'91 454 TBI falls on face on acceleration when Hot

vacuumbed · July 19, 2023

Hi everyone,

I have a 1991 P30 which is an RV chassis with only 68K miles, it has the 454 TBI. I am baffled by this issue.

When cold, starts and runs beautifully, a computer controlled high idle upon cold start and then it gently slows down to regular idle speed and idles very smooth. When I begin driving it is great until it reaches full operating temperature and then loses all power upon low speed driving. However, if I floor it then it will take off and go. But until then, it feels like someone put a towel over the air intake drowing it out. That's just the impression that I get while trying to accelerate.

First thing I replaced, was the fuel filter. Then a new distributor, and the cap/rotor, and the wires and plugs. I used AC/Delco plugs. Then I rebuilt the TBI, replaced the TPS, MAP sensor, and the computer temp sensor, which is the one on the front of the intake manifold. No change.

I have thought to check the fuel pressure, but I don't have a guage. Then this happened. I was out driving it and it was acting up. I pulled in to the car wash bay with a hot engine, and pressure washed the engine really good, wich also cooled it down a bit by the time I was done. Drove it out of the car wash and it ran great!!! The thing must like to be clean I guess LOL.

When it acts up, the temp guage reads around 210 degrees. I am thinking this has to be something simple. It can't be a plugged CAT or a fuel pressure problem, because these items would act up on a cold engine I would think. Could this be a timing issue? I have not checked the timing yet.

Thank you in advance for helping me.