Why won't my car idle right? Options

[mike_the_man]

(IMG:style_emoticons/default/agree.gif) with what Geoff just said. A hunting idle is often caused by a lean mixture. Once you're sure everything else is good, adjust the ECU. Sounds like you're getting very close.

An exhaust leak will usually backfire. I had a bunch of leaks where the heat exchanger bolts up to the head. If you stick your head down there with the car running, you can hear it backfiring, and can see or feel exhaust blowing out as well. When I had exhaust leaks, it caused a pretty eratic idle. It probably wouldn't hurt to crawl under and make sure everything is sealed up. I can't remember the correct torque for the nuts, off hand.

[BPGREER]

I do need a new AAR. Mine does not open all the way when cold. It does close when hot however. I think I will double check the TPS, and climb under and try to figure out whether or not I have exhaust leaks. If I do, is it normally just a matter of tightening bolts? Time to go get a little dirty. (IMG:style_emoticons/default/biggrin.gif)

Brian

[mike_the_man]

The AAR shouldn't cause a problem with the idle when warm. The cat might idle a little low when cold, if the AAR isn't opening all the way, but it should have no effect when warm.

Crawl under and check to see if you can feel or see any exhaust leaking out around the head. If so, try torquing the nuts. I can't remember what they should be torqued to, but it's not very high. Be careful when tightening, as the studs have a tendancy to break. When I do it, I start at a lower torque setting, and slowly work my way up to the max torque.

Hopefully somebody will post the correct torque. If not, I know I've asked before.

[mike_the_man]

Check out this thread on exhaust leaks.

exhaust leak thread

[BPGREER]

Mike,

Thanks for the link. I do feel some hot air coming down from somewhere in the vicinity of the heads, but not sure if it's pulsing or steady. I have very little experience (OK, none at all) with exhaust systems. I'm a little lost on some of the terminology. It appears that there are 2 round tubes on either side that bolt up. I imagine these are the most likely locations of exhaust leaks. The ones more to the front of the car are pretty well shielded. Is it just a matter of removing engine tin up there to get at it? Am I missing something? Thanks.

[Bruce Allert]

To get to the exhaust stud nuts remove the tin surrounding the exchangers. Those flat headed screwdriver slotted screws hold them on. sometimes they need a little persuading. A BIG screwdriver really helps. If I remember right there are just 2 per side. Once removed its pretty much open to get a socket on the nuts. The torque on them is 14 lbs. Good luck.

.....b

[TheCabinetmaker]

I don't use a torque wrench on exhaust studs unless it's a new head and studs, and then work your way slowly up the torque scale. They can and will break off. Just do it by hand . You just have to have the "feel" to know when to stop. If they are loose you will know it. Oh, a wobble type extension is the best tool to use.

[BPGREER]

Thanks. I got the tin off on one side, but the drivers side piece is on there to stay. I sprayed some liq wrench, hopefully it'll come off easier when I try next. Are there any other locations I could have a leak from?

[BPGREER]

I got up under there, and made sure everything was tight where it bolts to the head. All seems good. I got back under with the car running, and I can't see, hear, or feel any leaks. My muffler is awfully loud though. I double checked my fuel pressure, and timing (both are fine) double checked for vac leak (nothing). I tried adjusting the ecu, it seems a little better when I went about 4 clicks ccw. Still not a nice steady idle. Any further thoughts???? I'm getting desperate.

[BPGREER]

Could a bad injector be causing all of these symptoms. I was reading an old thread that suggested similar muffler noise/backfiring, but didn't mention any strange idling. Just a thought.

[ChrisReale]

Dont listen to these guys, they're all wrong. The real reason your car wont idle is because it is a 914 They never idle right (IMG:style_emoticons/default/laugh.gif)

[redshift]

(IMG:style_emoticons/default/laugh.gif) he's right! Had you goin!


M

[mike_the_man]

Yup, we're all doomed to eratic idling.

Hmmm, turning the ECU knob ccw should lean out the mixture. Usually a lean mixture causes hunting. Did you try turning it cw? What happened when you did?

How does the car accelerate? Is it just at idle that it runs poorly? If so, then it's not likely an injector, although it is possible. You could try pulling off spark plug wires one at a time. If you pull on off and there is no change in the idle, then there is something wrong with that cylinder. Either fuel or spark.

Another thing to check is your MPS. Does it hold a vaccuum? Also, how much vaccuum is your engine pulling at idle? I believe it should be around a steady 15in/hg at idle.

I'm kind of starting to guess here, but keep posting and I'm sure we can figure this out. I know how frustrating it can be, I've been there myself.

[BPGREER]

How do I test to see how much vacuum I'm pulling at idle? Is testing the mps the same? Also, the muffler is really loud at idle. When the car accelerates, it quiets down, and seems to run well. When I turned the ecu cw, it seemed to make the idle worse. ie. the searching more pronounced. I will go try pulling the wires. Thanks for the suggestions Mike.

Brian

[mike_the_man]

To test vaccuum, you need a vaccuum gauge. I bought one, but most local FLAPs will loan them out. First of all, pull a vaccuum on the MPS, around 15in/hg, I think. If the vaccuum drops, it needs to be fixed or replaced. I believe the acceptable levels are listed on Brad Anders page, I can't remember them off the top of my head.

If the MPS checks out good, then just T in the vaccuum gauge in the line that goes to the MPS. The engine should pull a steady 14 - 15in/hg at idle. If the gauge fluctuates too much, that could cause an unsteady idle. At this point I'm pretty much guessing, but these are pretty easy things to check.

Let us know how it goes.

[Qarl]

(IMG:http://www.funfilesandsmiles.com/smileys/2738.gif)

[BPGREER]

Awesome, thanks again Mike. I'll have to go pick one up when I get a chance. This problem is driving me crazy. (IMG:style_emoticons/default/headbang.gif)

[Jeffs9146]

Secondly, since yours is a 73 2.0l do you have the ballast resistor for the CHT and the right I think its the 017 CHT?

I would check the CHT first!! It is not expensive to just replace it and see!

Jeff

[BPGREER]

Is it easy to test, or should I just buy a new one. I think they're about $40 at PP. BTW, where exactly is it located?

[BPGREER]

Just thought of something that may/maynot have anything whatsoever to do with this. My cold start valve when connected floods the engine. Therefore, I do not connect the elect to the injector there. The fuel line is pressurized and does not leak through the injector. I don't know what sends signals to that injector, but it must be messed up. Could this have anything to do with my poor idle? Thanks again.

Brian