New here so I am sorry for such a long first posting, but this problem is driving me nuts and I have posted on other board with good responses, but nothing that turned out to be the correct problem yet. Hopefully someone here can lend some insight.
I have a 2000 D2 with 128k on it, and over the past few weeks I started noticing a tapping or rapping sound, but only at highway speeds.
It first started at about 70 MPH/2500 RPM and sounded more like a piece of the wheel-well rubbing on a tire and clicking, or possibly something contacting the fan, not a really "metallic" sound it didn't seem.
The sound seems to go away immediately when I let off the gas, but comes back as soon as gas is applied again, so it seemed to be only under load at speed, so I thought perhaps something was rubbing or hitting the fan, but couldn't find anything.
When stationary the noise does not happen and engine sounds fine from idle right up to high RPMs.
Oil is fine. Reads a bit high on dip stick, but has since mile 1 that I have owned it and I always drain well, and fill with amounts spec'd in book. That has never been a problem for 128k now. Just a wierd stick I guess. Diff's and T-Case are all full as well.
Took out plugs and replaced with new champions. Still the same.
Front driveshaft out...same noise. Viscous fan out...same noise
Had a shop look at it and they thought it might be the flex plate, but scoped it and couldn't tell from that. Said most likely $800 + just to get in and check it. Ouch.
Followed up on the cat idea from another board and driver's side cat had a bit of a rattle, so I replaced them in the hope it was one of the bisquits in the cat rattling around and then flipping back into place when speed/pressure changed, but that didnt help. At least I have new high flow cats.
Any ideas? I would hate to pay someone to pull the transmission off to check the flex plate and have that not be it. It doesn't make sense to me that it would only do it after a certain speed or under a really heavy load, say up a steep hill, at decent speed only. Once it starts now it will do it at pretty low speeds as I slow down but keep load on it, but once I stop I cant hear it anymore to check. But with flex plate, isnt it constantly spinning? Would speed really effect it so much it would go from perfectly normal to a pretty loud banging/tapping sound? Also, no oss of drive from transmission, just lack of power when it gets really loud and starts missfires.
Deffinetly changes with RPMs. At say 1500-200 after it has started it is a low pitched sound but deffinetly not 1500-2000 times a second. More like only a few. Kind of like a manifold to Y pipe leak sound, but rev it and frequency increases as does pitch of sound. More a rapping sound then, and louder. but again. I could drive 40-50 miles of side roads and it drives fine. Only have I noticed it on highway or going up a very long, steep grade at over 40 MPH. That is more recent. At first it was only on highway.
I did look inside front inspection hole and found the allen screw I have seem mentioned in other posts. It was indeed showing that it had been rubbing something at sometime, but after removal they problem still exists, same as with it in there, so that wasn't it.
Still getting some missfire codes and the p0171, P0174 fuel trim codes after it really does it bad, and do now notice a lack of power when it is happening and then service engine light blinks till I let it coast a bit and then back to normal. Also getting some p03xx missfires here and there and an intermitant "Gear 3 incorrect ratio" code.
Really driving me nuts now after swapping out cats with that not being the cause, and looking at possibility of pulling transmission off to the same end.
Anyone else have an idea I might try to look into?
John,
Just to pick out part of what I have read, if you are showing lean codes along with the 3rd. gear code, that is normally always the MAF failing which will also cut you power back.
As for the misfires, how about your plug wires, how old are they and what brand?
Mike
I was thinking the coded might be MAF as well, think it is odd thought that is only happens when that loud noise kicks in. Coincidence? Seem odd.
Perhaps it is two seperate things, but they seem to be tied together.
The wires are pretty new. I put on Magnacor 8mm blue set last year, so they only have say 20k on them or so. I also swapped out the old Bosch 4 plugs the other day because I have been reading that they have caused issues in the DII. Put in a set of plain Champion Coppers and things still the same.
I would change the MAF on the outside chance that your actualy getting a leaan backfire under load.....then i would take the rear drive shaft off and give it a go...at least then you've eliminated front/rear drive line.....
I might try to do a swap out with one that works to see if it changes anything.
just a bit tight on the $ right now after the 300 for the new high flow cats and looking at possibly pulling transmission to check flexplate. But Then again, sounds like I will need a MAF anyway and if it solves it then it is well spent.
Could a lean backfire be that loud? would it change pitch with RPM? From low click/sputter sound to high clacking at higher RPM? Asking because I have never heard one before.
Sorry John it can be really hard to discribe...every intake and throttle body is different making the sounds different as well. If you have a buddy with the same truck swap the MAF and give it a run, but as you say it will be money well spent on the new one. I think i would be looking at a second opinion about the flex plate before i spent the BIG bucks to have it verified.....most of the flex plate noises i've heard sound like the bottom end of the motor is ready to explode.....
Let me get this straight, you threw all these parts on the trucks before even attempting to diagnose the CEL not thinking it would do anything.
You know an ounce of prevention is worth a pound of cure.
heres a thought, instead of throwing parts at everything and getting out the parts shotgun how about learning about the systems first. You know learn to diagnose like us techs do instead of pulling out the shotgun.
You will find it saves in the longrun.
And it allows you talk out of your ass when the need calls for it.
BTW, we call that hesitation under load.
__________________
I work on Rovers. Got a question just ask.
I didn't mean to say that I have thrown parts at it.
The cats I replaced were rattling, so I fixed them and also thought it could possibly be some of the sound I was hearing, as it was also coming from the area of the cats.
I did try to diagnose the CEL. I had missfires so I checked the plugs, and also put in champions because I hear the Bosch 4s sometimes have issues with the DII, and they were $10 total. I cleaned the MAF, checked airbox fit, read levels off the o2 sensors via ODB software, also tried monitoring fuel trim through that as well.
Taking off the drive shaft, and the fan was just time spent removing and putting back on, and a way to make sure it wasnt coming apart on me.
As for your last comment...I believe the name of my original post used the term "under load".
Sorry for the confusion if you think I sounded like an idiot, lol. But I did check many things and only things I put money into were cats, which were on their way out anyway, and $10 on plugs.
Was looking for some advice from a more experienced person on here to help "learn to diagnose like us techs do" as you put it. Not to get blasted.
HELP! Very loud tapping at speed/under load only?
Linear Mode
