Engine/Transmission (1998.5 - 2002) Engine Miss at all RPMs and p0234 code!

[MattW]

Looking for ideas on what might be the problem on a 98. 5 24v.

It sounds like it is missing at idle and just about any other rpms. Also it seem rather guttless. I am not sure if it is related or not but keeps throughing a p0234 overboost code. I can run a scan and clear the codes then idle the engine for a couple of minutes and the rescan and the p0234 code is back. Will the p0234 code cause the truck to run lousy or is it even related? I have replaced the lift pump and fuel filter and the MAP sensor. Also replace the injectors. Nothing seemed to make any difference at all. I think maybe the VP44 is going out, but just want to make sure before I go spend $1500.

 

[C.Solomon]

Are you running any fueling modules?

Like a edge or tst

 

[Turbo Tim 1]

Try changing the MAP sensor, that is the manifold air pressure sensor and is what would give you the Overboost code. Sounds like it's bad.



On Edit: just re-read things and see you changed the MAP, I think you need to find out where the 0234 code is coming from, that will screw up things. You definantely changed the MAP and not the IAT right?

 

[MattW]

The truck is bone Stock. And yep, I am sure I changed the MAP sensor.



Thanks for the replies so far. It really stumps me that it (p0234 code) comes back at idle. That kinda rule out the possability of the boost really being high.

 

[MattW]

Truck is Stock.



Sorry for the double post. I am kinda new to the forum thing.

 

[C.Solomon]

Check the wiring running from the MAP sensor to the ECM.

Might be a bad ECM.

Have you tried resetting the ECM lately?



Could be a number of things... .

 

[SSkinner]

The P0234 will not cause vehicle to run rough. In my experience with this code, on a hand full of vehicles it is a software issue. It causes no vehicle performance or running problem. Verify the turbo wastegate opens and have someone with a diagnostic tool verify it's not boosting over 20psi or if there is a boost guage that should work also. This code is set if the controller sees over 22psi of boost. As for the rough runnig if the transfer pump,

fuel filter are flowing proper fuel volume and there is no other fuel deliverly issue like one certain cylinder missing. The most likely cause is injection pump. They sometime don't set codes. Hope this helps.

 

[MattW]

That helps! I have reset the ecm. The fuel pressure is good, filter is new. The only thing left seems to be the ecm and the vp44. This problem has been around for along time. Just now getting around to trying to fix it. I was under the impression that when a vp44 pump was going out it doesn't last very long. Maybe thats not right. I put all new injectors and the symptoms didn't change at all.

 

[SSkinner]

In the time have workied on this trucks I never replaced a ECM for rough running concern. It is 99% the VP44 pump providing everything else is ok. I found the fass transfer pump is best product to replace the OEM one. It is a very good pump. It flows more fuel then to OEM ones which helps keep the pump cooler and helping them last longer. The plus to the fass pump is it is a push pump not a pull pump.

 

[woody052576]

hi there! i have a cummins with a bad miss?do u have any ideas?