I have primarily two words:
INTAKE LEAKS

This is part of the back-to-basics program.

One poster already suggested checking all the injectors for leaks. Good idea.

Also -

Pull off the fat accordion hose from AMM to throttle body. Examine for leaks. Look hard. Part is under $15. They don't last forever. Grab decent spares from junkers when you get a chance.

I'm assuming you already checked all vacuum hoses.

That means check your pcv/flame trap system too. The fat vacuum hoses for that can get very hard over time, so could lose vacuum where they fit their connector nipples.

Hear a hiss when you shut off engine or pull away from a stop?
If so, likely the check valve is bad. 3/4-inch diam tapered cylinder thing, black and white, maybe 3-4" long with its fat tubing, sticking off top of intake manifold.

Throttle body gasket or intake manifold gasket. I've read here, you can test these and all other intake leak possibilities with an open-valve'd propane torch. RPM's go up when the propane gets sucked in through bad gasket or seal. I think a partially open torch valve is enough. Fully open torch would likely be hazardous.


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DAMHIK: Don't Ask Me How I Know - - - Sven: '89 245. 951 ECU, open-front airbox, E-fan, IPD sways, E-Codes, amber front corner reflectors. 500 mi/week commute. '89 245 #2 (wifemobile). '90 244 (spare, runs).