3.2 Carrera with a poltergeist

[GH85Carrera]

Sorry this is a long post but I figure I will give all the important info up front.

1985 3.2 Carrera. 165,000 miles overall. 15,000 on total rebuild of engine. In June I took the wife with me on a 5,500 mile road trip and the car ran flawlessly. I drive it at least once per week. The fuel pump was replaced at 135,000 miles. The two crank sensors were replaced during the engine rebuild as well as the 02 sensor at the rebuild.

A couple of weekends back I took it for a drive just to get it up to full operational temp. I stopped for a 6 pack of beer for the garage fridge and when I went to go home, the starter spun nice and fast but no starting. I replaced the DME relay in the parking lot with a lot of cussing and it started but ran horrible. It was cutting off and I was happy I only had to go three blocks to get home.

I scratched my head and other body parts and drank a cold beer. I figured it was the infamous coil issue so I replace it with the Bosch silver on my shelf. It had a MSD Blaster 8222 but was replaced by the Bosch. I go for a drive and it runs flawless. Get home to move cars around so I can put it up in the normal garage spot and it will not restart. I manage to push it into position and go inside to shower and contemplate the problem.

The next weekend It fires up and I move it back to my work bay in the garage. I figured the coil was a POS Bosch silver but I can't find any other replacement so on goes another Bosch silver. While I was in there I replaced the fuel filter which had 30,000 miles of use. The car restarts and runs fine. I go for a 25 minute drive and it restarts and runs fine. While chasing gremlins I took off the auxiliary air valve and hosed it out with carb cleaner. I pat myself on the back and figure it is fixed.

My other car goes in the body shop for fix some cosmetic rust issues. That means the 911 is the daily driver for the week. Monday it runs the 8 mile 12 minute commute to and from work flawlessly. Tuesday I go to meet a friend for lunch. 10 minute flawless drive. After lunch I start and go to the other end of a shopping center parking lot to get some fruit. After a 10 minute stop I got going back to work.

At the busiest intersection in town while waiting on the long long red light the engine goes to 2,200 RPM, drops to 2,000 and drops to normal, then does the 2K rpm routine again. Then it stops dead. I manage to restart but it dies. I have to restart several times before I can get it to stay running at 3,000 RPM and get through the intersection. It is pretty much a straight shot at 60 MPH back to work so I stay in the right lane and nurse it back to work. It will run like a bat outta hell then die. I just pump the gas pedal because I can't think of anything else to do and it will start running. I can accelerate and it dies, over and over. I finally make it back to work and shut it down. When I went to go home it fired up normal and ran perfectly.

This morning It fired up and just a mile from work it started shutting down and cycling from fine to dead. I get to the office parking lot and let it idle. It stated going to 2,200 and 2,000 and back to 900 and back to 2,000 several times but it does idle for the 20 seconds I sit there.

My conclusions:

It does seem to be heat related. I don't think it is the DME relay. I might be the DME itself.

I looked long and hard for any bad vacuum leaks but vacuum leaks to open then seal up on their own. I have never heard of an random intermittent fuel pump, and the pump would not make the RPM go up to 2,000 RPM.

The alternator is putting out a steady 13.4 to 14 volts. The starter spins freely and fast. The fule pump sounds normal and does not have the noisy grinding sound of an old pump. I will try to rig up a fuel pressure gauge to monitor that.

I am stumped right now. What is your best guess and advice on what to repair or replace?

[ischmitz]

If this is the DME it would be the ICV related to the drivers. Or you could have an issue with the harness to the ICV or the ICV itself. There are three wires going to the IVC. The center is +12V and the two outside wires are sending signals to open and close. It's balance is what defines the ICV valve position. If the "closing" signal gets momentarily interrupted the valve slams fully open and there is your issue.

Wiggle the harness to the ICV while the ignition is on but the engine is not running. If you hear a distinct click from the ICV rather than the normal vibration there is your issue. If it's inside the DME it can be repaired. Try tapping the ICV to see that makes it happen.

Ingo

[ganun]

question....would a sticky ICV prevent a start?
In addition to the tests Ingo suggested, wiggle and tapping, I would add checking all 3 sensors even though 2 were replaced 15k ago, and the third one is the cyl head temp sensor. If it sends a cold engine signal to the ecu it could impact idle speed. It seems to me. Somewheres, the expected values for these sensors were posted recently. I'd check them hot and cold.
Air flow meter flap free
Distributor cap rotor and advance working smoothly.

Just thinking out loud here.

[ClickClickBoom]

These cars all use the same ICV......

DODGE MONACO 1990
EAGLE MEDALLION 1988-1989
EAGLE PREMIER 1988-1990
PEUGEOT 505 1987-1988
PORSCHE 911 1984-1989
PORSCHE 924 1987-1988
PORSCHE 944 1985-1989
VOLVO 242 1983-1984
VOLVO 244 1983-1988
VOLVO 245 1983-1988
VOLVO 264 1981
VOLVO 265 1981
VOLVO 740 1985-1988
VOLVO 745 1985
VOLVO 760 1983-1990
VOLVO 780 1987-1990
Please refer to catalog for application details.

I replaced mine and my gremlins went back to the gremlin warehouse.

[GH85Carrera]

Originally Posted by ClickClickBoom

These cars all use the same ICV......

DODGE MONACO 1990
EAGLE MEDALLION 1988-1989
EAGLE PREMIER 1988-1990
PEUGEOT 505 1987-1988
PORSCHE 911 1984-1989
PORSCHE 924 1987-1988
PORSCHE 944 1985-1989
VOLVO 242 1983-1984
VOLVO 244 1983-1988
VOLVO 245 1983-1988
VOLVO 264 1981
VOLVO 265 1981
VOLVO 740 1985-1988
VOLVO 745 1985
VOLVO 760 1983-1990
VOLVO 780 1987-1990
Please refer to catalog for application details.

I replaced mine and my gremlins went back to the gremlin warehouse.

Did you find one of those vehicles had a cheaper cost for the ICV?

Those valves are pricey.

[PabloX]

Originally Posted by GH85Carrera

Did you find one of those vehicles had a cheaper cost for the ICV?

Those valves are pricey.

https://www.amazon.com/Injection-Speed-Stabilizer-Control-13170679/dp/B01E73BA68

No idea on the quality of this part.

[Frosticles]

From your description it does sound to me like some kind of air leak. Get the WD40 out & start spraying around gaskets to see if it cures it for a second.

[GH85Carrera]

Originally Posted by Frosticles

From your description it does sound to me like some kind of air leak. Get the WD40 out & start spraying around gaskets to see if it cures it for a second.

It does sound plausible, but I have never heard of a intermittent vacuum leak. One that leaks then seals itself and leaks at strange times. I am not saying that is not the issue, just I can't see that. I did a thorough visual inspection. Every single rubber hose and connector was replaced when I did the engine overhaul just 15,000 miles ago and I finished that in Jan 2014 not even three years yet.

I drove it home again this afternoon. Once again it ran perfect for the commute home. I have borrowed a friends old pickup so I have transportation and I will park the 911 until I can figure out my next step.

Please keep up the suggestions.

[Frosticles]

When the engine rocks it could be opening then closing the leak?

[GH85Carrera]

It is more like some ghost turns off the ignition and after pumping the throttle (what else is there to do?) it will start running. There is no real bucking in 4th or 5th gear. It will quit just sitting there at idle. No bucking at all.

And to be clear I do not believe in ghost at all. It is just a convenient description.

By the way, the tach keeps reading and does not just drop so I figure the flywheel sensors are working.

[bigel]

^^^^^
This sounds to me like an electrical/brain (DME) issue. The engine just quits with no sputtering/bucking? Something is sending a 'kill' signal to the ignition.

That's my superiorly untrained opinion.

[DanielDudley]

My cylinder head temp sensor was bad after two years. However, I doubt it would be able to produce the symptoms you are describing. Check your connectors.

[TibetanT]

First, I am not an expert but your car has the same type of Motronic type systems that my 1987 944 uses.

I would check all your ground wires for clean contact. Also, in my experience 15k miles on new sensors is plenty time for checking, testing and possible replacement.

The symptoms you describe have happened to me with my 944, and it was the reference/speed sensors that were beginning to fail.

Hope this helps, and that you find a solution to this "poltergeist" problem.

Good luck

[ClickClickBoom]

Originally Posted by GH85Carrera

Did you find one of those vehicles had a cheaper cost for the ICV?

Those valves are pricey.

1990 Dodge Monaco, $40.00, by a 12 pack and call it good, starts idle weirdness, pull one out of the dirty dozen and throw the bad one at the kids on your lawn.....

[gomezoneill]

Pull the ECU have it rebuilt/checked.

[brianlay]

Really no point in guessing, educated or otherwise.
Time for some methodical troubleshooting.

[ClickClickBoom]

ICV is a wear item, anything with moving parts and some solid state ones can be candidates (if improperly mounted or bad wiring) check all individual components, if that fails you, you gots bad wires/connectors.
Testing the ECU would be my last operation, but opening it up and looking for obvious faults couldn't hurt, I did on mine, I wanted to see if I could see where the smoke genie lives without letting her escape! She remains enslaved and pushing electrons around.

[DanielDudley]

Originally Posted by brianlay

Really no point in guessing, educated or otherwise.
Time for some methodical troubleshooting.

When all else fails. But diagnosis matches symptoms to problems, and points in some direction. I finally replaced my newish temp sensor, even though it ohmed out OK, in fact within a few hundred OHMs of the replacement. But the car was almost impossible to start, and ran poorly. The exhaust smelled very dirty, so I took a tip from Hugh, and trusted my nose.

Maybe I ''wasted'' a couple of bucks having my DME checked out, but it eliminated that as the problem. And of course at this point, I'm pretty sure my new DME relay was defective (intermittent) right out of the box, which meant I was making things harder on myself, and not easier.

BUUUT... if I had it all to do over again, I would buy the Bently Manual, as everyone who owns one says to do, and follow the procedure outlined in the manual, instead of doing endless internet and U Tube searches to find out how to test individual components. I did break down and by a digital Volt Ohm meter, and that was a great investment. Then, and only then, I was able to test out the speed reference sensors, check for continuity and voltage, and pretend that I knew what I was doing. And the car seems to run OK now.

The problem is, that when you go around and mess with a lot of things, you never really know what fixed the car. In my case, with the car cold, and barely running, I simply unplugged the temp sensor still on the car, and plugged the new one in without even installing it. The car ran so much better, that I had to assume that there was something up with my old unit, even though it was practically brand new, even though it seemed to test out ''within range''.

Get the manual. I hear Santa is coming early this year.

[GH85Carrera]

I have had the Bently manual for many years. I have the a Fluke volt ohm meter and I know how to use it. I have owned this car for 20 years, and I know it. The only other time I had an issue like this was for sure a bad coil.



The black goo started oozing out of the coil. The symptoms are the same. but after three different coils I have to hope one of them is OK. I really wish there was a solid reliable replacement. The OEM black coils are great but they are 30 years old or more and no way to know if they are just off the shelf or had a hard life.

I will keep testing and working on the issue. I promise to report back with a answer to what the issue was.

[Tea Tray]

Sounds like an intermittent electrical connection. Whenever I work on my car I always check any visible connectors for corrosion. After cleaning I apply dielectric silicone grease.