B2600i fuel or spark problem... and where?

Howdy, i'm a new member, but ive found lots of good advice here in the past, this time i could not find a close duplicate of my problem. I have a 1991 B2600i 4x4 ext cab. Ran fine a week ago, always does right?

The Problems:
Started it up, and it dies a second or two later, start it up again right away, and it stays running at idle just fine. If you wait about 10 seconds, it will repeat and die and then idle fine the second start. The Other problem, started same time as this, under hard throttle in netural from idle to WOT it bogs/stutters very hard and acts like it going to die but it doesn't. Will randomly/repeatably stutter several times when driving down the road, under acceleration will stutter randomly and cut out for a split second over and over again like my spark or fuel is cutting out.

Whats been done so far:
New spark plugs, replaced the bad capacitor in the ECU, made sure plug wires were connected properly and corrosion free, put seafoam in it, flushed/changed oil/filter.

What i'm gonna do:
Bench test MAF sensor, 02 sensor and TP sensor, check out the coil, Check fuel pressure.


Questions:
Anybody know whats going on? Or have highly suspect parts?
Anyone have a ohm resistance rating for the 02, or do i have to test by the book while running/back probe it for voltage?
Also, how do i fix my sticky/stuck tachometer?

More B2600i knowledge at MazdaTrucking.com

You can try going here: http://www.troublecodes.net/

and see if you can find some help there.

Figured it out, Thanks for the replies. Guess what Fellas? It was the ECU! Curse of the b2600i. Swaped my dads b2600i ecu into my truck (one year apart, 1990 and 1991), started and reved perfectly. I replaced the capacitor that went bad but i was being rushed, i think there might have been corrosion on the negative capacitor copper track on the board. I'll take it apart and take some photos and see if i can fix it.

Well i haven't seemed to fix it yet, any body out there have a g618 or g630 ecu for 89-93 b2600i? I'm scraping the copper tracks trying to find breaks, but i cant see anything broken. Cant find the problem.

Anyone have a ECU???

See http://b2600i.com/ecm.htm

There are business online that repair these and guarantee these.

They were one of several i have found, personal problem, i'm almost broke, cant afford $300. Life sucks sometimes. Hopefully one will pop up somewhere.

You indicated that the problem was went away when you swapped in the one from another truck, and then the problem came back. That indicates that you eliminated the ECM as the potential source of the problem. This is similar to a situation I had with a B2200 a number of years ago. I had a second truck that had problems and so I swapped parts from my known good truck to the truck to isolate the problems. You may just have a bad ground wire like I did, and your problem is going away when your engine gets hot. I would try swapping things like the distributor, cold start valve, Mass air flow sensor, and the other things you mentioned, since doing that doesn't cost you anything. The secret here is to test the parts on the known good truck and see if the problem shows up there. The problem symptom will follow the problem part.

mazdatweaker_2, im sorry i guess i didn't type that out clearly, i swapped my dads ecu in and it ran great (problem went away, didn't come back with the good ecu), then i swapped my original back in and it ran like crap (as it did before). Purchased a used working g630 ecu on ebay, should be here in the next 7 days.

Sounds like a decent ECU will get you running. B2600i.com has a pretty decent try out and guarantee if that used one doesn't fix it.