timelord

Hello,you have helped me out in the past,hope you can again,have a doozie of a problem.

Just finished rebuild of my 94 396,engine and tranny.

Car will run from 30 seconds to 1/2 hour but will eventualy die.

Car ran fine first night for a few minutes had no problems.

Were preparing for trip home went and had breakfast,car ran fine.Finished eating and were going to hit the road started up but shifted into reverse it died and would not restart,,,,,,,changed coil and ICM,,,,, still would not start,waiting for tow tried it and it lit,got in car and headed for garage only made it halfway,,,car started stuttering,all the needles(tach-fuel-alt-oil went crazy) . It restarted after a while and died the same way landed at the garage.Engine will rev to 6500 but when it gets stupid it starts seesawing 3000-3500 and no matter how much gas you give it it just continues stuttering and eventualy rpm,s keep going lower until it dies.

Tried 3 diff ECMs,2 diff.opti(Dynaspark and a regular),tried diff. MAF,rechecked every wire on top of the engine and replaced iffy ones.Undid and buffed every ground wire,body mount and bolt. Still dies,,,,

When it runs it is perfect,,,,,just cant figure out what is causing crazy needles and dying.

Any guesses or suggestions would be greatly appreciated!

Thank you!

Serge

Fatdog2

Sounds fuel related. Do you hear the fuel pump making the fuel pump noise that it does?What is the fuel pressure?These are things I picked up along the way.When it dies and you cannot restart did you press the accelerator to the floor and try to start and did it start?Could be a fuel pump relay I've been told if the car dies out.Do you have any codes.Sorry for the long post.Hope this helps.

timelord

The pump primes (255 gph) and works every time. When it dies you can stand on the MAF and nothing changes,no gas,half gas floored gas,,,,it is a crapshoot it decides if it starts or not. Quite a frustrarting qwirk !

Injuneer

Did you scan it for codes? Did you check the ground connections on the stud that holds the ICM to the head? When you changed the Opti, did you check both ends of the short Opti harness for damaged pins or corrosion? Does the connector at the Opti still have the security clip?

Fuel pump can heat soak. Is the 255 LPH (not gph?) pump a Walbro? There was a major problem with poor quality Chinese counterfeits of the Walbro.

Might be time for a data log using Scan9495. See "sticky" at top of "Computer Diagnostic....." forum.

timelord

Will ask Rick to check these things,,,,, he is now changing injectors and fuel filter.was reading the 94 firebird no start and will check your solutions from pages 2 and 3 (CLT etc.).

Redid every ground on the car,wires,nuts,bolts and body.

the 255 is a walbro that has been there for about 6-8 years( was that in counterfit timeframe)

Am forwarding this to him,he will be better able to answer!

Thank you sir,,,will be back with answers soon I hope.

timelord

Changed injector and fuel pump,started up great and idled perfectly without throttle ,,,,,for 3 minutes !!!!!!!!!!1

He sent me a video but cant figure out how to upload it to here from my computer.

GaryDoug

With the wildly fluctuating gauges, it sounds like an electrical problem. It's possible you have an alternator that is shorting out after a few minutes. Try running with the alternator disconnected.

timelord

Not alternator.
Still starts hard and wouldn't stay running.
It kicked hard back on the starter 1 time.

What ever it means it does it as soon as it starts to warm up. It acts like the timing is changing causing it to stall. It won't start untill it cools all the way down.

Fatdog2

Did the person replacing the ICM check it when it was hot?Also was heat sink grease used and not die electric grease?Sorry for all the questions but some members would pull the ICM and take it to autozone (cold) and have it checked and it checked fine.But when hot it would crap out.Also gobbs of heat sink greese has to be used or do the Icm mod On Shoebox's site like I did but I still used gobbs of the stuff.Very interesting thread.My02.

timelord

The Autozones and others either dont have machine for ICM anymore or have one that doesn't work. Tried 2 diff. ICMs. He has found a scanner and will be doing code scans shortly. Gobbs of grease used(not sure which).

Will let you know as soon as I hear from him.