Ugh. Replacing the MAFS did nothing. I also cleaned out the throttle body - nothing changed. The search goes on. I guess I'll be diving into the world of testing sensors at this point. Life was so much simpler with the carburetor. Any sensors stand out as the first to look at?

 

***SOLVED***
Went back in to clean and re-gap sparkplugs. #4 gap was zero gap!!! In the process of testing the compression on #4, I initially left the extender thing in and that must have crushed the spark plug. Wow - amateur move. Problem is I don't know exactly what fixed the problem now. I will put the old MAFS in just to see if my $72 was necessary.

 

As I remember your problem preceded your compression test when the plug got damaged. But yes by all means verify the MAFS performance and post the results.

 

I re-installed the original mass airflow sensor (MAFS), and the car runs fine with it as well. I left the original in. My original problem was not the MAFS. I'll either sell this extra one (which I *know* works) or I'll save it for the next time I have running issues. It is the original Bosch part.

I can also say that the car runs better than it had previous to the recent engine missing problem. So not only did I fix the problem, but I improved things. Here is my list of updates

1] Replaced spark plug wires, rotor, and distributor cap. The rotor and distributor cap had never been changed (200,000 miles). The removed distributor cap looked fine - looked brand new in fact. The removed rotor looked terrible - the contact end was wearing through. I was very surprised that the new coil wire and rotor didn't solve the problem. It might have - but again by this point the compression tester extension was lodged in #4 and the plug end was squashed (rookie mistake).

2] I cleaned the fuel injectors - probably the first time in this car's history (we bought it with 55,000 miles back in 1999). This was a DIY project. I rigged up a series of tubes and hoses to allow the straw from the carb cleaner to pressurize the injector without leaking and then used a 12V car battery to power the injector. I recall that the carb cleaner did not blow through initially for third one I did as if it were clogged. I let the carb cleaner soak for a while and then tried again and it pushed through. I was again surprised that this action did not solve the problem (but who knows since the plug was still squashed to the extension).

3] I sprayed the MAFS with the appropriate solvent - but honestly it wasn't dirty. This probably did nothing.

4] I cleaned out the throttle body probably for the first time ever. It had plenty of gunk along the walls, and those two little holes may have been plugged up.

5] I readjusted the timing belt by one rib on the cam pulley. It had been very loose to the right of that pulley and may have slipped. Then I re-tensioned the timing belt.

So one of these 5 steps solved my poor running problem. One or more of the other steps served to improve engine performance to the point that it runs like a new car again. Next I plan to change the timing belt and pinpoint an oil leak. I will start a new thread on the oil leak. I also plan to replace all of the small vacuum hoses - several appear very worn and brittle. Then with any luck I will enjoy another decade of or more of trouble free driving.

Thanks everyone, especially lev, for providing advice along the way.

 

Keep that MAFS for the future, now you have a known good one! And, good that you caught up on the motor maintenance, 200k on a cap and rotor is a bit much... Hard to say what was causing problems but you had a few candidates, a bad rotor would be my first guess.

When is the last time you changed the ATF, PS, brake fluid? something tells me they may need attention too... Cheap preventive maintenance now that you are at it.

 

Brake fluid was flushed last spring when I replaced all rotors, calipers, soft lines, and shoes. The red fluids are probably overdo. I've done them but not recently. Thanks for the reminder.