Tonight drive under its own power... But not for long

1995 lt1 73k. Tow package

So got this car that has not ran in 4 years. Put jump box on it and it started up, I could not believe it. Changed oil and gave it once over. Leaking high pressure PS hose had to be replaced, so did that. So today started it and let it run up to temp (1st time) and all well so took it for a gentle drive put about 10 miles on it of stop and go driving. Filled up has tank and drive it home. When I got to my street I put a load on motor (Power brake) to see if it actually had any power and it stumbled and started to surge idle and knock and barely ran maybe 30 seconds at 200rpm than died. Turn key and sounds fine on starter but when it tries to fire off knocks really bad and won't start. Wtf?

Personally sounds like the timing went all wack. Like the wires were suddenly swaped around. Understand this car ran for over and hour and never missed a beat. It was so smooth and quiet. How did it suddenly die? Any ideas where to start?

if you have an inspection camera capable of going through the spark plug hole I would look inside the cylinders to see if maybe a valve came loose.

Due to when and the circumstances of how the problem started I would think it would be something internal sadly.

goldwolfnhn wrote:

if you have an inspection camera capable of going through the spark plug hole I would look inside the cylinders to see if maybe a valve came loose.

Due to when and the circumstances of how the problem started I would think it would be something internal sadly.

I think that if I scattered the motor you hear something strange when turning over on the starter. It sounds fine.

I bent a pushrod on my 86 GMC crew cab dually, cranked over no problem with no sign of anything wrong until it actually fired, then it ran very rough as due to the pushrod that bent I had a completely dead cylinder.

also got a truck at work cranks beautifully, but once it's running the engine sounds like it's going to explode.

so you might have just got something that bent, stuck, or something, the inspection camera might be a way of seeing if anything happened inside a cylinder and all you have to do is pull a plug, otherwise pull the valve covers and check the valve train that's what I would say. I had my 94 RMW running with two misplaced plug wires, so effectively had two dead cylinders, it fired up no real problems and I even drove it for an hour and a half going up to 60 mph, the car ran rough but no real noise or anything.


though I do tend to think in worst case scenarios, you said the problem started when you put the engine under strain, so I doubt it would be a sensor going out at that time, plus the valve cover is easier to pull off then the timing cover, especially if you have an LT1 equipped with a mechanical fan.

I have not touched the car since Mondays disaster and today I turned the key and it started right up and ran smooth, idles smooth and revs fine. Explain that??

I don't know the symptoms of a bad optispark but could this be it? I had a V6 Fiero years back and it would do jekyll and hyde things like this and it was the stator in the dizzy. I have a new coil and ignition module in route to try, they were cheap.

It running today should eliminate the thought it was a fuel issue as that would not fix itself.

You need a fuel pressure gauge. The fuel pump wiring is lousy in these cars, especially inside the tank. If you're handy with a soldering iron you can fix it easily. Intermittent fuel pump failure is a real possibility.

Always replace the ignition coil and Ignition Control Module (ICM) with quality SMP. Delco or Delphi parts.  They are wear items on these cars.

Check the coil wire for corrosion on either end. Always use a thin film of dielectric grease inside plug and coil wires to seal out moisture.

Check the ground wires on the ignition coil stud for breakage. This is a common problem.

With the car idling, remove the blue vacuum hose just ahead of the "home plate" resonator and use your finger to check for vacuum. If so, your opti is ok. If not, you should take it apart and clean/reseal it, and replace the cap and rotor while you're in there.  NEVER throw away a stock optispark base - the mitsubishi sensor is no longer available and rarely fails.  But the 4-pin harness that connects to it does.

Well issue is not fuel pressure.
Sits at 38 idle goes over 40 under load. But I did find something funny. These were just hanging from the wires.
.... Where they mount? Could this cause issue discribed? [You must be registered and logged in to see this link.]

they mount to the front of the cylinder head, and I would think it might be possible, as the one is your ignition control module and the other is the coil so if the plugs had too much strain on them they could cause intermittent signals which would cause problems with how the engine runs, there should be a heat sink that the ICM mounts too, otherwise you might need to go junkyard hopping.

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I bet that will cause an issue!

Like mentioned above the ignition module should be mounted to a heat sink and then bolted to the head.

Look what I found at junkyard. [You must be registered and logged in to see this link.]