Muffet

hi, have been searching a lot but i havent found a post that solve my idle problems...
the first time that i had the problem was about a week ago, in the morning (the temperature should has been near 3ēc)... i started the car, wait a moment to warm it up, and start driving... 5 minutes later the problem starts... the idle between 1000-1500 rpm and sometimes between 2200 - 2700...
then, i check the vacuum lines and the one that goes to the boost sensor was cracked... i replace it and one of the problems has gone, idle speed stays high, but does not fluctuate...
if i shift a few times near the redline, the problem stops for 2-3 minutes...

what can i do?
by the way, my engine is a 91 s5, with 60.000 miles...

sorry for my english, i'm from chile...

inflatablepets

It sounds like you might have more vacuum leaks to look for. BTW, not bad English for being from Chile. There are a bunch of American kids that type much worse.

Muffet

could be... but why after pushing the car to redline the problem stops?

Muffet

i replaced another vac line, but there is no change...
i had read a lot of post in the forum, and a lot of people talk about thermowax... what's that? in the fsm i can't find it...
whats the tecnical name

thanks...

matts86fc3s

you do have another vac leak somewhere... see, when you push your car to high rpm's or to redline, your car is dumping huge amounts of fuel into the engine, and when you let off, there is still a bunch of fuel left over to be burnt, and if you have a vac leak, it will be enough air to compensate for the extra fuel and will idle ok untill that extra fuel burns off, then your getting more air into your engine than fuel, cuaseing your idle to increase so it will dump more fuel into the engine to compensate. ****, that probly sounded complicated, sorry. i dont know another way to explain it. your car is 13 years old, wich means most of your vaccuum lines are 13 years old and after that amount of time they tend to harden almost to a plastic and crack. just the slightest little crack (even if unseen to the naked eye) will cuase high/rough idle. we hook cars up to the fog machine at work all the time only to find the rough/high idle was cuases by a vaccuum leak we would have never found withought the fog machine. anyway, thats what i think is. could also be your b.a.c. valve failing... or anything of that nature

Muffet

thanks for the reply, i think i will have to look better for vac leaks....
i already replaced 2 lines, and they were in realy bad condition...

by the way, whats the thermowax, just to know :d

Muffet

today i replaced about 2 meters of vac lines (4 of them were in really bad condition), all the ones that were under the upper intake mainfold, and a few more... the other ones seems to be perfect.... i started the car, and the idle was perfect, but when the temp increases, the idle stays in 1500rpm....
in the "test drive" a few times the idle start going up and down (just 200rpm), but then it desapears....
i think that the last time that someone adjust the tps was whit the vacuum lines in bad condition....
do i need to adjust it?
thanks