help! Problems on the road!

[Shed]

left for trip this am, 25 miles later throw code PO234, engine overboost. She went into limp mode. Feels like the tranny is not wanting to shift down after a climb. I have a huge headwind, gusts to 45mph. Culd the wind be giving me too much air and fooling the MAF sensor? I'm worried... Any ideas are helpful! Shed

[DmaxMaverick]

Not "too much air".

Many, if not most, aftermarket intake systems experiencing this will be most susceptible to the P0234 (among other MAF and boost codes) with a dirty air filter element. The dirty filter alters the flow characteristics of the intake air, skewing the MAF and MAP values. This can result in overfueling due to inaccurate MAF values. Using almost any power box or programmer expedites the process.

Possible causes:

Incorrectly adjusted boost valve (if you have one, installed in the wastegate actuator hose).

Obstructed/delayed wastegate and/or linkage (debris, corrosion, wear).

Too much programmer/box power for current load and/or conditions. Not at all uncommon with any other "power" mod, especially a boost valve.

Loose/leaking/disconnected wastegate actuator hose. Check entire hose condition, and connections at both ends. If it bleeds pressure, it will delay wastegate opening.

[Kennedy]

This could be partly from the intake kit (not recommended) or also a version of the 2001 limp mode. They limp from fuel supply, boost etc. Some thimes with DTC's and some times without.

[Shed]

sorry to take so long to get back. Thanks for the info. I'm not running any chips or programmers, so that's out. As for hoses, there's nothing I see or hear leaking at idle, truck sounds fine. When this happened, I got no check engine lights, I just scanned it and I got that code. I cleared it. Once I dropped the camper for a return home it ran perfect unloaded. Now pulling a 12' flat bead with 3 golf carts on it and it's fine still. Like you said JK, it acts like the 01' phantom limp, which it did before, had it reflashed and now a few years go by and it's back! I hope that's it. Gonna clean the filter, and MAF And hope. I know JK, I got get with you and have you get her squared away. Hopefully soon, if only money grew on trees! Thanks again, and any other suggestions are always welcome! Shed

[Mark Rinker]

Headwind was creating great amounts of drag, you had to put your foot further into it than normal to compensate and give desired ground speed.

You got deeper into the fuel rail pressure, timing tables, so your EGT temps went up, turbo making more boost as a result of hot exhaust....and BING you are back at the overboost code.

Remove the headwind, or remove the winddrag load (camper?) and you're back to 'normal'. Whatever that is.

Get Kennedy's LB7 tune. You'll slap your forehead like the V-8 commercials. :D

[Kennedy]

When this happened, I got no check engine lights, I just scanned it and I got that code. I cleared it. Once I dropped the camper for a return home it ran perfect unloaded. Now pulling a 12' flat bead with 3 golf carts on it and it's fine still. Like you said JK, it acts like the 01' phantom limp, which it did before, had it reflashed and now a few years go by and it's back! I hope that's it. Gonna clean the filter, and MAF And hope. I know JK, I got get with you and have you get her squared away. Hopefully soon, if only money grew on trees! Thanks again, and any other suggestions are always welcome! Shed


This is one of the more common phantom limp modes of old times. I believe that most people who experienced this did not understand what was going on. You would not believe how many people think no SES light= no codes. This is not the case.

[Shed]

thanks again everyone. I think it's a mixture of what you have all said. I'm a bad boy, I let the filter go way too long. I cleaned it. The wind that day with the load was killin me. I had to keep in the throttle hard just to maintain 55mph, and you are right, she was hot, and had a ton of wind drag. Pulling home with a slight side/tailwind I had zero problems, and temps were way down from the trip up. Lesson for me on the power of wind. Thanks to you all for your expertise! You really helped! Shed