Cascade Crew

[alloy]

Ok, I’m too close to this problem and need fresh points of view

Car is now running like crap again. At idle it stalls and tries to die, even backfires now and then. It will clear out for a little while, and then do it again. It’s not even drivable now. Tach drops to zero, then jumps back up and down as engine tries to stay running.

Earlier I replaced the pickup coil and module and that seemed to cure the problem for a while, but it’s worse now-much worse.

Ok this time:

Replaced ignition module with spare-no change

Replaced EGR valve and EGR temp sensor because EGR would leak vacuum off. Also replaced MAT sensor under the plenum. No change, but needed EGR anyway.

Swapped coil out with a spare-no change

Disconnected MAF sensor-no change.

Cap-rotor-plugs are NEW

02 Sensor is new.

Disconnected brown timing wire, no change…….well not much anyway.

Checked the TPS sensor with my Auto X-Ray and it’s got a nice voltage progression from idle to full throttle. No jumps or gaps in the voltage readings.

Also checked the IAC and it seems to be working ok. The X-Ray unit shows it moving and registering ok.

MAF relay-since I found a bad relay for my fog lights, I picked up a new relay and tried it in both the MAF power and MAF burn off positions-no change.

My thinking with the back firing leads me to think it’s an ignition problem, but what to check next? Fuel pressure is about 38 psi at idle, and pressure holds after engien is shut off.

Help me before I shoot something. Haven't decided which to shoot, the car or myself

[Dewey316]

if there was not change with the ESC disconneted, that could be the issue. try hooking your timing light up to with the timing wire like it should be, you should be getting somewhere around 20* of timing, if you are only getting say 6*, you know the issue.

[alloy]

Ok, You may have lead me to the answer.

Just took my timing light and checked the timing, and I've got 6 with the ESC wire disconnected, and it jumps up where it should be when reconnected and the engine restarted.

But, with the engine running holding the timing light on, when the stalling happens the timing light quits, and start again. The coincides EXACTLY with the stalling of the engine. So, now to find out why this is happening. I'll check voltage at the coil to verify that isn't the problem, and anything else will have to think about it for awhile. Am to tired now to think. But the timing light idea put me on the right track I believe. It seems to confirm it is ignition causing it.

See, just needed a new set of eyes to look at the problem. Thanks!!!

[Twilightoptics]

If you aren't getting the timing it will get VERY hot, and you'll start melting things....... :: cough :: like valves :: cough ::

[92RS shearn]

I was thinking timing issue as well. My first thought was a bad vacuum leak. I take it you aren't getting any codes thrown at you?

[alloy]

No, no codes other than when I disconnect the ESC wire or the MAF connector.

[Dewey316]

I didn't notice plug wires on your list. maybe check the resistance on them. at least the #1 wire, we know somewhere along the line spark isn't making it to the plug.

[alloy]

Well the wires are old, but real good jacobs wires in very good condition. There is no noticable "spark leak" out of the wires to any place on the engine.

As I said earlier, the tach drops to zero, and it's just like the power to the ignition is being shut off then back on. But what the heck would do this? Ignition switch bad???

[Twilightoptics]

When was the last time you replaced the coil?

I had the same thing where power gets cut off then back on, tach drops to zero, with a crane points conversion box. Running no ballast it would overheat and shut down.

Maybe something along those lines, or the coil might be bad/connection somewhere?

[92RS shearn]

You dont have any loose grounds, or something becoming a ground that shouldnt be. I know you said you checked the wires, but maybe something else that has worn through its casing.

[alloy]

Well I have a MSD coil on the car, and a spare stock coil. Swapped the stock coil and no difference.

I'll start checking grounds tomorow and worn wiring. Not sure what else to look for, but the timing light got me pointed in the right direction I beleive.

Anyone know anything about the ESC module and how it works?

[chevymad]

Couple of things.. find a way to disconnect your tach. Sometimes they can short and cause exactly whats happening to you. Also the toothed wheel that is part of the distributor shaft. It triggers the pickup coil. There are tsb's out on it. The original style are known to crack. The crack becomes another magnetic point, triggering the pickup at the wrong time. Causes all kinds of commotion. I've run across a couple of these. Couldnt see anything wrong with the trigger wheel until the shaft was pulled from the distributor then it was obvious. Most new aftermarket distributors use a different style trigger wheel now.

Just like with a shorted tach, any short in the trigger side of the ignition will cause the same problem. Hook a test light to the negative side of the coil. Should flash evenly while running. Since the timing light is going out intermittantly I would expect the test light to follow suit. If it does, test the positive side as well. If the positive side has a steady 12v then you know its a problem on the negative/trigger side.

Disconnecting the timing connector "should" eliminate any problems with the ecm or esc modules. With the timing connector disconnected the module sends the spark signal through an internal bypass, then amplifies this signal and sends it to the coil. With the timing connector disconnected you should only have the distributor, coil, and tach wiring in the system.

[alloy]

The distributor is out of a 92 caprice cop car. My original dizzy was badly rusted and I just replaced it when I replaced the pickup coil and shimmed up the end play. Are there TSB's on the 92's also ?

I'll pick up another good test light tomorrow. Mine fell apart after 20 years of use (imagine that) I was going to use my DVM to do this, but a light is a much better idea, easier to see.

I was thinking that disconnecting the ESC wire would take the ESC module and computer out of the loop, and you have just confirmed that for me.

I'm not sure how to disconnect the tach, but I have an extra gauge pod here and will try and figure a way to do that.

I'll let you know how it goes. Thanks for the help.

[1LEWannabe]

well, if ya come to a dead end with the ignition stuff, here is something to try also. on my Z28, when it was acting similar, what turned out to be the problem was the fuel sock in the tank was plugged. take your fuel hoses off the motor and blow compresed air through them...if this fixes it i will send ya the bill later.... naw, really, if it fixes it you will need to drop the rear axle and tank and clean it...

Josh

[alloy]

Thanks for the idea Josh. I have around 42 PSI of fuel pressure, so I still think it's ignition.

Brandon,

I picked up a test light, but not the kind I wanted. It uses those little red diode type lights that look like a glass fuses. It lights up, but the responce time of the light bulb lighting up is very slow and I can't really see the pulsing of the light very well. But what I can see is I've got a steady 12 volts at the positive side of the coil.

I had to go into work early today, so didn't get much accomplished on it. I did get another pickup coil and cleaned up my old original distributor and will drop it in tomorrow. There are no cracks in it I can see. This shoulld eliminate the pickup coil and trigger mechinism from the list of potential problems (I hope).

[alloy]

Ok, I just finished changing out the distributor and pickup coil and no difference with the timing wire connected, but with it disconnected it runs ok. Not good, sounds "labored". But when it start acting up I pulled the timing wire and it smoothes out and runs ok.

I'm not sure if I was just too tired to catch this before, or it's something new. Was sure I checked this, but.................at least I'm making progress (I think you would call this progress).

Anyway, since it runs good with the timing wire off, I'm thinking this is leading me to a computer or spark control module problem. I can get a computer at work, but just don't want to throw a $140 part at it in the hopes it will cure the problem.

Now I've got to find a way to check the computer and spark control. Any suggestions?

[chevymad]

Computers the worst thing to check. Only way to check it is to make sure everything else is good, or "replace with known good part". Hate when a manual leads to that. I'll have to think about the ESC.. What you really need now is a lab scope. Check the wave forms going to and from each device. Sometimes you can get by with a voltmeter in AC mode. If you can see the glitch, but much harder.

Best thing now.... who's the nearest crewbie with known good parts?

[Twilightoptics]

we never determined if my ECU was bad or not....... but when we tried mikes, my car did the same troubles.....

[alloy]

Well looks like I'll be picking up a computer then. No one to borrow one from that I know of. I really hate to do it that way, but looks like the best option right now. If it's not the computer I can take it back. There are some perks to working at a parts store, not to mention being a manager also

I looked at the pricing wrong for the computer, it's $79 then I get 20% off that. It's the $140 core I was thinking of. But I have a commercial account, so no core for me. The core is deferred thankfully.

Will let you know how it goes. Probably tomorrow night.

[alloy]

Well thanks to Paul I know it's not my computer causing the problem. He graciuosly loaned me a spare computer of his to try, but no difference.
Still runs ok with the ESC wire disconnected, but like crap with the computer controlling the engine.

Guess I'll order the ESC module tomorrow. Not much choice I guess. Not too many more things to try to solve the problem.