Occams Razor and fuel pump pressure after priming?

[massacre]

You might have to check the pin outs, if they match then I think you should be fine

 

[timtimtimajim]

Can I swap the good ECU from my 93 5 speed (the X I'm having a problem with is an automatic)?

Yes you can swap the ECUs! The auto trans doesn’t have any control from the ECU. So no issues there and no trans codes either

 

[MrQ]

Yes you can swap the ECUs! The auto trans doesn’t have any control from the ECU. So no issues there and no trans codes either

That's not technically true. There is computer control of the tcc lockup and 3-4 shift. However you shouldn't have an issue with swapping the ECUs just for testing.

 

[timtimtimajim]

That's technically not true. There is computer control of the tcc lockup and 3-4 shift. However you shouldn't have an issue with swapping the ECUs just for testing.

Oh yah you’re right. I stand corrected! I knew after I posted that something didn’t sound right

 

[davidk]

Thanks, guys!

 

[davidk]

FIXED!!
I took the X to a mechanic who I imagine had a breakout box (I think that is what it is called) and he discovered the problem was no computer output telling the fuel injectors to pulse. The inputs were all fine. I guess that is why there were no fault codes, all sensors were working OK. I got a rebuilt computer for $135 from local auto parts store and the green X is back on the road.
The upside is this was ONE HECK of a learning experience, thanks to all who made suggestions. I learned more about the 1st Gen X engine management system in the last month than I had in the last 20 years.

 

[bammbamm]

Awesome! Glad to hear it's back up and running.

 

[MrQ]

Glad that got you back up and running. Those old EEC IV computers are cheap compared to the newer CANBUS units.

 

[davidk]

Aargh!!! The green X just failed the California smog check!! After a new computer, too, that's gratitude for you. The CEL came on under load (only) on the dyno, and the NOx were in the 700's both 15 and 25 mph. Still light pinging on hills. No CEL while driving. Hooked my code reader up: KOEO is 111, CM shows both 172 and 176 codes (HEGO sensor fault), KOER is 111.

Possibility the new computer is bad? Time to replace the cats or O2 sensor? Any and all opinions welcome!

 

[MrQ]

Off the top of my head, did you match the calibration on the old ECU with the new one? There were specific calibrations for California emissions, unless your truck was NOT originally bought in California.

Nonetheless, it is doubtful the new ECU is bad. You might have a vacuum leak somewhere. Its very rare to have both O2 sensors go out, I doubt they are bad.

 

[roscoe 0202]

check the timing if the nox is high and it pings i'd bet it is advanced 10 degrees with the pip pulled
roscoe

 

[davidk]

Off the top of my head, did you match the calibration on the old ECU with the new one? There were specific calibrations for California emissions, unless your truck was NOT originally bought in California.

Nonetheless, it is doubtful the new ECU is bad. You might have a vacuum leak somewhere. Its very rare to have both O2 sensors go out, I doubt they are bad.

You were correct Mr. Q. ECU is correct. The O2 sensors are good, EGR is good, cats are good. The problem was several holes on the underside of the plastic pipe that goes from MAF to the throttle body (probably from rubbing on cables), causing vacuum leak with run lean with really high nox readings. Holes patched with silicone - passed smog with low nox!