Engine/Transmission (1998.5 - 2002) Bucking or missing in 4th and 5th gears.

[ROADWARRIOR]

Recently installed a new VP44 and the truck ran great, at least I think. Then one day while accelerating good up a hill in 4th gear, the truck starting bucking/missing pretty good. After that, it ran good the rest of the day. Got home and had a 238 overboost code. I thought this was odd with the Smarty boost fooling and the Comp box boost fooling. I cleared the code and regreased all my MAP sensor connections and cleaned the IAT and MAP sensors. Truck ran good for a while and now it is missing/bucking whenever in 4th or 5th gear giving it anymore throttle than necessary to hold speed, this includes partial to WOT, it will miss to redline. It's not as bad as the first instance and now there are no codes. I tried a APPS reset and that didn't help. The carrier bearing mount is tight. I also checked for AC voltage off my alternator and it measures ok, and 14. 03vdc. My other thought is when I had the injector lines off, I noticed the #4 line end that terminates into the crossover tube had what appeared to be residue on it, possibly from a bad connections. The crossover tube also showed this brown discoloration on the bottom side. Also the injector line ends have grooves worn in them from where they were tightened against the tubes. Is this normal? I'm wondering if I have a leak inside the head causing the miss. The miss may be there all the time but only obviously noticeable when on the throttle. This miss does happen with the box off also, only less pronounced.



Thanks,

Dan

 

[ROADWARRIOR]

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[ROADWARRIOR]

I found the Comp's male MAP plug had green pins, this was even with the connector filled with grease??? Anyways, I cleaned it up and I would say that it got about 70% better. So, I completely unhooked my Comp from the circuit and I will give that a try tomorrow. One thing to my surprise was my cruise EGT's went from 800 on the flats to 600 after cleaning the MAP connector, so I think my mileage may improve some. Keep in mind I haven't had any codes other than one 238 about a month ago.



Dan

 

[Alphacowboy]

I had that problem as well, bucked under hard acceleration, BUT, only when the Comp box was on. What connector are you using on the pump tap? I ditched the scotchlock pile of crap last week for a posi-tap connector, and the surge is gone, and it runs alot better at WOT now with the box on.

 

[Graphic man]

what is your fuel pressure like??



it could be a bad box, but take a look at the fuel side of things also,



the bucking/missing sounds to me like a fuel issue.



Scott

 

[ROADWARRIOR]

Alphacowboy, I don't have my pump wire tapped at all.



Graphic Man, my FP is steady at 12 to 14psi with my FASS 150.



I put on 100 miles now and the bucking hasn't happened since I bypassed the Comps MAP plugs. I think the corrosion migrated past the pins and up into the wires themselves.



Dan