MPFit

Back together, no fix. The vacuum line I replaced cleaned both EGR codes AND Thermactor codes. However, Engine- once warm- doesn’t run right. I may replace Tastat next. Code I got while Engine was cool and warm was 21: ECT out of range. I’ll replace ECT (which is only a few months old) and Tstat (not sure of age). The engine compartment is extremely hot, and the Fuel Pump and EEC relays are very hot to the touch. If sputters, stalls, and bogs are my symptoms- while hot. I hear a snap/click in the exhaust when it sputters.. backfire? Preignition? Not sure.. will replace O2 Sensor once tested- will look for a Multimeter that measures Hz so I can test the MAP sensor also..

MPFit

Ok, another update; It now happens while cold.
it starts shuddering from startup now. This all began after a car wash. I thought it was water on connector- but they would have dried by now. Then thought water in fuel but I’ve ran two tanks so far idling to test at temperature.
Codes recieved last; 12 and 21.
12- Can’t control idle (High)
21- ECT voltage out of range.
i tested ECT Harness and it was good will test Sensor asap.
dont know where to go with High Idle. I pulled Idle Control sensor and it wanted to stall assuming it’s working- and checked that it is clean.

raski

Replace the thermostat and go from there. If you are not reaching normal operating temperature within a certain time period, you will set a code for the ECT. If you suspect the CAT, you can verify that easily with a vacuum gauge. Don't have one? Every auto DIY'er should have one.

MPFit

Thanks. As mentioned earlier vacuum pressure with guage tested normal (22mmhg give or take 2-3 mug). Upon throttle it dropped and recovered quickly. Cats seems like it fits as the truck was bought without an ECT sensor (or Spout). So I assume it had been running rich. I changed plugs and they didn’t indicate much so it may have not been run until the decided to sell it. Exhaust is original, the O2 Sensor when pulled is sooty- not gunked just sooty. I’ll pull plugs to see how they look. Tested ECT this morning at complete cold and it tested fine- values seemed correct regarding temp. Will warm up engine and retest. O2 is only sensor I haven’t swapped yet. I’m kind of running out of ideas honestly. I have to assume fuel or electrical.. maybe coil? But it seems like it’s getting worse at cold also. Codes are almost all cleared I undid negative lead this morning and will reconnect, warm up and retest for something to go on..

MPFit

Also, as it started as a problem when warm-

MPFit

raski

If it now acts up cold, I doubt the O2 sensor is causing it. It isn't really in the equation for a few minutes after a cold start. If your vacuum quickly goes back up after goosing it, your cat is fine. Pull the battery neg off to reset. If you can verify you are running at around 195 degrees and you still get an ECT error, you need to verify proper sensor resistance at 195. Look for faulty sensor, plug or wiring.

One thing might be worth a look and won't cost anything to do. The processors of that time and its current age had issues with the capacitors . I believe its behind the passenger kick panel. If you see bulging, leaky capacitors inside, that's a problem. If you investigate, disconnect the battery first. You could also check your resistance of the dist. pickup coil and the primary and secondary windings of the ign.coil.

MPFit

Thanks for the direction. The ECU is good- it’s actually a replaced one. Original had leaked capacitors so I found an exact match and got it- no capacitor leak on this one at least. I will take a look at resistance on coil - any tips where to find info on that test procedure? I’ll recheck ECU to verify no corrosion but it’s been in truck for a few weeks (I had issue with no codes being thrown / read and went to replace it)

MPFit

Resistance checked normal - 1.2ohm between the metal on the connector and 8500 between ignition coil plug spike and positive of the metal.. ECU looks fine.
ive heard these can fail when hot however- should I heat up the engine and retake to verify it’s not dying?

raski

There's been so many updates here. Can you state what codes are you presently getting after pulling off the negative cable a while to reset. Check KOEO AND KOER codes when engine is warmed up and go from there.