So having put my car back together it was running really lumpy and low on power at low revs (cold or warm it made no difference). Hard to pull out of junctions etc. Garage did a compression check (all good). Found out that cylinder 2 was not getting much fuel. Swapped injectors (which are new) - made no difference. They have said that the fuel from the metering head to cylinder 2 is insufficient. They suspect that the metering head is faulty. Is this something I can look into or do I have to send it off to get it looked at? Any expert help most welcome!
Firstly you need check system pressures before spending on parts you may not need. In the 16v section theres a fantastic write up on setting / checking fuel pressues. Id recommend doing this first
Thank you, will do, although car is getting good pressure to the metering head (new lift pump/main pump fuel filter and accumulator). Probably picked up some crud from the tank. Pity as I was looking forward to using the car. Would it harm the engine to drive the car as it is. Its very low on power.
If its is underfueling then you may be running lean on one cylinder which isn't good. Was the main fuel pump a genuine bosch pump?
Hi there, eveything was genuine bosch stuff, new injectors, etc etc. once the things moving it seems much better but at idle its lumpy as a an old dog with no power. never stalls though so its idling fine. Just on 3 cylinders it seems!
They said the tool wouldn’t adjust it. Couldn’t locate. Attached are the readings no idea what they mean though
Doesn't sound like a very competent garage, anyway those dont look right Uk mot is 3.5% limit, if your reading is infact 8.88% then that need dropping right down to 1.8-2.0% This is adjust by the 3mm allen bolt inside the air metering unit thats accessed from the small hole on the top between the rubber boot and fuel distributor
According to that your CO level passed as OK, so I'm thinking whatever they're measuring it on is confusing things because it's set up to read with the decimel point moved one place over (if that makes sense!), so 0.300 is really 3.0 for our purposes... though as said earlier the limit is 3.5, so don't know what's going on there! If so might suggest your CO is 1.55 and actually quite good? Low CO2 potentially indicates incomplete fuel burn in the engine itself, presumably the MOT wanting it to be between 14-15% shows what's acceptable... that's a narrow band and as yours is off by some margin suggesting it's quite bad? Your HC is also very high (MOT threshold on older cars is 1200 ppm I think?) hence the fail on that alone, but I think even at the legal 1200 that'd be considered very high and maybe indicates quite a bit of unburned fuel exiting at the exhaust. I remember you writing a while back on another persons post that your 3mm hex adjustment was difficult? I'm just throwing thoughts out there, may have got things completely wrong.
Meant to add, your oil temp. at time of testing... surely it'd be much higher if car was fully warmed up or is that the minimum they'd do it at?
thanks for replies. I am struggling to reset the 3mm hex adjustment. I will try that again as it may well help. Why would fuel not be burning in the cylinder? Over fuelling?
Im also going to do the test where the injectors squirt into a bottle when pulled from the block to see what is really happening.
Will you keep us all posted on how you get on? Keen to learn a bit more about emissions, but got to admit I struggle to get my head around alot of it. When you're reading about the theory, it's difficult (for me at any rate) to grasp, but you having actual test results to compare with, I'm finding useful. I noticed on one of my daughters past MOT's for her 2016 Citigo that the CO and HC figures were virtually the same as I'd been given at the same test station for my almost 30 year older '87 205 GTI and both passed! That's why I mentioned them maybe getting the decimal point in the wrong place, I say wrong but maybe it's more that latterday testing equipment by default are set for modern emission standards and need to be reset when an older car comes but is sometimes overlooked? It was interesting that if I adjusted the Citigo's CO reading similarly by one decimal place it's readings fell back to what they should be for a modern car to pass and was also more or less the same as those in the previous / subsequent tests. Found this on-line... can't vouch for it, but so far it's the only thing I've seen that refers to pre-cat engine emission values. When it comes to HC's I think every 200ppm is roughly quivalent to 1%, so in your case 1469ppm converts to approx. 7.25% when the supposed ideal is a max. 250ppm / 1.25% Hopefully someone can tell me if I'm misunderstanding or not.
Thank you I have been looking at some great online videos of the metering head for these vehicles (thanks Greygoose and RetroVW). The thing has all kinds of things that could go wrong, for instance ports have little filters in them. Never knew. Could be partially blocked. Didnt know individual ports can have fuel flow increased/decreased. Because the car had done nearly 300,000 miles on the original injectors/seals there is every chance that the thing has been adjustedd over the years and now its got all new injection components it needs put back to factory. So ive picked up a spare metering head to go about rebuilding one. It was cheap so worth a go.
Okay so a little update. Was struggling to locate the co adjuster. Lifted the flap and the co adjuster appeared. Or rather what’s left of it. It’s completely rounded, prob seized. So it could never be adjusted. Got another metering head/flap so will fit that. Have checked that the screw moves (much easier to check that when off the car)
Got a replacement metering head and flap for £50. Bargain. Co2 screw not rounded off. Car runs fine just about to set co2 using the method on RJ’s guide
