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[vic]

Omega 2.2 ecotec 2000 estate auto (65k miles)  New GM camshaft sensor fitted two weeks ago after Tech 2 diagnosis.(worked great and solved limp home problems)
At first daily startup OR when car has been left for a minimum 3-4 hours it runs like a dog' engine misfire and wobbles about and sometimes backfires (like the backfires in the carb of my old vauxhall victor or viva). Only does it for the first minute and then disapears altogether and no problem from then on. When playing up I've disconnected the MAF and suddenly it evens out and problem gone. I've done a carb cleaner job on the MAF but that made no difference. I'm doing a cam cover gasket (pukka GM kit) change this weekend and cleaning out all the breathers as the plug wells had oil in them. Is there anything else I should be doing whilst I'm in there to iron out this problem/
As always your thoughts would be appreciated.

[tunnie]

So if the car is started from cold without MAF plugged in it runs ok?

[vic]

Hi Tunnie,
Yes mate it does!.
Put the MAF back in for next 'cold' start and it's lumpy again

[Kevin Wood]

Sounds to me like the MAF may be on its' way out.

After a while the system goes closed loop so the fuelling is corrected.

I wonder if this has anything to do with your recent emissions issues?

Kevin

P.S. haven't forgotten about the maintenance guide.

[vic]

You may well be right kevin. I'm beginning to appreciate that very little of the engine management system functions in splendid isolation. I'm hoping by following the advice I'm getting from those with 'more understanding that I can work my way through the problems as they present' to get the engine running properly.

As regards the maint' guide.............Hey I've been following your's and the boy's exploits with the gas coversion with interest, so I know you have been a busy man, no worries. Good luck!

[david_omega]

i would blame the MAF for the problems, i had the same fault, put a new one in and she was mint. only had 38k on the clock back then too! (the good old days!!)

[vic]

Thanks for your input Simon.............Took the cam cover off this afternoon in preparation for fitting a new gasket. Found a 1½ inch split in the underside of the rubber trunking between the MAF and throttle body which prompts two questions when considered with Kevins thoughts that the MAF may be on it's way out.

a) Could this be the culprit causing my 'first minute lumpy running?

b) Is there a way of testing the MAF? [size=10][size=11][size=10](bearing in mind I don't have a known good one to substitute as I write).[/size][/size][/size] I'm reasonably handy with a multimeter having done a fair bit of electronics as a hobby for the past 20 years.
Went to my local vauxhall dealer this afternoon in hopes of replacing the split air trunking only to be told "Sorry the part you need is no longer available and out of production".
However, after much comparing of different bits it appears it is very 'similar'  to that used on a calibra which is still available.So parted with a few sheckles, test fitted it which appears OK. Won't know if the replacement is successful till after I put everything back together. When I took the trunking off the throttle body I did notice the butterfly looks a bit cruddy' (maybe I should strip and clean the throttle body whilst I'm in there :-/) The ripple effect appears to be  alive and well and living in N.E.Hampshire

[Kevin Wood]

Sounds very much like the split is your problem.

And a slap on the wrist for me for committing the cardinal sin of assuming it's the big, expensive part without verifying the cheap and easy.


a) Absolutely, yes. It will cause the MAF to misread by admitting unmetered air, so as good as a faulty MAF.

b) Not that easy but with live data you can check that the readings are in the right ballpark if you know what typical values are. You can also look to see how far the fuel trim has had to adjust the fuelling away from the value based on MAF output.

Kevin

[vic]

Thanks Kevin,
Trust me' I'm sure your crystal ball is no better than mine, so no worries about the diagnosis. 20/20 hindsight has always proved beneficial to me if you know what I mean. What has been valuable was your comment about the MAF being on it's way out which started a chain of thought at my end, especialy after I discovered the split, which prompted my question.  I have some tranferable knowledge from my hobby, but it's so useful to compare with folk who know more than I. Don't know what values to expect from the MAF so likely I will keep my fingers crossed when its all back together. Have to say I'm feeling more confident 8-). I will let you know a result when its done and perhaps you can share 'the buzz' ......Good luck tonight

[vic]

Appears my optimism was premature and I'm not out of the woods yet...."rats". Still have the problems I started with, lumpy running for the first 30-60 seconds.
So far I've
*Replaced the split air hose between MAF and throttle body
*Cleaned all breathers
*Fitted new GM cam cover gasket
*Cleaned butterfly in throttle body
*Fitted new spark plugs
I've now noticed a misfire under load (sometimes power goes altogether, like dead engine, for about a second then comes back in again) which actualy I think was there before but I put it down to oil in plug wells.
*Is it still the MAF?
*Is there anything else I can check before shelling out for a new one ?
* Any idea on a part No and price?
Be interested in your thoughts guys please!
Vic

[vic]

"Ouch"...........Been to my local Vauxhall dealer this afternoon £112.00 for a new MAF (that will knock a hole in this months pension when it arrives).As the parts man said though "you could fit a new one and still have the problem"....Dosen't inspire confidence :-/

[Kevin Wood]

Might be worth getting the Bosch part number off it and looking on Ebay. They are often generic parts and available cheaper than the stealer.

Kevin

[vic]

Will do! as my next move, thank you kevin . What's the conventinal wisdom on pattern parts for these, any idea? I know pattern parts are frowned upon for many applications.

[jonnycool]

Might be worth getting the Bosch part number off it and looking on Ebay. They are often generic parts and available cheaper than the stealer.

Kevin

Yep, I bought one off ebay the other day for £40 and it solved my long-standing emissions light problem. worth a try at that price

[vic]

Thanks Johnny, I was reading your posts the other day with interest about your MAF. Just nipped out onto the drive and quickly whipped off the MAF (getting quite quick with familiarity, it's been off and on so many times in the past couple of weeks.)  I have several No's on it; The maker is siemens and the body has the following Nos:
*5WK9 606
*90 530 463>PBT-GF30.
* bar code label 57959009.
I probably appear to be 'dense, ( I'm keen to learn so any advice is welcome) which of these do you think is the 'part No I need