Express Van 5.7 L misfire


#1

I’ve got a 1999 Express Van 2500 with the 5.7 L engine. It’s got ~ 150K on it, and I’ve owned it for three years. Have replaced distributor cap twice (paid trusted mechanic) in the last two years.



Calling the current problem a misfire is not strong enough. When driving it, I’m concerned I’ll not be able to get where I’m going. Will idle ok, but attempting to accelerate results in no power and more sputtering. Took it to a different mechanic (open on Saturdays) and they replaced the distributor cap and rotor because, they were “burned up.” When I went to pick up the van it was raining hard (as it was when this problem came up again this year) and the motor still had the same issue. The mechanic said he had taken it out for a test drive and it ran fine. I took him for a ride and it was all I could do to cross the street, turn around and drive back to the station. He and another mechanic at the station tore into it some more and came up with #7 consistently returning a misfire. Tried new plug wire, new coil, carb clean around the intake manifold and all made no change. Checked ECM and it is sending the signals open injector.



They want to replace the #7 injector for $400, or all eight for $1200. My problem is since the motor can run fine one minute and crappy the next (typically around wet), it just doesn’t sound like an injector. I also expressed that since I was worried I’d have to get out and push the van back to their lot, it sounded like a lot more than just one injector. In other words, if I was mis-firing on just one cylinder, I’d have been able to drive the thing just fine… but this van wasn’t drivable.



So… I think they’ve ruled out the coil, and intake plenum gasket. The rotor and cap have been replaced. ECM they did some diagnostics on.



Any ideas?


#2

bump


#3

I totally agree with you about this problem being more than just a single injector causing this trouble. The problem may be with the airflow sensor so I would check that out. I would also make sure the crank and cam sensors have the proper signal waveforms while the trouble is occurring.


#4

I thought about the sensors also.
But usually once a sensor goes bad, it doesn’t come back and run well at all.
My condition SEEMED to be aggravated by relatively heavy rain.
In other words, it ran well most of the time.


#5

That could mean there is a bad electrical connection somewhere. Possibly the ignition system as that is a common trouble area but it may be somewhere else.


#6

The vent screen in the distributer that prevents moisture in the distributer may be clogged.


#7

Even if it were a fuel injector, Auto Zone auto parts has fuel injectors for, only, $65 each. The shop’s price to you shouldn’t be more than $100 each. http://www.autozone.com/R,APP238138/vehicleId,2538401/initialAction,partProductDetail/store,1140/partType,00120/shopping/partProductDetail.htm