Engine/Transmission (1998.5 - 2002) Bad miss unber heavy load

[DSeamans]

I noticed it a week ago while aggressively passing someone. Then today I was hauling a trailer and going up a steep hill in 5th, it really started bucking. The harder the pull, the harder it misses. It does it anywhere from 1750 to 2500 rpm. Last year when it got cold, I would feel it just a little, but stepping on it and it would go away. Now, the harder I push the pedal, the harder it bucks. The tach jumps almost 100 rpm. Its only done it since it got cold again. Right at 30k miles ago, I replaced the VP, injectors, turbo, transmission and clutch, and put in the airdog. When it happens, temp is normal, fuel is at 18lbs, preturbo EGT is 8 -900*, and boost anywhere from 15# to 28#. The MAP is less than a year old and cleaned less than 3k ago. Taking the EDGE off still does it, the higher the level the worse it is. Any ideas where to start looking? Sensors, ECM, VP? Sorry this is so long, but I wanted to give as much info as possible.



Thanks for any help,



Dave

 

[JLandry]

Dave,



Dumb question maybe, but have you checked for trouble codes after an event like this? If yes, what are they?



Thanks,



John L.

 

[bromano676]

try the apps

 

[DSeamans]

No codes. After I thought some more, I remember a couple times this summer when it did something similar except it was at idle before the engine was fully warm. Coasting out of the driveway with the clutch in I would hear a short miss and see the tach drop and then come right back up. It was very sporadic and only at idle. Today's started when pulling a good hill. I wasn't increasing throttle when it happened. And I only feel it in 5th and 6th gear. Through 4th gear and it accelerates smoothly no matter how soft or hard I step on it. Its only under heavy load with the boost up. My gut says VP but I don't know what else could cause it. If it was a gasser, I'd say it was a week fuel pump, running out under load.



Dave

 

[georgej]

Dave

I had a miss that started when the weather turned cold a couple of years back. There were no codes and the miss would come and go. Jim Anderson noted in TDRV about many gremlins being produced by electrical connections that had oxidized over time and recommended disconnecting and reconnecting various sensors. In my case I did the map sensor and smartbox power module and cleaned the battery posts. I may have unplugged the VP connection also but whatever I did ended the miss. It has now come back(truck has been idle for about three weeks) ,today,on a 20 mile trip. I only did the battery and map sensor to see if I can pinpoint what area is causing the occasional miss.

Hope one of these suggestions works for you.



George

 

[DSeamans]

Connections

George, thanks on that answer. I hadn't thought of that and it definitely makes sense. I'm usually pretty anal about connectors and use cleaner and dielectric grease. I've done the batteries, but haven't done any others in a while due to time constraints. I'll get at it at least by the weekend and let you know!



Dave

 

[ROADWARRIOR]

Check the Edge Map connectors for sure. I've had similar problems twice and both times it was the Edge harness Map connection and ot cable. I got sick of dealing with it and sold the Edge box after I sent it in for repair the last time.



Dan

 

[georgej]

Dave, After cleaning the battery posts and map sensor, smartbox connections the miss has stopped on my truck. I think that if it comes back next year or so I'll just clean the map sensor connection to see if I can pinpoint it. Have you got a chance to check your truck?

 

[DSeamans]

Not yet

Things have been too hectic and I'm out of commission right now. Hopefully tomorrow I can get it in the garage. Wife and kids think they own it during the winter!



Dave

 

[Sticks]

What is the boost gauge doing when this happens, more to point, how much boost?

I had issues with my Edge EZ getting into an argument with the VP, would defuel @ 21+/- psi then dump it back in. READ - boost fooler feature was not working like it should.

EDIT - After re-reading your initial post, is it an engine miss, or erratic engine speed. I don't wonder if your clutch is slipping under load or got wet (oil).

 

[DSeamans]

Better but still does it

I cleaned the batteries, grounds, IAT and connector and the MAP connectors and the main edge connector. I used dielectric grease on all. It is better, but still does it around 2100 -2200 rpm when I'm on it pretty good. Its not the clutch as the rpm drop when it does it. Boost is 23 - 26lbs when it does it. Boost fooler would do it. Now that everything is cleaned I'll have to pull the box again and see if it still does it. And I have to rebuild my buddy's rear diff and my father-in-law just came home and the brake pedal on his 99 goes to the floor. It never ends with these things.



Dave

 

[ROADWARRIOR]

When you pull the box, make sure you pull the Edge MAP connectors out of the equation. That is how I found mine the last time.



Dan

 

[Sticks]

Might want to try to relocate your ground for the Edge as well.

 

[DSeamans]

update -slightly different symptoms

Sticks - the Edge is grounded to the batt terminal.



Now, its not just full load. Cruising anywhere from 40 -65, 4th -6th gear, 1600 -2000+ rpms, almost no load, and then slightly increasing load, like pulling a small hill, and it misses pretty bad. My wife even felt it and she couldn't hear or feel a wheel bearing about coming apart on her jeep. Step on it a little and it goes away until until I get rev'ed up and it comes back. Could this be the VP44 getting weak? Low power and it misses, pump up the pressures and it keeps up? I replaced it about 40k ago from MWFI. I haven't thought it was right since I put it in. When I changed it, I added the AIRDOG, the 1. 6's, and the hybrid turbo. I felt like there should have been more power, as it didn't even feel as good as before the changes. The biggest thing was the EGT's. Cruising they were OK, but pulling a load and I couldn't hardly touch the go pedal and they were at 1300. The 1. 6's and hybrid were supposed to be great for towing. Could all of this be tied to a pump that wasn't right from the start?



Thanks for the help,

Dave

 

[Sticks]

At this point with our symptoms, I'd say the time for a professional diagnosis is in order before you roast something.



Coming and going is odd. Just because you have a new turbo, pump and injectors does not mean they are not suspect. Depending on the install, some contamination may have gotten into the fuel system (or oil for the turbo) post filter and is causing problems.



There are things to look for. Wetness around an exhaust manifold mounting or post turbo, what type of smoke is coming out the tailpipe when it does happen.



If this came into my shop (where I used to work), I'd pull and test the injectors, check the oil for fuel contamination, perform a cylinder compression and leakage test, check the valves to see if one of them is sticking, get a scanner hooked up and see what the timing is reading if it can be duplicated on demand, air in the fuel (the right conditions can cause retarded timing on one or more cylinders = no bang but wet cylinder), make sure the turbo is not hanging up... and if all of this proves OK, pull and bench test the VP.



High EGTs point to over fueling or extreme timing on either side.



You have it narrowed down to a RPM range, can it be done in all gears? May need a steeper hill to duplicate load.



No codes definitely points to mechanical issues.