View Full Version : 1.8TQS fluctuating idle and intermittent misfire, HELP.

03-24-2017, 12:24 PM
Hi all,

Bought a 1.8tqs that had a rough idle, no problem i thought, as was told it was a throttle body issue and the car drove great when driving. (classic one right...)

Anywho, i replaced the TB from one I got of a pal, still doing it.... ive had a fiddle with few other bits and cant figure it out, my heart sank when it didnt fix it, my brain thought the worst, head gasket, cam-belt, valves ETC
But the car does actually run fine, i drove all the way to southampton and back, no worries, but at low rpm and at idle, its fluctuating and misfiring ????

im thinking:
Air leak,
Dump valve,
Coil packs,
or long shot, the custom exhaust it has ?

Other symptoms, fuel gauge doesn't work.
Temp gauge rarely works.

i have uploaded vids of it doing its thing. can you help gents, want to get it fixed ?




03-24-2017, 12:28 PM
Maybe im wrong but i believe that a coolant temp sensor could cause a rough idle. [confused]
but that wouldnt explain the fuel gauge not working.

03-24-2017, 12:34 PM
Replace your coolant temp sensor. Easy enough. Drain some coolant from the radiator via the drain plug on the front of car.
Not my pic but figured no one would mind. I do it with the bumper still on, but I have an S4 bumper.
http://i1052.photobucket.com/albums/s444/MrSnickelsnizer/coolantd1_zpspz8cq2mb.jpg (http://s1052.photobucket.com/user/MrSnickelsnizer/media/coolantd1_zpspz8cq2mb.jpg.html)
Then do a throttle body alignment with an audi/vw scan tool that is capable.
This is the one I use in a pinch. Not good by any means and the controls suck but it works. Should probably scan some codes while you are in there..
And do a boost test if you haven't already. Even cars that run well enough may have slight leaks.
I would check fuel level sensor wiring under access plate in trunk, for the fuel level problem.

03-24-2017, 12:47 PM
cheers will give that a go, the Coolant Temp Sensor screws in at the bottom of the rad doesn't it ? is it the same as the CTS on the 2.0 engines ?
and would that cause it to run like that, never thought it could be the coolant responsible LOL.

03-24-2017, 12:57 PM
Coolant sensor does weird stuff to these cars. I have always replaced them with oem sensors when I get one. Saves headache down the road. Same with the ignition system. Ditch the icm module and oem coils if you have them. Obviously there are other things you should read up on about these cars. Lots of various things which can go wrong and cause problems. Headlight switch, fuel filter, wheel bearings, pinch bolt, valve cover gaskets, timing belt, etc. Good luck :P
Fyi you'll know when the maf, injectors, or coils go bad. Car runs like it is ready to explode. Massive misfires.
N75 or diverter valve generally are noticed under load in my experience.

03-24-2017, 01:01 PM
coolant temp sensort is in the back of the motor on the rear coolant flange.