86 Fiero GT chugs in 4th and 5th gear

[rakoczyg]

I am the orginial owner of a 86 Fiero GT. The car has 138k on it. Since last year I have been having a problem with it that no one so far has been able to solve. When the trans (manual transaxle) is in either 4th or 5th gear the engine chugs, (especially going up hill) just like one of the plugs is missing. This is an intermitt problem, does not happen all the time and sometimes very little, or sometimes really bad. Over the past 3 months I have put close to $1,000 into the GT at my local GM dealer to clear up the problem to no avail. This is what I have had done to it so far:
1. Tune up, new plugs, new dist cap and rotor
2. New plug wires
3. The dealer cleaned the throttle body
4. The dealer ran some type of GM cleaner through the engine to clean the injectors and valvles.
5. Replaced the fuel filter.
6. I found a leaky vacum hose and replaced it.
7. I have added Techron to the fuel on two occasions.

Has anyone out there have a clue what could be causing this? When this occurs the engine service light does not go on, so there are no codes for the dealer. Seems like the engine chugs more often when the car is running at full warm up than when cold..... but again not always. More going up hills than on the flat, but again not always.

Any help would be appreciated.

Jerry

 

[Oreif]

Did the dealer verify the fuel pressure under a load?
Another thing it could be is a weak ignition coil, bad ignition module, or the pick-up coil is corroded. To see if the pick-up coil is corroded, remove distributor cap and look at the bottom/middle of the distributor. There should be what looks like a coil of wire with a connector to the ignition module. It things look slightly corroded, You can remove the ignition module and clean the connections. If the coil of wire is really bad it may need replacing. This involves removing and disassembling the distributor.

Since it does it under extreme loading, It's most likely fuel or ignition related. Since you say it happens more after it's warmed up, My guess would be the ignition system.