Heavy Vibration and Misfire after long uphill Climb

[gbsharon]

After many searches and fixes, I have decided to post about the trouble I have been having. 99 2Dr, 200k miles. I have recently done fuel filter, MAF, plugs, wires, cap, distributor, seafoam on injectors. I am getting a vibration while climbing long uphills at speed. I live in a hilly area, and the truck doesn't have trouble climbing short and steep hills, but only long hills at highway speeds. The truck will climb okay initially, but then will start to shake and eventually throw a code if I don't back off. It is throwing the #4 cylinder misfire. I have checked the coil on cyl #4 as well as had a mechanic in it and it checked out ok. Additionally, trusted mechanic stated that injectors all check out ok. Truck runs well on flat ground and uphill at lower speed. Truck also starts and idles fine. Next thing I'm looking at is crank position sensor. Can anyone think of other parts that may be causing these symptoms, or any additional diagnostic procedures I can use so I am not randomly guessing at parts to be replaced?
Thanks!
Grant

 

[Justin S]

How did you check the coil? If its saying cyl 4 it's probably either weak spark, fuel, or low compression

 

[gbsharon]

I wish I could tell you. Most recently the mis has been cylinder 4, but is sometimes stated as random as well. I was stumped and brought to my mechanic, who stated that he went through cylinder 4 (plug, wire, coil) and reported that it all checked out. At that point, I elected to just take the truck back because I didn't have the time to have him continue to investigate.

 

[Jrgunn5150]

Sounds like a converter clutch.

 

[gbsharon]

Sounds like a converter clutch.

Interesting that you believe it is trans related. Would this be the case even if an SES was thrown? SES isnt thrown all the time. Is there any way to test this? I have luckily found a hill where I am able to replicate the shake.

 

[Jrgunn5150]

Tap your brake pedal and see if it unlocks, it could just be the lockup of the converter puts enough of a load on it to make the misfire really noticeable.

 

[gbsharon]

Tap your brake pedal and see if it unlocks, it could just be the lockup of the converter puts enough of a load on it to make the misfire really noticeable.

I actually was thinking it was my TC. However, I went up the hill that I get this mis on with OD locked out and i still got the shudder followed by SES. I have yet to try tapping the brakes. Will this get me more info?

 

[Jrgunn5150]

Tapping the brakes will force the converter to unlock. If it still shudders, but less, then you know you have an engine issue. If it disappears, the converter would be suspect.

Having my own recent converter issues, I've done a ton of research lol. A misfire can cause a converter to unlock, and a converter locking, can cause a misfire. It's maddening lol.

 

[gbsharon]

Now that I think about that it may make sense- I feel the vibration but do not get SES unless I continue to feed in light throttle. If I back off when I first feel it it usually goes away or when I get it I back off and it usually goes away as I start slowing down. I will try tapping brake and update with results

UPDATE: Took the truck up the steepest hill I could find. Punched it from 0 to around 45 and got the vibration. Tapped brakes and no change. Tapped again no change. Tried accelerating and the vibration got worse. Top of the hill is a stoplight. As truck decelerated the vibration persisted. Sitting at the light it was vibrating then after about 5 seconds the truck settled back to normal. Ride after that was normal until I shut it down at my house. So not TC. The P.O claimed to have done plugs and wires, and they look good, but I may do them again with Delco platinum (not sure what's in there now). For some reason my mind keeps coming back to Crankshaft position sensor. Any thoughts?

 

[Jrgunn5150]

Pull the cap, check the rotor and see if it has excessive play. Also, for free, you can unhook the CPS and make sure it's clean and hooked together well.