1994 Ford Ranger • 4 cylinder 4WD Manual • 185,536 miles

Probleming I am having is sometimes the engine idles fine then it just loses rpms, engine stumbles, some times stalls out. Do notice a smell like I'm burning racing fuel. Possably running rich. I only run 87 octane gas. I took it to a garage and had it hooked up to a monitor, O2 sensor was showing low voltage and MAF sensor voltage readings where all over the place. Replaced both, still same problems. It already has a new fuel pump, filter and ERG valve on it. I did the resistance and voltage test on the coolant sensor and they hwere with in specs. Went over all the vaccum lines and they are ok. Running out of options. Any ideas?
November 20, 2010.

Has the fuel pressure regulator been checked and monitered? Also, you have hit everything. Something has to be working one minute and not the next. The maf sensor has my attention. Now that it is replaced, do you still get the same readings from the new maf? If so, have you checked wiring for internal breaks?

Checked fuel pressure reg. 40 psi KOEO, 34 psi Engine idling, 40 psi Engine idling, vacc line disc at regulator. Checked resistance of air temp sensor and it is working fine. Coolant sensor working fine. I took the IAC Solinoid off and checked resistance. Resistance was within specs, however I noticed the plunger wasn't down. Seems like the spring is weak. I pushed the plunger down with a small screwdriver, applied power to the solinoid. You can here the solinoid activating but the plunger is not moving. Thinking this may be causing my rough idling problems?

Nov 20, 2010.
That would do it.