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I’m having a starting/running issue on my 1986 and I’d appreciate input on where to look next to trouble shoot it.
History:
When I bought it the car ran good once it was warmed up but horribly when it was cold. I found the hose between the cold start valve and T on the intake was badly cracked and letting unmetered air in. Once replaced the car has always started and ran very well. A few weeks ago I was replacing a few fuel lines and the connector on the CPS broke due to age. I replace the CPS and the car ran as good as ever. It would start right up and once warm would hold ~700 RPM idle.
What happened:
Last Saturday, I was driving to run an errand and decided to take the 928. I had gone about a mile or so when the car stumbled and died as I was rolling up to a stoplight. The engine had only been running a few minutes and I had been driving it very easily. I tried to restart it but nothing happened. We pushed the car into a close parking lot and towed it home later. Of course I had cranked it a bunch to get it restarted but despite spinning like it should it was doing nothing.
What I have done:
Once I got it home I started troubleshooting it. I removed the back two spark plugs and both were bone dry so the car was not flooded. This lead me to believe it was a fueling issue. I first determined the fuel pump was not running. I jumpered the relay and the pump runs fine. I replace the pump relay, LH relay and EZK relay. Now the pump runs fine and I’m getting fuel into the cylinders. I checked the spark and I was getting spark on some of the cylinders but not all. In the mean time I have been reading lots of wiring diagrams and tip sheets for finding what is wrong. I was leaning towards an ITU having failed until last night…
For grins and giggles I tried to start the car again, I held the gas pedal to the floor and cranked it to clear any fuel out. It spun well and “hit” a few times like it wanted to run. I took my foot off the gas and tried again, it turned fired right up. It ran rough for a few seconds like it was burning off extra fuel then settled to a fast idle. The car ran great for 3-5 minutes. Then it started to stumble and run extremely rough, like only 2-3 cylinders were working. I turned the car off and tried to restart it. It would not start. I let the car sit in the garage for a few hours and sure enough, it fired right up. The only difference between then and the last week was the temperature. It has been 60*ish until yesterday when it turned much cooler. Last night it was maybe 40* in my garage. Would the temp sensor on the intake manifold cause this problem? I have also discovered that some of the vacuum lines were routed incorrectly. I doubt this is causing the problem as they have been like this for a while. I plan on correcting them anyway.
Any ideas on things I have missed or where I should start looking?
The last time when you "fired it right up," did it also run fine and then start to run rough and die?
You've hit most of the areas I would have recommended from my similar experiences, but could the Temp II sensor be a possibility? That's the sensor for the computer, as opposed to the one for the gauge...
That's a great reference, I wish there were one for the S3 :-(
For the OP, on your car it's in a similar location but fairly nearby is the gauge temp sensor...from your description I'm not 100% sure to which you're referring...
Based on the Bertrand's link, I had the two sensors mixed up. The sensor I was looking at was in the air side of the intake manifold not the coolant passage. Now that I know which sensor to check I'll try it and see if it functions correctly.
Ok, so I messed with it more today. It fired off quickly on the first turn of the key and ran smoothly for 5 minutes then it stumbled and died. I tried to restart it and it wouldn't start. I checked the vacuum lines, injector grounds and tried to check the temp II sensor. There are three sensors on the front of the engine, one in the air runner on the intake manifold and two in the coolant passage on the intake manifold. The picture I saw of the sensor looks like one on the coolant passage but I would think the ECU would need air intake temps more than coolant temps. This is throwing me off.
After letting the car sit for a while I tried to start it again. It fired right up and ran for 5 minutes or so, reved just fine like nothing is wrong. Once again it stumbled and died after running for 3-4 minutes. I had my GF crank the car for me so I could check for spark and there was no spark from either distributor. What would cause the car to stop sparking once the engine starts coming up to temp?
EDIT: the tach jumps and moves when I'm cranking during the no start so I think the CPS is still working.
Temp 2 is the critical sensor that controls the engine fuelling at all temperatures. The air temp sensor make adjustments to ignition timing, retards timing if intake air temp rises above about 40degC.
The problem could be the EZ-F ECU, but still may be the CPS.
Temp 2 is almost directly under the cross brace, with a Bosch two pin plug. The temp sensor for the dash gauge is slightly further back and on the earlier car has two separate spade connectors.
Yes, the air temp sensor is the one in the bottom of the engine air filter housing.
Here's the sensors in my car. I think #1 should be the Temp II because it's in the intake manifold air runner but everything I've read said it should be a two pin style connector not spade connectors. This has been throwing me off.
Yesterday I checked #2 because it matched all of the descriptions that I've read. But it didn't seem right to check a sensor in a coolant passage that I'd supposed to measure air temps.
01-23-2015, 04:33 PM
Rough or non-starting and running 1986
