Ignition timing, 1997 4.0?

[2seater]

I guess I have sort of hijacked my own thread. If I should repost the following in a new thread??

Checked both coolant and intake air temp sensor readings before starting this morning. Both read 35degF. Five mile trip home from work, and the intake air remained in the 33-35 deg range, so no heating of the incoming air. I could not find any sort of preheat to the air cleaner or duct. After stopping and restart after ten minutes, intake air showed 44deg and cooled back down as started moving. Coolant temp came up gradually into the 190deg range, so temp. sensors look about right. Home thermometer indicated 34degF.

MAF at warm idle shows .5lb/min or a tiny bit more. I goosed it a bit while rolling and it jumped up into the 10lb/min range. Converting those numbers to grams/sec which I am more familiar with is approx. 4 gm/sec idle, and 75 gr/sec for moderate acceleration. Those figures seem reasonable when compared to the Buick which I have tested for many years. The idle reading is just slightly lower than the Buick 5gm/sec and the moderate power reading converts to about 99 hp. Maximum readings for a stock '90ish 165hp Buick 3800 is around 130 gr/sec or about 17lb/min if my conversion is reasonable. If I knew the voltage or frequency range for the MAF readings I could give it a whirl on the flowbench. GM uses frequency and I "think" Ford uses voltage?

The lean code on both banks comes up more frequently but is listed as a pending code? In any case, fuel pressure is 39 psi key on and 30 psi engine running. The pressure rises about 4 psi on shutdown over approx. five minutes, which I have seen many times before (warm trapped fuel). Manifold vacuum @ idle is 21 in.Hg and rock steady. I need to see about a software upgrade on my scanner to be able to see what the O2 sensors are actually doing? Could both be bad? No codes for the O2's. Are the intake manifold gaskets a problem child on this engine? I cannot find any vacuum leaks or bad hoses at this point.

 

[2seater]

This is an update on the operation of this engine: From watching the calculated load vs ignition timing, my gut feeling is it is working properly. Could probably use more timing in the cruise mode, but I have a different issue to pursue right now.

I found I have the most up to date software in my handheld scanner, but it won't show anything from the O2 sensors, also shows max. lean on the fuel trim. I also tried PC based software for OBD2 and I get the same result? All scanners work fine on an '05 Chrysler, so I don't believe it to be a software issue. I get no O2 codes only the two lean codes. The tech. people @ Auto Xray feel it is either a communication or PCM problem. The assumption is the fuel trims should go rich if the O2's are dead or if trying to correct a lean condition? Does anyone have luck reading the O2's and fuel trim? Opinions would be welcome.

 

[2seater]

For what it's worth, I found FORScan free software to use with an ELM327 cable that works well. Designed for OBD2 Fords. It turns out the O2's are working properly and the short term fuel trims dance back and forth. Interestingly, it even found the defect in the intermittent wipers.