Hello to this august group. I hope some of the brillant mechanically-inclined minds that no doubt reside here can help me. I am trying to revive a 91 NA I bought two months ago. It will run and accelerate well at any throttle position when first started up to about a half mile. Then it starts stumbling. A quarter throttle will almost kill the engine after it has run for a minute or two under load. The problem is not noticeable when the car is running in neutral.

The car speed can be built up by feather throttling the engine but any more gas than that and the engine loses rpms and power. The compression tests okay. A timing light makes the plugs look like they are firing well.

My 30-year old fuel pressure gauge only goes to 15 psi so I can't test that yet without another investment. The exhaust system has no converter and new low restriction mufflers.

Anyone know what I should look at next? None of the service manual's suggestions make sense to me, given the wailing acceleration the car will produce for the first minnute or two. I'm baffled.

 

i have the same problem and i cant figure it out when it is cold and not under load it will run fine and idle fine but after it warms up and goes under load it boggs down to the point of almost stalling if you find out what causes this let me know

 

Presumably you have checked/replaced the really easy things...fuel filter( both the main and the pumpsock in the tank) and soft lines?

 

what about temperature sensitive things.. like the coolant temp sensor? find the resistance values for it, and check them constantly as it gets warmer, compare.
you could also just unhook it and see what happens.

 

Whats probably happening is that its running like crap when it goes into closed loop. When you first start your car and its cold, it doesn't use the O2 sensor and the car runs off a pre-set map, thats why your car runs ok when cold.

Maybe the o2 sensor is a good place to start?