1994 Mazda B4000 barely running.

[Firebird]

A while back I made another post with several questions about my newly purchased truck. Well I never got to the bottom of one of the issues and it is getting much worse.

From the beginning, any time I go full throttle, the car acts like it is hitting a rev limiter and the motor will not rev any higher. It used to just be when it was over 3K rpms, but now it does it at any rpm when WOT. Now its to the point that if I go over around 1/3rd throttle at any rpm the motor wont rev. Every so often, usually on the highway I will loose all power and any throttle pressure at all will cause this result so I end up having to just coast for a ways and then for some reason it drives like usual.

When I go to start it when its sat for any period of time more than about 10 minutes it fires up first crank, idles for about 2 seconds and dies. It will do this over and over unless I start it using about half throttle and even then its a pain to get it to finally idle on its own.

It really seems like a fuel issue to me. I replaced the plugs(all of them looked fine, but this was 2 months before the problem got much worse), wires, TPS, and ran seafoam through it. I kind of think it may be a fuel pressure regulator problem, but I can't seem to find it anywhere along the fuel rail. Any tips guys?

Thanks in advance.

 

[rags]

Have you check the fuel pressure? You didn't mention if you changed the fuel filter! if not give that a try first if it hasn't been changed in awhile.

 

[Firebird]

Have you check the fuel pressure? You didn't mention if you changed the fuel filter! if not give that a try first if it hasn't been changed in awhile.

I did change the fuel filter, I actually did that the day after I got it. I haven't checked the fuel pressure, I need to find some time to rent a gauge and check it out. Do you know where the FPR is? I want to check that out and see if maybe its bad.

I got to thinking about when I changed the plugs a while back and they did look like it was running a little lean.

 

[rags]

FPR is on passenger side front in fuel rail, small vacuum line going to it. Also could be your mass air sensor acting out if you are suspecting a lean condition.

 

[Firebird]

FPR is on passenger side front in fuel rail, small vacuum line going to it. Also could be your mass air sensor acting out if you are suspecting a lean condition.

I looked all the way up both fuel rails, but I may have missed it. Thanks for the info.

I figured that about the MAF, and this is the first non GM vehicle I have owned and I assumed it worked similarly, so I disconnected it, hoping to send it into open loop mode, and it really didn't run much different. I only had it that way for a a day or two and now if I do it, it runs the same. The CEL/SES light comes on after its been run a while, especially when it sits at 1900rpms for some weird reason, but will go off and on, and the second you restart it, its gone and wont show up on a diagnostic scanner.

Every so often, especially tonight, trying to take off from a stop is hard even slipping the clutch a lot while giving it a lot of gas, and when its cold it really pulses a lot. In 1st and 2nd gear it just hops up and down and doesn't really accelerate. Once its warm I can rev to maybe 2700 rpms, and thats at less then half throttle, any more and it hits some kind of fuel cut off just like the rev limiter. These trucks don't have a ton of power so having to shift around 2K rpms and cant go over 1/3rd throttle most of the time really makes it hard when 90% of your driving is on the highway.

I am almost certain its a fuel issue, but on this truck I am having trouble figuring out what to look at since I really don't know much about it. Is there by any chance an in-tank fuel filter?

 

[Donnie strickland]

There is a "sock"- type filter on the intake side of your fuel pump, but since it's in the tank that's a lot of work to check. You really need to do a fuel pressure check first to see what you've got.

Re the FP reg, top of the motor, front of fuel rail, vacuum line and braided fuel line going to it.

 

[Firebird]

Fuel pressure is about 33psi at idle, around 40psi at WOT. Sound right?

 

[Donnie strickland]

Key On Engine Off 35 - 45 psi
Key On Engine Running 30 - 40 psi


So it sounds like the FP is ok. Have you checked the coil pack?

Also, do you have any trouble codes?