Mechanics

93 - I AM STUMPED

1993 Mazda b2200 • 4 cylinder 2WD Manual • 150,000 miles

I have a 1993 Mazda B2200 2.2 liter 4 cylinder with 2 barrel carb & 5 spd manual transmission. I bought the vehicle and by the time I made it home from a 2 hour drive (the day I bought it), I recognized that I had purchased a problem. Turns out that the rings were cracked on #3 and shattered on #4 cylinders. The truck had a remanufactured head and what looked to be a rebuilt carb when I bought it. I had the engine rebuilt (long block) and drove it some and it ran like a champ. Quite peppy for a 4 cylinder.
It also had a pretty badly rusted fuel tank (at the seam), so I replaced it not long ago. The only other problem recently was that whenever the head was purchased, the seal on the back of the head (nearest the firewall) did not have both keepers on it, so it blew out. I sealed it and pressed it back in. Naturally, draining the remaining oil and replacing.
The following is a list of new parts that have been put on the vehicle since it started running rough.
Plugs and wires, breather element and filters (filters are for smog stuff connected to the breather), starter, battery, fuel tank, fuel filter, (mechanical) fuel pump & vacuum advance.

The equipment replaced all did need replaced, but none have fixed the problem. For instance, the fuel pump had a slight leak and the vacuum advance didn’t hold vacuum, etc.
The truck starts great but idles at about 3000 RPM for a couple of minutes while warming up, then idles down to about 800 to 1000 RPM after depressing the accelerator.
While there is no load (vehicle is out of gear or clutch is depressed, the engine will rev throughout its entire range with no issues. However, when driving, at some point in each of the gears it loses power. It is quite noticeable and seems to have started after the fuel tank was changed. There does seem to be a spot in the pedal just before WOT that works well. However, when pulling hills it needs WOT and doesn’t quite have it.
The truck has 2 catalytic converters. One is attached directly to the manifold and the other is about 4 feet back. I have taken the exhaust system off behind the first Catalytic Converter and it didn’t help. I am not positive that the #1 catalytic convertor is good or bad.
When it "surges" which is not a power surge, but more a drop in power, the tach doesn't seem to move, there is just no power. Naturally the tack will eventually drop off, but when it initially starts to act up, the tach doesn’t move.
I am at a total loss and now I am quite confused. Any help would be greatly appreciated. I did a paid answer the first time and had a gentleman tell me to check for vacuum (which I did and he also informed me that I wasn’t driving a power house. I know it’s not a V10, but I also know how peppy it was and peppy it IS NOT now. The engine has excellent compression and has only 3000 or so on the rebuild. Really, until the fuel tank was replaced there was no lack of power issues. What am I missing?
Avatar
Denny Bouse
March 8, 2011.



Check out the related content below while we wait for the question to be answered by a professional mechanic.