Re: 90 ZR-1 running bad.
 

Take a look at this thread (thanks to Michael R)

http://www.zr1.net/forum/showthread....m+pull+michael

Re: 90 ZR-1 running bad.
 

Sorry to sound like I can't make up my mind, but I'm asking myself if the injectors could leak after they get hot? That would make a hot restart problematic, a flooded motor doesn't run well.

Stupid question, how long between fuel filter changes? I'm thinking that the coils didn't fail yet due to alcohol. I'm looking for something that would make a car run badly after a hot restart.

Any other electrical component that would suffer from heat exposure, like injector and or ignition coils, would become progressively worse over time. This doesn't seem to be supported by your description of your car's symptoms.

If you have a scanner I'd hook it up and do a hot restart, maybe it would tell you something. Or after a hot restart and the miss returns stand behind the car and smell the exhaust. If it smells lean, not enough fuel, injector coils are top on my list. If it smells rich, something is not lighting the fire ( ignition system has to be the suspect?) or something is providing too much fuel ( dirt in the fuel system?).:o

:cheers:
Tom

Re: 90 ZR-1 running bad.
 

First: Are you getting an SES light? Are there any stored codes? If so, make note of them, disconnect the battery for a minute or two, then drive the care again to duplicate the problem. Recheck for stored codes. Research stored codes & proceed.

Given that it misses badly after a hot re-start, after eliminating "air" you should be able to identify whether "spark" or "fuel" with no special tools in about 30 min.

The basics:

1. Engine running, pull each plug wire. Noticable difference, cylinder fire OK. No difference, miss cylinder identified.

2. Engine off, pull 1 plug wire, insert spare plug, lay on plenum. Start engine, gradually increase gap from plug to plenum (or engine ground). Good spark = blue 3/4" to 1" jump. Weak spark = orange. Weak spark either wire or coil. DO this procedure for each cylinder. If 2 dead cylinders & they are "paired" cylinders, definitely bad coil.

3. If steps 1 & 2 check OK, high probability of fuel injector on cylinder with no noticable change in miss as identified in step 1. Given it's a 90 model and the propensity of injector failures in 90~92 LT5's, I would replace the entire set. Be sure to replace all fuel system o-ring seals while you're in there. Those seals are now over 20 years old. All fuel injector upper and secondary lower o-ring seals (should be Viton) come with new injectors. You will need the lower primary seals, fuel feed & return block seals & the fuel rail pipe & regulator seals.

Here's a tech reference for the lower primary seal replacement.
http://jerrysgaskets.com/store2/root...roducts_id=446

In any event, replace wire #2 at minimum. I looked in my spare wire pile but do not have a #2. Sorry.

Re: 90 ZR-1 running bad.
 

Are the primary and secondary injectors (RC) the same injector? Every injector that I have researched has a separate part # for the primary and secondary. I'm going to try to use my employment here at Tony Stewart Racing to get a reasonable deal on a full set of injectors.:)

Re: 90 ZR-1 running bad.
 

The car is rebelling from under use, and not enough 7k RPM blasts!
;)

More than likely injector as most have concurred. I wouldn't suspect any ignition problem with that low of miles, but it is always possible. Only sure way to tell is to put it on an engine analyzer. I'd change the plugs, and you can probably tell which one is not firing well, and then you can just check that one ignition path to make sure it is getting spark to the plug. If it is getting nice hot spark, then injector more than likely. I believe the primary and secondary injectors are always different across manufacturers
:thumbsup:

Re: 90 ZR-1 running bad.
 

Actually, we have a variety of sources for injectors here at TSR, but I'm not sure if they would have a suitable injector. FAST is a company that has injectors for the ZR-1. Has anyone tried them?

Re: 90 ZR-1 running bad.
 

Just ordered injectors from John Banner at FIC. We'll see what happens. Need to send e-mail to get gasgets from Jerry?

Vapor lock???
 

I'm dubious w/ regard to vapor lock for a couple reasons:

1) Vapor locking, in the sense of the fuel pump loosing its prime, pretty much went away with in-tank fuel pumps and hot fuel return (to the tank) lines (since deemed unecessary and dropped from use on the LSx engines, no?)
2) But, even if you're referring to vapor that might form in a heat-soak situation near the exhaust, the Reid vapor pressure at 100*F is only around 7#. Tho vapor pressure is not linear; exponental with a change in temperature, in fact. Not sure what it is at say 200*, but I doubt it is anywhere near normal pressure when the switch is turned on. At 45-50 psi (switch turned back on) I'm betting any vapor resulting from heat and pressure leak-down would immediately revert to a liquid.

I'm going to keep looking for some difinitive answer to the vapor pressure question, but I'm betting it is electronics failure (injector coils?) as a function of heat soak.

Just my 2 cents...

P.

Re: 90 ZR-1 running bad.
 

I agree with you Paul. The info you wrote about is why I can't ever recall/or heard of a "vapor lock" in a modern day electronic fuel injected engine. Don't have any real engineering data to dispell the possibility of vapor lock however.

Re: 90 ZR-1 running bad.
 

jerry is good people, met him in BG a few years ago. can't think of another person I'd order from other then him