Hi all… So I’ve consulted all my car people and the internet and still don’t know where to begin fixing my problem… Here is the problem: At about 40-50 mph when I’m just driving steadily (not actively accelerating) there is often a shudder/rumble strip type noise & vibration/slight jerk you can feel. It immediately stops if I let off the gas or if I give it more gas. It runs perfectly aside from this one issue.
Notes about the truck: AWD with options for manual selection 4hi & 4lo. V8 automatic trans.
Here’s what I’ve been told could be wrong:
Bad/low trans fluid
Trans filter needs to be changed
Dirty fuel Injectors
Needs tune-up
I have noticed that fuel injector cleaner seems to fix the problem for up to one day after I’ve added it to the tank, but after the first day it goes right back to doing it. A few days ago was my most recent add of injector cleaner, and it helped greatly the first day, but since then it seems to be “shuddering” more than what it has been previously. There are no errors or engine codes popping up, everything else works as it should, no leaks, no burning or using oil, etc.
So my question is do you have any ideas what might be causing this? Or where I should start with myself or having a shop diagnose things? Because the fuel injector cleaner seems to help I’m wondering if I should just replace one or more injectors? Or is that a waste of time/money?
Well, I certainly hope that you have–at the very least–checked your trans fluid to see if it is low!
That immediacy aside, your list contains some good “suspects”, but I want to introduce another possibility. The speed range that you mentioned–as well as the “rumble strip” sensation–is an indication that you could be having a problem with the transmission’s torque converter lock-up mechanism.
I strongly suggest that you take your vehicle to an independent trans shop (NOT to a chain-run place like Lee Myles, Cottman, Mr. Transmission, or–God forbid–AAMCO) for diagnosis. Whether the solenoid that controls the TC lock-up needs to be replaced or not, you can have the trans fluid and filter changed while you are there. That needs to be done ~every 30k miles, but most people fail to do so, and wind up with early trans failure as a result.
Concur w/my colleagues above, this sounds more like a lock-up torque converter or driveline problem than an engine problem. I’m guessing the same as VDC above, the lock up function on the torque converter is the culprit. You may just need a new lock up solenoid installed on the transmission. I’m not aware of any diy’er method to diagnose this, other than just replacing the lock up solenoid and see what happens. I think it might be possible to disable the lock up function temporarily as a diagnostic technique too, but I don’t know how that’s done, maybe just pulling a fuse. Usually it’s best to get a well recommended inde transmission specialist shop – ask your mechanic which one is best in town – to offer an opinion before messing with the transmission yourself.
Unfortunately I have not checked the fluid yet because there’s no dip stick on this one. I did however call a highly recommended trans shop and he actually told me this same issue “lock-up” was a likely culprit. Taking it in Weds to have diagnostic run and will update. Thanks for the advice!
I’m curious to hear the shop’s theory on this part… It ALWAYS does the rumble strip noise, every time I’m in that coast/slow acceleration mode, aside from the 3 times I used the fuel additive.
I’m just glad nobody (including the shop) really seems to think it’s the trans getting ready to go! I’ll update when I have an answer from the shop. Thanks again!