Need help with rough idle - Please

[MMiller]

I have a 88 3.2 coupe.

Recent work I've done.... Replaced fuel lines, removed everything down to and including the intakes. Put new fuel lines in, new intake gaskets(12) and spacers(6), sent injectors off to be refurbished, new head temp sensor, Replaced lots of rubber items along with new vacuum lines.

She roared back to life and runs great.....however she is now a bit fussy at start up, Idle is high(around1100) and irratic, rough with slight popping.

Thoughts on what I may have missed or adjustments I need to make?

As always thank you in advance

Mike

[kidrock]

Mike, I'm going to take a couple of WAG's here.

1) After replacing items that are the main contributors of vacuum leaks, you may have eliminated any existing leaks and may now need to adjust your air/fuel mixture.

2) Your issue may be something as simple as re-adjusting your base idle at the throttle body (make sure to jumper your B & C plugs at the diagnostic port).

3) Worst-case scenario is that after putting everything back together, you may have not tightened or torqued something back together correctly, resulting in a larger vacuum leak than what you had before (ask me how I know this, LOL). Use carb cleaner spray or ether to double-check your vacuum...maybe even pull your oil filler cap to see what your motor's response is.

Good luck, I'm sure it's something simple.

[Targa Me]

I would look for vacuum leaks.

[JohnJL]

Agree with the above, particularly looking for leaks. Popping and high idle is often lean due to leaks.

[MMiller]

Thank you Gentleman....

I will look into possible leaks that I over looked or created.

Mike

[E Sully]

To see if the Idle Control Valve is working, have someone turn the key to the run, not start, position while you put your hand on the ICV and see if it vibrates as the DME sends it's initial signal. If it does not vibrate, then it is time to check the ICV and DME to see which is at fault.

I would bring the engine up to operating temperature, install the wire jumper into the test port, and set the base idle to 880 rpm. ('86 and ealier 3.2's used 800 rpm.)

Next I would remove the oil cap. If the rpm does not drop, then look for a vacuum leak. Make sure the line from the oil tank to the valve that connects to the throttle body is connected. Make sure both vacuum lines are connected to the cruise control servo, and check this rubber hose on the metal vacuum line. My hose was cracked at this point and needed repair.

[MMiller]

Thanks Ed....great stuff here. Question/comments about items in bold below.

I replaced the vacuum line from oil tank to TB but it was not as thick of wall tubing...any chance that vacuum is enough to collaspe it?

Also I removed the cruise control servo while I was in there as the cable was broke and had other issues.... did not recall there was a vacuum line that went to it. I just looked in the parts catalog and did not see one. The 88 looks different from the earlier ones?

I rebuilt and freshened up the brake booster part you have in the yellow box so I think I'm good there but will check again to make sure

Mike

Originally Posted by E Sully

To see if the Idle Control Valve is working, have someone turn the key to the run, not start, position while you put your hand on the ICV and see if it vibrates as the DME sends it's initial signal. If it does not vibrate, then it is time to check the ICV and DME to see which is at fault.

I would bring the engine up to operating temperature, install the wire jumper into the test port, and set the base idle to 880 rpm. ('86 and ealier 3.2's used 800 rpm.)

Next I would remove the oil cap. If the rpm does not drop, then look for a vacuum leak. Make sure the line from the oil tank to the valve that connects to the throttle body is connected. Make sure both vacuum lines are connected to the cruise control servo, and check this rubber hose on the metal vacuum line. My hose was cracked at this point and needed repair.

[E Sully]

I looked through the PET and the manual and the cruise control part# is the same. As you can see there are 2 vacuum lines to the cruise control servo. I would believe this could be a problem if you have the lines open in the engine compartment. I would not be concerned about the line you replaced. I installed the engine in my 1973 and did not use the cruise control and just capped all the unused lines.

[MMiller]

Where is that unit located? In the engine bay? If so I do not believe I have one.

Originally Posted by E Sully

I looked through the PET and the manual and the cruise control part# is the same. As you can see there are 2 vacuum lines to the cruise control servo. I would believe this could be a problem if you have the lines open in the engine compartment. I would not be concerned about the line you replaced. I installed the engine in my 1973 and did not use the cruise control and just capped all the unused lines.

Looking in the PP cataloge I fine these part # 911-617-123-02-OEM

This is the one I removed that is supposed to be the 88-89 part but I don't remember vacuum lines going to it..will need to look again.
And part # 944-617-121-00-OEM

[E Sully]

I cannot say for sure since I don't have an '88, but this servo is what I showed on my engine. If you have it would be in the drivers side engine bay by the shock tower.

If you follow the first steps and there is no change when the oil cap is removed, then you will need to look for a vacuum leak.

[dan88911]

Hi Panerai, I have been following your thread. I have a similar issue however slight.

I did some searching came across a thread titled "87 3.2 idle issues", posted by
Jimintampa.
To say the lease I found a lot good imfor. there.
Another member posted in that thread, db-cooper has some real good imfor. as well.
Sorry I don't recall how to link you to it.

[MMiller]

Originally Posted by E Sully

I cannot say for sure since I don't have an '88, but this servo is what I showed on my engine. If you have it would be in the drivers side engine bay by the shock tower.

If you follow the first steps and there is no change when the oil cap is removed, then you will need to look for a vacuum leak.

Thanks again Ed, I will follow your suggestions

Originally Posted by dan88911

Hi Panerai, I have been following your thread. I have a similar issue however slight.

I did some searching came across a thread titled "87 3.2 idle issues", posted by
Jimintampa.
To say the lease I found a lot good imfor. there.
Another member posted in that thread, db-cooper has some real good imfor. as well.
Sorry I don't recall how to link you to it.

thank you I will search that thread out...

[nettles503]

Originally Posted by E Sully

...Make sure both vacuum lines are connected to the cruise control servo, and check this rubber hose on the metal vacuum line. My hose was cracked at this point and needed repair.

Could someone please tell me the part # I need to fix this? I have the same cracked hose on my car. Thanks!

[MMiller]

Dan see if this is the one you are looking for

Pelican Parts - Product Information: 930-110-328-05-M100

If not it may be on this page

Porsche 911 Carrera Motronic Fuel Injection (1984-89) - Page 6

[L8apex32]

Speaking from a learning 911SC owner's perspective, the popping at start up/idle is either lean (pops in intake) or rich (pops in exhaust).

At cold start up, the car should run more rich. If you are lean at cold start, then you'll be VERY lean, even too lean to idle, at warm idle.

If you are too rich at cold start, and it leans out and runs better at warm idle, then you may have a too rich condition instead of an air leak (too lean) condition at cold idle.

I hope this helps in some way.

[everforward]

Maybe try replacing the DME relay with a new one. The reason I say this is because it functions similar to the oxygen sensor relay in the non DME cars (<1984). I was having a similar issue to you with my SC and after research and less than $15.00 I was up and running again when cold starting. Good luck.

[nettles503]

Originally Posted by Panerai

Dan see if this is the one you are looking for

Pelican Parts - Product Information: 930-110-328-05-M100

Thanks Mike, that's the one I need.

($139.00 for a vacuum line! Oh well, I don't really need two kidneys. )

[MMiller]

Update...

So with all this chatter about Ghetto smoke machines I ended up making my own. It worked great and was able to chase down all the leaks and address them.

The car is running much better. Idle no longer hunts, was high but reset to around 900. It pulls really strong above 2K all the way to redline so I think I'm really close to having it sorted....

However it is a little weak below 2K RPM's. At take off you can tell it's not crisp sort of makes a pft pft pft sound out the tail pipe as you take off.....just not crisp....but once rolling runs great!

Any thoughts on final adjustments/tuning that can be made?

Thanks

Mike

Smoke machine..

[scarceller]

Hi idle speed can be as simple as the idle micro switch not closing (making contact).
This switch is on the ThrottleBody.
With engine off, at the throttle body open the throttle a tad just off the idle stop and you should hear the switch click open and then it should click again as the throttle plate returns to idle stop.
Even if it does click you should check it with test light or Ohm meter to be sure it is closing and reads 0ohms when the plate is on the idle stop. The switch opens with about 2degrees off idle stop.

If this idle switch does not close then the DME runs off the Part Throttle maps in the software. With the switch closed it runs off special idle maps for fuel and ignition. If it fails to close it will idle high.

[MMiller]

Thanks Sal, I did check it was working correctly with my meter but may need to revisit it to dbl check