87 3.2 idle problem
 

Hi all, I have an idle problem I need some help with. With the engine warm the idle hunts from 850 -910 RPM. When I put the jumper in the plug to adjust the idle the idle settles right at 880 RPM. When I remove the jumper the idle starts hunting again. Last week I took the car to my local dealer to have the idle mixture checked with their tail pipe sniffer. When they used their idle Jumper tool in the socket the engine cycled about 250 RPM. When they removed it the engine went back to 850-900 RPM idle. What do you think is going on. Thanks. [/B]

The way I understand it, the jumper bypasses the volumetric control, and based on the AFM setting ( with co machine ) and the ICV Manual setting. You want them to match, jumped and non jumped.

Couple questions...Hows your O2 sensor? Did they test is with it plugged in and then unplugged. Any difference?

Also, did you test your ICV? It should be buzzing ( moving back and forth ) properly as soon as power is applied. Key to ACC will do it.


Again, there are folks that know far about this than me but, id eliminate all variables.

87 3.2 idle
 

Hotshot, the O2 sensor is fairly new. Tried it with the sensor connected and disconnected . It did not make a difference. We did find with the sensor connected the CO was .8, with it disconnected the CO was 2.2. We could not seem to get the CO down by adjusting the VAF mixture screw, I think that maybe that’s another problem. I thought the ICV only came into play when the engine is cold. Is that correct?

ICV controls idle whenever the throttle is closed at idle, by metering air around the throttle butterfly. CO and idle need to be adjusted with the O2 sensor disconnected and ICV jumper bypass installed.
Check for vacuum leaks! I found it cheaper to get a wide band 02 sender and guage and build a co tester installed at original o2 sender bung and fiddled with both idle and CO adjustments. make sure idle switch is working. I only dropped the Allen wrench in the engine twice before I taped a string to it!

i would say your are running a little rich..adjust you fuel mix

ivan

Tail pipe sniffers are for smog purposes only since they only monitor the exhaust after the cat has already scrubbed the noxious gases. The test port before the cat is the correct way to monitor the mixture. After the cat is useless.


Cheers,

Joe
87 Carrera

87 3.2 idle
 

I should have mentioned my car has a cat bypass. With the O2 sensor disconnected, the exhaust is so toxic it sets off my CO detector in my garage with the garage door open with in 5 minutes. I have used my vacuum smoke machine but did not find any large leaks. The only leak I found was a small leak at the throttle body shaft. I will try my LM-2 tester today to see what I have.

Please tighten down all your head runner bolts. They become loose on the 3.2 motor and let air in. This will make your idle very weird!!! Years ago a small Porsche shop owner told me to tighten mine and as soon as I did my idle went back to normal.

911 3.2 idle
 

Do you mean the intake manifold bolts? Or the head stud nuts? Kevin

kev..when was the last time you had the CO adjusted fuel mix..i can smell all the way here to Europe;-)

Ivan

btw do you have A/C?? if yes start your engine and put your A?C on ,then step on the gas and let go ,if it dies rightaway --it is too rich....

Kevin, the intake manifold bolts. Over the years they become loose. Mine were. Very common . Tighten to about 16-18 foot pounds. Using a allen type wrench that you can attach to the torque wrench. I was s as amazed when the mechanic was right.

Easy thing to try first. Let me know what happens!

87 911 3.2 idle
 

Just took the car out with my LM-2 tester connected. With the O2 connected at idle I got 14.7, at 3000rpm I got 15.0, at WOT I got 13.1. With the O2 disconnected: at idle 14.2, at 3000rpm I got 14.6, At WOT I got 13.5. These numbers do not seem normal. Any thoughts. Also the standard chip is installed in the ECU and I installed the LM-2 sensor threaded into exhaust.

87 911 3.2 idle problem
 

Bump

Adjust your idle mixture so that it is 14.7 without O2 sensor connected to the ecu first. Then retest with O2


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Do what the owner of this site says to do , put back the O2 sensor !!! Your car was made for it. Also, put back the cat. Any Subaru family wagon with a Soccer team and a golden retriever will pass you like you are standing still anyway !

87 911 3.2 idle problem
 

If I adjust the idle without the O2 sensor connected to 14.7 how will that effect the mid range? Also should I install the SW chip I have for the car? I am going to check the torque of the intake bolts next.

The mixture should be ok using the afm screw alone to set the idle mixture. The o2 sensor should compensate for vaiancies around that.
Use the chip you will use normally as all chips will have a different fuel map to set the idle mixture for that chip.


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Nick, I checked the torque on the intake manifold bolts and found them all to be loose. When I put the torque wrench on the I felt the bolts break away,then I could turn them 1/2 a turn To hit the 18 pounds of torque. As far as I know this engine has never been apart. I wonder if the thermal blocks are compressing over time. I will finish putting the car back together tomorrow and I will see if it made any difference. When it did the vacuum leak smoke test before I torqued the bolts there no smoke from the base of the runners. I would have thought it should have showed a leak. Kevin

After the things I have noted I have done to solve my idle mixture problem, I still have the problem. When I adjust the VAF the mixture does not change. Any suggestions?