Audi Repair: slight backfire/bad hesitation, air flow sensor, fuel starvation


Question
audi a4 avant
1.8  20v petrol
1998
134,000 miles
Not Modified


hi greg

thanks for your reply.

you mentioned the diverter valve on my car but its not turbo so has not got a diverter valve,
and i also removed the throttle body few days ago and thouroughly cleaned it with suitable cleaner and also cleaned and checked all breather pipes and theres no leaks.

i also checked all sensors with multimeter with guidence of autodata cd, and the Oxygen sensor! and there all working fine, vag-com does not report any error codes.

my car is still backfireing/popping through exaust only when warm, no probs when cold! and ive recently taken it a drive down the motorway at high speeds and is hesitating really bad at about 80/90mph maybe its fuel starvation? but would fuel starvation cause it to backfire on decelleration?

ive spent a lot of money at garages trying to sort this prob and no one has got any idea to wat it could be,
the only thing now i can think of is either catalytic converter or fuel pump or fuel filter but again would they cause it to backfire?

as i put above this car has done 134,000 miles so do you think it would need a CAT at this mileage? and do you think it has any chance of sorting my problems.

im really sorry to bother you with such awkward questions but this is my last hope.

any help and i would be so gratefull.
thanks.


ps.
forot to put my name on last post sry.

thans in advance

Colin Fletcher.

UK.

Answer
OK,,,, you live in UK. Sorry ,but in US where I live we don't have 1.8 non turbo engine, I work on audis every day but I never saw 4 cyl. non turbo engine. Anyway
I have seen cats going bad after 60 000 milles, but some of them are good for ever, they usually set a fault or make a lot of noise.
I don't know if you have mas air flow sensor, but if you do try to discconect it and drive. it may read crazy amount of air and ECM is trying push for more fuel.
good luck    greg