dgkinba

I got my triple black 1994 LT1 about 1 1/2 years ago. It has 133k miles. The previous owner indicated a complete? tuneup was performed prior to my purchase. It has flowmaster exhaust and runs and sounds like a real beast. But.....about a year ago on rare occasion it would start running rough a couple of minutes after starting while still as slow speeds. Hitting the accellerator would cause the roughness to go away. About a month ago, it got worse and on my way home it stalled twice at stop signs while still cold. Now, it will do the rough running routine almost every time while still warming up. Or rare occasion, it will hit a dead zone for just an instant at slow running speeds. This morning, for the first time it died when I was almost to work so it was all warmed up. At first it would not start, not even hit at all. I cranked for a bit. Scratched my head, did the key on, key off, key on, key off, key on, key off, cranked a little more and it started.

Does this sound like a fuel or electrical problem? Any suggestions?

formul89

I would replace the fuel pump relay first. That seems to be the most common place to start.

Get a good fuel pressure guage and check pressure when engine is stone cold at the first key turn. It should spike to 38-42psi. Start the engine and let it idle and watch the pressure after the engine warms up. Then, remove the vacuum tube from the FP regulator and see if the pressur goes up.

Replace the fuel filter also. If it is plugged up, that will cause a fuel pressure issue.

Next would be the fuel pump itself.

dgkinba

Thanks. I'll try the relay and filter first this weekend and let you know.

onedef92

Could be a bad plug wire(s) or a coil wire, too. Open the hood at night or in a darkened garage, then pull the underhood lamp fuse. Look for telltale electrical arcing along the wires.

RogerZ06

I had hose cracked near the throttle body was giving me same symptoms.

MK 82

Finish the troubleshooting before you change the relay unless you like buying parts you may not need.

formul89

The relay costs $9.50 at NAPA and an hour to put in. Just change it because it will go sooner or later anyways.

Don't be cheap.

Oh, and try replacing the courtesy light bulb in the door. That might work too.

theadmiral94

In addition to the above suggestions,

check/clean MAF (only use MAF cleaner, other products may damage), especially if you have a oil-soaked air filter (e.g. K&N).

check the O2 sensors.

check ground points (e.g. driver side bell-housing).

HOWSER

I had similar issues with both plug wires and a cracked plug in the past.

dgkinba

I picked up a few parts and the man behind the counter said my problem could possible be the throttle position sensor. Symptoms have usually shown up when my foot was off the pedal or at very slow speed. I've looked at other threads and it appears to be very straight forward. Is the TPS a possibility and are there any tricks to changing one on a 94 LT1?

NEVRL8T

Any codes?

dgkinba

Nope, no codes. Check Engine light came on once 6 months ago but went off in a short period of time. Guess it might have recorded something then, but i haven't had it hooked up to check.

formul89

Since it is non-adjustable, take the old one off and put the new one on. Pretty easy and the PCM will do the rest.

Try unplugging the Mass Air Flow sensor and drive it around the block. IF it runs better unplugged, that might be your problem. Clean it first and replace if that doesn't work.

dgkinba

I bought the fuel pump relay and fuel filter. I had to take the relay back once I got the old one out, wrong fit. Installed relay, looked at filter and said "oh my gosh" and decided to have that done by a mechanic. Anyway, after installing the relay I have now driven it 4 times, not a sputter. The simle $9 relay seems to have solved the problem. Kudos to "formul89" who nailed the problem on the first reply. I didn't mess with anything else, so thanks to formul89 for solving my problem! I guess i was fortunate as the list of potential problems continued to grow. Thanks to all who responded, I'll keep the list in case the problem comes back.

formul89

Excellent! Glad it worked!

pcolt94

Good that your fixed and can’t argue with success. But I am troubled by the facts and events as I understand them. One of the main functions in life of the fuel pump relay is to pressurize the fuel system before cranking. But once it starts and oil pressure comes up, the pressure switch for the fuel pump closes and puts 12 volts to the fuel pump. The relay them becomes secondary to engine run. Even with no relay installed in car, the engine will still start with additional cranking.

I can’t see how the relay could cause a runability problem or relate to these symptoms when it is not even necessary for normal engine operation provided all other systems are operating properly. It seems like the original problem could be still hiding in the dark. Just my opinion to keep an open mind about the situation.

formul89

I was thinking the same thing also, but I was having the same exact problems even with a brand new fuel pump, fuel filter and switch in my '94. Replaced the fuel pump relay and the starting problems are gone.

In this case though, I am leaning towards the fuel filter as being the culprit because the OP replaced that also and the car had driveability problems.

MK 82

Don't confuse him with facts. Of course it was the relay. He fixed his window motor by changing the courtesy light bulb.

formul89

Enough.

dgkinba

Ok, so maybe the relay is not the final answer, but I've driven the baby every day since I replaced the relay and not a single sputter or shutdown. Prior to that, it had acted up every day for a week. The guy I know at Autozone said he couldn't believe it was the relay either. He thought it might be the throttle position sensor. At any rate, it it comes up again, I have many ideas to search out.

Since there is some humor involved, my left rear turn signal light burned out yesterday. Maybe that was the problem. I had to take the courtesy light bulb back.