95 jimmy bucking

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BAD SVT

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Figured i'd start a new thread on this. A new problem has developed. It might be a little hard to troubleshoot here, so i'm probably gonna pay a shop some diag fee to tell me what it is. But if anyone has an idea, pls post thx. So here's the problem: I'll start by saying this problem is most definitely an RPM/LOAD issue, and it only happens between 1 & 2k rpms. As the truck accelerates, it upshifts fine. However, as soon as the rpm needle drops to about 1500k rpms at cruising(40-50m/h), the truck starts to buck slightly as long as i keep my foot perfectly stationary. And at this point, i can see the rpm needle bouncing up n down. But when i step on the gas, the bucking goes away.. This also happens when i'm on a slight incline. Speed seems to be inconsequential as this happens between 15 & 30m/h also. So far my guesses are Idle Air Control Valve, Mass Air flow sensor, Cam sensor, or tranny. Lol. I know wide spectrum of possibilities... Thx
 
Nothing ventured ...

Try a scan and see if anything shows up.
Maybe you get lucky ?
 
clean egr . had same problem and thats what mine was
 
BAD SVT said:
Thx guys. I'll try the egr cleaning first & see if that helps. Then do a scan. I guess that'll be part of the diag steps that a shop would take...
Click to expand...

The difference being that a shop would do the scan 1st..:eek:
 
ferretx9 said:
The difference being that a shop would do the scan 1st..:eek:
Click to expand...

Good thing, cuz it isn't the egr. There wasnt that much sludge in it really. I guess i've gotta shell out 90bucks for this one...:mad:
 
Just an update to this: I never did take it to a shop to get it looked at. I've been driving it this way since. Nevertheless, its become obvious over time as its gotten slightly worse that it just might be the tranny or whatever it is that controls the RPM/tranny. As the temp recently dropped, now from a cold start when i put it in Reverse, the rpm needle starts to hunt wildly as the truck bucks back n forth. Also when i press on the pedal, the truck doesnt engage. Odd thing is when the truck warms up, it all goes away. Anyone have any more ideas? If not, i will NOT be replacing or fixing the tranny. I just did that last year. No way i'm spending a grand on fixing it. I most likely will be disposing of it & picking up sumthn else.
 
BAD SVT said:
Just an update to this: I never did take it to a shop to get it looked at. I've been driving it this way since. Nevertheless, its become obvious over time as its gotten slightly worse that it just might be the tranny or whatever it is that controls the RPM/tranny. As the temp recently dropped, now from a cold start when i put it in Reverse, the rpm needle starts to hunt wildly as the truck bucks back n forth. Also when i press on the pedal, the truck doesnt engage. Odd thing is when the truck warms up, it all goes away. Anyone have any more ideas? If not, i will NOT be replacing or fixing the tranny. I just did that last year. No way i'm spending a grand on fixing it. I most likely will be disposing of it & picking up sumthn else.
Click to expand...

Start with the simple and clean out your throttle body and you did mention you were going to clean your EGR but did you?? Also inspect your TPS for any erratic readings when its still cold and the resistant reading could be erratic and it may need to be replaced.

Start with that and also check all your vacuum lines for cracks and replace any damaged lines. Post back and lets see about getting your jimy running 100% again soon.

Molson02536
 
Molson02536 said:
Start with the simple and clean out your throttle body and you did mention you were going to clean your EGR but did you?? Also inspect your TPS for any erratic readings when its still cold and the resistant reading could be erratic and it may need to be replaced.

Start with that and also check all your vacuum lines for cracks and replace any damaged lines. Post back and lets see about getting your jimy running 100% again soon.

Molson02536
Click to expand...

Thx. I already cleaned the EGR. I havnt done anything about the TPS tho. I figured if sumthn was wrong, the "Service Engine Soon" light would've come on. I'll try replacing the sensor just in case. And i doubt theres a vacuum leak. Any leak this large is sure to throw a lean code. I'll check again. Other than the ones on top of the engine, there isnt any other vacuum lines anywhere else, right?
 
BAD SVT said:
Thx. I already cleaned the EGR. I havnt done anything about the TPS tho. I figured if sumthn was wrong, the "Service Engine Soon" light would've come on. I'll try replacing the sensor just in case. And i doubt theres a vacuum leak. Any leak this large is sure to throw a lean code. I'll check again. Other than the ones on top of the engine, there isnt any other vacuum lines anywhere else, right?
Click to expand...

Nope and keep up the great work and post back. ;)
Molson02536
 
You would hear a vacuum leak as you increased idle speed. Would lead you right to the problem.
Throttle Position Sensor would be my guess. It will do this as you described.
Good luck.
 
10r said:
You would hear a vacuum leak as you increased idle speed. Would lead you right to the problem.
Throttle Position Sensor would be my guess. It will do this as you described.
Good luck.
Click to expand...

Thx for the addition. But i'm pretty sure its the tranny like i described. It slips when cold & is fine when warm. My research online leads me to believe that its the pump inside the tranny that works hard when the fluid is cold & thick. But it's job becomes easier when the fluid is heated up a bit. And i got the 'SES' light read just in case there's a pending code. None...
 
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