1999 B2500/5spd stumble and bucking

[andrewb70]

Hello Everyone,

This is my first post and I hope that I can get some genuine help, because I am stumped. Some quick background on me, I have been playing with cars since my teenage years. I am not a professional mechanic, but I consider myself above average in terms of my wrenching abilities. I have built several hot rods from the ground up, but my daily driver truck is kicking my butt.

I have owned this truck since it had 28K miles. I am the second owner and I knew the first owner personally. Since I have owned it, I have taken good care of it, etc...etc...etc...It now has 108K miles.

A while back I started having the dreaded "rough idle" issue. To make a long story short, this lead to a head replacement due to recessed valves. The head replacement solved the rough idle problem, but now I have a new (did not have this issue before) problem.

ISSUE: There is an occasional, but persistent stumble when taking off. It tends to occur more if the engine is lugged down. It cuts out, almost like a momentary ignition cut. I can usually catch it if I press the clutch in, but occasionally it will stall.

The stumble also occurs under when accelerating and also while cruising at a constant speed. The whole truck will buck and jerk, as if the ignition is missing.

There is also a stumble when the throttle is "blipped" off idle with the truck not moving. It acts much like a lean stumble on a carbureted engine.

Items replaced in the last 2 month:

IAC
EGR valve and tube
Head
Timing belt and tensioner
Plugs, wires, coils
Crank sensor
Water pump
Upper water neck
Both coolant temp sensors
Accessory drive belt
Thermostat
Upper and lower radiator hoses
Air filter

I have also verified fuel pressure at the rail (65psi). The MAF has been cleaned with proper cleaner as has the throttle body. There are no codes.

When we replaced the head we paid very careful attention to the cam timing marks. We lined up the cam with the triangles, the oil pump with the diamonds and the crank with the dot. Once the tensioner was set, we rotated the engine two revolutions and confirmed that all the marks were still lined up. Once it was assembled, we reconfirmed the diamonds and the triangles through the inspection plugs with the balancer timing mark at TDC.

I know this truck has a lot more life in it, but the recent repairs have me frustrated.

Any and all help is greatly appreciated!

Andrew

 

[Denisefwd93]

I don't see catalytic converter on your list, we've had 2 non-believers in the past 2 weeks find bad catalytic converters

 

[rednik]

I’m having the same issue with my 97 2.3. I’ve replaced the cam sensor IAC and a whole lot of other stuff. The cam sensor fixed it for about a day then it came back. Idk about you but mine won’t do it if it’s a cold start. I thought for sure the timing was off but I verified it. Have you had any luck?

Is there any way to test the cat?

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[JJNOLA]

Check and Clean your EGR. When's the last time you changed your fuel filter? Could be clogged injector too.

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[JJNOLA]

Check and Clean your EGR. When's the last time you changed your fuel filter? Could be clogged injector too.

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Sorry I see you already swapped the egr. What about the DPFE and vacuum regulator? OEM parts? Did you hook the vacuum lines up correctly? I put Chinese parts on mine and it didnt like it, but I've since removed the whole egr system, tube and all. I'd still try a thorough fuel system cleaning.

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