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VW Lupo 1.4 BBY 2003 - Misfire on cylinder 1? #

Posted by Jason Mills on September 20, 2010, 8:53 pm

Year of Manufacture *: 2003
Engine Size and Code *: 1.4 - BBY
( Optional ) ECU Type: Magnetti Marelli
( Optional ) Scanner Used: Solus Pro / Vantage
( Optional) Fault Codes: P0301

Looking for some reassurance / ideas before embarking on purchase of new ECU. Vehicle has very sporadic misfire, can run for miles no problem then drops to three cylinders. This can also happen whilst idling. Switch off ignition and leave car for a few hours,start up and its fine and can be for days. Vehicle posts misfire cyl 1,after all usual checks it appears to be losing switch signal to only no1 injector, ECU pin 96. This has been checked through the loom and even internally in the ECU to rule out harness/connection fault. Has anybody had a similar problem or any thoughts if something can be causing this other than ECU fault?
Cheers.

Re: VW Lupo - Misfire?

Posted by Mark Carter User icon on September 20, 2010, 8:57 pm, in reply to "VW Lupo - Misfire?"
Mark Carter

Hi Jason, is the injector switching off the cause of, or the result of the misfire?

Modern cars, Its all wizardry and witchcraft

Re: VW Lupo - Misfire?

Posted by Jason Mills on September 20, 2010, 9:10 pm, in reply to "Re: VW Lupo - Misfire?"
Message modified by board administrator September 21, 2010, 3:38 pm

Pretty certain its the cause. Ignition,compressions etc all good. All other data looks OK. Smoke tested OK.

Re: VW Lupo - Misfire?

Posted by Peter Mutlow User icon on September 20, 2010, 9:17 pm, in reply to "Re: VW Lupo - Misfire?"
Peter Mutlow

Evening Jason,

These sort of faults can be a pain to diagnose properly. You do not describe what your "usual checks" are but I assume you have changed plugs etc. As Mark suggests, the ECU will switch off the injector to the offending cylinder if it detects an ignition misfire.

Regards

Pete M

Re: VW Lupo - Misfire?

Posted by Jason Mills User icon on September 20, 2010, 9:30 pm, in reply to "Re: VW Lupo - Misfire?"
Jason Mills

Plugs,coils and injector have been moved to other cylinders but fault always appears on cyl no1.
Regards.

Re: VW Lupo - Misfire?

Posted by Nigel Yardley User icon on September 20, 2010, 9:36 pm, in reply to "Re: VW Lupo - Misfire?"
Nigel Yardley

We had one of these with a burnt valve, and i can confirm that injector does shut off when misfire is detected.

Our misfire was obviously more permanent than yours, but it gave me a chance to do some proper testing.

have you tried cylinder leakage test, just to be sure..... our engine people reckoned it was very common fault....

Re: VW Lupo - Misfire?

Posted by Jason Mills User icon on September 20, 2010, 9:50 pm, in reply to "Re: VW Lupo - Misfire?"
Jason Mills

Just sitting here thinking cyl leak test as the only test I haven't carried out, as compressions were even it was discounted. Am aware or poss valve problem but as it is sooo intermittent just seems hard to beleive its a mechanical issue. Yes I know nothing should be dismissed until proven..
Thanks Guys.

Re: VW Lupo - Misfire?

Posted by Colin Hedger User icon on September 26, 2010, 9:59 pm, in reply to "Re: VW Lupo - Misfire?"
Colin Hedger

Hi Jason,
I know it does'nt help you much, but I've been struggling with this, not on a lupo but a Polo with BBY for ages.Luckily its a long standing and understanding customer.
I've done the same as you (lots and lots of time!)but found the compression down v slightly on the offending cylinder.
Stripped it down to find slightly burnt valves .Complete top-end overhaul later and - you guessed it still the same!
Customer doesnt use it much and prepared to 'put up with it' for now.

Frustrated of Staines.

Colin.

Re: VW Lupo - Misfire?

Posted by Fiachra Purcell User icon on September 27, 2010, 9:50 am, in reply to "Re: VW Lupo - Misfire?"
Fiachra Purcell

Had the same fault as you recently with a Polo. Misfire Cyl No 1. Removed the head and even though everything looked alright, I poured petrol on the valves and cylinder No1 exhaust valve leaked quite badly. I could not see anything wrong with the valve or seat. Sent the head to a machine shop for pressure testing. He said he got a lot of these from 2 VW dealers. The valve seating is the problem . Re cut the valve seats and replaced all exhaust valves. Engine is purring like a kitten now. Hope this helps.

Re: VW Lupo - Misfire?

Posted by Mark carter User icon on September 27, 2010, 1:20 pm, in reply to "Re: VW Lupo - Misfire?"
Mark Carter

As noted earlier, a cylinder leakage test should have found this type of fault. HTH

regards Mark

Modern cars, Its all wizardry and witchcraft

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