Engine/Transmission (1998.5 - 2002) What is going on with my truck??? HELP!

[Clmsnow]

What is going on with my truck??? FIXED!!!

After re-installing my turbo Sunday night(had to replace oil return gasket) I took my truck for a spin. About 1-2 miles down the road, at about 60-70mph the truck acted as if it stalled, for just a second. I let off the throttle, then it did it again about 5-7 seconds later. The best way to describe it is, when/if you start to run out of fuel, the truck almost dies for a split second. Unfortunately I have run my truck dry before and this is EXACTLY what it felt like. I thought maybe it was just a fluke but it did the same thing again this morning on the way to work. One right after the other, only two times, and only for a split second... . and about 2-3 miles away from home Maybe air in the lines??? But why happen now, for the first time in 120K miles... and why right after I had my turbo off??

 

[nps]

Any codes? You can try the APPS reset. Otherwise it could be the start of the dead pedal and a failing VP44.



Don't know what the turbo would have to do with it - just coincidence perhaps.

 

[DieselMinded]

Things happen at the worst time ,,, my ECM died when my Tc/VB was setting in the garage and ready to be put it :<



Whens your last Fuel Filter Change ?



if you think it has some thing to do with your charger swap the only thing over there you could of hurt was the PCM its behind the air box ,,, im not sure if anything you could do to it would give your symptoms tho.



goodluck



DM

 

[Clmsnow]

Last fuel filter change was 4 months ago. No codes. . it just says "P done". As for the PCM, I have the AFE system and had it off a few times. What does the PCM look like and what could I have done?

 

[DieselMinded]

I would change the fuel filter then get the fuel pressure checked and go fro there ,,,



the PCM is the box mounted on the firewall behind where the air bax was,,, I would just role that out as being the problem . and look into fueling issues



DM

 

[nps]

PCM is a square box that sits on the firewall under the pass side hood hinge - a couple of big plugs with wires going into it.



Don't know what you could have done to it unless you dented in the case. It gets involved with the transmission (for autos) but the fueling decisions stay inside the ECM.

 

[Clmsnow]

As for fuel pressure. . my gauge reads 16-17psi at the time it happened.

 

[TORQUE THIS]

Could be the APPS.



ToolManTimTaylor experienced the same issues at one time. I believe the fix was cleaning the ground wires on the block. One is near the oil filter, and the other under the front bumper near the oil pan.

 

[Clmsnow]

Anyone have a picture that I could see of the APPS. I'm unfamiliar with it.

 

[PC12Driver]

I think the fuel pressure at full throttle would be the main concern. That's where the damage to the VP would happen. How much you seein' WFO?



The APPS (accelerator pedal position sensor) is located on the front of the engine, mounted on the top of the intake manifold, just in front of the intake horn, mounted by three bolts. It's in the black plastic box (curved top) directly above the injector pump. To reset it, disconnect the batteries for several hours (overnight), reconnect the batteries, and slowly depress the accelerator pedal to the floor a few times.

 

[DieselMinded]

http://www.3d.otisnet.net/apps.htm

 

[Clmsnow]

I'll give that a try, thanks.

As for fuel pressure at WOT... it is about 10psi. Seems fine to me, it has always dropped down that low at WOT. Does this sound like an APPS problem??

 

[PC12Driver]

10psi should be fine. 5-6 psi should be the minimum (depending on who you ask).



It could be the APPS, since that's what tells the ECM what the throttle setting is (our trucks are drive-by-wire; there's no mechanical linkage between the accelerator pedal and the fuel pump). So if the APPS drops voltage for a sec, you could get a stumble. But if it's dropping voltage somewhere in mid travel, I don't think a recalibration will fix anything. Can't hurt to try, though.



Have you disconnected the batteries lately?



Do you get the stumble right after full throttle runs or will it happen during normal cruising?

 

[Clmsnow]

I did the re-set tonight so we'll see what it does tommorrow. As for disconnecting the batteries lately... . I just replaced both of them about a month ago. The two times it has stumbled it was at cruising speeds; about 60-70mph, not necessarily right after a full throttle run. I was reading up on this tonight and someone mentioned something about the screw on the pump cover. I have the blue chip plate/cover on my Comp box. Is this what people are referring too? There are no codes and all my gauges look normal when it happens.

 

[DieselMinded]

People have cracked the VP44 Circuit board when tightening down the tap screw with the blue chip cover



Just FYI



DM

 

[2-ND TIME]

fueling

Sounds as if when you let off the throttle ( too quickly) you are reducing the Manifold air pressure MAPs and from there the ECM is telling the FPCM to reduce fueling ( fuel advancement cam). This is done with transistors so it takes nano- seconds to do.

Try this . Letting the throttle off slower and see if that takes the cut out away???

Will also reduce the wear on the driveline.

 

[PC12Driver]

The two times it has stumbled it was at cruising speeds; about 60-70mph, not necessarily right after a full throttle run.

If it happens during cruise it's not a case of anything playing catch up. Something is causing the fuel flow to cut. Or the VP is starting to flake out.

 

[Clmsnow]

Yes..... only happening while cruising at 60-70mph. How would I know if the pump cover messed up something... and why would I need one if I am already over 100k Miles??

 

[PC12Driver]

Let's try the easy stuff first. Turn off the Comp. It could be sending bad data down the CAN BUS or spiking the pump. If the problem still exists, try unplugging it (from the pump cover and the data link; leave the MAP circut in place for boost fooling).



Start with that and check back in after running it for a while.



Also, will it cut out with the cruise control set? If so, that would eliminate the APPS.

 

[Clmsnow]

It hasn't happened yet today after resetting the APPS. I'll run with the Comp off for a few days and see what happens and report back. I rarely use the Cruise control so I can't say it has happened with it on yet.