weird idle
 

hey guys, i have a quick ? on the idle. Wen the car starts it will idle at 750 but when i start driving it, for some reason the idle adjusts itself to about 1400. What could be wrong

mine does the same since swapping in an rtek'd n333 ecu. Going to try and track it down in a few hours. The throttle plates are set to provide an idle of 750, but it seems the bac valve just increases it. I don't have the idle adjustment for the bac valve either.

I've been told to be nice, sort of, for my smart ass comments, but the urge has me about to explode. So, please accept this reply in good spirits. Like it was explained to me: HEY DIPSTICK, MORON, ASSWIPED, RETARD, look at the top of the page. Says, new RX owners, yeah you, read this before-BEFORE-BEFORE-asking dumb questions. Boy do I feel better now. Sorry, not you, just do it. Good luck and peace. RUF RUF RUF

would that imply you've got the answer to my problem mombodogs? I've done so much reading here over the years and I still don't know :(

Messalem and Blowtus, do I have exact answer, yes. The answer is 1st-what car, what year, engine, turbo, etc. I will tell you one thing, and this is in all honesty. After my first attempt at telling the club to help, not asking for it, I, me, read post after post, thread after thread, and started out at square one. Trouble codes, then vaccum lines, then ACV, BAC, AWS, UIM, TPS, ABC, CBS, ESPN, AND FOX SPORTS EXTRA. Get my point! These people aren't getting paid to help us, but they do want for us to do most of the legwork. I'm very serious in saying that I am 2 months into this club, and from all the reading I have done, I could probably fix 75% of '"MY CAR" from reading. And as far as the idle, it was a new AFM, and TPS for me. Hopefully, one of the boys will help, but more info on car would make it easier. Peace. RUF RUF RUF

Dirty throttle body
Sticking throttle cable
Malfunctioning cold start fast idle system - i.e. clogged coolant passages, bad thermowax
Bad / sticking BAC valve
Cruise control cable sticking
Bad / misadjusted TPS
Bad clutch pedal sensor
...maybe intermittent vacuum leak?


-Ted

the only variable in my equation is the ecu. perfect idle with the old ecu, (and perfect bac function) the new one likes to creep the bac valve on. it's an 88 s4 turbo, if that's of any interest.

Now see Blowtus, every time I post people have to see how much of an ass I've made of myself, but it gets answers. Just kidding. Like I said, Im new, but from like what RETed pointed out also, its just a matter of taking time and checking it all tell you find it. Im sure RETed is tired of that Hawaiian weather. Send him a plane ticket to Australia, and maybe he will come fix it. Smart man, listen to him. Good luck, and happy idle.
Peace RUF RUF RUF

have you not read anything, or do you just like posting rubbish? I don't have any of the problems Reted has pointed out. I was almost going to post up my own 'another bloody idle problem thread' thread, but hijacked this one instead and can blame it all on Mesallam :) :)

I guess I'm not really expecting magical answers, but I don't like being told to search and read when I know my particular problem is not going to be easily, or at all, found, amongst the 478 idle threads already in existance.

so then post everything you've done to try to troubleshoot the problem when you ask about it. It helps you to not get a list of that same stuff as a suggestion.

either I'm missing something big, or everyone else is...

When I use my n318 ecu, the idle is a rock solid 750, with no bac valve assistance. the bac valve works as it should. When I plug in my n333 ecu, the idle sometimes gets down to 750 when coming to a stop, but if I give it a slight rev it will sit at about 1300, and fluctuate occasionally. when I turn the air con on the idle drops a corresponding amount, the bac doesn't apply additional correction. if I unplug the bac valve the idle is fine, but then obviously I have no bac valve function :)

Is a 600ish rpm increase the bac valve on max duty cycle? Has anyone heard of an ecu failing in such a way as to send a permanent full duty cycle signal to the bac valve?

BAC IC drivers have been known to fail due to shorts through the wiring.
Maybe the N333 ECU has a blown driver?


-Ted

don't see how I'd account for the occasions when the unloaded idle does drop to correct levels, if that were the case though?
Amazing how frustrating what sounded like a simple ecu swap can be... hopefully I haven't gone and solved the major issues only to be stopped by a dodgy idle :(

shorts in wiring can be intermittent, every little bump moves wires at least some, which could be making or breaking a contact.