Limp Mode - Problems

[KaNGiX]

Ok heres my problem. My VX keeps going into limp mode. Now im on the road for work about 800 miles from home. I need my truck to work so i took it into the local Izusu dealer to have it fixed. Now ill describe the series of events and maybe someone can chime in. It seems to me that the dealer is just throwing parts at it hoping it will fix it.

It all started on my way from Charleston SC to Charlette NC. I was going down the interstate i went to make a move to pass and got on the gas pretty good. And it went to limp mode. I limped it to my destination (about 20 miles). I shut it off and took it to autozone to have the CEL read. It came back with a code which i forget what it was now. But i did research here and the code kinda lead to the MAF sensor. I got the CRC cleaner and cleaned it put it back on. The CEL cleared up and i returned to Charleston SC problem free running great. I thought that i had fixed it till about 2 days later it started doing the same thing.

Now i did more research and came to the conclusion i best get it into a shop. I scanned the local area only to find 1 Izusu dealer. So i take it there.

They get into the shop and after there diag. they tell me the MAF sensor is bad. I order one from St charles izusu they replace it and tell me its fixxed. Next day same thing limp mode. I take it back to the dealer.

They run another diag and tell me the PCU is bad. Powertrain Control Unit? Anyway it was covered under the extended warrenty so they replaced it. Send me on my way. Again the very next day i start working and bam back into limp mode. Back to the dealer. Diag. again and tell me my 8" touchscreen is interfering with the PCU (which i didnt by cuz its been there since like 7 days after getting it a year ago) Anyway to make the mechanic happy we killed all the power to the PC/monitor. He says that will clear it up. Same thing next day back to limp mode. And here i sit in a rental car.

Now one thing i notice is that it seems to trigger into limp mode when ive been out driving for a few hours like 2. If i shut the truck off it seems to reset itself for a bit but not long. But the problem has yet to clear up and they have done about 1100 dollars worth of work. And its just like day one.

I knew i was in for a treat when i took it to the Izusu dealer and they ask me who makes it.

Now this guy at work said his town car was doing the same thing. He said it ended up being a tiny metal spur in the a shift control selenoid pack? He said the dealer did the same thing just threw parts at it.

Anyway sorry for the long post with any luck maybe someone went threw this hell. Thx again any advise would be great and appreciated.

[Knigh7s]

have you tried general maintenance? Fuel filter, spark plugs, new oil, pvc, air filter, etc...

If it only happens when you "get on" the gas, I would think maybe your fuel filter...

This happened to me when the summer heat hit, when i got on the gas she just kinda stopped going, wouldn’t accelerate at all... Then I noticed my temp gauge was rising pretty bad. She went into "limp" mode and would not accelerate above i think 50-60mph on the freeway...

[KaNGiX]

that kinda describes the problem. Yes all was done minus the plugs.

Its been hotter then a demon down here too. 110 + heat index with 100 humidity.

Up north in buffalo it never happened

[johnnyapollo]

I had something similar happen to me - in my case everything would be fine, then when the AC kicks in the RPMs would drop, the AC wouldn't engage and it would die with a CEL code indicating some MAF issue. I looked up the CEL in the VX workshop manual (you should download the free copy of the CD if you haven't gotten it already) and it indicated that the MAF wasn't returning a signal within the 5 or 6 second window, which forced the CEL and put the truck into limp mode. This in turn prevented the AC compresser from engaging as it requires a minimum tach (and the AC keeps trying, which dips the tach each time and eventually killed the idle).

So using the manual, I went down all the troubleshooting procedure (which is also basically what your dealer/mechanic did to troubleshoot). I ended up going through every process without finding a fix - each led to a different item and each was testing using an OHM or AMP meter to ensure the signals were within tollerances. So I finally just took apart the entire intake and using gasket material, re-made a new gasket attaching the throttle body to the plenum (mine had a small tear fixed with permatex - I figured it might have been enough to cause a leak, which may have been causing the MAF issue - that was my thinking, anyway). While I was putting everything back together, a small boot leading from the harness to the front of the block just fell off - turns out there's a temp sensor there that wasn't fully clipped - I guess it had worked itself off and because it's covered by a rubber boot, you can't tell by look or even by feel without pulling on the wire - it even felt like it was on by hand and when the truck was first started, it made contact but the vibration of the truck eventually caused a break in the connection. This temp sensor was what was causing my issue - once firmly reattached the CEL didn't come back.

I'm not saying that you are having the same issue - but I think it might be heat related. I've found that when it's really hot my VX becomes very sluggish, even with the AC off. With the sensor feeding back wrong information, everything at the intake adjusts the mix and when it wasn't getting the right reading, it dumped the CEL and went limp. Nothing in the manuals would have led me to this as I guess it's outside the realm of usual issues. With it being so hot and since you didn't experience the same issue up north, I think you should take a look at the sensor and wire leading to it - it's right under the throttle body.

Oh and for those of you wondering why my TB is back in the front, I removed the SC plenum and replaced it with the old to have my drive rebuilt and still be able to use my daily driver.

-- John