GolfGTIforum.co.uk
Model specific boards => Golf mk2 => Topic started by: DarnPB on 18 January 2007, 23:33
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This is my first thread on this site so hi to everyone reading. I live in Spain and recently bought my second Golf II 8v GTI. It is a 1991 model with the Digifant engine management system.
When I bought the car, it was running very badly. Idle all over the place, bucking on the over run and initial power take up, expensive to run although it had plenty of power. I did what I normally do when buying an older car, replaced the plugs, dizzy cap and rotor, leads, then I noticed that the mass airflow sensor cap had been tampered with. On a closer look, the cap fell off! So the mass airflow sensor I changed for one from the scrappers. This changed the car. The idle became stable and the engine ran alot smoother, but was still bucking.
I put the car into a Bosch specialist over a weekend only to be told that they had done their best, but the engine was low on compression, so it was impossible to tune properly. I found this very hard to believe. The car did however run alot better, but still no cigar.
Now I am not a novice when it comes to engines, and although I do not have a compression tester, I don´t believe my car has a compression problem. There is no smoke from the exhaust to speak of, even after an over run, it does not use oil or water and the plugs are not oily. The engine oil is also a respectable colour and the car has plenty of power (more than my last one.).
But can anyone tell me if compression can affect the emissions? The car failed the Spanish equivilent of the MOT on emissions today with a reading of 9.3. Now I intend to get a second opinion on the compression diagnosis before I start thinking about tearing down the engine. Has anyone else had similar problems and what was the final diagnosis that put the car right?
Any feedback would be greatly recieved.
Thanks. :undecided:
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have a read through my digifant tuning guide in the MK2 maintenance + info section, it tells you everything you need to know to make a digifant engine run right :)
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I have just completed a load of testing on the engine with reference to the Haynes manual and everything was in limits. I then went to set up the CO level with reference to the same manual and the info on this site. But, I have found on the MAF sensor that the adjusting screw is missing!! I don't know if this would have been removed by the garage or it was just missing. Would there be any need to remove the adjusting screw and what would be the result??
Do I just replace the screw or the whole top of the airbox?
Bemused!
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With regard to the mixture screw: I have checked parts catalogues in the past such as ETOS and ETKA, and it does not seem as though the mixture screw be purchased seperate to the AFM. There is a good possibility that the adjustment screw is a common metric size which could be replaced with a metric allen head bolt.
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The MAF has an allen bolt not a screw, if it was missing you wouldnt be able to get the mixture & idle within specs since it would be allowing air to flood past the metering unit, in effect giving you a massive air leak.
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I thought as much. The CO is off the scale. I´ll take my meter to the scrappers tomorrow, er, today, and pick out another one that´s complete. I´ll let you know how I get on.
Thanks guys.
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Right. I got a serviceable second hand airbox from the scrappy today after testing it with the meter. I fitted it to the car and commenced round two of tweeking the CO. It is alot better but still high, ranging from betwen 2.8 and 4. It was 9.3. (I´m using a friends GUNSON CO meter which has seen better days!) But I have run out of adjustment on the allen plug. I´ll go for the retest tomorrow with tongue firmly emplanted into left cheek and see what happens. Hopefully they will allow me to make adjustments if I am too far out.
Any more ideas on why the CO is so high and why it cannot be brought back into the playing field?
Not out of the woods yet!! :huh:
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You could try replacing the coolant temperature sensor. It is the blue sensor located in the plastic coolant flange on the front of the cylinder head. These can often fail and cause the Digifant ECU to overfuel. Buy a genuine one from Volkswagen, the aftermarket products are not very good. Cheers
Ben
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I assume you've warmed it to 80 degs, disconnected the blue sender & breather & reved the engine over 3k 3 times ;)
I've had this when the throttle body was stuck too far open, due to missalignment of the idle switch (too far in, holding open the throttle) and the same when the throttle cable was too tight. Make sure it hits firmly up against the throttle stop.
Check for air leaks too, I'd replace all the vacuum tubing, and don't forget the blanked off connection round the back that is often overlooked :)
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I did all the above and all I can think of is that the engine management computer is getting the wrong info, which indicates a bad sensor. I will replace the water temp sensor tomorrow. But what would happen if the lambda probe was not up to scratch? Still can´t believe its poor compression.
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It could be the lambda if one is fitted, in the UK we didn't get them on the MK2 as std, not sure if the same is true for Spain.
I'd start with the blue sensor, and work through all the vacuum pipes looking for perished hoses including the one round the back that is usually forgotton about ;)
If it has a lambda, replace it with a quality Bosch universal type, I put a no-name brand one in my gfs Polo and it lasted a fortnight! Bosch one in now and its been fine ever since and flew thru the MOT.
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Well the bloody thing failed on emissions again today! Is the lambda probe only fitted to cars with a CAT?
When I get back to Madrid (Home) I am going to start from scratch. When I changed the cam belt, I noticed that previously, the lay shaft was in the wrong position according to the book,although the dizzy was correctly positioned. I will start by putting everything in the car as advertised then start trouble shooting again. A friend of mine has an identical car, (my old one that was crashed and he rebuilt) so we can trouble shoot by transferring components as required.
I´m now thinking that the ECU has been played around with. If this has been re-chipped, could that affect the emissions?
:sad:
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yeah the lambda was only fitted to cars with a cat, its worth getting all the timing reset, don't worry too much about the position of the intermediate shaft pulley, its the dizzy position that matters :)
My digifant tuning guide also have the procedure for resetting the static timing, and setting the ignition timing correctly :)
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Well I've been right through the engine and everything appears to be normal, except the emissions that is. It is now in a garage with specific instructions from me. The compression he said was a little low but perfectly acceptable for the age and mileage of the car. Should be about 160, actually is 140ish. But this should not cause the high CO. He double checked everything that I did and concurred with my findings. The only other thing now to check would be the fuel pump pressure which he is going to do this afternoon.
I suggested the ECU but he thought not.
Any thoughts anyone?
Getting desperate.
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have you replaced the spark plugs with a decent set of tripple probes, perhaps they are sparking at the wrong time?
It might be worth swapping the ECU, it may have been remapped for a different engine and swapped on at some point. Also, maybe the injectors are faulty, or have been replaced with a set of the wrong rating dumping too much fuel in...
Might be worth getting the pressure at the fuel rail checked also, perhaps a blockage in the return is holding the pressure up too much? There is a bolt in the end of the fuel rail, if you remove it you can attach a pressure guage there :)
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It had crossed my mind that the ECU had been buggered about with, and the car has a suprising amount of power. The spark plugs are new multi electrode ones. I did the resistance check of the injectors as per the Haynes book of words, and they checked out electrically. The rail pressure was I hope checked today, I'll know tomorrow. I'll keep this all posted, it might help someone else out in the future.
Thanks for all the inputs. Much appreciated. :smiley:
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Well the final word is that low compression is causing high emissions. I may be getting the power and nothing externally is indicating that I have a problem, but if the oil rings are faulty, then fuel is finding its way from the combustion chanbers and mixing with the oil. When this gets warm, the fuel evaporates and ends up in the breathing system which is then sucked out by the induction system and back into the combustion chambers, thus inadvertantly causing a rich mixture and high emissions. So the injector and the digifant system is working and doing its job, but obviously cannot detect what is going on downstream of the sensors.
I will try and put it through the test again with the breather pipe disconnected. Apparently, the emissions with the breather not connected are down as low as 0.8. But it looks like I have a project for the summer. 1.9 conversion??? Another post.
:smiley:
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could just be its been overfueling in the past, and the oil is full of fuel. This is why you need to set the Idle & CO with the breather disconnected and the engine side plugged ;)
Try changing the oil, see if that helps :)
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The oil is only 6 weeks old. One of the first jobs I did when I bought the car. I did all the set ups according to your set up posts and the Haynes. I will change the oil again though. For the sake of forty or so Euros, I'm not gambling much. Looking forward to building another engine though, (I'm an light aircraft piston engine specialist) so I'm not too broken hearted. :smiley:
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cool, look for 2.0 bootom ends from MK3 GTIs and Passats, engine code 2e :)
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Well I got the thing throught the test today, but by more foul methods than fair. I disconnected the breather going to the induction manifold thus creating a massive air leak, then wound up the idle to make it run. It ran, but disgracefully, with NO power, BUT, the emissions went down to 0.2. Just glad they did not look under the bonnet! I don´t suggest anyone use this method of passing MOT´s, but my circumstances were somewhat unusual. Once I got round the corner, I put it all back to where it was. Next job, pull the head off and make a decision. Will be doing that this weekend when I go home.
Cheers.
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totally off subject here but where bouts in spain you living? im livin in marbella and loves it plenty apart from the monsoon style rain that keeps breaking my car and then when the rain doesnt break it I end up breaking it trying to fix it its a viscious circle!
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I live in a tiny village in Guadalajara, a stones throw, (literally) from the Madrid province. Madrid is about half an hour away by car. Where in Marbella are you? The outlaws have property in San Pedro de Alcantara.
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who are the outlaws? im actually just outside marbella itself just accross the road from sierra blanca. Ive heard of Guadalajara before but dunno why.
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Outlaws=wifes parents, ie the inlaws.
Guadalajara is to the east of Madrid. Outbound on the A2 towards Zaragoza and Barcelona. Incidently, the A2 is one of the most dangerous roads in Spain. Lost a friend on it two years ago.
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The N340 is the most dangerous stretch of road in europe its nicknamed "calle de la muerte" or road of death to you and me. They all drive like nutters down here and totally fcuked out of their skulls on all sorts hence the massive death toll! Its terrible sorry for your loss mate. San pedro is well known to me my mate lives up in benavista. So you been out in Puerto Banus recently? or do you prefer to keep the inlaws away from you?
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Hoping to get down there sometime this year. Could hold a first annual meeting of the Spanish GTI forum club.
My e-mail is cob427@tesco.net
(Sad address but I used to have a Cobra)
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yea defo sounds good. theres a guy I know with a mk2 valver aswell so he could join the, guy's an even better mechanic than me he jet hosed his engine on sunday and then wondered why it was fooked. you on MSN?
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He has condensation in his ignition system.
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yea I know but a really shiny engine bay :laugh: