keet

So I just bought a 1990 C4 coupe with auto trans and about 40k miles on it. The car ran fine on the test drive and fine while I drove around town today, about 20 miles or so, getting on it every now and then. On the last bit of my drive I took it on the freeway, when I floored it it accelerated a bit then sputtered and popped and wouldn't accelerate any more. If I slightly gave it some gas it would accelerate slowly but if I gave a little more pedal it would hesitate and sputter. Any thoughts???

Yukon Corleone

Welcome

I have a 1990 also. My guess is either the fuel pump or injectors, both of which I replaced. The injectors were replaced in 2000 and the fuel pump in 2007 and I have owned my 1990 since new.

Tod Stiles

You might want to try a fuel filter first. It's one of those things that people don't replace and then the car is starved for fuel under acceleration.

Welcome to the forum!

aklim

Check your fuel and spark. That or toss parts and hope to get lucky before you go broke.

MrJoelieC

Did you put 87 gas in? or bad gas?

I would do as others have said... go as empty as the tank as you can safely... fill with Premium and throw a can of dry gas and fuel injector cleaner in but even before that I might Start with the Fuel filter.... then y may need to check fuel pressure situation if it's only got 40k miles it may have been sitting a lot and there may be a lot of gum in the tank that is knocking loose and clogging the filter and injectors...

aklim

I'm not sure if 87 will do that. Bad gas might. I can run 87 in my car and have in a pinch when there is little else there but the amount of retard isn't that much.

If he wants to pull the pump out he can empty the tank. I'd skip the snake oils that are "cleaner in a can". IF the gas is suspect, I'm not sure I would want to hotwire the pump and have it pump all the fuel out unless it is a little bit left. Gas and a battery nearby I just don't like.

MrJoelieC

Meh, You are probably right on the 87...

Oh Come on... Sometimes I like testing the the effects of Gasoline...And Fire.... You Know... For science... LOL

aklim

Yesterday, I saw a plume of black smoke on the highway near my ramp. Got on the off ramp and saw that a minivan was in flames, cops were stopping traffic and fire trucks were arriving. This was no more than 100 feet from a gas station. If the fire had gotten more intense, I'd have driven away. Instead, I pulled into the gas station to watch.

kael

Uh, ethanol versus not maybe? Forget what year that changed.

I'd check fuel pressure that the fuel rail first, make sure to flip the ignition more than once to get max pressure. If it's low, likely the pump, not the filter.

Could check the fuel flow rate, might be easier to replace the filter.

aklim

Doubtful unless maybe E85.

Won't work. At least on mine. First flip pressurization, yes. Afterwards it has to wait for a bit before it does pressurization again.

If it is old, just replace.

Nokones

Could also be the fuel regulator. If it is the fuel regulator, check the oil to make sure there is no gas in the crankcase. In any case, you need to check the fuel pressure and it needs to hold without the engine running. If it drops off than it is the fuel system.

aklim

Could be but until he does fuel pressure and spark check we are guaranteed to be guessing or throwing parts.

Nokones

Agree. If the pressure does hold, I would replace the ignition module and wires. The plus side in throwing parts at it is that you will have all those new parts that hopefully won't fail next in the future.

aklim

Had a bad ignition module out of the box. Problem is that now you introduced new variables. Also it is a bad and expensive habit

Nokones

Thank God he has a L98 and not a LT1 with an Opti-Spark. It should be easy to figure out and work on it.

kael

My '87 cannot have ethanol. Not the E85 stuff, can't have just plain mix. I learned the hard way.

This didn't change until later years.

aklim

Injectors are a possibility but what else screwed up?

kael

ECM/MEMCAL, other bits that don't expect the changes associated with ethanol. May be some plastics or other materials that breakdown with long exposure.

For mine, less than a couple of gallons in, engine was running terrible, if at all.

I'm in Iowa, ethanol gas is everywhere, and worse, cheapest.

aklim

Thing is, there isn't much change. We have 93 octane here and most places except a marina will have up to 10%. Fuel runs through the lines but the only thing is that on my 91, nothing seemed to change. I haven't had enough time with 100% gas to really know if there is a slight MPG change but I suspect it will since the energy content is slightly different. Why it does that with your car, I honestly don't know but am now curious. Your original injectors are Multec and that I can understand since it eats at the coils.

keet

UPDATE:
Ok, i added cleaner to the fuel, changed the plugs, wires, ignition module, and fuel filter, still wants to stall when giving it gas. Starts fine, a bit of a rough idle (just a little). Used one of those automotive stethoscopes on the injectors, all sounded the same/even (doesn't mean they aren't clogged though). I guess the next steps are checking the fuel pressure? Any other suggestions?


Thanks!