gti 8v hesitation at low rpm

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rutter123
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gti 8v hesitation at low rpm

Post by rutter123 » Tue Mar 18, 2014 9:54 pm

although running well and the idling probs now sorted, there is still a little hesitation between 1500-2500rpm, def not a misfire, if it's foot to floor it feels fine but under gentle acceleration its there, timing has been set with a strobe according to manufacture settings (and the vacuum advance seems to be working ok) new coil, plugs, leads, diz cap and arm, fuel pump good, fuel pressure reg checked and ok, new fuel lines, dosen't seem to make any difference whether the engine is hot or cold, it dosen't stall and starts ok even when hot. have tried advancing/retarding timing a few degrees but makes no difference, feels like a low speed fuel starvation prob but not sure, any ideas?
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demag
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Re: gti 8v hesitation at low rpm

Post by demag » Tue Mar 18, 2014 11:27 pm

Dirty injectors?
Dave.

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rutter123
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Re: gti 8v hesitation at low rpm

Post by rutter123 » Wed Mar 19, 2014 10:56 am

Yeah could be will run some injector cleaner through it.
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Re: gti 8v hesitation at low rpm

Post by Way2go » Wed Mar 19, 2014 6:17 pm

rutter123 wrote:Yeah could be will run some injector cleaner through it.
That stuff causes more problems long term than it solves!

Best to remove them and get them cleaned by an operation with an ASNU ultrasonic machine and serviced with new filters, 'o' rings and pintle caps. It'll feel like a new car. :D
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rutter123
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Re: gti 8v hesitation at low rpm

Post by rutter123 » Wed Mar 19, 2014 7:34 pm

So ii have read today they cause more harm than good and a waste of money, money better spent having them pro cleaned, a local fuel inj specialist said they can do them for £17 each but didnt mention the caps or orings?
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Re: gti 8v hesitation at low rpm

Post by Way2go » Thu Mar 20, 2014 3:24 am

£17 each is about what is cost me in the past but of course it's worth asking the question whether that does include the new filters, pintle caps and O rings. (It should do.)

If you get the opportunity of viewing the servicing take it, it's especially interesting to view the differences and uniformity of fuel metering tests both before and after the servicing.
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Re: gti 8v hesitation at low rpm

Post by rutter123 » Thu Mar 20, 2014 4:23 pm

Yes have seen on youtube the before/after results, but i'm still not convinced the injectors are causing the prob, i think this is more airflow related? Is it possible to physically see if they are dirty or is it more internal than that?
90 BX Tzd turbo 294k SORN undergoing major surgery
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Re: gti 8v hesitation at low rpm

Post by Way2go » Thu Mar 20, 2014 6:23 pm

It is internal, so no really external evidence. The pintle caps may show signs of external carbonation, but it's more the internal crud that needs to be ultrasonically completely cleaned out because of its affect on the various spray patterns, their efficiency and delivery.
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Jaba
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Re: gti 8v hesitation at low rpm

Post by Jaba » Thu Mar 20, 2014 9:07 pm

My GTi has always had a tendency to do this, but only when hot. I have had the injectors cleaned and cleaned all h2o from the fuel tank to no avail.
What does improve it is to tweak the co reading above the legal limit. Keeping it lower just at MOT time.

Another throttle housing might reveal the source in your case though - just guessing BTW.
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Re: gti 8v hesitation at low rpm

Post by rutter123 » Fri Mar 21, 2014 7:44 pm

I will give the CO adjuster a few turns back in as it was wound out 3 1/2 turns to bring the emissions down for the MOT, have checked the plugs today, which were very white so i guess its running a little lean.
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Re: gti 8v hesitation at low rpm

Post by adamskibx » Fri Mar 21, 2014 7:59 pm

Could it be a dirty air mass meter?

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Re: gti 8v hesitation at low rpm

Post by rutter123 » Fri Mar 21, 2014 10:28 pm

adamskibx wrote:Could it be a dirty air mass meter?
air mass meter or airflow meter? same thing-do you mean the sealed part on top of the airbox? ive read somewhere that cleaning the tracks in here can cure? how to clean and what with? running out of options. just as a matter of course today i changed all the newly fitted bits i.e plugs,leads, diz cap and r arm,tps, coil, and fitted all the old ones back on, it made no difference wotsoever, the flat spot is still there in the same place. too lean? will richen the mixture setting a few turns and go from there.
90 BX Tzd turbo 294k SORN undergoing major surgery
90 BX Tzd turbo estate 46k awaiting surgery
65 Peugeot Boxer Van the new workhorse
52 Toyota Rav4 180k Bulletproof Jap reliability

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Re: gti 8v hesitation at low rpm

Post by rutter123 » Sat Mar 22, 2014 11:09 am

Richened the mixture up back to its pre MOT position, made no difference, still hesitating, next step airflow meter track clean.
90 BX Tzd turbo 294k SORN undergoing major surgery
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Re: gti 8v hesitation at low rpm

Post by Way2go » Sat Mar 22, 2014 3:40 pm

rutter123 wrote:Richened the mixture up back to its pre MOT position, made no difference, still hesitating, next step airflow meter track clean.
It must be worth getting your injectors serviced before trying this work? If the spay patterns are defective or weak then mixture adjustments will have no great influence and interfering with the tracks on the airflowmeter if unneccessary risks permanent damage.
If Injector servicing doesn't cure it, at least you are starting from a known good position.
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Re: gti 8v hesitation at low rpm

Post by rutter123 » Sat Mar 22, 2014 8:24 pm

Point taken, unknown territory there, injectors being cleaned at boxer motor works in Ashford next week £80 full clean and refurb.
90 BX Tzd turbo 294k SORN undergoing major surgery
90 BX Tzd turbo estate 46k awaiting surgery
65 Peugeot Boxer Van the new workhorse
52 Toyota Rav4 180k Bulletproof Jap reliability