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

22K views 42 replies 9 participants last post by  Gen1dak 
#1 ·
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.

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:
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 one too but didn't fix it.
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 dont see how a part could have failed by coincidence when the work was being done, Im 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.
 
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#2 ·
Sounds like it might be the fuel pump, check the fuel pressure. Since it's fuel injected fuel pressure is crucial for proper operation. Also I think you might want to have an ignition timing of 10 BTDC, it builds a little more torque at higher speeds for more power. It's possible but don't hold me to it that your ignition timing is why you get buckling at 45 ish.
 
#3 · (Edited)
The fuel pump and pressure was checked several times and is on spot...and remember that it ran great perfect before hand. This all started because I received a smog notice. I took it in and it failed due to a bad catalytic converter so I had a new cat installed and took it back for a second time and it passed which also excludes the o2 sensors. Not to long before I smogged it I noticed that it was leaking a little coolant which is the original reason I took it to my friends shop, but in doing so we noticed a few other things it needed cause the truck doesnt get driven much plus its 23yrs old. I get the truck back and BAM......major noticeable shudder and jerking not to mention the misfire/sputter at low speeds. Makes no sense but everyone has given up and cant figure it out.
 
#4 ·
Ahh Ok, well fuel pressure is out. Timing is a possibility... It could be a great many things, could be a transmission issue but I highly doubt that, highly. Without looking at it I couldn't tell you where else to start, but usually problems like this are somehow someway fuel related. If not possibly spark related but you already replaced the ignition. I would maybe mess with the timing a little more, just incase. And I know exactly what you mean by the truck not being driven and it being old, I had restored my ram van and well sat for years in the florida sun and everything was rotted. So far I custom built the transmission, had a custom built dynotech driveshaft, upgraded the 7290's to 1350's. New tires, new hoses, new rad, new rear end suspension, new shocks, new new new new new. ..... Next I'm building a new engine for the thing.
 
#10 ·
I don't know how to check proper function other than visual inspection which I did and have also replaced two dist caps, two rotors, 2 sets of wires AAND 2 coils. I have vacuum advance on my 67 Mustang and although it may be better it doesn't make sense how it would cause the bucking Ram.
 
#12 ·
You know what came to mind and it's very possible, you are having an EGR valve problem. If you open an EGR valve at idle it chokes the engine, if you open it under load then the engine will bog down because it doesn't produce max power. So it's possible you have a malfunctioning EGR valve.
 
#13 · (Edited)
A change in timing from 10 degrees to 6 degrees will not cause sputtering.
The TBI engines do not use mechanical advance nor vacuum advance distributors, nor do they have frigging POINTS!. The ignition advance is handled by the computer....electronic ignition advance. Chrysler first implemented electronic distributors in 1972 and rapidly phased it into all models in short order, with widespread use in 1973, and while vacuum advance carried on for many years after, it was gone before the first TBI units. (The first computer-controlled units were the Lean Burn models in 1976). If you have swapped a new distributor in, that pretty much rules out the ignition pick-up in the distributor.
You replaced the injectors....but in the original throttle body? Even they (throttle body) need to be rebuilt occasionally. The part-throttle mis-fire makes me think of a vacuum leak. Either the throttle body is leaking or maybe the EGR isn't working properly. Try capping off the EGR ports on the throttle body, as well as on the EGR side, see if that helps.
It is also possible that the intake manifold may not have been seated properly and is leaking, but I'd focus on the other issues first.
While the TPS may have checked out, how old is it? I'd toss it. Ditto on the O2 sensors. Remember to reset the computer by pulling the battery cables for a few minutes. You don't have codes, but the computer must be reset to see new sensors.
Worst case, you may have a failing computer. Check all those vacuum lines. Might just be a leaky hose or an open port.
 
#14 ·
A change in timing from 10 degrees to 6 degrees will not cause sputtering.
The TBI engines do not use mechanical advance nor vacuum advance distributors, nor do they have frigging POINTS!. Chrysler first implemented electronic distributors in 1972 and rapidly phased it into all models in short order, with widespread use in 1973. If you have swapped a new distributor in, that pretty much rules out the ignition pick-up in the distributor.
You replaced the injectors....but in the original throttle body? Even they (throttle body) need to be rebuilt occasionally. The part-throttle mis-fire makes me think of a vacuum leak. Either the throttle body is leaking or maybe the EGR isn't working properly. Try capping off the EGR ports on the throttle body, as well as on the EGR side, see if that helps.
It is also possible that the intake manifold may not have been seated properly and is leaking, but I'd focus on the other issues first.
While the TPS may have checked out, how old is it? I'd toss it. Ditto on the O2 sensors. Remember to reset the computer by pulling the battery cables for a few minutes. You don't have codes, but the computer must be reset to see new sensors.
Well that is why vehicles have issues, getting rid of old fashion ignition lol... See I assumed he had an old fashion ignition because he was able to do timing adjustments. I'm use to the magnum engines so much that don't allow you to do traditional timing adjustments. But anyways I already realized maybe an EGR issue. But I spend most of my time designing the engine instead of fixing them. Kind of like the engineer makes it but cannot fix it and the mechanic fixes it but knows nothing about engineering it. Certainly I can fix it but not over a website haha. Kindof like that funny commercial of the doctor trying to perform heart surgery over the phone haha. Anyways thanks for coming in and saving me.
 
#19 ·
I might look into egr it sounds like its not working and chokeing own eng. If I remember right all sensor dose is regulate vac pressure to egr its self. So test it with vacc pump make sure its opening and closeing right.
 
#23 ·
Smog test won't always rule out a bad egr. The way they used to do it in missouri the car woulbe at idle so egr wasn't used. Then they went to a running test on a dyno. That was more accurite but the tecs blew up or broke a lot of older cars. So now cars over a certen age don't get tested. I think its 96 or older cause now they just go through data link.
 
#24 ·
This is why I like both my trucks no egr on ether one. 82 blocked off and they did away with it on my 01. My 94 vortec played hell with egr valves. They carbened up about once a year and run bad and studder.
 
#25 ·
Yeah you're kinda stuck in the middle there. Common sense would tend to say since it passed testing it should be okay. I tend to think you should focus on areas affected by the recent work. And old TBIs need rebuilds. My experience with TPS is one day they work, next day they don't work so well, but top of the list is something vacuum related. Idle and WOT tend to hide vacuum leaks. EGR could've been contaminated during work, something got jammed. Rule out old stuff by clean-sweeping it. Get new parts.
 
#26 ·
I just replaced the EGR valve and it still didn't fix the problem. I also removed the vacuum line loom and tried spraying the lines and everywhere else and couldn't find a thing. I know how to work on cars but I'm not very technical when it comes to how sensors work etc. For instance I have no idea what a bad TPS sensor does or would do if it were not working properly. The only thing I can try next is replace the TPS and if that doesn't work I am completely out of ideas and dont know what else to do other than take it to someone who knows these 1st gens really well and pay a lot to hopefully fix it. At this point Im thinking that even someone like that wont be able to diagnose it either.
 
#27 ·
The throttle position sensor works like a resistor. It regulates voltige to computer from the micanical link of the throttle cable on opposet side of throttle body. So basicly when the throttle is at idle the voltage comeing from sensor is at its lowest point so computer slows timeing for fuel injectors. And as you open throttle voltage increses to sensor telling computer to increse timeing to injector till you finaly hit wide open. Now that's not technical deffinition. More the way I understand it. Fisher price.
 
#28 ·
one thing I've seen cause this issue is a broken tone wheel for the distributor, or loose distributor shaft bushings. The pickup gets a mixed signal when either the shaft moves, or if there's a problem with the tone wheel. The distributor pickup itself can also cause this sort of concern. easy thing to check out, just pull the distributor out, check for shaft play, take the pickup out, and verify that everything is ok in there.
 
#29 ·
I changed the TPS and just like I thought it didn't fix the problem. I haven't checked the tone wheel in the distributor yet but I really don't think that's where the problem is either. It ran perfect before the intake manifold gasket and radiator work was done.....all of the other parts that were installed were only purchased at an attempt to make the issue go away.

After hashing this out with my uncle who was a mechanic for years, we both agreed that the problem must be that the intake manifold gasket wasn't installed/seated properly. I really didn't want to have to remove it and re-do the gaskets but at this point I have weeded out ALL other possibilities and this last option makes the most sense because it ran good before it went to the shop.........crap!!! I appreciate any additional input you guys may have
 
#33 ·
Is it at all possible that the cause of this problem could be caused by the Air Injection Crossover Tube? Both sides have significant exhaust leaks at the flange where it connects to the exhaust manifolds. I bought new gaskets and installed them today but realized the threads on both sides inside the exhaust manifolds are stripped and you cant tighten them down hard enough to seal at the flanges. Since those are emissions related I wondered if that was a possibility.
 

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#34 ·
I doubt that any leaks at the air injection tube connections are causing such a severe affect on drivability however it's still a air leak that needs to be tended to. If the holes are stripped, you could tap, re-thread them and use new bolts.

When you mentioned that you replaced the fuel filter, which one did you replace? Not sure if it's the same on a '90 but I had an '88 and there are two filters - an inline canister style mounted on the driver's side frame and a fine metal mesh style in the fuel tank. The fuel tank filter can get gunked and chunked up from infrequent driving and easily cause drivability issues.

A faulty EGR, cracked distributor cap and a random vacuum leak may also be the culprit although from your previous posts, it sounds like you have investigated those issues. The bucking you describe sure sounds like an ignition timing issue. For years, Chrysler used a nylon tooth, single roller cam timing chain sprocket in their non hi-perf small blocks. They are prone to premature wear and even breakage. You can set the timing all you want but a worn sprocket and/or chain will bump it off, sometimes minimal or alot until you reset it again. Worse yet, the chain could jump a tooth. Not the end of the world as the Chrysler small blocks are virtually indestructible but still not a happy experience.

Get rid of the cheapy single roller sprocket and chain and swap in an OEM double roller 340 chain and sprockets. The sprockets are all metal and the double link chain is heavy duty. It's an economical, no worries way to ensure rock solid ignition timing and peaceful motoring. Set the timing and forget about it! Just trying to help.:wavey:
 
#35 ·
The issue I have with that idea is the truck only has 69k on it and ran perfect before it went to the shop. The filter I replaced was the one mounted near the frame rail......and again that was another part that was thrown at the truck at an attempt to fix the bucking/misfiring. It also has full great power at WOT and even chirps second.
I appreciate your input
 
#38 ·
It could be the TBI but I am thinking that it has got to be the manifold? The only doubt I have is that I can't detect any leak in the manifold with carb cleaner and if there was a leak I "should" be able to find it. I really dont want to take it off in fear of that not solving the issue. Decisions decisions!
 
#43 · (Edited)
For some reason I was thinking you'd already addressed that. Typically, it's not the actual distributor in these models, rather, it's the ignition pick-up inside the distributor. Either way, you now have a new pick-up with the new distributor. With all the other stuff you've done, you should be rolling for many, many miles to come, and despite the total cost, it's a pittance compared to a $30,000 (plus interest) car note. Good job sticking with it. All too often these trucks just get pushed off to the side and forgotten over what ultimately turns out to be a relatively minor problem. Keep 'em rollin'. Keep in mind, if at some point down the road you cannot get certain computer-related parts, it's not that difficult to roll back to a carb and earlier ignition system. So far we aren't in that situation (I have a 1990 Ramcharger), but it's an option.
 
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