Looking for some suggestions: I have a 1990 8v PB engine GTI and it stutters/shudders under part (50-75%) throttle at higher speeds. This is most notable when going up an incline 3000-4000rpm in 4th or 5th gear. Any ideas? Feels like it could be ignition, timing or fuel related. It goes away if i back off or on full throttle. I have checked the timing and its bang on 6 degrees. Plenty of E5 fuel in the tank. Distributor and spark plugs look fine. Engine is running really nicely otherwise - pulls strongly and idles fine. I had this last year just before my crankshaft pulley failed (bolt worked loose I think). I've check all the pulley bolts and main crankshaft bolt and all are super tight. I'm not sure the two are related. Thanks
Check the plug onto the MAF, I had one with loose pins and corrosion. Check all the vac lines, including the hard plastic piece, right up to the clocks. You could have a worn section on the track in the air flow meter, sometimes retensioning the wiper and cleaning the contacts helps. Worth having a look at the big plug onto the ECU too.
Thanks Tristan. I'm slowly working through these - its an intermittent fault though and only happens at speed so difficult to diagnose. I wondered if one of the ignition leads might be arcing or maybe its running lean and not getting enough fuel at higher revs without WOT.
@R1ch - we are brother's from another mother! My 1991 PB is also behaving similarly and here is what I have tried to date to no avail: I have checked ECU connections and wiring, replaced fuel filter, spark plugs, distributor cap, rotor arm, HT leads, genuine blue temp sensor, checked and replaced vacuum hosing, re-done a number of electrical connections particularly grounds and a couple to the ISV. Next on the list is a new distributor and then the metering head potentiometer tracks and I do have a new fuel pump on standby but I don't believe that's the issue. I got a new distributor but you can also open the distributor and check/replace the hall sensor - I just couldn't be bothered with the ballache and will replace the entire unit. I was supposed to go back to Ireland in late March but that went for a burton but will get there around October all going well. If it's not the distributor(hall sensor) or the AFM - I may have to check how good my insurance for vehicular fire damage is....
@costel1969 - not sure if you are still having this problem. I spent an hour or so checking the vacuum lines and making sure they were clamped tight - did see anything obvious though. I also cleaned up and re-torqued the knock sensor. I've covered a good 100miles since and not had the issue again so hopefully its sorted now.
Hi R1ch - I went through the vacuum lines already and couldn't find anything but I replaced them anyway - no difference I got a brand new knock sensor (Bosch) and replaced that as well - SFA of a difference, my GTI is being a real beeyatch!!!
have you opened up the air flow meter and made sure the wiper arm is running on clear tracks? … Ignore that, just seen you are checking that next.
That's on the list along with a new distributor next time I'm home - they worrying thing is I can see the AFM cover has already been off at some stage in the past. If either of those do not work I have only 2 options left: (a) Subcontract Rubjonny and or Tristan for an all expenses paid trip to West Limerick (b) Burn it to the ground but only after it's got a damn good trashing....
If I have learned one thing on my digi 8v journey is that they really are the sum of all their parts. The exact same issue can be caused by different things, and you have to tick them all off to get to the bottom of it. The AFM is quite a clunky bit of kit, and they are getting worn out now. Can’t hurt to clean it all out and see how it goes. Even if it was opened at some point, chances are that was 10 years ago and it’s due a look over anyway.
Check the bung on the rocker cover (under the round plastic thing)... can't remember exactly what issues it causes when it goes but they're prone to failing and it's an easy check. Also worth checking earth strap between rocker cover and ignition coil.
And maybe check the alternator is putting out the correct voltage at high revs... again easy check if you have a multimeter.
Double check your air flow meter is the correct one - 7zap gives 037 906 301 as the VW part number (Bosch have their own), which tallys with the one on my own '91 PB. They may all look identical but there's differences to the internal boards which can vary, for example because of intended market. May not be the original there now. Touch wood I've no issues with the one on the Golf, but did look into these in a bit more detail for the 205 a few years ago... they're pretty much the same thing though. If yours has already been opened (and bear in mind there's also always the chance it's not the original lid / part number that was put back on, as it's easy to break them) the decision's more or less made for you to go back in, but if it's never been opened I'd caution against it until you really read up on things in detail as there's very little you can realistically do but lots that you can inadvertently upset. With the 205 I got a guinea pig to work on first so as to have the original as a fall back if the worst came to the worst. Adjusting the sweeping arm to run on a fresh arc is one adjustment you'll read about, cleaning the existing track is another if it's not too badly worn and can help. Adjusting the spring tension is yet another, but that's much more involved and will have a direct effect on CO, so a gas tester is essential. The images below (post clean up / adjustment) are from the guinea pig 205's, it'd been previously opened and the lid stuck back on by a cack handed chimp. The original sealant should be a translucent golden colour, and thinly / well applied. You'll be able to tell straight away if it's still factory sealed. The printed board pictured below... some of the black rectangles have bled and are blurred, that's because they've been exposed to moisture in the air. If it's bad enough it'll effect the proper working of the AFM (if it can even work at all) which is why you shouldn't open them unless you really, really have too. Seems there was a trend years ago to tighten the spring a few notches to improve performance... apparently didn't do anything of the sort but might be worth seeing if it was previously done and you need to get back to factory? The spring is stong, you'll read comments about it losing tension etc. over the years, personally I don't see it and wouldn't risk tampering if it's not been touched before, different story if it has been. The guinea pig AFM had, had it done and 3 x clicks back again set it up to where it originally would've been... the adjustments needed are that small. Big subject, just scratching the surface here... there's other things worth checking such as the pivoting flap etc. but there's lots out there giving genuine guidance and worth checking first.
Talking about this again got me looking up the old references I'd found a few years ago. Even then the sites were already quite beardy / old school in format but so too is the subject matter I suppose. There's others but the ones below I personally found very useful / written in plain english that I could follow... https://www.gomog.com/articles/AFMadjust.html http://www.clarks-garage.com/shop-manual/elect-22.htm Here's a reference to the now being reproduced (chinese) boards, seem to get the thumbs up from that particular person though others (on the main 205 GTI forum) would tell you otherwise, however at around £25 and new ones unobtainable they're probably worth a punt if all your other options are spent. https://www.thesamba.com/vw/forum/viewtopic.php?t=717137
Cheers Z this is very informative - when I get back I will try the distributor first and if no joy then it's down the AFM road I go.
Remember my diji that I fitted to my 3A 2.0 ,before fitting the TT cam was fluttering @ idle,with the cover off you could see this,decided it would most likely be worse with the cam was described as have a lopey idle by TT,pretty sure I went 2 clicked tighter on the AFM and much improved. Fitted the cam and it was still ok but later fitted TT cam chip with knock sensor spacer ,4bhp increase dyno'ed by them and noticed a smoother idle. IMO its important the throttle body and AFM are cleaned out as well as the ISV, learnt this on my 89GLI mk2 which ran rough after repairing several air leaks ,this car always performed better than any of my stock diji cars ...one out of the box really considering it had some kilometers on it and most likely more as it was a JDM import car and in those days many had been "clocked". Oh and a word of warning don't adjust the AFM unless you understand what you are doing and don't work too far out of original settings...ask me how I know and lucky I had a spare......
Was aimlessly putting different things into eBay and this thread must've sub-conciously prompted me to search for 'Bosch L-Jetronic'. This wee tool popped up for not much cash... yes, it's basically a glorified 5mm hex key, but if you're going to get into fine tuning the AFM you'll soon discover finger pressure changes can effect the CO quite a bit. The knurled wheel allows you that degree of control which you don't get with an allen key or similar. Search Franklin TA56 for the one pictured or there seems to be an identical Draper version - 19610, though I can't 100% confirm that. The list of vehicles on the rear of the packaging brings back some memories!
