Just bought a 92 Z with a LB9, very stock, the car starts fine, seems to run a little rough, tough to tell with the rotten cat. Revs and drives fine for about 10 miles. (this distance was dead on 3 straight trys at diagnosing this.) Then it starts missing badly and won't Rev. stumbles, Starts losing power so badly that you cannot fully engage the clutch or it will die. Eventually the car stalls out and won't restart. It might fire and ping along for a sec but thats it. If you leave the car for several hours, it will fire right up like nothing ever happened...

I changes the O2 sensor to be sure it wasn't that when going closed loop. The plugs were just put in by the previous owner. They look fine and gapped out ok. (a few were a little black, other were perfect). Fuel pump was replaced by previous owner. Seem to have good fuel pressure but I will check it this week.

Any ideas on where to go now? Injectors? (need to test). Why does waiting always seem to help the car start? Its gas consumption seems high.

Anyone with past experience with this issue?

 

Ignition Control Module - in distributor under the rotor button - about $40 I think. It gets hot and stops working. Make sure you use the dielectric grease (should come inside package) as directed (on the plate), or else it'll stop working again very soon.

 

thanks, i will give that a try.

The funny thing is, the car starts fine, but slowly loses power until it won't make any power. Then the car has to sit. after a couple hours it starts, but runs poorly. let the car sit overnight...fires right up and runs as normal.

thinking about changing out the coil, plugs, wires, and ICM....

 

Well, the ICM gets hot and fails. You can have it tested, but it will pass the test since it's not getting hot on the tester like it does in the car.

Usually, years of lacking the dielectric grease (and thus low conductivity) means alot of resistance - resistance in electronics = heat build up.

 

Honestly? It sounds like an injector or three are going out. As the injector windings warm up, they get weaker. I would try a simple Ohm test on them and go from there. I had similar symptoms and found two dying injectors...

 

I figured since the car sat for 6 years off the road (previous owner), its worth updating the ignition items.

I am going to test the injectors tonight. Never done it before. I will look for any unusual numbers when i check the injectors.

thanks for the help...always looking for ideas. My first Camaro had a carb, the second a computer carb, now TPI. Why i am always having to learn something new!?

 

I started the ignition parts replacement (coil and ICM) but didn't finish yet. I did a cold check of the injectors but came back with 10 ohms on all 8. Need to do a hot check.

Check the TPS and got a reading of 0.4. When I tried to adjust it, I found that someone had stripped to lower screw head! Now a 2 minute adjustment is a major headache....

 

When you test the injectors don't forget to test them both hot and cold..

 

Had same problem, injectors...

If I remember right, the way it was found to be injectors was with a node light. It was really dim, but can't remember if it was just the few bad injectors, or if the issue put a draw on all of them...

 

OK, after checking the car two days later, it started, but ran rough, then died. So i hooked up a borrowed fuel gage. It read 13 psi....over and over.... I guess the 6 years in storage did not please the gas in the system. Looks like i have a fuel system rebuilt. The lines are rusty, the filter is old.... and who knows what is in the tank.

The previous owner said he just replaced the fuel pump.....not sure if i believe it but I am sure if he did, its pumping all the crap from the 6 years into the old lines.

Not looking forward to dropping the tank....

thanks to everyone for their suggestions.... I did replace the coil and ICM already. Anyone have other thoughts as to what else can go bad in 6 years of storage?

 

Mouse nest on top of manifold under plenum with some chewed FI wiring and vacuum lines... What I found in my car when I first got it.

 

I have already found quite a pill of those "helicopter spinners" that fall from trees under the plenum behind the runners.... How the heck did they get under the hood and under the plenum?

 

ok..i feel stupid..... NEVER trust the gas gage in a car you just bought. No fuel pressure because the gas was out of gas! Now I get 43 psi with the key in the on position. about 37 psi with the car running.

If i turn the car off, the fuel pressure bleeds to zero in about a second or two. If i jsut turn the key on and run the pump, then shut off, the pressure slowly bleeds down over the next 30 minutes (?) and keeps going. Injector bleeding by?

haven't taken the car out for drive since replacing the ignition components... don't have enough gas in the car to get to station..... coming soon.

 

I stand by my original assessment of dying injectors. Check them thoroughly before you replace them, though...I have been wrong before.

 

Any updates on this? Did you resolve your issue?

 

Curious how the story ends. I have similar problem but I don't notice any pinging it just die after about 5 miles. 3 hours later we repeat the process. Anyway, I've gotten a lot ofdifferent advice, however the dealer tested it and said "injectors" I got it home and put a ohm meter on the first one and got 5.9 ohms cold. I tested 4 others and they were in spec but differed by about 2 ohms. Anyway, since one is bad my son is in the process of replacing all. I'll update when we have a result this afternoon?

I was actually looking on the forum to see if it is nesseaary to pull both plenum runners off. The pasanger side looks a little more difficult so aside from changing the gasket was wanting to know if its ok to be lazy.