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Matt, Engineer
Category: Car
Satisfied Customers: 20380
Experience:  Honors degree in Mechanical Engineering, worked 8 years as a Formula 1 engine engineer.
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Have a 2003 Isuzu FRR 20 GVW box truck. Owned it since 2010

Customer Question

Have a 2003 Isuzu FRR 20 GVW box truck. Owned it since 2010 I believe. Was running fine until per about a year ago. Until recently, when it was driven, it would all of a sudden go into a sort of "limp mode". Pulling off to the side for a few minutes, then restarting, would sometimes help. Now we can't even get it to the freeway only a few blocks away. Awhile back the problem was really bad and we were stranded in Tucson AZ. Spent a fortune on getting the fuel pump replaced, and that did the trick up until a year ago. We sent it to two different local tractor/trailer big rig "experts", and after several hundred dollars paid to each they insisted they could find nothing wrong. I insisted that they go through the entire fuel line, from fuel tank to engine, and they claimed they did.
Would like to replace the truck, but this isn't practical at the moment, and I need to send it out almost every weekend. When we first bought it there were no such problems, and we took it on round trips to from LA to Tucson, Reno, Las Vegas, all over the place with no problems. Has a nice short wheel base that my drivers like, but this engine bogging down issue is really a pain that needs to be solved ASAP, and what's worse is that two separate experts are stumped (but charged me anyway). About 200K miles on it. Thanks!
Submitted: 6 months ago.
Category: Car
Expert:  Matt replied 6 months ago.


This sounds like an electrical actuator or sensor at fault .Usually when you can cycle the ignition key on / off and then restart the engine and the fault is gone temporarily this indicates that this is an electrical component causing this issue.

This could be a wiring issue as things tend to expand when hot and its possible a poor or partial electrical connection is being pushed apart on one of the major sensors so check the connection plug and wiring to the following;

Airflow meter

Crank position sensor

Cam position sensor

O2 sensor

Throttle pedal position sensor

unplug each in turn and use some switch / contact cleaner spray on the pins to ensure its all grease / dirt free

Also worth checking the connections to the fuel pump for the same reason - unplug each in turn and give them a good squirt of switch / contact cleaner - Not WD40

and also unplug and inspect the main power relays and fuses for signs of overheating or corroded terminals - so the ones for the ECU and the fuel pump

And also unplug the wiring loom connections in the engine bay one at time and inspect for corroded or recessed pins.

Expert:  Matt replied 6 months ago.


do you still need help?

Bear in mind that the site takes a deposit from you at the beginning and this is held by the site until you rate my answer at which point the cash is split between the site and the expert. I am only paid for my work on this question if you rate my answer, using the star system at the top of the screen. Please do not forget! Thank you

Customer: replied 6 months ago.
Need to locate a mechanic who can implement your suggestions. I'll let you know when I've found somebody. Further, the truck would need to be road tested for a great distance (5 hour drive?) before I'm at the very least confident that your suggestions actually worked. Remember that I already brought the truck in to several "experts", none of whom solved the problem and all who are still completely baffled.
Expert:  Matt replied 6 months ago.

Fair enough

if you can let me know your locaiton I'll try to help locate a mechanic?

Customer: replied 6 months ago.
Expert:  Matt replied 6 months ago.

trry this firm

Customer: replied 6 months ago.
RWC Group is one of the losers that I brought the FRR to, who failed to find anything wrong with the truck, despite the fact that the aforementioned problems still exist, and after paying them several hundred dollars for absolutely nothing.I will try to find someone else on my own this week.
Expert:  Matt replied 6 months ago.

in that case I'll opt out to see if anyone else can help

good luck

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