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MG ZR 105 Trophy SE
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4 Posts
Discussion Starter #1
Hi guys, my first post here and of course it's a problem with the car 馃檭

My 1.4 ZR has developed a habit of lurching forward under certain acceleration, it seems to mostly happen uphill/on flats when accelerating gently through about 1500-2500RPM, made much worse if you're in higher gears like trying to go uphill in 3rd/4th. Seems to happen in all gears and at all speeds throughout that rev range. Putting the clutch in, or flooring it/dropping a gear and powering past the rev range it occurs at both solve it but obviously this is less than ideal. Sometimes it's very light juddering you can barely feel through the pedals, other times the car kangaroos back and forth (usually at the worst possible moment like mid-roundabout). I've seen similar threads on here suggesting its likely to be the ignition coils, I've changed both of them plus the leads, and also the rear lambda sensor as it was showing as a fault code (PO141 O2 sensor heater circuit bank 1 sensor 2) on an OBD reader. It was also previously showing a misfire detected fault which hasn't returned since changing the coils. Engine management light hasn't come on for either of these faults, so I'm hoping the previous owner hasn't messed about with the ECU or disabled the management light or something.

Figure I may as well replace the front lambda sensor as well however it looks like an absolute pain to get to and very very seized, the rear was hard enough to get out. Otherwise kinda drawing a blank now as I'm not sure where to look at next, and don't want to keep simply throwing new parts at it and hoping for the best.

Was hoping some of you who know this car better might be able to offer some advice!
 

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MG ZR 105 Trophy SE
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4 Posts
Discussion Starter #3
sounds like your coil packs are breaking down, id try a set of coils and leads and new spark plugs
I'd already changed them all, but is there a chance one of the coil packs I bought was faulty?

I do have two spare coil packs and a spare set of leads so it's not a problem if I need to swap it all 馃榿
 

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rover_25
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123 Posts
its possible, out of interest, were they genuine coils or aftermarket, rovers are quite fussy, also make sure you have just normal spark plugs, these rovers hate Bosch super 4 spark plugs, maybe try a fuel treatment
 

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MG ZR 105 Trophy SE
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4 Posts
Discussion Starter #5 (Edited)
its possible, out of interest, were they genuine coils or aftermarket, rovers are quite fussy, also make sure you have just normal spark plugs, these rovers hate Bosch super 4 spark plugs, maybe try a fuel treatment

It was these spark plugs I got for it, these ignition coils and these leads.

Didn't particularly want to spend too much at the time in case it didn't fix the problem :cry:

edit: Also the intake air temperature on the ECU was reading 40 on a cold night night while it was driving, if that's any kind of red flag.
 

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MG ZR 105 Trophy SE
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4 Posts
Discussion Starter #7
those coils and leads ave very poor reviews
Was driving when it suddenly died at idle at some lights... checked error codes and there was a fault regarding the MAP sensor. Looked under the bonnet (thinking yay another bloody problem) and discovered one of the wires plugged into the MAP sensor was broken, which I must have disturbed while checking out the engine. :confused:

Hastily janked it together with a keyring wire stripper and the back of a spade connector and it works perfectly, no error codes, lurching, nothing. I have a feeling the copper was making **** contact inside the wire, and it just finally snapped.

Thanks for your help regardless :)
 
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