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Old 16th December 2016, 21:13   #1
Rick-sta
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Default Diesel 75 auto driving a bit odd

Hi all,

Over the last couple of weeks my dad's mentioned a few times that his 75 diesel auto has become a little less responsive and a bit hesitant. Today I took it out and have also noticed the same thing. It seems to want to shift down a gear a lot of the time now whereas before it would stay in the same gear unless you really put your foot down. It also like to hesitate for about a 1 to 2 seconds deciding whether it should shift down a gear or two or not.

Power wise it feels fine, but just not as quick at responding as it used to be.

anyone had anything similar on theirs and came across a solution?
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Old 16th December 2016, 21:19   #2
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If it were me.I'd try unplugging the MAF sensor temporally and see if there's a difference.
Also try the sports/normal/snow switch in each mode,my friends SLK had become disconnected and was in one mode,until reconnected,,although on the Rover this should revert to 'normal'.
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Old 16th December 2016, 21:28   #3
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I'd agree with ken ref the maf rick
I recently had the pleasure of assistance from mike noc who plugged his box of tricks into my car
His reader said the maf sensor reading was on the low side
I had noticed the car was a bit slow and hesitant to accelerate
I had a spare maf which I duly fitted
Upon which I have pleasure to report an immediate improvement
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Old 16th December 2016, 23:24   #4
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If unplugging the MAF doesn't do the trick you could try checking the intercooler for leaking joints and cracks. I had a similar situation a couple of months ago with the car changing down on gentle slopes and then up again. Another symptom was smoke under hard acceleration, the problem turned out to be a crack in the plastic endcap of the intercooler radiator. Once replaced the the car seemed to pull better and no longer changed down unnecessarily. Made a huge difference to the feel of the car.
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Old 17th December 2016, 00:07   #5
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Has the transmission fluid been changed? If it's old and tired then it can affect gear changes.
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Old 17th December 2016, 00:21   #6
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Quote:
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Has the transmission fluid been changed? If it's old and tired then it can affect gear changes.
I was just going to ask the same
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Old 17th December 2016, 13:48   #7
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cheers for the replies, was thinking possible maf or intercooler issue.

Intercooler top hose is new, and the O-rings are fine. whether the intercooler itself has a problem I'm not sure. could probably do with being flushed out as it made a big difference on my ZT. EGR has been cleaned within the last year too.

Transmission fluid does need changing, been one of those thing I decided to leave alone until it showed signs of needing doing, since I've heard of so many stories of others changing the fluid and then having issues afterwards. but would have thought that would just cause jolty gear changes.

I'll try unplugging the maf at some point and see if that helps, whats the early signs of a faulty maf? As power along the rev range is fine on the 75, doesn't show lack of power below 2k, the power's just not instant as the gearbox decides to take a second to think about what gear it wants to be in.
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Old 17th December 2016, 14:10   #8
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Quote:
Originally Posted by Rick-sta View Post
cheers for the replies, was thinking possible maf or intercooler issue.

Intercooler top hose is new, and the O-rings are fine. whether the intercooler itself has a problem I'm not sure. could probably do with being flushed out as it made a big difference on my ZT. EGR has been cleaned within the last year too.

Transmission fluid does need changing, been one of those thing I decided to leave alone until it showed signs of needing doing, since I've heard of so many stories of others changing the fluid and then having issues afterwards. but would have thought that would just cause jolty gear changes.

I'll try unplugging the maf at some point and see if that helps, whats the early signs of a faulty maf? As power along the rev range is fine on the 75, doesn't show lack of power below 2k, the power's just not instant as the gearbox decides to take a second to think about what gear it wants to be in.
in my experience of owning autos (my last 8 cars) it startes with a slightly lumpy change and then it starts hanging onto gears longer and hesitates on downshifting

so pretty much what you are experiencing Phil-T4 is the man as always

most issues are with people using the wrong ATF fluid trying to do it on the cheap
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Old 17th December 2016, 14:27   #9
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'IF IT WAS ME'........... Great to see another thread raise so many different options,

But really 'If it was me' then I would source my nearest T4 guru and get a diagnostic..... after all we have some great members that do a T4 service, and it eliminates the guessing games

Hope it gets resolved quickly
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Old 17th December 2016, 14:30   #10
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I thought my problems might have been gearbox related, so had the atf changed, but without any improvement. I was quite surprised to find the crack in the intercooler casing because I wouldn't have said the car was particularly down on power, and it certainly didn't have any of the limp home mode issues described by some with failed intercooler O rings. It will be interesting to hear what it turns out to be, so best of luck with an early diagnosis!
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