JFG

First, I want to say thanks for all the helpful ideas and suggestions I've gotten from you guys on the forum. Even though I rarely post, it seems like all of my questions have already been answered. But this one has me really stumped.

The first sign of the problem happened when my hydraulic clutch went out, and I got stuck driving home in 2nd gear. It was almost 15 miles running at 4,000 rpm when the motor suddenly died. After a few seconds it started running fine again, and I got home with no problem.

After I got the clutch fixed, I took it out for a test run (about 30 miles). And about a mile from home, it sputtered a bit and the motor completely died. I towed it home, and it had no ignition spark at all. After some research on the forum, I figured it had to be the ICM, coil, or Optispark.

Since the ICM seemed like the most likely culprit, and the cheaper part, I thought I would try that first. So I ordered one on ebay, as well as a coil, since they were cheap, and might be bad also. Yesterday, I installed the new ICM and coil.

The weird part is that now it will start, but only stays running for a second or two before it dies. If I hit the gas pedal while it's running, it will rev up a little with each pump. But as soon as the gas pedal stops moving, it dies. Doesn't matter where the gas pedal is, it could be on the floor, but if it's not moving for a second the motor stalls.

I tied swapping the old coil and ICM. The old coil gave the same results, the old ICM seems to be dead as a door nail. I also checked the codes. Module 1 (CCM) had an H74 (LED display dimming output circuit open or shorted to ground) which doesn't seem to apply here. Module 4 (ECM) had an H41 (Cylinder Select Error). Which may indicate a problem with the ECM or PROM.

This is where I'm hoping you guys can offer some expertise. What is the most likely cause, or where should I look for the problem? Some things I thought are maybe the new ICM is bad, or not the right one for my car. Or the dreaded Optispark is bad. Could also be a problem with the ECM or PROM. I was also wondering if the ICM screwed up something when it blew, or maybe a problem with something else is what took out the ICM? Or it could be a completely unrelated problem? I'm perplexed and could use some helpful advice.

Thanks in advance,
John

charliet615

John, I have a 93 also, never had the problem that you mention, however I would look at the fuel pump as a possible cause. Put a fuel pressure gauge on and check that first.

antfarmer2

and try checking your temp switch on the water pump and connections and unplug your maf and test.

JFG

Actually, the 93 uses a MAP sensor instead of a MAF sensor, but you might be onto something. The first test I did when I got it home was to spray some carb cleaner into the air intake while trying to start it, to see if the problem was spark or fuel. I'm wondering if the carb cleaner might have damaged the map sensor or another sensor?

JimLentz

Check that your MEMCAL is seated properly in the ECM. Your ECM may have failed or have a cold solder issue. I was getting odd codes on my '92, which uses the same ECM, until I sent it in to have all of the solder joints redone. ECM has been great ever since.

JFG

Thanks to all for the suggestions.

I checked the fuel pressure, and it looks good. It comes up to about 46 when the key is first turned on. It never dropped below 38 when running. It jumps to 46 temporarily when I pump the gas pedal. After shutting it off the pressure dropped about 2lbs. in 20 minutes.

Also checked the MAP sensor. Voltage runs about 4.4 to 4.6 with no vacuum on it, and drops below 1 volt when pulling 20 to 25 inches of vacuum.

I also attacked a timing light, and it keeps flashing even when the motor is still spinning, but dying. Also had someone start it while I sprayed carb cleaner into the intake manifold, which keeps it running as long as I'm spraying.

So it looks like it's not an ignition problem at all, but a fuel problem. I'm going to start looking into TPS, injectors, and ECM. If anyone has any further suggestions they would be greatly appreciated!

antfarmer2

Did you look at the temp sensor yet?

93Rubie

Why not test the Opti-Spark or other stuff instead of taking WAGS.

https://www.youtube.com/playlist?lis...fOSbxBy4ciZrDv

JFG

Finally got a chance to test it, and it looks good. 4.8 - 4.9 volts on the wire to the sensor. The sensor had a resistance of 5,900 ohms at just under 50 degrees. From what I've read, things seem to be in the ballpark.

Also I tied to start it while it was disconnected. It started once and idled for a few seconds, but wouldn't start again, and the exhaust smelled heavily of gas. Which I guess is what could be expected.

Tom400CFI

It's not your TPS; that's working and evidence of that is that when you "throttle it", it fires/runs for that instant. Not the opti either; you've confirmed spark when dying -good diagnostic move there.

My car exhibited the exact same symptoms when my "VATS was messed up". In reality, my VATS wasn't messed up; I bought the car and it had the wrong key. It's odd how you symptoms came on, but what does the "security" light do, Key on?

Asside from that, it seems your ECM isn't pulsing the injectors any time other than when you're stroking the TPS. I don't know why other than my security system guess -and even that doesn't make sense; it shouldn't crank if the VATS is engaged.

Do you have access to a scan tool?


.

JFG

I took a quick look, and that is quite a collection of videos. I'll be watching them this week, and thanks for all the helpful info.

JFG

Thanks for the advice. My security light flashes, and when I turn the key it goes out. My understanding of VATS is that it has two parts, one prevents the starter from cranking, and if they bypass that, there is another part that prevents the injectors from firing. It seems like the injectors are trying to fire, since it will idle for a second, but definitely not getting the right fuel/air mixture to run normally.

I haven't tested the TPS yet so there is a possibility of a problem there. Maybe 93Rubie's videos have some answers. Otherwise I'm thinking it's way past time to get a factory service manual, and a scan tool.

JFG

Finally found my problem!!!

First, I want to say thank you to everyone for all of the helpful suggestions. I also wanted to post the outcome so anyone else with similar issues can learn from my mistake.

The problem was the cheap ebay parts. Particularly, the ignition module. (Forecast Products 7138 from carpartssupplier123). The coil works fine. I have saved a lot of money buying parts on ebay over the years, but once in a while I do get burned. One good thing that came out of this was I did get a shop manual (CD version on ebay for just under $50). I know I must sound like a pathological cheap skate, but I am on a very tight budget right now.

After studying the shop manual and running a lot of tests, I wasn't really coming up with anything. I traced the problem to the injectors not pulsing right. When I put a test light on one of the injector leads (thanks to 93Rubie for that trick), the light pulsed for a few seconds when the motor was first started, or when somebody was pumping the throttle, which was timed perfectly with how it ran. So the problem was in the ECM, or one of it's inputs. All the sensors tested out in the normal range.

So I got to thinking about it, and it ran fine before the ignition module died. So, aside from the very slim possibility of a completely unrelated problem happening at the same time, what could have changed between then and now that could be causing this problem? And the most obvious answer was the ignition module!!! So I got one from NAPA (for almost 3 times what I paid on ebay), and it started and ran perfectly. Just to be sure, I swapped them back and forth a few times, and it ran great on the NAPA, and horrible on the ebay one. The only explanation I can think of is that the ECM not only triggers the ignition module, it must also get some feedback from it that is used to calculate the injector pulses. And the ebay module somehow was firing the coil, but not sending the right feedback to the ECM.

Anyway, I did get it out for a nice long ride in the beautiful weather yesterday which felt so good after struggling with this problem for weeks. We got dumped on with snow today, which makes me extra grateful that I got that opportunity.

Thanks agin to all!!!

93Rubie

Glad you fixed it! I'm sure you learned some things in the process as well.