jmj951

I'll try to make this short. Changed too many things at once, and have a mess on my hands with only two days left to fix. 1986 turbo, started with a stock engine setup (had 951 Max chips). I installed the Lindsey Injector harness and sensor harness, replaced the DME temp sensor, cycling valve, and ISV, new plugs, and Vitesse MAF kit with new injectors. First I replaced the injector harness only (includes the knock sensor connector), started the car, ran and idled fine. Then I decided to change the sensor harness, all of which I did very carefully, double-checking everything. While the intake was off, I realized it would be much easier to install the MAF kit, so I did that as well, including the new injectors. Reassembled it, started it up, idled great! And the narrow-band O2 sensor gauge was now completely stable, which is a marked improvement. Had lots of other stuff to do that day, so I closed it up and felt great about having completed it all with no problems. Not so fast...

Next day, I went for a short drive. Seems to be running great. Turn around, pull up to a stop light and briefly lose power, but am able to keep it running and pull out onto the highway. Almost a complete loss of power, requiring me to feather the throttle extensively to keep it running, and am able to get it back to my neighborhood. It dies while I wait for the left-hand turn, I am able to restart it, go one block into my neighborhood, then it dies again, and won't restart this time. I walk home a few blocks, get my wife to steer the car so I can push it back. We return to the car approximately 10-15 minutes after I parked it, and I ask her to try to start it just in case. It starts right up, idles great, and we drive it back to the house. Dies in the driveway. Starts back up, dies again, won't start anymore. I get under the hood and have her try restarting several times. There is a LOT of clicking going on each time the key turns on. For one, the cycling valve was clicking like crazy. I pulled the connector, put it back on, and it wasn't clicking anymore. Still wouldn't start. Let it sit another half hour. Starts right up, I pull it into the garage. But now, the idle is unusually high, around 2200 RPM.

If I can draw any generalities from what happened, it's that it won't run when it warms up, but will run and idle fine with good A/F mixture when it's cold. When it dies, it appears to lose spark, because it just completely cuts out and when I'm able to restart it, it seems to be burning fuel in the exhaust. All vacuum connections and electrical connections have been checked more than twice. I really screwed up by doing too much at once (because I'm on a very limited time schedule here) and it's almost impossible to go back, because I had to cut out original wires and hoses. I really need help with diagnosing this. If I don't get it figured out before I leave, I won't be able to leave the car with my family to drive it regularly, and it's going to sit and rot for a year (car is in Chicago, but we're living at a Navy base in Naples, Italy). Please help!

GreyDog

OK, kind of wild guess, but if the narrowband is completely stable when the engine is hot, then its showing that the O2 sensor is not working properly or connected properly at either end (it cycles on-off voltage to the ECU and would reflect that on the gauge when engine is hot), assuming the sensor is connected OK given all the work you've gone.

That would cause the ECU to not know proper fuel mixture, other symptoms start from there.

Also, the car may run OK at cold idle/running since the ECU does not use O2 signal until the sensor warms up and sends proper signal. So, perhaps also relates to the OK-Cold, Not OK Hot engine symptom ?

Hope this helps...

jmj951

To clarify, by completely stable I mean just up & down a few clicks on the gauge, but still within the 'stoich' range. The O2 sensor itself was not one of the changes in this process, so that shouldn't be part of the problem. I'm not sure, but I think we're looking for something that would make the DME cut out the spark. The more I think about this, the less I like the sensor harness replacement project, because it just seems too kludgy - T-ing into (soldering) wires on the KLR and DME harnesses. The pictures on Lindsey's web site for the DME and KLR plugs actually look good enough to allow me to back out the sensor harness change, so I'm probably going to end up doing that. First I'm going to put the old DME temp sensor back on the car - just in case.

Tedro951

I'd start with a really careful examination of all connectors. I dont think the O2 sensor will cause the car not to run.

jmj951

Just verified all of the new DME connectors are in their correct sockets, the DME-soldered wire is definitely in the right place, and the KLR-soldered wire is on the right wire. Will try a few more tests and post back.

JohnKoaWood

I am betting it has something to do with the Vitesse chip board and its settings for closed loop operation (warm motor). Or the lindsey replacement harness.

The DME temperature sensor tells the DME when to change from open to closed loop. It sounds like when you get to closed loop, it begins running completely off.. this is NOT caused by a bad O2 sensor, but can be caused by faulty wiring, especially in the 12V signal to the MAF you installed.

I would disconnect the MAF power and connect it directly to the battery, drive the car to temp and see if the fault re-occurs, if it does contact John at Vitesse for more guidance regarding the chip board interction with the DME..

Also, not to be a ***** or anything, but WHY are you using a NB O2 gauge with everything else you have installed, you should at the very least have installed a WBO2 to trully tell what is happening, the NBO2 is notoriously bad to ever try to use as a tuning aid, and you have crossed firmly into the land of needing to fine tune the car.

I cannot say it enough times, teh FIRST modification to be made is a WBO2, everything else should come AFTER.

Tom M'Guinn

I'd start by checking for spark when it is not starting, to confirm your sense that it is an ignition issue. None of the things you mention should jeopardize your ignition really, but if yours is dead you might check that the spark plug wires are secure and in order, plugs are right for car, etc. If you have spark, then it's probably an a/f mixture problem. Start by looking for vacuum leaks, since cold-start enrichment can help a motor run better when cold if it's got a vacuum leak. High idle is often a vacuum leak too. Any chance you switched the isv and aos hoses on the I/c and jboot? Did you use the correct dme temp sensor? What happens if you unplug the tps?

fast951

Johnathon got hold of me. After checking a few things, the car is running again. It appears that he did not have the chip/board fully seated in the DME socket and was not making contact.

jmj951

Thank you John Vitesse! I cannot thank you enough. JohnV provided a very methodical approach to diagnosing the problem, confirming it was a no spark condition, taking the KLR out of the loop, and finally narrowing it down to the DME.

Believe it or not, the second time I put the chip board in after we initially resolved the problem, it still wasn't strong enough to keep from wiggling loose (thanks to John that he recommend leaving the DME open for my second round of testing). 3rd time - I used a lot more pressure than I was comfortable with using, and finally, it seated really low on the board with a nice, solid little thud. The pressure differential between the original chip and the new chip board threw me off. Now, to close her back up and tackle one last problem - the belts. That will be another thread.

fast951

You are welcome, Glad I was able to help.

Tom M'Guinn

Unseated chip board -- that was going to be my next guess.... Glad you found it -- John could diagnose the Mars rover from his armchair...

(p.s. to John, we've had a few clear days, and everything is perfect so far with the new part.)

GreyDog

Awesome, great news !

jmj951

Spent over two hours on the road with it today. Very smooth, MUCH better fuel management based on the limited info I see on my AFR gauge. I purchased this mainly to prepare for future upgrades, but the entire project has also resulted in the car running better.