Engine/Transmission (1998.5 - 2002) Help me diagnose this problem...

[JyRO]

Fellers -



Any help you can give me I appreciate it.



This past weekend (12/11 & 12) I was towing my trailer to PA and back. I'm not sure when the problem started but at least on the way back I noticed the following.



At 65 m. p. h. with the cruise set and pulling around 9,000 lbs worth of trailer, when I would start up a slight to mild grade, the engine would start missing at the additional throttle that the cruise would give it to pull the grade.



The missing was very slight, such that it sort of felt like I was driving over ripples. The miss only cut out about 10% power I'm guessing. I ruled out the cruise control because I'd lay my foot on the pedal, hit the cancel button on the cruise, and it would continue to miss. Any throttle pedal modulation and the miss would stop. Also, it came and went, once it started doing this while pulling grades it didn't seem to stop doing it on the grades after that. Its like it would reset when I stopped for fuel, but after a while again on the road, it would start the missing on the grades again, and I'd reach down with my foot and tap down on the pedal a bit to stop the missing up the grade. Or else I'd just use my foot instead of the cruise and just loose a bit of speed up the hills.



At first I thought the LP might be getting bad and starving the VP / engine of fuel causing the miss. But the miss occured at what I'm guessing to be in the 40% - 50% of throttle pedal travel. If I pushed down past that it would smooth out and accelerate hard. Let off a bit it would smooth out and run well. So I'm not sure that it would be the LP. I'm still not ruling it out either.



The miss would send the truck into a very light vibration ... like I said, it felt like I was running over ripples, the vibration felt like about 5 or 6 hertz.



I meant to check the codes last night, but forgot. I'll do that today when I get home and see if it set any.



But first I'd like to know what you guys think. Thanks.



P. S. I got to race a couple PSD's up Monte Eagle going east (southeast) on I-24 going toward Chattanooga. They had small trailers with ATV's, maybe 1,500 lbs. I had my trailer empty at the time (~4,000 lbs) and out pulled the both. It was fun and also led me to believe I have no LP issue, but I'm no genius.



- JyRO

 

[SnoKing]

Maybe it was TC Shudder! SNOKING

 

[JyRO]

No sir, manny transmission for me (see sig. ).



- JyRO

 

[Hohn]

Sounds like an electrical glitch to me. Did it only do this in a narrow APPS range? Would it do it in other gears? Other speeds? Other RPMs?

My first inclination would be APPS.

 

[Dukenrock]

Could it be the sign of the fuel pump or transfer pump going bad? If you let off the gas and kept it at a slower speed did it go away?

 

[KYLE4]

You need to put a set of guages in that thing it's like a running a full time diagnostics pyro boost fuel pressure. It sounds like fuel pressure via lift pump that is typically the problem when the truck will stumble Hohn could be right though. did you run ignition diagnostic yet any codes

 

[JyRO]

Hohn - I thought about the throttle position sensor (I can't remember exactly what APPS stands for, but its the throttle position sensor, right?). I thought it might be that as I was driving. It did do it only in that range ... as best I could tell.



Other gears? Other speeds? Other RPMs? I found it difficult to simulate this driving condition in any other gear. For instance if I load the engine similarly in 3rd gear (same amount of throttle for an extended period of time), that's got to be one steep hill to simulate it in 3rd gear. 5th gear would be the most reasonable, but then I'd start becoming a road obstruction to try that on the interstate. Any lower gears would be dangerous to try on the interstate. Same with RPMS and speed ... I found it difficult to simulate in anything but 6th gear.





Dukenrock - It could be the LP, from my thinking. And yes, it did go away when I'd let off the throttle, even just a bit. However, it would go away if I pushed on the throttle a bit too. So, that doesn't seem like a fueling issue, but I'm not ruleing it out.





Kyle4 - Need is a strong word. But I see your point. Having a set of gauges on it during these periods may have been excellent diagnostic set of tools. I haven't checked the codes yet. I'll post those results tomorrow.





Fellers - I got to thinking that as many fuel-ups that I did on this trip, it could be that I got a dirty load of fuel. Maybe some debris slipped passed the regularly changed fuel filter and lodged into an injector. Maybe at lower power demands the 'miss' either wasn't noticeable or not present due to lack of fuel demand. And maybe when I pushed harder on the pedal the injector pump pressure would increase fuel pressure enough to push substantial fuel past the obstruction and it would smooth out. But at just the right level of fuel demand and not so much fuel pressure, it couldn't get enough fuel in there. So, I'm thinking about the possibility of dirty injectors too.



If I get no codes, I may put the stock injectors in and see what happens. If it goes away, I'll send the 275's out for cleaning.



Keep the helpful info coming in, and thanks!



- JyRO

 

[Dukenrock]

I understand those pumps went out around 60,000 miles. (Bosch pumps?) How many miloes are on your truck?

 

[Dukenrock]

You sound like you are experiencing exactly what I did on a trip from AZ-FW pulling a 12,000 lb boat. My truck started missing and it would come and go. It actually shout flames out every so often. Thought it was fuel. On the way back water seperator, flushed injector system. Didn't fix it. Dealer said it was a bad fuel transfer pump-They replaced it. (Warranty) Didn't fix it. Then they said it was the other pump. The expensive one! They were not going to warranty it since I had a Banks Kit! (That's another thread!) I ended up looking at things myself and ended up finding the injector timing wire from the Banks Kit loose. I recrimped it and it took care of my problem. It's funny though because everyone was looking toward the problem as a fuel issue. That's whay I asked about yours. They told me there was a big problem with the Bosch pumps going bad around 60,000 miles. ***You don;t happen to have a Banks Kit, do you?***

 

[JyRO]

The LP's fail frequently. My first one at 45k. Now there's 77k or so on the truck. Original VP. No Bosch system. EZ with elbo & 275's ... that's it.

 

[barbwire]

Mine did that(missed at cruise speed),and about 3 weeks after I noticed it, the lift pump went out!!!!!! When the pump went out , it went out and left me on the side of the road.

 

[Lsfarm]

May be one of these

JyRO, try unplugging the EZ, sometimes they will have either a bad connection or an internal electrical glitch and cause a 'miss''



Next and this seems like a stretch, but check your driveshaft 'U'Joints!! I had a vibration only under load, that came and went like you are describing and it turned out to be the rear 'U'Joint.



I doubt that it is the injectors, check the easy items first.



Hope this helps, Greg L

 

[DieselLady]

Hohn - I thought about the throttle position sensor (I can't remember exactly what APPS stands for, but its the throttle position sensor, right?). I thought it might be that as I was driving. It did do it only in that range ... as best I could tell.



Other gears? Other speeds? Other RPMs? I found it difficult to simulate this driving condition in any other gear. For instance if I load the engine similarly in 3rd gear (same amount of throttle for an extended period of time), that's got to be one steep hill to simulate it in 3rd gear. 5th gear would be the most reasonable, but then I'd start becoming a road obstruction to try that on the interstate. Any lower gears would be dangerous to try on the interstate. Same with RPMS and speed ... I found it difficult to simulate in anything but 6th gear.





Dukenrock - It could be the LP, from my thinking. And yes, it did go away when I'd let off the throttle, even just a bit. However, it would go away if I pushed on the throttle a bit too. So, that doesn't seem like a fueling issue, but I'm not ruleing it out.





Kyle4 - Need is a strong word. But I see your point. Having a set of gauges on it during these periods may have been excellent diagnostic set of tools. I haven't checked the codes yet. I'll post those results tomorrow.





Fellers - I got to thinking that as many fuel-ups that I did on this trip, it could be that I got a dirty load of fuel. Maybe some debris slipped passed the regularly changed fuel filter and lodged into an injector. Maybe at lower power demands the 'miss' either wasn't noticeable or not present due to lack of fuel demand. And maybe when I pushed harder on the pedal the injector pump pressure would increase fuel pressure enough to push substantial fuel past the obstruction and it would smooth out. But at just the right level of fuel demand and not so much fuel pressure, it couldn't get enough fuel in there. So, I'm thinking about the possibility of dirty injectors too.



If I get no codes, I may put the stock injectors in and see what happens. If it goes away, I'll send the 275's out for cleaning.



Keep the helpful info coming in, and thanks!



- JyRO

APPS stands for accelarater pedel position sensor, yes the same as a throttle position sensor. I think you should check this out before going to fuel problems. If the problem goes away with increased throttle you may just have a bad spot in the sensor where you usually hold the pedel at. Seems to me that if you give it more fuel on a hill and everything runs good that all the fuel systems should be okay.

 

[JyRO]

Codes checked...

Fellers - I said I had no Bosch system, but I meant no Banks system. I read Dukenrock's reply a few replies back and in my mind I thought 'Banks' when I read Bosch and just didn't think about it. I do have the VP and Bosch injectors.



I checked the codes and none were set. I don't know for sure but I would think that if it were an APPS problem, maybe there would be a code? Hmmm.



barbwire - that's why I'm not ruling out the LP. I'm going to put a gauge on it and check it out.



Who knows the procedure for re-calibrating the APPS? I think I'll do that & unplug the EZ and see what happens. The problem is, I'd have to have the trailer hooked on and tow on the interstate to see if the problem goes away.



So since no codes are set, this is going to be trial and error, I guess. :{

 

[GFrance]

I don't know if resetting the apps will help your problem or not, but it's worth a try.

Diconect both batteries for half an hour, then reconnect. Turn key on don't start, slowly depress accelerator pedal to the floor & release slowly. Turn key off then start truck apps should be reset.

 

[2-ND TIME]

bad APPS

This is what I have been experiancing for years. This is most likely bad APPS the off- idle cct pins 1/2, idle cct 1/6 if you have a multi- meter check the resistance of the 2 pin outs for resistance and they should be < 125 ohms contact ohms pin 1 is bottom left 2 is above that and pin 6 is bottom right. hope this helps if not have more info.

 

[Fishin Guide]

I too have the same issue going on. I have an auto and I have ruled it out as the problem. I have good fuel pressure (12psi cruise, 6-8WOT). My problems started out about a month ago and can only be felt in lockup, but I'm sure it's there all the time. Cruising or accerating gently, it's still there. It has no hestation and will accerate as fast as I could want to go.



I have tried recalibrating APPS, cleaned MAP and IAT, unplugged box and tried different configurations of connection, cleaned all electrical connections and applied dialectric grease, changed air and fuel filters, check u-joints, ect, ect.



I am looking for the answer here too. I do get some fuel pressure variation (approx 1 psi) under cruise conditions. I am gonna recheck the torque on the injector high pressure lines.



If you get it figured out, please post it! I still chasing my issues down.



Dave

 

[monkfarm]

You might not have to send those 275s out to the laundry, that cummins injector cleaner works pretty dang good I think. (made by valvoline) Mine smokes some when I put in a good dollop of it in the fuel.

 

[Fishin Guide]

Actually, I don't have 275's in my truck. I do have some Don M EDMs and they were installed new about 1 month prior to all this. I could try some fuel cleaner, but I'm pretty sure they are okay.



But, I cannot rule anything out at this point.



Dave