Cable type throttle non-responsive?

isuzu

#1

I was just cruising on the highway then suddenly power got cut and the check engine light came on. I pulled over to the side to find out that my throttle does not respond at all. Stepping on the pedal virtually does nothing. The car was just idling at 1.1k rpm and I tried revving the engine via the throttle body already yet no response. I managed to crawl the vehicle to a nearby gas station to check everything out. The OBD2 scans came out negative. No fault codes were found. I tried multiple sensors already to no avail. I’ve also tried unplugging the battery for a good 20 mins to hard restart it, yet it still doesn’t work. I’ve exhausted all possible solutions to my capability, what else could you guys suggest?
I drive a 06’ Isuzu D-MAX


#2

Taking it to a knowledgeable shop for diagnosis.
You’ll spend a lot less that continuing to change parts at random.

Your car probably has a “drive by wire” accelerator system. The gas pedal sends a signal to the ECU, and the ECU adds it to the other “engine demand” signals in the ECU and drives a motor that runs the throttle plate. Since the engine will idle but is totally nonresponsive to the gas pedal, I’d start by checking that aspect of the engine’s operation out first. It may not be throwing a code because the other “engine demand” signals are all within normal ranges but the ECU doesn’t know you’ve pressed the gas pedal… which would suggest the accelerator pedal assembly itself (it contains the transmitter).

First check for any blown fuses. Then take it to a competent diagnostician. You’ll save a bundle of money in the long run.


#3

Does this truck have a diesel engine?

If so, when it was scanned for codes, was the scanner capable of retrieving diesel OBDII codes? Because they’re different between the gas and diesel engines.

Tester


#4

Excellent question. I’m unfamiliar with Isuzu’s naming protocols, but “D-Max” would suggest you’re right. I’m embarrassed that I didn’t catch that one.


#5

Yup, it’s a diesel. and I’ve borrowed the scanner from my mates who also drive isuzu’s which were also diesels. It was able to pick up a code from their vehicles before.


#6

Taking it the shop would probably my last resort as shops here in the Philippines tend to overprice their services. But it’s still a consideration…

Anyway, I highly doubt that it has a drive by wire as it still has a cable type throttle. We’ve visually inspected the throttle itself and the pedal assembly. everything seems to be functioning properly as the throttle still turns when I step on the gas pedal.

Fuses are all intact as well.


#7

Best of luck with the codes, but if there are none you might want to consider that the principles described in my post apply to diesels as well as gas engines.


#8

Yup! Thanks a bunch, mate! Still have a lot of ground to cover before we find that fault.


#9

Here’s how the diesel engine is controlled in your Isuzu.

I’d be looking at the accelerator sensor.

That’s the electronic accelerator pedal on the floor.

Tester


#10

I’m afraid that mine’s still the old school direct injected engine. The newer isuzus have the common rail system with the electronic throttle already. However mine’s still the old cable type pedal-to-throttle system. It does have a throttle position sensor attached to the throttle however… Could it be that one? I’ve tried revving it via the throttle itself but nothing really happened. still stuck at idle.


#11

Yup. If the ECU doesn’t have a signal that the throttle has been pushed open, it won’t increase the pulsewidth of the injectors.

You seem much more knowledgeable than many of our posters. I tip my hat to you.


#12

I’ll go have my mechanic take a look. Thank goodness you could swap out that part for a new one.

Anyway, I always watch when people work on my car. I eventually pick up a few things by simply observing! hahaha Thank you!


#13

Does it have a fuel filter/water separator? Have you changed it recently?


#14

Yup! Sedimentor has been cleaned out.


#15

Anything that senses the throttle valve position could be a culprit, like the throttle position sensor or if you have one, the ecm’s accel sensor. That would normally be the first place to start testing absent any diagnostic codes. If that’s not the problem, there may be a mechanical fault inside the throttle body preventing the accel cable from moving the throttle butterfly valve(s) like it should. That would probably require the removal of the throttle body to know for sure. The removal of throttle body is a very easy job on my Corolla, maybe a 45 minute job, but it can be much more difficult and time consuming on other vehicle designs.

Not sure if diesels use cats in the exhaust system or not, but anything that clogs the exhaust system could possibly cause this symptom too.


#16

Update: Truck’s up and running again! It wasn’t the TPS sensor!
The culprit was a loose sensor on the Injection Pump. Funny how the problem could be solved so easily. hahaha Thank you to everyone for helping me out here. :slight_smile:


#17

Glad you are back on the road with a reliable ride.!! Thanks for the follow-up.

Injection pumps do seem to be a common source of diesel engine problems.


#18

Just discovered that many diesel engines don’t use throttle bodies or throttle plates. The rpm is controlled by the fuel feed rate, not the air intake rate. Newer ones do use throttle valves, used to provide vacuum signals for emissions purposes I guess.


#19

Sincere thanks for taking the time to let us know. Congratulations on getting the problem fixed.
George’s post has only emphasized that I don’t know a lot about diesels. If I ever buy one I’m going to have a very steep learning curve!

Happy motoring.


#20

Around 1975 VW had a diesel version of the Rabbit. That car got really good mpg and was popular for that but was really really slow at accelerating. My coworker, a mechanical engineer, had one and loved the mpgs, just lived with the slow accel. Not in a hurry when you’re driving to work after all. One day after the car was maybe 5 years old I asked if it was it reliable, etc. He replied “Oh, it’s been very reliable. The only thing I’ve had to replace is the injection pump, twice” … lol …

Apparently Colorado mountain country cold weather can play havoc with diesel injection pumps, the diesel fuel gets really thick in very cold weather.