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Matt
Matt, Engineer
Category: Car
Satisfied Customers: 20941
Experience:  Honors degree in Mechanical Engineering, worked 8 years as a Formula 1 engine engineer.
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I have a 2004 Rodeo 3.5l direct inject that will idle AC on

Customer Question

Hi I have a 2004 Rodeo 3.5l direct inject that will idle for Hours AC on and everything,,
BUT as soon as I put it in gear and drive I get about a mile and it stalls???????
the ECU has been flashed, the old dealer told me it was the engine harness, yeah right $800.00 later it still dose the same thing..... No codes are given from any scanner...
Any thoughts?
58k miles
mint condition
Submitted: 11 months ago.
Category: Car
Expert:  Juan Crespo replied 11 months ago.

What's the fuel pressure right before it stalls?

Customer: replied 11 months ago.
That I have no way of knowing,, Like I said it will Idle for hours and once you start to drive you get a mile down the road it stalls, it will start right back up and another mile down the road BAMM samething
Expert:  Juan Crespo replied 11 months ago.

I'm sorry, but based on your reply I won't be able to work with you. I'll opt out so others may try. Please don't reply until another expert responds or the site will revert your request to me.

Expert:  Matt replied 11 months ago.

This could be an airleak after the airflow meter, any air dragged in here isn't 'seen' by the ECU and so not compensated for and can lean the engine out and can also allow the engine to rev up when not desired causing rough running.

As its a mechanical fault it tends not to turn on the fault light and you can sometimes hear a 'hissing' noise with the engine running.

Check the hose clips for tightness and inspect the trunking for any cracks or splits and also all the vacuum system, the small bore pipes and fittings for cracks and missing parts.

The best way to locate a leak is to have the engine running and warm and then spray lighter gas /propane around each joint in turn. If the engine rev's up you've found your leak.

Now you might think that spraying lighter gas around a hot engine isn’t wise, however the flash /ignition point of gas is about 400°C so you need a naked flame or spark to set it off and I’ve used this method for many years without incident.

Work your way through each possible joint one at a time and you should find it. I use a slightly flattenedpiece of brake pipe and some rubber hose from the can of lighter gas to provide a spraying 'wand' and allow a direct blast of gas into each area, especially those difficult to reach with large implements.

It’s also worth getting the fuel pressure checked as if this is low due to a blocked filter or faulty regulator or even a poorly pump will all result in insufficient fuel being delivered to the engine

Might also be worth cleaning out the throttle body as these get clogged up with carbon and some brake cleaner washed through helps free things off.

Might also be worth checking the wiring and connector to the airflow meter for any signs of corrosion or damage. you can do a quick fault find if you unplug the meter and run the engine without it.

if the engine condition is the same then chances are the meter or the connection to it is faulty

Air leaks are very temperature dependent as gaps can open or close up as things expand with heat, so the weather and engine temperature can effect them.

This leads them to be quite intermittent in the case of mild leaks

its also worth cleaning the airflow meter by removing it from the car and spraying the exposed sensor wires inside the tube with a brake or switch cleaner - ensure that the cleaner is one of the old fashioned, non Eco type that does not leave a residue

On no account touch the sensor wires with anything physical as they are extremely fragile

Customer: replied 11 months ago.
She will idle for hours if I let it the engine runs and revs up and drops right to idle and stays there comes up slightly when the ac is on, I will check all the air lines again recheck fuel pressure but sitting still everything is fine, and once you start driving all is good and then it just dies; starts up and off you go for about a mile and then stalls again.
things Ive done
replaced the whole throttle and TPS the dealer had it and put a new engine wiring harness on it; claiming that was the problem!
when that didn't work they flashed the ecu charged me 800+$$ and gave up, said they didn't have anymore info for Izusu.
was wondering if the Crank shaft sensor might be causing it? seeings that it is only when driving dose it stall.
Expert:  Matt replied 11 months ago.

OK thanks for the extra information

if there's no vacuum leak and the fuel pressure is good then I'd agree that a faulty crank sensor is a possibility

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 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.

Customer: replied 11 months ago.
all of the plugs have been checked and i did that a about a month ago, the heat issue himm I'm not thinking so due to the fact that it will idle for over an hour if or forever if I let it, I was going to replace the Crank sensor see what happens then move to a new fuel pump and filter just to see if there is something there but when it stalls it will start right up as soon as you hit the key that's why I don't think it's a fuel issue or pressure.
Expert:  Matt replied 11 months ago.

hello

if you can measure the fuel pressure with a mechanical gauge then this will show if the fuel pump needs changing or not

as they're quite expensive to change

Customer: replied 11 months ago.
Will do and get back to you, as I am dealing with a family emergency right now..
Thanks
Buck
Expert:  Matt replied 11 months ago.

understood

just get back to me on this post

hope everything works out

Customer: replied 11 months ago.
Okay well we checked all fuel issues we have 36 psi on start up and shut off or when it quits, it's not a fuel issue it is some type of electrical? there is something telling it to shut off after a short time, the time varies each time, you can start it let it idle how ever long, rave it up and it's fine start driving and it might be 20 sec or 20 minuets, and boom shuts off.. new engine harness as stated earlier and all plugs and connections have been gone over by myself and two other mechanics. no codes from three different scanners. Sent the ECU to some place in San Fran and they put it on their { Isuzu } scanner and found no problems. so I'm back to square one.
your thoughts Matt
Expert:  Matt replied 11 months ago.

hello

ok this is getting tricky

if you has access to a scan tool that can do live monitoring so you can look at the following:

engine speed

throttle position

lambda trim

lambda reading

engine sync ( cam signal)

then take the car for a drive so you log the results when this happens

you could also see if you have spark directly after the event ? as if there's no spark then there's either no power to the ECU or the crank sensor has packed up