. I ONLY use the manufacturers factory service information which is the exact books that the dealer receives.
Your going to find alot of missing information in those generic books.
