NightHawk

Well, I am really stumped on this problem with my '87 NA. Hope somebody out there has some ideas. I have about 2500 miles on since I rebuilt my motor. It has been running great since. Last Monday, it ran kinda rough to work and home. It was the coldest day of the year at about 10 degrees. I thought I had the timing advanced too far and was getting detonation. I tried adjusting timing, but no improvement. It would run at low throttle, but choke when you crack the throttle. Now it has gotten worse and will only stay running for a few seconds. I have done a compression check, and both rotors are testing about 80 to 85 PSI. I replaced the air flow sensor and the entire throttle body and solenoids. Runs exactly the same. Fual pressure checks OK, and I even switched fuel thinking maybe it was bad. I am out of ideas????????? Can anyone think of anything I might be missing?? Thanks for any ideas!

darkwaveboi

Your only running 80-85psi on a 2500 mile rebuilt engine?

Somethings wrong here...Did you rebuild it yourself?

Did the temp gauge reach operating temps while it was running? The car will bog/feel weird if you try to floor it before it is completely warmed up.

NightHawk

Yes, I rebuilt it myself. It has been running very strong since. My Haynes manual says 85 PSI is "normal".????? The engine was up to operating temperature and I wasn't really flooring it. Just trying to rev past 2500 RPM.

darkwaveboi

Have you checked your cat converters? What mods do you have?

Usually rebuilt engines run good strong 110-120+psi when professionally rebuilt. But i cant down on nothin, you got ur hands dirty

rxseven

85psi is the minimum spec below which a rebuild is recommended. I think you might have to open the engine back up and see what happened.

NightHawk

The only mods I have are: removed aux. port valves, polished intake ports, and cone filter on intake. You mentioned the cat converters.?????? I hadn't thought of that. Were you thinking that rust came off the inside of pipes and plugged the cats???? That kinda makes sense based on how it started running poor and then got worse over a short time. It definitely is bahaving like it can't exhaust. The only other thing I could come-up with would be low flow on primary injectors, but it seems odd that those would not just fail suddenly????

NightHawk

Well, Darkwaveboi is the man! You hit it on the head. I cracked the exhaust off the manifold and fired it up. SHE RUNS SWEET again! I took the midpipe section out and the precat insides had broken loose and plugged. Well, I can tell you that those aren't going back in there! Lucky for me, we don't have to pass inspection here. Thanks for the help guys!!!!!!!!