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Strange Gearbox (I think) Issue.

887 views 4 replies 3 participants last post by  capncoolio 
#1 ·
I'm going to do my best to describe this issue, but it was certainly strange.

Going along earlier tonight, I noticed a slight rumbling on take-off. I didn't think much of it, because the car hadn't warmed up properly (it was sitting at around 65*C). However I noticed shortly after (rather inconveniently,as I was attempting to overtake at the time) that the gearbox refused to kick down past third gear and the rumbling became much more violent under acceleration. Upon stopping at some lights, the whole car was shuddering. Here's why I write "I think" in the title. This shuddering felt A LOT like the engine was being starved of fuel and this is reinforced by the fact that cycling the engine once (turning it off, putting it in park, starting it again) seemed to fix this issue.

Two noteworthy things:

1. When stopped, I attempted to rev the engine slightly (while it was shuddering). The shuddering just got worse.
2. Manually selecting 2 didn't appear to have any effect before I cycled the engine.

Does anyone have any ideas as to what this might be? At this point I'm suspecting MAF, but there are a lot of people having issues with the gearbox control board. (It's a '99 C240 with a 722.6).

Any help at all is appreciated.

It's an Australian Market production model by the way, with the 2396cc 18V V6.
 
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#3 · (Edited)
Thanks for your reply!

One thing I have noticed is that the part of the grille the air intake sits behind is actually blocked off with plastic between the slats; part of some sh*tty Australian de-tuning regulation.

Could this mean my car uses some method other than MAF to regulate fuel injection? Or is it irrelevant?
 
#4 ·
That sounds more like the common wiring harness issue than the MAF. Every few years the wiring harness and sometimes spark plugs and coils need to be replaced or you will get misfiring like that. It starts off being intermittent upon acceleration and gets worse over time.
 
#5 · (Edited)
I'm... probably not going to like the answer, but how expensive does it get to do coils/plugs/etc (wiring harness) work?

I mean, I know a guy, I might just ring him and ask.

Incidentally, I've had misfiring before (EDIT: NOT in this car, I mean to say I've felt it before), strangely the car wasn't misfiring at higher RPM, just lower. Also, it didn't stall.

It didn't feel like misfire either, it seemed too consistent; more like a really violent vibration. Mind you, that could be the harmonic balancers...

EDIT: I've heard the common wiring harness issue is more relevant from 91-97 models. I don't know if I've mentioned, mine is a 99.
This exact model here: http://www.redbook.com.au/cars/research/used/details?R=85538&Silo=Spec&Vertical=Car&Ridx=1&eapi=2
 
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