Loses power at high speeds

[atvbuddy]

I have a 1988 Corolla LE that loses power and stutters at speeds in excess of 60mph. I have a feeling a may be a fuel pump issue but I am not sure. Any suggestions?

[Evo_lucian]

Originally Posted by atvbuddy

I have a 1988 Corolla LE that loses power and stutters at speeds in excess of 60mph. I have a feeling a may be a fuel pump issue but I am not sure. Any suggestions?

you gonna have to be alot more detailed if someone is gonna help you, does it sputter during accleration or decellaration ? High or low throttle input ? Have you checked the gas filter, air filter etc ?

[Frozentide]

Originally Posted by Evo_lucian

you gonna have to be alot more detailed if someone is gonna help you, does it sputter during accleration or decellaration ? High or low throttle input ? Have you checked the gas filter, air filter etc ?

I agree, a bit more info is needed. Too many variables to be able to point you in the right direction.

My advice, try and figure out exactly what is happening when and why, even if you dont know or understand exactly what is happening, and then ppl on here will be able to try and help better.

[eage8]

I'm going to go with... your car only has 90hp

[bcp477]

Fuel starvation, with a carbed engine, is definitely the most likely cause for this issue. Low fuel pressure, leading to a low fuel level in the carb float bowl, is very often the cause. So, you may well be on the right track here (a bad fuel pump would cause this). However, a clogged fuel line, clogged filter, ignition problem, dirty/clogged carb jets (especially in the secondary)....etc., could in fact be the reason, instead. So, you need to examine all of these possibilities, before a final diagnosis can be made.

[atvbuddy]

I recently replaced the fuel filter, spark plugs, and air filter. The problem occurs when I have been at a speed of more than 60 for more than a minute. It does not expirence any problems accelerating up to this speed and when it stutters it seems to recover if I let up on the throttle.
I am fairly inexpirenced in working with carbs. Is there a way to test for low fuel pressure?

[90 GP]

Check vac hoses for leaks. In particular the vac hoses that attach to the advance unit on distributor. Also check the vac hoses at EGR valve .

[90 GP]

Could also be a clogged catalytic converter.

[bcp477]

It is most likely not a vacuum leak, as vac leaks usually won't create much a driveability issue much above idle rpms. If the ignition is not advancing as it should....it could cause such an issue....but, probably not also, as the car is running fine UP TO 60 (and the problem only exhibits at sustained speeds...after a period of time). As described, fuel starvation is certainly the most likely cause. Since you changed the fuel filter already...and the car runs fine at lower, variable speeds....I really am suspicious of the fuel pump (fuel pressure). You can plumb a pressure tester into the fuel line, after the pump, but it's not worth the trouble, as pressure for a carbed engine should only be 3 - 4 psi. I would look hard at the fuel pump, check for leaks, etc.....and after that, I would be suspect of the carb itself (a carb overhaul might be in order). I am pretty confident that the problem lies in that direction. The fuel pump, I believe, is a simple mechanical one....so it should be cheap. As part of checking the pump, I would remove it and be sure that it appears OK. This is easy to do. If you replace the pump....and the problem persists.....then I would expect that the problem lies in the carb itself.

[Donald]

Take the fuel filler cap off and try it again. A clogged vent will give the same symptoms.
If it works fine with the cap off, then you know it is a vent.
If it is a vent, replace the cap and try again, if it is not the cap, it could be the charcoal canister.