98 STS stalling on idle Help plz!!

[LuckyB@FIDO]

Hi there!

long story short, i just change the engine of my 98 sts (due to a blown head gasket) to a 99 sts engine, the engine runs fine when im on drive ... But as i stop 75% of the time it stalls ... start back up fine... but still this is pretty upsetting.. the mecanic that installed the engine doesn't understand ...

please help me with this issue ... ive just spent 3000$ for the engine change ...

thanks in advance!

[EcSTSatic]

Did you miss a vacuum line?
I can't even begin to imagine the questions regarding computer compatibility, sensors etc. The days of simple swaps are over!

[Ranger]

Got codes?

[lusterblade]

pull the codes first, but the first things that come to mind when u mention it stalls while slowing down or stopping is the throttle body, egr valve, and pcv valve should be cleaned

[Ranger]

[LuckyB@FIDO]

first of all thanks every 1 for the replies .. i will try to pull out the codes .. just need to find the post on how to do that hehe ... ill post them on here a lil later tonight ...

Ok! now I do i clean those valves ! lol Do i have to take the engine out .. is it a default on the engine ... cuz the engine has a 6 months warranty on it .. ill be so happy if i can get it fix on the warranty ..

I do have an appointment tomorrow to get this checkout ...but if it's easy ill do it myself

[lusterblade]

here you go..Had the same problem a few months ago where it would stall while slowing down. I was actually told by dealers and mechanics that my trans was gone ($4000 fix) or that my solenoids needed replacements (>$1000 fix),
no problems after i did these three things thanks to this forum...
1. Clean the Trottle body (instructions in Tech Tips section)
http://www.cadillacforums.com/forums...ttle-body.html (How To Clean the Throttle Body) (How To Clean the Throttle Body)
this didnt help much for me but still should be done.
2. Clean the EGR valve (again from tech tips section)
http://www.cadillacforums.com/forums...egr-valve.html (How To Clean The EGR Valve) (How To Clean The EGR Valve)
Mine was very carboned up/ sticky. took a while to clean. it might need replacing depending on how bad it is.
3. cleaned the pvc valve (i think thats what its called). this took like two seconds with carb cleaner.

[Ranger]

Another thought comes to mind. If the TCC is sticking on, the car will die when you come to a stop. It is much like stopping a standard transmission without stepping on the clutch. It should set a DTC if that is the case (P0742 - TCC System Stuck On) Lets hope not as that can be an expensive fix unless it is the disengage switch on the brake pedal that is not disengaging. I think that same switch disengages the cruise control.

[LuckyB@FIDO]

Wow ... that is good news !! i hope that is just it .. cuz otherwise ... hehe .. as long as it's under 200$ ..
just 1 question .. i think my car has a OBDII would the EGR clean up procedure would be the same ?

ill try to do this asap ...

Ranger .. what were u talking about on the last post TCC ?? expensice?? im scared .. heh
if it would help .. i realized that the rpm goes up and then down right before stalling and it is not always constant .. i dont understand .. sometime it will only do it after 10 min of driving ..

well guys i really wanna thank you again .. y did all the mecanic i went to were like ... i have NO clue what it could be .. and u guys can actually almost pin point "issue" amazing!!

thumbs up for cadillac forums!!

[lusterblade]

yes obdII would be the same procedure for cleaning the egr valve. We know these issues because alot of us have experienced them...good luck
btw pull the codes so we can give you a better answer.

[dp102288]

Well if the tcc was stuck on the rpms would never go up as you were coming to a stop, they would only go down until stall (if it is like a manual transmission).

[Ranger]

TCC problem is like $2000 because the trans has to come out, but from what you last said I doubt that is the problem. The engine would die before you got a chance to idle. Like I said, it is just like stopping an standard transmission without stepping on the clutch. I'd give the EGR valve a good cleaning. Make sure that the pintle valve is not sticking anywhere in its full travel. The engine will die at idle with the EGR open.

[LuckyB@FIDO]

Alright!! ill try the EGR clean up .. ill need to get the ratchet but all good ... the car is currently a the garage .. i brought there this afternoon .. im currently at work .. and still no phone calls ..
i will try to do it on the up comming weekend ....
I was also reading an other thread in the tech tips ... an there talking about the PCM ... that it could cause a staling problem .. Ranger u did post some stuff on there ... im wondering .. It might be my PCM too ??

anyways thanks alot for helping me .. ill be checking the forum later for replies ... and ill keep u guys uptodate with my resolution :P!!!

[dp102288]

Yeah do keep us posted for future references.

[Ranger]

Anything is possible, but the PCM is not high on the priority list for the symptom you discribe IMHO.