Wanted to start a spearate thread that may help me keep all this straight.

I checked all warning lights, and the only one that didn't come on during start-up was the rear spoiler light. The PO had the original tail removed and installed the Turbo tail, so all the workings are gone. I'm not sure if the ! light coming on is due to the spoiler modification?

As far as IDLE, I'm going to try following the other threads. Should I start with a DME reset? Is there a better place to start?

I think I'm going to start with a wash, and see if you folks wake up before I go wayward. Thanks, and gutten morgen (sp?)

BTW- coffee is nice and hot if any of you want to stop by and help.

 

I have had a rough idle a few times since I bought my 964. Every time it was because the battery was temporarily disconnected (and also when I changed my chip). I tried the DME reset / spirited ride trick, not much of an improvement.

Every time I ended up bringing it to my mechanic and he resets it with the hammer, 100% improvement every time. I don't believe that you can duplicate the instructions forced into the computer with the hammer by simply driving it hard for 30 minutes. My car is a 1990; maybe other years are better at adapting to driving styles. Get it reset by you mechanic and enjoy the car! That’s my $.02.

 

I'm no expert, so don't ask me to explain how to trouble-shoot these things, but looking back at a number of threads about rough idle, these are some of the suggestions put forth as to reasons for a rough idle at start-up (in no particular order):

DME requires reset
clogged fuel filter
failing fuel pump
oil contamination of the air flow system
blocked carbon cannister
leaking Vacuum lines
leaks on the air-intake lines
faulty oil breather lines
blocked fuel lines
faulty oxygen sensor
faulty cylinder head temperature sensor
incorrectly fitted spark plug lead
broken distributor belt
problems with the airflow meter (MAF)

Marc

 

Hawk,
I wouldn't be surprised if the PO simply decided he'd had enough of the spoiler light and simply pulled the bulb. The spoiler light should come on at startup and extinguish at about 5-7 mph. If he jumpered the connector in the engine compartment, the light should still come on at start-up. What year is your car again? I believe the 91s and later you could simply disconnect the spoiler control module on the passenger side under the dash, however I don't know whether the light would still come on at startup or not. I think your warning light is unrelated to your fluctuating idle.

As far as the idle is concerned, I would try two very easy things first. Clean your ISV (Idle Stabilizer Valve). It's very easy, and others have had good results when they purged them of all the oil and gunk that accumulates inside. After you have that all cleaned out, do a DME reset.
Disconnect the battery for at least 15 min.
Reconnect the battery.
Start the car and let it idle for 2-3 min.
Go for a spirited drive of at least 15 minutes, attempting to use the entire RPM range of each gear (notice I said, "attempting").

Try those two things and see what happens. They're very easy to do, and a good place to start. Good luck.
Brian

 

well- here's what I've done so far- thanks smokin for getting me started.

I pulled the ISV and ran some carb cleaner thru it- nothing coming out, so I wonder if it isn't new with the last maintenance (60K). I reset DME, and then had a blast. I let it idle for a few minutes before launch, then I made a very noble attempt at hitting all the RPM ranges. It's the most fun I've had in the car yet!!

the bad news- no real help on idle. It's somewhat more stable sitting there, but if I rev it a little, then it takes a few seconds to settle back in. It's gone from 1100, down to about 1000, with smaller surges than before.

I'll check some of the other things- MAF, O2 sensor, etc that I can get to. Thanks for the advice.

 

I had this and it was caused by the fact that the cover holding on the air filter was loose, causing the thing to flap around and vary the air flow beyond the adjustment capability of the DME.
Just worth a checking, because if it is this, your fixed in 30 seconds. Good luck

 

Jason Andreas gave this tip a while back:
Make sure that when you reseal the flap you use a silicone sealer that states "safe for oxygen sensors" on the bottle.
Brian

 

Hawk,

I found the article I was telling you about. On the 10-pin connector in the engine compartment (Facing engine on right side) you need to jumper pins #3 and #7 to each other. You can CLICK THIS LINK to see how to eliminate the dash warning light because you are missing your electric spoiler. This link has a few pictures if you arrow down a bit in the article. This is exactly what I did to eliminate the ! warning light.

Good Luck

Rick

 

Pulled the air box yesterday- it's been drilled. Does that account for ANY roughness?

 

Hawk... I doubt it... Just make sure it's all buttoned up correctly.

 

if you clean the ISV (the correct one), and the airbox, if you start removing vaccum hoses, be careful not to snap the T-fitting connecting the vaccum hoses. I did such a thing, and had to find a replacement. I hit the local Ace hardware store, and got a poly-something or other replacement, not the fragile hard plastic stock fitting. I'll post later as to whether this fixed the idle issue, now that I've cleaned the correct ISV. I cleaned another sensor, not the ISV prior to today- oh well.

Oh yeah- don't drop the nuts holding the airbox to Air flow Mete- they get lost in the engine bay, never to be found again. M6 replacement size, in case you need it.

 

Usually the main cause of a rough idle is a lean fuel mixture condition.
This and other sources may be the result of:

1. intake air leak
2. bad plug wires or mis-aligned plug connector
3. bad spark plugs (most forget about replacing the lower set of plugs)
4. an O2 sensor "driving" the mixture too lean
5. a mis-adjusted AFM
6. low fuel pressure
7. weak ignition coil/coils
8. weak/bad ignition module/modules
9. bad/dirty injector/injectors
10. bad distributor cap/rotor

Check out here ( www.systemsc.com/diagnostic.htm ) under Poor Running.

 

I cleaned the ISV and the AFM, both of which were not real dirty, but I did it anyway. I put everything back the way it was, including the T hose fitting I broke, and got zero results. The idle is still approx 1K, give or take a few surges here and there. It seems to reset itself after a quick shot of throttle, something that took a few seconds before, but the surging idle is still there.

I'll try a few other things, and maybe one of the guys at our Councours Event next weekend may have some suggestions, but right now I'm changing the oil on my Pontiac.

Oh well- I got to know where all kinds of stuff is, including one of my screwdriver heads, on the engine. Note to self: always use one-piece tools when working on the car.

 

Hawk... Have you pulled the rotor caps yet? I'd look there and I'd also install a new fuel filter... They are fairly inexpensive and easy to install.

 

I'll look into the caps and filter this weekend if I have time. The idle's not bad enough to warrant immediate attention.

Thx again.