Here's the problem. I just got my car back together after rebuilding the motor and took it out on the freeway. It drove great, but about an hour into the drive, it started stumbling under moderate load in 6th gear. It got progressively worse, and the motor shut down completely.

The fuel pressure looks good at idle, but I haven't had a chance to monitor it under load yet. The plug wires and opti are brand new, which makes me think the problem's either the coil or the ignition coil module. The coil is an MSD with about 30K miles on it. The ignition coil module is stock with 90K miles on it. Also, the car isn't throwing any codes.

I know it might also be fuel related, but the weird thing is the stereo also shuts off then comes back on by itself during all this, so I think it's probably electrical. The problem also seems to get worse once the motor warms up.

My question is, before I go out and start replacing parts, is there any way to test the coil, ignition coil module, and spark plugs?

 

That is really odd, I am having a very similar problem since my rebuild. Search my name, I have thought it was alot of things, and what it does has changed kinda. Funniest thing is, m radio cuts off randomly when I turn it up high, never did before.

I thought it was alot of things, still looking.

 

BTW, under very heavy load, the car doesn't just stumble, it will shut off completely.

 

You can reasonably test the coil, opti, and wires in one shot by putting a spark tester (NOT to be confused with a spark gap tool) on the end of each plug wire to ground and ensuring that the spark is good and strong. If it's able to jump the specified gap (as indicated on the tools package), then it should be good to go. They're available at most any auto parts store for $5-8...mine looks like a clear tube with an alligator clip and an adjustable screw that allows you to set the gap distance.

 

Check fuel pressure WHILE DRIVING.. If you check fuel pressure while car is off and it reads normal it doesnt always mean that there is a sufficant amount of VOLUME. It may have normal fuel pressure under low load but as the injector pulses get longer you may be running out of volume causing a drop in fuel pressure, generally cause by a faulty fuel pump.

BTW- Good luck

Brian

 

Where is all this advice when we are trouble shooting my car. I had to read this a few times before I believed it was you