1990 Dodge D150 318 Sputter Jerking Bucking BAD while driving 45mph +...idles great

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goodoledodge

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1990 Dodge Ram D150
Engine
5.2 318
I have seen several people complain of this problem but I still haven't seen a solution, just a bunch of ideas and the thread dies. This started to happen ONLY AFTER a bunch of work was done by a family friend skilled mechanic. The truck ran PERFECT before the work was done and the truck only has 69k miles on it. Originally I took it to the shop due to a small leak in the intake manifold gasket and my friend ended up doing all sorts of other things it needed for free I only had to buy parts. A lot of the parts you see on the list were because we were throwing parts at it trying to fix this problem.

Symptoms:
When I put it in 1st (its an auto) and take the rpms up to 2000-ish it starts missing and sputtering like a misfire or fuel issue, if you floor it the sputter goes away and pulls good. It will do that through ALL gears but when you lean into the gas it smoothes out AND you can also let off the gas and again it smoothes out. It clearly isn't running right but has full power under WOT. When you get up to 45mph+ and try to maintain the same speed like setting it on cruise control that's when the severe bucking, jerking starts......its really bad! It only does it when feathering/holding the throttle in the same position.......it WILL NOT do it when you floor it or when you let off the gas completely. This is not suspension related or tire balance, I know this is an engine problem for sure.

Here is everything that was done:
New Intake manifold gasket
New coil, wires cap & rotor & plugs (tried 2 sets of all these parts trying to fix the issue) I went BORG Warner the second time currently have a Blaster 2 MSD coil and even tried an autozone coil too but didn't fix it so I kept the MSD.
New Coolant temp sensor
New MAF sensor
New fuel Filter
New fuel injectors
New catalytic converter
New battery
New Valve cover gaskets
New oil pan gasket
New radiator
New water pump and thermostat
New Hoses
2 new sensors that plug into the bottom of the radiator
New motor mounts
oil change
tranny fluid change
Timing is set right at 6deg BTDC (I'm at sea level)
The truck was originally supposed to be 10deg BTDC but there is a recall 588 sticker on it for EGR valve that says timing should be at 6deg BTDC and it runs good as it is now.

The TPS, EGR and other sensors were also tested including the fuel pressure for the fuel pump. Everything seems good and I just don't see how a part could have failed by coincidence when the work was being done, I'm convinced it has to do with the parts that were changed. There are NO CODES either. No one can figure this out and if someone on here cant help me Ill have to take it to a master old school dodge mechanic after I research one and pay a lot of money to be fixed.

Please help me.....I can wrench myself and have also given many hours of trying different things. Today I just checked out the valve springs but again nothing is wrong there either. I have also used about 2 cans of carb cleaner trying to find a vacuum leak....but I cant find any leak whatsoever.
 

SmokedRam

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I don't see an O2 sensor change on your list there...I know it doesn't seem like an OBD1 O2 sensor would cause a lot of issues, but it has been my experience that they can. A lot of times a faulty O2 wont set off a CEL either...just something to think about.
 
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goodoledodge

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1990 Dodge Ram D150
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5.2 318
Getting a smog cert is what set this whole situation in motion. It failed the smog but because of a bad cat so I had a new cat installed and took it back for a second time and it passed. I smogged it with the intake manifold leak and didnt do any of the other work until AFTER it passed smog.
 
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goodoledodge

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1990 Dodge Ram D150
Engine
5.2 318
No they look great and the emissions smell right. Yesterday I pulled the plugs myself even though the previous mechanic already had installed 2 different sets trying to make the problem cease. I got a little excited to see the gap on all plugs was set at .25 so I gaped them to .35 and still nothing.
 

88rambigblock

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I had that problem with the old tbi, but I took that off and put on a 500 cfm carburetor AMD that solved my problem. Just my 2 cents worth.
 

jimmy-r

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1993 d150
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5.2 magnum mfi
i have the same bucking and jerking issue. and like you have changed everything. timing gears, chain, plugs,wires, every sensor except exhaust o2. and still it idles like a dream but at 45 mph or so bucks and jerks. and there is a loud metalic ping not like fuel ping but metal hitting metal. i had left the auto OD unplugged when i had the dash out once. ran like crap. would that have anything to do with it? desperate
found an old service bulletin that suggested the oil pump drive gear will wear causing bucking, surging, pinging and lack of power. that will be my next attempt. any thoughts?
 
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goodoledodge

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1990 Dodge Ram D150
Engine
5.2 318
i have the same bucking and jerking issue. and like you have changed everything. timing gears, chain, plugs,wires, every sensor except exhaust o2. and still it idles like a dream but at 45 mph or so bucks and jerks. and there is a loud metalic ping not like fuel ping but metal hitting metal. i had left the auto OD unplugged when i had the dash out once. ran like crap. would that have anything to do with it? desperate
found an old service bulletin that suggested the oil pump drive gear will wear causing bucking, surging, pinging and lack of power. that will be my next attempt. any thoughts?

Regarding my truck, I know it has nothing to do with anything trans related and is isolated to the engine alone. When it's in neutral and I give gas to keep the rpm's at 2000 it will slightly sputter which is what is causing the bucking at higher speeds. In fact it will buck at all speeds but becomes increasingly bad to where it seems damaging. I'm going to change the intake manifold gasket AGAIN and if that doesn't work I'm going to try rebuilding the TBI. If that doesn't work I don't know what else to do. It ran great before it went into my friends shop where they did lots of minor repairs including the intake manifold gasket.
 
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goodoledodge

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1990 Dodge Ram D150
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5.2 318
The whole time I had a bad distributor. I replaced with a new one and it finally runs smooth. I have had this problem daily driving for well over a year, what a relief to drive it now.
Just hit 71k miles
 

Deblackmon3

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1990
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LA 318
The whole time I had a bad distributor. I replaced with a new one and it finally runs smooth. I have had this problem daily driving for well over a year, what a relief to drive it now.
Just hit 71k miles

Only the distributor? Geez, that sucks you spent all that money and then it was a simple fix. At least you won't have to worry about any other problems for a long time!
 

rambam!!

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My 89 was doing the same thing you were describing and it was the distributor cap and rotor was all it was then it started doing it again and all I had to do was clean the cap and rotor connections and it's ran like a champ.
 
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