Chevy & GMC Vans

Hi!

I started to have this weird problem with my van. After I got all the fuel lines and gas tank installed (also replaced the fuel pump and filter) the engine started to kind of choke on fast full throttle rev up but worked fine when slowly increased the throttle. Also the SES light came on, but no codes except 12. After that I took both ECM fuses off so it resets and then engine ran just fine, no problems.

Since the last time I turned my engine running yesterday and same problem but with backfiring to intake. SES light lighted on and tried to get codes again. This time It gave codes 12 and 51 (PROM problem). After couple of re-ignitions SES light went off and engine ran fine, but after a while engine ran like before and SES light came on for a while and then off. Couple of times the SES light starter flashing for while and went off and by that time engine idle changed bit higher.

Today I fired up an engine again and ran again just fine (probably because of reset because the battery was disconnected) but started this weird functioning again after one test drive. And with backfire also and once again ECM gave only code 12. Well after couple cups of coffee and strong words gave it a new try. Well this time result was the same but much less backfiring AND ECM wont give any codes, not even this 12 what it should.

Also some backgrounds. There is new air filter and O2 sensor (about ½year old) and new vacuum lines from vacuum tank to engine fitting and to cruise control servo.
Also new fuel lines, fuel pump and fuel filter. Before I changed the pump and lines the van have been on garage about half of year without usage.

So question is, where should I start?

I also added a video to clarify what I mean.
http://www.youtube.com/watch?v=mY0Iux5o ... e=youtu.be

I would be really thankful for fast responses, because I need to get this van running soon.

EDIT: Model is 1990 and engine is 4.3L V6

Pull the O2 sensor before the cat and drive it.

If it improves, then I would look at the cat.

I cleaned all the connections which I could spot today and tried again. Now it died while idling and gave a code 43. Turned ignition off for a while and and then back on. The code was still there. So it tells that the Electronic Spark Control was failing?

I'm shaking my head.The wandering codes are troubling.Find and try cleaning all the grounds you can find.For now make that your main focus.The TPS could have carbon build up that could cause this issue too.I am assuming it is a TBI or it should be one..

It is TBI, VIN Z. I checked TPS today and it gave nice and steady voltages for whole range, no notches or peaks. When idling, voltage was 0,5V and on WOT 4,7V, and as long as I have checked forums those voltages should be fine. Also today during Idling in Park motor suddenly died and gave code 43. Checked also the injectors and those were spaying fine, no pauses or anything when pushed pedal to the floor. But one thing i noticed was that the place under the air cleaner, near where the fuel lines meets injectors had massive amount of oily soot/dirt, probably from the breather line. I cleaned most of it but didn't help and actually the code 43 was appeared after the clean up. Can you tell me that is the fuel pump running all the time when engine is running? Because if it shut down even for a while there might be relay problem.