Strange problem, 1991 Mazda b2600I

I'd guess fuel injection pressure regulator. Are your plugs somewhat dirty and maybe wet even though they're new?

They may be. Also a piece of porcelain may have fell in when I was changing them, because it also developed a noticeable and consistent tick after I changed the plugs. It's just running so rough right now. How would I test the fuel injection pressure regulator?

When my 1992 B2600i (manual transmission, 2-wheel drive) had those symptoms, it was the ECM.

Injectors

I had the same issue with mine. it was stumbling while idling once the engine warmed up. I spent many days trying to trace the issue. Did a compression test and leak down test and found no issues with the engine, checked for vacuum leaks and In the end it turned out to be the on board computer under the kick pad on the passenger side. I hit it with my fist and the problem went away. I suspect the computer will eventually shit the bed and I will have to replace it. For now its running fine, doesn't miss a beat.

I own a 90 b2600 and have been fighting with all sorts of problems. I've gone into replacing the cam chain and counter balance chain and guides. Valve springs and seals and a host of other things to get better gas mileage. So here's what I've found out. All the things I've read on everyone who owns these trucks has a love hate relationship with this truck. I wonder. Has anyone bothered to check the float and sending unit in the tank? I've noticed that when I'm on empty and fill up again that I only can put in about ten gallons and I have a 14 gallon capacity. Also. Have you had the timing checked? When I first bought my truck. The timing was at over 9 degrees. The base is 5. But with hi mileage it seems to run happier at 6. One way to check for a stretched timing chain is to remove the valve cover. Or if your timing is anove 6 degrees. It may be time to replace a few things. Improper timing can lead to a host of problems. If you are so inclined. With a mechanically inclined friend you can do it yourself. Rock Auto is a good source for parts. And they are alot cheaper than most Auto parts stores. Oh. And of course you'll need a shop manual. I've replaced the fuel regulator. The ignition control module as well. Also. There is one thing that most people completely ignore. A little sensor right on the front of the intake. It's the air temp sensor. It gets oil on it so it won't work properly. It needs to be cleaned from time to time. Hope this helps. Good luck!

If your truck won't start and you've checked​ starter. My suggestion is to look at the key switch. I am experiencing a problem with it not kicking over sometime​s. I know the switch is going bad. Seeing that we have probably turned that switch at least a million times in the in the life of that truck. Things wear out.

Ok young funk. The e.c.u.s' or computers on these trucks had an issue from the factory. If you know anything about circuit boards you'll know what a capacitor looks like. These are Mitsubishi computers. And they had a nasty habit of capacitors leaking on the board If this is the case, it can be repaired. But. If the damage is really bad, you may need to replace it. But It is easy to inspect to see if that's the case. On the right side kick panel is the ecu. Disconnect your battery before yo unplug the computer. then remove the cover. if you see the circuit tracers are eaten away the it may be time to replace it. You can find a link on B2600i.com. Also. check the fuel pump relay to see if its working properly. Also. You can get a cheap fuel pressure tester from harbor freight. As far as your gas mileage. The sending units on these trucks after so many years go wonky. As i stated in a previous post. i still have 4 gallons left when it hits empty. Also. There's a switch on top of the trans that's a neutral safety switch. That goes bad as well. That will cause rough running during startup. I hope this gives you good starting point in which to diagnose your problems

Replaced my ignition coil and it was like buying a new truck. 8 $ at junk yard. It's a must. Hope this helps. Not enough spark caused all my problems. Couldn't believe it

I have a 89 b2600i when cranking over it sounds off time a little I have spark no fuel and no start it pops like off timing I have new ecm relays distrib and fuses and still no pump I'm in 800 buck and still at 1

my 90' Mazda B2200 FI runs rough...poor power too. Almost like it's on 3 cylinder's. It only has 31,430 miles on it original. Was my 83 yr old father in laws. I cleaned the injectors, new regulator & new dampener, was leaking. Still runs very rough. New set of plugs and wires too. what next?