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Bucking and jerking not running right

13K views 105 replies 12 participants last post by  tommyboy8072002 
#1 · (Edited)
HI I have a 1996 Chevy C3500 5.7 manual transmission. I let the truck sit for 4 to 5 months to have my transmission rebuilt. Drove the truck for the first time after all of the work was done. Broke down and was running like crap so I changed the following Plugs, wires , rotor , cap , fuel flitter, Ignition control module and coil ... I also put fuel treatment in the gas tank and went with high octane with non ethanol fuel. Still not running right bucking and jerking when under a load. with high rpms runs fine. NO CODES. I don't understand ran fine the day I parked it
:confused:
 
#56 ·
The engine performance wont be affected by a Defective VSS. The trans on the other hand....:D
The speedo can jump around on that particualer vehicle while the thing is in PARK no less. Usually a cluster problem, or a ground problem, mostly the cluster at least that I have seen.
 
#57 ·
Thanks Everyone for trying to help me with this truck. When I pulled the transmission out to have it rebuilt I did notice all of the bolts on the bell housing didn't have any studs on them. I don't know if its because its a 5 speed manual transmission if that is why or not. my obd2 did clear the codes because I have a code reader. I ran 8 gage wire from the frame to each head made a difference. Not popping anymore. And its charging the battery. Before it would always discharge. But still running a little rough. But not like it was. I will drive the truck and see if the codes come back. When I unplugged the MAF sensor It quite. Once I plugged it back in it stays running. How do you clean the MAF. I will check the wiring with my test light or my ohms meter. let you all know what I come up with. Also check Fuses. Yes when I parked it. It ran fine.

Thanks
Tommy
 
#62 ·
Vehicle Speed Sensor.Controls shift points or shift light with stick shifts,dash control,in part also controls fuel curve and spark advance along with crank sensors.Because it is a replacement trans,the last touch theory might come into play.
A easy way to detect a clogged cat is to pull the upstream O2 and run it like that re-leaving the back pressure.If that resolves the issue then the cat is clogged.
 
#60 ·
bucking

MAF sensor cleaning is easy. Unplug it, remove it, use a MAF spray cleaner to the inside of it...you should be able to see a small screen inside it, just spray it down good. Any dirt or debri on that little wire in there will cause it to read incorrectly. Just the spray, dont try to wipe it off or use a brush to clean it. Bolt it all back together and see if you have improvement.
 
#61 ·
If you are not getting codes related to the maf or lean codes you can do more damage than good trying to clean it. I would see if the codes come back. I still think you have grounds missing somewhere. You had circuit codes on several sensors. This is usually a broken ground or missing voltage issue. Standards and automatics from what i have seen have grounds on the transmission bolts. Grounding the body to the engine as you did may have partially solved the issue by supplying a non direct path to ground.
One thing you could do if you have a volt meter is check to see what the voltage is on the map sensor between the b+ and ground IN THE CONNECTOR.
 
#63 ·
Just took a look at the ground distribution on that vehicle. Seems the grounds are on the front right of the engine. One set is attached low on the block and the other set is on the front of the right head. I believe the low ones are also where the battery cable is attached. It does not appear on that truck there are grounds on the bell housing. Sorry to send you on a witch hunt:pain:
 
#64 ·
Yes It was running fine. Till I pulled out the transmission. No codes yet. It's starting to do the same thing again popping and running rough. While driving. seems like it was to brake down on the side of the road. I Think its getting too much gas. I am wondering if its the Ignition Control Module even though its new. Has anyone gotten bad parts At Auto Zone?
 
#75 ·
I suggested ground wires on the head because several years ago we built a 351 Ford powered kit Ferrari California Special which uses an MSD ignition system. The owner doesn't like the multiplicity of ground wires and keeps removing them. We've been through a couple, three fried MSD boxes already as a result. He was back a couple months ago with symptoms very similar to yours so I replaced the box and built new head grounds; again! Problem solved for now. So in your case, if it's high voltage getting back into the MSD from a lack of head grounds, the electronics are fried, maybe not out to lunch, but certainly limping.

This is not to say there aren't other causes or contributors that I don't know and can't answer because it isn't my head under your trucks hood.

I will say after having sat unused for some time it could be the injectors or the poppet’s at the end of the injection tubes, the failure of the poppet’s is well documented for the Vortec engine. A cleaner sometimes helps if it's gunk that can be dissolved and washed away, if it isn't or doesn't, the problem will remain. It was suggested that you look at the plugs this can be helpful. Certainly a poppet that's dribbling will show as a fuel wetted plug this can be black carbon to gas wet. A poppet that isn't lifting would probably result in a cylinder not firing or not firing hot enough to keep the plug clean so the plug would most likely be oily wet, maybe a bit fuel wet as well. But this can be a bad cam, lifter or valve as well. A miss firing ignition will probably show wetness on several to all the plugs. A vacuum leak will dry the mixture out make it look lean, one or more of the plugs will be light to white in color where the mixture is lean resulting in a high operating temperature in that cylinder. Keep in mind that checking plugs that are in a failing engine can be deceiving because in many cases the engine can't be run enough to bring it to operating temperature nor put operating loads on it, this will result in the plugs appearing carboned or even wet. It can also lead to conductive paths on the insulator so the plug doesn't perform correctly even though the root cause problem of the engine has been fixed; new plugs would be required in this case. Which is something you’ve already done with no improvement? Not to say it won't need a fresh set again, just pointing this out.

Bogie
 
#72 ·
At this point you need to pull all the spark plugs out, keep them in order that they were removed and look at them. Are some black and some clean? If so...the injectors would be a problem.
If you have a scanner that gives live data, look at the fuel trims and the injector pulse width.First look to see if they are both pretty close to each other.
A fuel trim that is going - > 5% ( like - 25% for instance) on one bank that means the PCM is trying to correct for a rich running problem limited to one side of the engine.
Most likely leaky injectors.
If the trim is going + > 5% ( Like +25% ) that means it is adding fuel to correct for a lean condition , like an intake leak for instance. Trims run from data supplied by the oxygen sensors, so if trims are moving, sensors are working.
Cylinders 6 and 8 burning plug wires may be indicative of excessive heat, from excessive fuel, caused by leaky injectors. Just sayin. Check it out post back here. LA Tech
 
#73 · (Edited)
Thanks LA TECH. I will check the plugs and also see if I know someone that has a scanner. I have been driving the truck for awhile now. And still hasn't brought up a code. I did forget to plug in my Wiring for reverse lights at the very top of the transmission. But I don't know if that has something to do with it or not. Anyways I am going to drop down the transmission a little bit and plug it in. I am also going to look for grounds while I do that. Hey LATECH do you know what the ohms suppose to be on the EGR valve and on the map sensor..?

Thanks again
LA TECH
 
#74 ·
I did something the other day to mine that helped. Bought a 3/8" OD hose about 3 feet long at Lowes. Removed the air cleaner assy. Started it and put one end of the hose in my ear, the other I moved around all of the gaskets and sensors(wiggled the MAP sensor) listening for a hissing sound. Found two leaks. One was the MAP sensors "bellows", the other was a broken o-ring on the hose adapter that plugs into the manifold that goes to the brake booster.
Runs better and only cost about a buck for the hose. 3 bucks for the o-ring.
ssmonty
 
#76 · (Edited)
I dont have values for the EGR. You can however, if you suspect the EGR , would be to cut a pop can open and make a blocker plate , for the EGR. Shape it like the egr gasket and slip it inbetween the intake and the EGR to block any flow or leakage. Super simple.
I am with bogie, my thoughts are problems with the injectors. Months of setting with todays quality fuels in them...LOL.
Probably corroded to death
 
#83 ·
You have to be a bit careful when reading plugs, fouled plugs can be too much fuel, oil, too cold a heat range, missfiring, leaking valves, wiped out cam lobes.

The only thing the crud tells you is one or more of those things are not working right. When you get some messed up and others not it's a pretty (especially if this is 180 degree intake and the fouling is not linked to one plane or the other) good indicator that the ignition is messing up but this ain't proof positive. On the other hand if the fouling tends to be common on cylinders feeding from one of the two intake planes, it raises the odds that fueling isn't consistent on one side of the carb/TBI injectors.

Bogie
 
#84 ·
Given that he tuned it up and still has the same issue , I am leaning to the only thing left here.The spider (injectors) are showing their age.
Number 3 plug is obviously fuel as it is Black.
It could be an ignition problem....but he allready changed all that and has the same problem.
IIRC he said he allready performed a compression test.
 
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