Poor performance, low RPM

Okay, I'm getting ready to throw parts at this 1993 B2200.

Truck has poor performance from about 1000-2500 RPM's. Very noticeable in 1st gear. Idle is smooth.... Truck does not die. It is just pulling away from a stop sign, it makes you wonder if it is going to make it across the intersection before you get T-Boned.

Mazda Dealer & Independent repair shop both told me I needed a cylinder head replacement. I didn't believe the Mazda Dealer, so I paid diagnoses & left. Took it to independent repair shop & they drew the same conclusion. Well, after a Clearwater Cylinder Head was installed, the truck performs the exact same way. Work was performed at Independent Repair Shop.

I have noticed the NUMBER 2 PLUG IS CONSISTENTLY WET!!!

So, I'd like to START with the IGNITION SYSTEM.
I know NGK Plugs are recommended.
How about the Cap & Rotor, what Brand???
Igniter, what brand???
Distributor, what brand???
Coil, what brand???
Did I miss anything??? Truck is BONE STOCK, would you recommend any performance ignition parts??? If so, what??? And what brand???

Truck is currently for sale in Brainerd, Minnesota. Just check out craigslist if interested.

I'm confused are you selling or fixing her up? Or is it a I'll sell it if someone wants it type of sale...

If you are going to fix her...

EFI or Carb truck?

I'd start with the ECU and fuel system if it's EFI truck... check for blown capacitors on the ECU and replace the fuel filter. check/clean the injectors, one may be stuck open, do you have proper fuel pressure... etc.

Same for a carb truck, check/replace the fuel filter and maybe the fuel pump.

I assume the professional shop performed a compression and leak down test to ensure your rings and block are good... hence the head replacement recomendation...

Wet with oil? Fuel? Coolant?
Any smoke out of the exhaust? White or blue?
Have you check for a good spark on that plug/wire? Try rotating the plugs, or just replace it since they are cheap enough!

I would check the compression on that cylinder!


And, as Dan has mentioned, if your truck is is fuel injected, first thing you need to look at is the ECM. It's located behind the passenger side kick panel. If that is OK, then there are several other things to check on an efi truck.

If carbureted, then you need to investigate the entire induction/emission system. I would start by looking for vacuum leaks and inspecting/cleaning EGR & reed valves. Check timing and distributor advance operation. Fuel filter. Clogged cat? Check computer for codes!

Also, some background on the truck would also be helpful. Has it been slowly getting like this for a while, or did it start acting up one day? Any difference in hot vs cold? Does it run better above 2500 rpm? Or is that all you can get out of it?

What kind of fuel mileage have you been getting with it?

Did said shop give any specifics as to what was wrong with the head? Warped, cracked, burned valves? Sounds like they were "throwing parts at it" too.

I would do a little more troubleshooting before I started throwing parts - at least expensive parts. You're not going to get any meaningful performance gains with ignition parts. Just go with OEM or name brand parts like you have mentioned... NGK on plugs and wires.

Take it back under a warrantee. They didn't fix the problem.

Truck is for sale, but it's kind of hard to sell something with poor performance like that.
Truck is carbed.
Not exactly sure what they did but both Dealer & Independent shop said I had bad valve seats & that was causing the poor performance. When original head was pulled, the seats were cracked.

Wet with fuel.
No smoke noticed at start up, tail pipe rusted away.
3 sets of plugs, always the #2 plug is wet with fuel.
Truck goes GREAT above 2500 RPM's.
RUNS GOOD WHEN COLD, BUT after warm up & idle comes down, it's poor performance again.

They had it for 2 years & went at it pretty hard for about 2 months. I would use the truck when I traveled back to MN from VA. Now I'm going overseas for 2 years & it is time to thin the herd of cars. The shop got tired of the truck. We settled on Labor at $30.00 an hour plus parts. So, it was a pretty much break even for the shop. You can get the truck to fail all day long, they just can't figure out why it has poor performance.

I'm really thinking something with the Ignition System, due to the WET #2 plug. At least I think that is the best place to start.

Easy to swap complete spark wires for #1 and #2, see if the issue then goes to #1.

For incomplete/no combustion in #2 in a carbureted engine, suspects have to be distributor cap and/or spark plug wires.

I'd look really carefully at the distributor cap. As I recall, one of the hold down screws kind of lines up with plug tower two and if you have carbon tracking, you should see where it has been shorting to ground.

Hope this helps.

Very true on switching the wires around.