Help Shaking over 45mph low RPM

[icebeast00]

96 nissan d21 hardbody automatic 103k. Have replaced transmission fluid, spark plugs and wires (and non foulers), fresh oil, new K&N air filter.

I have a shake in my truck that I can't pin down. It shakes and stutters/sputters when i get 45-55 (haven't tried it over 55), but only when i am decelerating. If i let completely off of the gas nothing. If I accelerate nothing. But if I let off the gas pedal and barely push (like if you were trying to keep a constant speed on flat ground) it shakes like hell. This is when the tach is at 2000 to 2500 rpm. If I turn OD off it goes away but then I can feel it when the car slows down to bring the tach back down to around 2000 but it is not as bad.

I have been driving around with OD off and that helps a little.

Any thoughts or help would be greatly appreciated!

[Rev_D21]

Welcome to NICO. Could be a bad u-joint on the driveshaft. Are we dealing with a 4cyl or 6? 2 or 4wd?

[icebeast00]

It is a 4cylinder 2wd. not to familiar with U joints, I will look into that. Any easy way to test it without replacing it?

[Rev_D21]

Lift the drive wheels off the ground and put on jackstands. While the transmission in neutral check the driveshaft for play or looseness at both ends. Also check the carrier bearing, the rubber sleeve it rides in can come apart allowing the driveshaft to move around which could cause a random road vibration. The fact that your vibration changes under a load tells me that it could be driveline related.

[icebeast00]

ok, i'll give that a try. Am i correct in assuming that there should be no play at all in the bearings. I'm not too familiar with drivelines.

thanks for the help!

[Rev_D21]

There should be no play at the u-joint. If they are bad they will chuck side to side while you turn the driveshaft back and forth by hand.

[osegundo]

When I had a bad u-joint it would only make noise when I was goin slow!! In my situation I didn't raise the vehicle or place on jack stands! I just crawled under and tried moving the driveshaft by hand... they're was excessive play on the u-joint!! Its not too complicated to replace and its very inexpensive!!

[icebeast00]

ok guys, sorry for the delay. weather here was crappy and I don't have a garage to work in.

I got the truck up jacked by the rear axle put the truck in neutral. The forward-most U joint had the slightest play in it, we are talking 1cm or so. The other joints all down the axle were rock solid. and the rubber grommet (carrier bearing??)for lack of a better term that the axle goes through is still cushiony (if thats a word) and is not cracked or dry rotted.

I double checked fluid levels (transmission and oil) they were ok. Everything on the air filter was good. Double checked tire pressure, same on all 4 tires.

Now since the bad weather I have to concrete filled tires in the bed of my truck for traction (2wd). I wouldn't think that would have any effect on the u joint play as long as i jack it up by the axle...correct?

So would that little play be the culprit or does this sound like possibly EGR issues?

Thanks for the help!

[Rev_D21]

Sounds like the drivetrain is tight. Going back and re-reading your OP it does sound more engine speed related. What have you checked so far?

[icebeast00]

I just got back from lunch and with the two weighted tired in the back of my bed it shook a LOT less. I could still fell the jumping/shaking but much less than it had been. Not sure if the added weight just muffled it.

I was also thinking that may signal that the issue is coming from the back end? U joint too tight at the rear axle?

A second thought, if it was engine related wouldn't the strain of the added weight exacerbate the problem?


As far as what I have checked just the fluid levels, fluids are fresh, and new filters, plugs and wires. Was considering taking out the EGR and spraying some brake cleaner on it but not sure how much that would help.

[icebeast00]

Okay so took the truck to the shop. Check engine light wasn't on, but they said they pulled an error code for misfire on cylinder 4. I had put non-foulers in, they pulled them out and said that was the cause of the misfire. They had no explanation for why it only misfired on cylinder 4 when I had non-foulers on all 4 spark plugs. The shake went away significantly, however it is still there. I ran it by Advance Auto Parts and pulled teh error code p304 misfire cylinder 4 and p1130 swirl valve control solenoid valve.

There seems to be all kinds of differing information on this part and whether it will cause the truck to run bad or not, and also whether it's easy to replace.

Beyond the mild shaking I am also getting horrible gas mileage, less than 10 mpg...

[Towncivilian]

Check the vacuum hose for the swirl valve control solenoid valve, it might be clogged or have leaks. See page EC-8 of the FSM for its location.

[Rev_D21]

Most 240sx guys disable the SCV. It acts sort of like a variable length intake runner in the fact that it changes the intake flow rate at cruising speeds to increase fuel mileage. Lots of folks disable it for maximum air flow rate. I had a number 4 misfire on my 96 KA24E and a basic tune up was the repair. Since it's all controlled by the dizzy I'd look from the dizzy to the plug.