My '85 L98 is having odd seizures at times, really strange incidents of seemingly whacked out timing or massive fuel dumping. There doesnt seem to be any rhyme or reason to when it happens. I thought it was a hot related problem but it happened the other morning after only driving about a mile or so. Over the last three years it only happened about 4 times but in the last month it has really started to happen a lot more often.

Whats happening is occasionally I will crank the car and it acts like the timing is off with a hard, dragging, odd start. The car will barely run with zero acceleration and massive backfiring thru the plenum. Whats really odd is when I stop, turn off the car and recrank, the problem disappears like there was nothing wrong. Sometimes it may take 2-3 tries but usually the first recrank ends the issue. It hasnt really thrown any codes altho the other night the check engine light did come on but went off when I turned the car off and restarted.

Has anyone experienced this type of issue? I am kinda at a loss because of the intermittent nature but I am afraid its going to have "the big one" and leave me stranded somewhere. I do have a spare ECM in case the one in the car has a tumor or something. The ignition system is completely new, so is the fueling system. The problem was occurring before all of that work tho.

The only things I can think of would be an ECM malfunction or the 9th injector dumping fuel. I just dont know otherwise. Any ideas???

TIA!!

 

When you say complete new ignition please break that down to what was replace. Did you replace the pickup coil?

 

I would say install the spare ECM and see if it still does it. Right off the top of my head I was thinking ECM anyway before I even read to that part.

 

I'll take a shot......a loose fuel line in the tank would produce those symptoms....fuel pump blows the line out partially, line goes back in place when you shut the pump off.....next time you start it, its oK....happened to me.....

 

Also easy to take a ohm reading of the pickup coil. I just changed mine. Thought the timing chain was bad at first

 

Yes the pick up coil is new along with an ICM and capacitor with the NAPA rebuilt distributor. The ignition coil is new as well. New plugs, wires, rotor and cap.

As far as fuel starvation, I would lean the other way because of the violence of the back firing especially as you try to accelerate. I just replaced the fuel pump and carefully checked all the metal lines for holes because of the miss I was having. Rebuilt injectors finally cured the last of it.

The 9th injector running wide open dumping fuel after an erroneous input from a bad CTS maybe? I dont know, I guess I will swap the ECM and see if the seizures continue.

With all the new parts I am kinda at a loss.

 

85's don't have all metal fuel lines in the tank...I think it's a rubber section that fits into the pulsator...that's what was blowing out on mine...you wouldn't have good pressure if its out....it would be good to know what pressure you have when this is happening...

 

The cold start injector is controlled by the cold start thermo switch on the front of the intake manifold under the throttle body. There is no connection to the ECM in any way. The cold start injector only works when the engine is cranking and it times out after 8 seconds and stops injecting fuel. It also will not inject fuel if the coolant temperature if over 95°. You could unplug the cold start injector if you think it's somehow getting power when it shouldn't. A leaky cold start injector is a little harder to diagnose. In that case you need to remove the cold start injector fuel line from the rear of the fuel rail and plug the hole.

The cold start thermo switch is easy to identify because it has a connector that looks like a fuel injector connector:

 

It would be simple enough to change that little bit of rubber out. When I changed the fuel pump I cut off enough of the feed, return, and vent lines to pull the pump. The feed line was in bad shape anyway.

 

Thanks Cliff. It sounds like there are two things governing the 9th injector. The CTS and a timer somewhere. Even if the CTS was malfunctioning, you would think the timer would self correct the issue if it is working correctly. Where is the timer function located?

9th injector block off kits are available on the 'bay and I have been considering this anyway as I rarely experience really cold temps here in NEFL. The CTS that governs this isnt expensive either.