Lee Smith

I have an '86 944na, and I'm having a real problem wiht the way it is running until it is warmed up. It chuggs and lurches, and generally feels like an old Desoto until it is good and warmed up. I never had this problem until about a month ago, and I checked for vacuum leaks and performed a general tune up. No joy. Anyone got any ideas?
Thanks,
Lee

sam

Ahhhh, ya got a vacuum leak! That would be my guess. How did you check for the vacuum leaks?

Lee Smith

Well, I just kinda listened for them, found 1 line split, but it does sound like there is still one at the top center of the engine.
Thanks for your help.
Lee

Marcus

I had the same thing on my S recently. It was solved by replacing the AFM. I think the temp sensor in the AFM had packed up.

I'm chasing an air leak on mine at the moment but it affects it more when warm than cold.

944mo

Is the car lobing and performing under par until the car reaches operating temperature? That is the problem that I have, but only when the outside temperature is under 40 degrees.

sam

I had a similar problem. Idle bad when cold, then smoothed out when up to temp. My theory was a vacuum leak. When the engine temp is at normal operating temp, the fuel control goes into closed loop where the exhaust gas is sampled, and the amount of fuel is adjusted for optimal burn. If you have an intake leak, you have more air than the default (cold engine) fuel setting and therefore not a clean burn. When up to temp, the O2 sensor will tell the "DME" to adjust fuel, and the leak will be compensated for.

I know that isn't very technical, but it kinda describes why intake leaks cause rough idle when cold. Of course if you have a bad leak, it may idle bad when up to temp.

I built a thingie to pressurize the intake on an N/A. I removed the MAF and plugged in the test set, connected to my air source. I pressurized it just enough to find the leaks and not blow up the intake boot.

After correcting the 2 problem areas, the idle is much smoother. I guess I was spoiled. I used to just open the drivers door, check in neutral, turn the key and it started. I didn't have to get in to mess with the throttle, and could go about the task of scraping ice/dew or whatever (including bird droppings) from the windshield.

Good luck with it.

Marcus

[quote]Originally posted by sam:
<strong>I had a similar problem. Idle bad when cold, then smoothed out when up to temp. My theory was a vacuum leak. When the engine temp is at normal operating temp, the fuel control goes into closed loop where the exhaust gas is sampled, and the amount of fuel is adjusted for optimal burn. If you have an intake leak, you have more air than the default (cold engine) fuel setting and therefore not a clean burn. When up to temp, the O2 sensor will tell the "DME" to adjust fuel, and the leak will be compensated for.

I know that isn't very technical, but it kinda describes why intake leaks cause rough idle when cold. Of course if you have a bad leak, it may idle bad when up to temp.
</strong><hr></blockquote>

As mine is a UK spec car, with no O2 sensor, the running just gets worse as the car warms up. Leak seems to be masked when cold by the fuel enrichment. Car would hardly run when cold before AFM was swapped.

Tremelune

Wait wait, is the wire right above the dipstick a vacuum hose? Because I think I've been having a similar problem (not as drastic, though, it seems).

Lee Smith

Yes, thats a vacuum hose, from the looks of it, thats the one that provides vacuum to your power brake booster.

Just to be on the safe side, and since I had a ton of it laying around, I raplaced all the vacuum hoses with new ones. No joy.

Hey sam. Could you send me the specs on building that test set of yours? That sounds like a killer idea.

BTW. What and where is the AFM?

Again, your help is proving invaluable, and I thank you all.

Lee

Marcus

[quote]Originally posted by Lee Smith:
<strong>BTW. What and where is the AFM?</strong><hr></blockquote>

It's the Air Flow Meter which is the device in the inlet stream after the air filter. Silver alloy box with a black plastic cap.

sam

I have a pic around here somewhere. Let me see if I can find it. Short answer is it is a 2 inch PVC cap that is drilled and tapped and connected with fittings and a valve to my air source.

Key is the 2 inch PVC pipe cap. The outside diameter of this just fits inside the intake boot when the AFM is removed, and allows pressurization of the intake and all the hoses and stuff. I don't think it will work on a Turbo. The cap I got at Lowes. About $.87.

I'm not that computer literate, so If I find the pic, I will send it to you directly.

David Floyd

I had this problem on my previous 84 944, changed the auxiliary air regulator and problem was gone.

I think it would be a Idle Stablizer on your 86.

Hope This Helps

<img src="graemlins/burnout.gif" border="0" alt="[burnout]" /> <img src="graemlins/burnout.gif" border="0" alt="[burnout]" />

sam

Lets see if this works:

Now for the real test,,,,, Did it work?

sam

Well, that didn't work worth a hoot.

Lee, I sent the pics to your MSN account.

David, believe it or not, one of the problems I found on my car with this tester was that the idle stabilizer had a significant vacuum leak out the case where the electrical connector hooked up. I temporarily plugged it with duct seal, and the new one is supposed to be delivered today according to UPS. The point is that the tighter the intake system, the less likely you will have that type of problem. Rather than "Easter Egg" a problem, I would rather analyze it and be more focused on the fix. The Idle Stabilizer for that vehicle is $120 US +-. It cost me less than a dollar, and less than 1/2 hrs time to test and find the leaks. A little more time to fix though.

Lee Smith

Sam,
Thanks for the pics. That will definately come in handy. If anyone else would like me to pass them on, just e-mail me and I would be more than happy to hit ya with them.

With all of your help, I found the AFM today
Still haven't got the problem fixed, but it is a daily driver, just been waiting for the weekend.


I'll set up a website to place the pics on it (by the end of the weekend) and any other pics and groovy stuff that comes up.

Thanks y'all,

Lee <img src="graemlins/beerchug.gif" border="0" alt="[cheers]" /> <img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />