Still having running problems

944_science · 03-08-2009, 02:28 PM

Input would be greatly appreciated. After troubleshooting and finding and fixing some issues the car is still dying randomly. What I've done:

General tune-up w/generic Bosch O2 Sensor
Battery
New FPR FPD
Injectors
Fuel Filter (Old one installed backwards??)
Speed/Ref sensor gaped
All new Vac Lines (Including under manifold)
Intake Gaskets
Cleaned ICV, Intake, Throttle Body
Intake boot looks weathered but OK
AOS seals
DME Relay is newish
Cleaned AFM track
TPS, DME Temp Sensor, Ignition Switch all checked OK
All Grounds Spotless

She ran OK (In fact quite well) all day yesterday after putting everything back together. However one last ride later in the day and I experienced tach drop/loss of engine power and could hear the DME relay clicking on/off. Got home pulled relay and it was warm. Experienced two other types of engine death today while idling: Engine sounds like it's taking its last gasp of air then dies, second is the engine just shuts off quietly. Neither time do I hear the DME relay clicking.

Put a fuel pressure gauge on the rail and there was no loss of pressure when engine died. DME? If so, what is the best way to test beyond putting into another car before I pull it and attempt to re-solder?

Thanks Again.

mikepellegrini · mikepellegrini's Garage

Sounds like a wiring problem. The connectors for the speed/ref sensors often have problems (where they plug into the engine wiring harness). You might try jiggling the wires while it's running and see if you can get it to die.

Another possibility could be bad grounds.

944_science · 03-08-2009, 04:56 PM

Yeah, It feels electrical. I cleaned the following grounds:

Two under the dash on the driver’s side
One in the rear hatch near the jack
One on each side of the front frame rails near the head lights
One in the battery box
Two on the back of the engine (one on the block and one on the clutch bellhousing)

Also tried wiggling sensor wires while running-no stalling though. I did notice a small split in the black rubber sheath at one of the sensors, I could see the silver coaxial like wire underneath. I'll tape it up.

Forgot to mention that I attempted to bypass the alarm per Clark's instruction but when I did the car wouldn't start. Anyone have issues with the alarm box causing stalling bad running?

944_science · 03-09-2009, 03:07 PM

Any thoughts?

kdjones2000 · kdjones2000's Garage

Sounds like S/R Sensors, and/or DME solder.

If it is dying when it gets warm, that seems to be a sign of bad/going S/R sensors.

Good luck with things, Keith

944_science · 03-09-2009, 03:55 PM

OK, thanks. Both the speed/ref sensors are new. I did gap them slightly high though, approximately 0.88-0.9 mm. I will try and set the gap closer to 0.8 mm.

alantica · 03-09-2009, 07:42 PM

Quote:

Originally Posted by 944_science

Input would be greatly appreciated. After troubleshooting and finding and fixing some issues the car is still dying randomly. What I've done:

General tune-up w/generic Bosch O2 Sensor
Battery
New FPR FPD
Injectors
Fuel Filter (Old one installed backwards??)
Speed/Ref sensor gaped
All new Vac Lines (Including under manifold)
Intake Gaskets
Cleaned ICV, Intake, Throttle Body
Intake boot looks weathered but OK
AOS seals
DME Relay is newish
Cleaned AFM track
TPS, DME Temp Sensor, Ignition Switch all checked OK
All Grounds Spotless

She ran OK (In fact quite well) all day yesterday after putting everything back together. However one last ride later in the day and I experienced tach drop/loss of engine power and could hear the DME relay clicking on/off. Got home pulled relay and it was warm. Experienced two other types of engine death today while idling: Engine sounds like it's taking its last gasp of air then dies, second is the engine just shuts off quietly. Neither time do I hear the DME relay clicking.

Put a fuel pressure gauge on the rail and there was no loss of pressure when engine died. DME? If so, what is the best way to test beyond putting into another car before I pull it and attempt to re-solder?

Thanks Again.

Just thinking out loud... guesstimating... A problem with the DME (itself - not inputs) if it is going bad (re-solder) would be more definitive. A cold solder joint would not be so happy about quitting work so often, it would stop working completely.

A chip that gets hot enough will work intermittently, but on this DME board, I would give it about a 5% probability.

This sounds like a power wire is loose (coil wire output) or corroded {coil wire inputs (Green & Black); battery or fuse wire - far enough up inside the wire that you don't see it} but is still too defined because it is happening so often, unless pressure (such as the fans starting & stopping) is thought of as an action of movement on the wire(s).

The DME relay itself and heat. What reason does it have to heat up? Only a lot of internal movement would make it heat up. Even though it is a "new looking" relay, could it be old enough to cause problems? Consider swapping it out.

The wires feeding into the fuse box underneath could be corroded enough to make the DME relay work and sometimes stop working, look over all of the wires for bulging or even the slightest hint of a white/greenish powder. A contact underneath the box could have a poor connection.

Overall, I think it points more toward a wire or relay problem than the DME itself. Heat also plays a factor somewhere because you mention that this only happens while running and not a cold start. A cold engine makes me lean more toward corrosion and continuous poor starting.

Good Luck!

944_science · 03-09-2009, 09:44 PM

alantica, thanks for the imput!! Coil is new and connections look good, but like you said, could be an internal wiring problem in the harness. DME relay newish meaning I replaced in November when I got the car, fixed my problems temporarily (tested relay Friday and is OK). I thought a hot relay could have been connected to old fuel filter being installed backwards causing pump to work harder to maintain flow? New filter installed and still died.

Never had the car die while fans turn on, it's been cold enough out that car runs cool. Had the car die while fuel pump jumped also.

If not DME as you said, I did find a slightly melted fuse, #14 I think, for the cabin fresh air blower. Spade end of fuse was dark. Also fresh air blower relay right next to fuse will click on/off if I touch it and also had corrosion on one of its spade plugs.

Game Plan:
Spring break next week so I will pull all relays and clean connections, a lot of the fuses look original so I will replace them. It's hard to get a good look at the bottom of the fuse panel but I will try again to get under there and check things out.

Check grounds again and general wiring, I will also check again for vac leaks as I just changed a bunch of hoses. Re-gap speed sensor and cross my fingers!

944_science · 03-15-2009, 07:50 AM

I think I might have found the problem- hopefully!

Grounds were OK
Re-gaped speed sensor
Taped up speed/ref sensor @ wire harness
Changed all fuses in fuse box (some were corroded)
Cleaned relay contacts

Ran great Friday.
Saturday morning I start it and wiggle the key once it's started, tach drops engine seems like its cutting out. Wiggle key again with same results. Drove the car periodically throughout the day but wasn't able to reproduce the problem. This morning I start the car, it runs for a minute and shuts off, does this three times. Weird thing is I can't get it to stall by wiggling the key. After that I drive it for 20 minutes with no problem.

The ignition switch checks out OK, but is it possible to have an intermittent switch? The car starts without a problem so I'm a little stumped.

-Thanks

944_science · 03-15-2009, 10:45 AM

OK, took it for a long drive a had one "blurp" where tach dropped slightly and two times where tach dropped dead. I pushed in clutch and put in neutral then back in gear and car came alive. This and dieing at idle seem to be the same issue, which lead me to thing it's not the ignition switch because I'm effectively pop starting it when dies at driving speed. I guess I'm out of ideas. Any thought before I pull the DME and resolder???

nynor · 03-15-2009, 02:35 PM

try putting someone else' DME in your car.

944_science · 03-15-2009, 03:08 PM

Good call nynor, anyone in southern Indiana have a working DME I can try?????? If not the electronics guys here said they would help me resolder/rebuild the board on mine.

JonA · 03-15-2009, 03:20 PM

Did you jiggle the DME relay with the car running?

Jon

944_science · 03-15-2009, 04:31 PM

Quote:

Originally Posted by JonA

Did you jiggle the DME relay with the car running?

Jon

Yeah, I've tried running it jumpered and have had stalling issues. Original relay tested bad, I ordered a new one that was DOA (bad solder) got a third one that's in the car now. I guess the relay could in fact be flaky as the original one was DOA, but it tests OK so I don't know?

nynor · 03-15-2009, 05:21 PM

Dme.

944_science · 03-15-2009, 05:30 PM

Quote:

Originally Posted by nynor

Dme.

LOL, yeah.

mikepellegrini · mikepellegrini's Garage

Here's a good thread on Clark's about DME's. http://clarks-garage.com/phpBB2/viewtopic.php?t=1909&highlight=dme+cold+solder

A cold solder joint or cracked joint can cause a lot of intermittant problems that are hard to diagnose.

The remedy they talk about in the above thread is re-flowing (re-soldering) the connections in the DME.

My kid did that to the DME on his 86 951 and it helped him - he was having the same sort of problems as you.

Another thought: if the gap on the speed/ref sensors is too great, they may not generate enough of a signal to work the computer. Greater gap = weaker signal. The signal has to be of a certain amplitude to trip the computer. Spec for the gap is 0.8 mm.

http://www.clarks-garage.com/shop-manual/ign-02.htm

944_science · 03-16-2009, 04:49 PM

Opened DME and found a lot of hazy solders and also some very minor water damage considering the hole in the battery box that I fixed! Overall the DME was in good shape and didn't appear to have been opened before. Re-flowed all of the solders, put back in car, held breath..........

Started right up, took it for 5 minute spin - no problems.
Second drive later on and again no blurps. I also changed the oil yesterday, man what a difference, Castrol GTX 20W-50. Cured my bouncy oil pressure gauge also!

mikepellegrini · mikepellegrini's Garage

Congratulations! I'll be keeping my fingers crossed for you.

944_science · 03-20-2009, 04:51 PM

Well I drove it all week with no hiccups or cutting out! It was definitely bad solder in the DME. Thanks to all who walked me through it. It's been a pleasure getting it running reliably. Just a few more issues to work out!!