high idle (3k) 993 3.6 coversion

[ssfrancis]

I'm in the final stages of swapping a 95 993 3.6 engine into a 74 carrera and I ran into a snag. Engine has only ~5k miles. Seems to be all wired properly, and all the loose ends in the vacuum bloked off. Engine started with out a hitch and idled normally the first couple times. I let it run for a bit, kept checking and adding oil. Smoked a lot, but is sat for a while before the last start.

Turned it off for an hour or two while made a nice DME mount then started again and it instantly went to 3k rpm.... now I can get it to idle.

Here is what I know:
- starts, goes to 2500rpm, then slowly rises to 3k ish
-Throttle cable not binding (with cable unhooked it sill sits at 3k)
- I can rev the engine but will come back to 3k ish
- Checked all plugs are seated properly
- Disconnected o2 sensor... no change
- Disconnected battery to reset

Feeling stumped...Any advise?

[ssfrancis]

btw- this motor was installed in an 75 911 previously. It all worked then.

[pors1968]

Make sure the throttle shaft sit properly on micro swicth for idle .

[ssfrancis]

I thought the 993 uses a Throttle potentiometer not a throttle switch?


I went out and started this morning.
Did the cold idle at 2k rpm then returned to about 1k rpm after ~30 seconds. good.

I let it warm up then reved a little now it sits at 3k again

Shut off and start back to 3k with a slow increase HELP!!!!
I'm looking for an intake leak but nothing obvious or findable with brake cleaner.

It seems to be a warm idle issue. thoughts?

It has a cintex chip that used to work fine... could it possibly have broken?

Thanks in advance.

[ssfrancis]

Any ideas? I'm stumped

[ssfrancis]

problem resolved.

993 fast idle problem persists...

It was the idle control valve. Disconnected it runs great.

[ssfrancis]

This is still proving to be a problem. Any advise is appreciated before I plunk down $300 on a new ICV.
I cleaned and tested the ICV per the 9v procedure and it seems to function properly with movement both ways, although one way is much further than the other.

When cold the engine starts and idles perfectly. As soon as it warms up a bit the idle starts to creep. If I blip the throttle by hand (disconnected cable) it revs they stays around 3k and will not return to idle. If I turn the car off then on it returns to ~3k idle. If let to cool it will idle normally.

If I remove the ICV plug all symptoms are gone.

Before I buy a new ICV what else should I check? Cylinder head temp sensor? DME?

It seems odd to me it is only an issue when warm.

[ssfrancis]

This Thread:
Idle problem with 3.6 engine

Seems similar to my problems.... no resolution though.
I do have a Cintex Chip, could that be the issue?
How can I diagnose?

[shahram]

It is most likely a vacuume leak. Take a big grip and squeeze the oil breather lines carefully, closer to engine, one after the next one and see what happens. The same with each of the vacuume lines.
I had once a cintex cheap which created a problem with high rmp. I returned it to Timmins and replaced it with one from Steve Wong.
You can test the Cintex cheap with another engine if you know somebody with a 95 993 or try to find a stock 993 Cheap w/o drive block.
One more: can you disconnect the O2 sensor connector and report back if that changes something?

[ssfrancis]

I spent a lot of time trying to find a leak. Sprayed starter fluid everywhere no change.
I haven't pinched any lines, but I'm hesitant to pinch the small ones for risk of damage.

The engine is out of the car again. But I remember unplugging the O2 sensor previously and there was no change IIRC.


When you had issues with the Cintex chip was it a really high idle (like 3k) or was it lower?
Was it all the time or did it change when warm?

[shahram]

I really don"t think it is the Cintex chip in your case. You stated you had normal idle the first couple of times. Chips don"t change behavior. The rev limiter on my chip was set to 5800 only and that was not right.
Your engine is getting to much air. It is not the ISV than it is comming from another source.

[wildcat077]

Check your allen bolts on your intake runners ... i had a few almost back out completely on me during a track weekend ...

Also agree that a SW chip is definitely the way to go,it eliminates any stalling issues with a lightweight flywheel as well !

Cheers
Phil

[sknandigam]

I'm experiencing the same issue with my recently purchased 3.6-converted SC. Running Cintex chip as well. How did you end up resolving it?

[ischmitz]

Is the ICV vibrating and moving at all or just going fully open when you plug it in? A damaged DME with a shorted driver for the ICV would cause this.

Ingo

[RL technical]

You said you mounted the dme nicely and then it didn't start re trace your steps, I've had a similar issue before with a broken wire when I mounted the computer to the floor during a conversion.

[ssfrancis]

Thanks for the input.
I'm just getting back to this after some downtime. I un wrapped most of the harness a while ago to look for damage.
I found that the engine harness recall had not been done (this engine was removed from a low mileage car in 96). A few wires were cooked. I replaced the entire engine harness.....no change.

I'll trace the main harness to the DME again to be sure.

Any suggestions on how to determine if it is the harness vs DME?

Still runs great with out the ICV plugged in.

[ischmitz]

The best way to check the ICV is to hook up a Hammer or PST2 and run the actuator test. This will quickly tell you whether the DME can control the ICV.

You could also run a bypass hose with an adjustable resistance (vise grips) instead of the ICV. Then hook the ICV up and observe the opening angle while the engine idles. See if it moves at all.

[ssfrancis]

A while back I bought a new ICV, so I dont think that is the problem.

After the new engine harness I was able to finally get the CEL light working (it wouldnt flash before). It is now throwing CEL 1144, which I believe is O2 sensor.

I disconnected the O2 sensor and with the ICV plugged in it seems to idle well even when warmed up. Could this have been a combination of a bad engine wiring harness and bad 02 sensor?

[ssfrancis]

BTW- here is a thread on the wiring harness recall.

Y I K E S!! Look at my 1995 993 engine harness

The replacement harness is surprisingly cheap though.

[-Levi-]

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