# Solved - Rough running & stall on idle



## richardkhill (Jul 20, 2015)

Driving home from work & the car started getting very lumpy & stalling on idle. I managed to limp home & do some research - looking like either MAF or coilpacks? Unplugged the MAF but nothing got better. Did a few other checks;

Plugs clean & good condition.
All hoses secure
MAF Cleaned (Carb Cleaner)
Throttle Body Reset with VCDS

I've attached the scan results (pdf) which shows a MAF fault. Is this the most likely culprit, even though nothing changed when I unplugged it? TIA

P.S. It's a 150 AUM engine


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## Hoggy (May 8, 2002)

Hi, Have you reset the fault codes since reconnecting the MAF, taken for a run & then rescanned ?
Coil pack perhaps, perhaps that engine doesn't record misfires.
Hoggy.


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## richardkhill (Jul 20, 2015)

So, cleared all the codes and attempted to run, but rough idle still there. Could also hear some sort of 'pssssting' coming from the engine!? Video here 




As it was still rough, I didn't even try a run round the block.

Scanned it again & no codes!!??


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## Hoggy (May 8, 2002)

richardkhill said:


> Scanned it again & no codes!!??


Hi, Not the MAF then. If plugs are O.K. It's probably a coil pack.
Disconnect & replace 1 at a time, the one that makes no difference is the faulty one.
Hoggy.


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## richardkhill (Jul 20, 2015)

I've unplugged & re-plugged the coil packs one by one, but couldn't hear any perceivable difference in the rough idle. So I pulled the plugs & found one of them quite wet (assuming fuel), would this also point to a duff coil?


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## Hoggy (May 8, 2002)

Hi, Plug or coil pack. As you've pulled the coils, more likely a dodgy plug.
Hoggy.


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## richardkhill (Jul 20, 2015)

Thanks Hoggy. Plugs are cheaper so I'll replace them first.


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## richardkhill (Jul 20, 2015)

Bit the bullet and fitted a full set of new coil packs & spark plugs. After making sure there were no error codes & starting the engine, the same rough idle was still there. And still no codes showing up afterwards either???

Really don't know where to be looking next [smiley=bigcry.gif] [smiley=bigcry.gif]


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## StuartDB (Feb 10, 2018)

look here for a vacuum leak










its a strange push-fit type of a connector which is supposed to be able to rotate slightly, I put jubilee clip on mine


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## Hoggy (May 8, 2002)

Hi, Get a compression check carried out.
Hoggy.


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## Wak (May 6, 2002)

Probably got a split hose somewhere check through the main boost hoses as well as vacuum hoses


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## richardkhill (Jul 20, 2015)

Problem Solved 

Having taken a breather and some time to reflect on the problem, I decided to go back and double check all the hoses.

Having done an N249 delete in 2016 & a catch can install a couple of months ago, I originally only did a quick visual check of all the connections. This time I was much more fastidious and was still satisfied that the problem didn't lie with the mods. But as I was leaning in to remove the DV for inspection, I just happened to notice, out the corner of my eye, something that didn't look right under the inlet manifold. On closer inspection, I quickly spotted that a blanking hose I had fitted over the spare vacuum nipple, on the underside of the IM, was missing!! This had been fitted in 2016 as part of the N249 delete. Two minutes later, after fitting a piece of spare hose with a bolt as a cork, everything returned to normal [smiley=bomb.gif] [smiley=bomb.gif]

So there we go!

I've learnt a couple of important lessons on this one; the biggest being - Check things thoroughly before making expensive assumptions  

I appreciate all the help and advice provided, especially from Hoggy. Thank You.

I'm off to write a thousand times "Don't make blind assumptions" :roll:


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## Pukmeister (Dec 27, 2017)

That 'psssssting' noise you mentioned must have been the engine trying to give you a clue. 

Glad you got it fixed, and thanks for the feedback.


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