'81 Cadillac codes

[Jamie]

Have an '81 SDV that was giving me a code 22 and 30.  I took the car to our local Chevrolet dealer and they first adjusted the idle but then diagnosed the problem as a faulty TPS and replaced it which didn't correct the problem so the second diagnosis was a faulty ECM which they replaced, but again didn't solve the problem.  They say they also tested the wiring from the ECM but that tested ok. They have now put their hands up and say there is nothing else they know to do.   Something they adjusted did manage to stop the code 30 but the code 22 remains

The only physical symptoms the car has is that the the ICM "ratchets" when the ignition is first turned on and the idle isn't too rough but isn't as smooth as I think it should be.

Any suggestions on what elso could be the problem? 

thanks,
Jamie
#21103

[Jamie]

spoke too soon...code 30 is back

thanks

[TJ Hopland]

What are those codes?

Which engine is this? 

Whats ICM?

[Jamie]

it is the 368 V8-6-4 engine

the ECM is the electronic control module

code 22 is the diagnostic code for "open throttle position circuit"

code 30 is the code for "Idle speed control circuit"

[TJ Hopland]

I dont remember with that vintage system can you monitor the TPS signal while the engine is running?  I know there was a way just dont remember if it was easy or hard to do.  Is the throttle shaft worn causing the tps to give bad readings and not letting the IAC do what its expecting to do?   Was the correct procedure followed to set the base idle? On mid 80's models that is critical.  I remember getting MAP errors because the base timing and throttle was set wrong. 

[Davidinhartford]

I feel your pain.    My 83 Eldorado was doing the same thing.  After replacing the TPS and ICM the Cadillac dealer gave up.   The idle would continue to go up and down.    They said: "Sir, this isn't a $100,000 XLR you know".     It is sad that there are no techs left old enough to have worked on these cars anymore.

They suggested a new ECM which you already replaced.    Another person on this board said it could be as simple as dry rotted vacuum lines.   Miles and miles of them.    I never did pinpoint the problem.   Finally I gave up too and sold the car on eBay for a loss.

[Jamie]

I am sorry to hear that you never found a solution to the problem...I had never considered the fact that it couldn't be fixed but maybe I should.  I have already spent more on the car than it will ever be worth but my wife and I enjoy driving it around on the weekends so I hope to keep it in tip top shape as long as I can afford to.

I have gotten some good advice on here and emailed to me from other members but it doesn't take much technical info. to go over my head..So, I am going to try the Cadillac dealership in Richmond next week since they were able to get it correctly adjusted for me 5 or 6 years ago. 

thanks
Jamie
#21103

[Roger H]

you could check the wires at the ecm.  the tps has 3 wires, a 5 v refrence,  a ground and a variable based on  throttle position.  unplug the ecm and with a diagram check the wireing and sensor as the ecm would see it,  move the throttle as you check the resistance.  also check all engine grounds and the basics.  since you have ruled out the two best guesses it may be  an odd wire loose or  ground connection,  an open means a temporary broken circuit and if it is not the sensor it must be a bad or loose connection

[76eldo]

The ISC motor and the TPS have a series of adjustments outlined in the factory shop manual.  I know I have an 80 manual, not sure about 81.

The ISC motors do go bad, so it could be that.  The dealership actually said that to you?  That's pretty rude.

In my area, there are a lot of dealerships that have closed up in the past year.  1 Pontiac store, 2 Chevy dealers, 1 Chrysler, and a very nice Cadillac dealer, all gone.  The ones that are left should be going out of their way to satisfy a service customer, because good service creates new sales.

Brian

[Dave Shepherd]

The idls control motor was a frequent failure, but 30 can also be set  by a bad cam as the idle control cannot compensate for the power loss at idle.