my 20v coupe hesitates when above 80mph

[chriscole]

My audi coupe 20v 7a. is acting funny when ever i go above 80mph it has a slight hesitation. I have to give it more gas and then its ok. but once i ease off the gas it starts to hesitate ever so slightly again. it only does this when i go over 80. When i come to a stand and set off when i get to about 40mph it is a bit jerky.

When i switch off the car and start it agian it runs fine. Is this a fueling problem or a sensor problem? My temp guage isnt working so i dont know if it is related.

It doesnt idle properly from cold but once the engine is warm it idles fine. i have changed the idle control valve and this hasnt made a difference.

any advice would be much appreciated. thanks

[jp_paul]

I don't think this is related to your faulty MFTS. There is also another sender at the back of the head, bulkhead end, which switches at 70degC as i remember, to give the ECU a signal for cold enrichment. You might also have a slow lambda sensor or failing MAF meter. Don't think it's a fuekl problem - these tend to be throughout the rev range.

Intermittent problems are always the hardest to solve. As soon as it packs up for good, it'll be much easier to find...

[kevinclaxton]

Hi, I had very similar to this on my 96 2.6 v6 cabriolet - almost identical. I asked various people and I had the fuel / plugs / etc. Then someone said plug leads or coils. I checked and the coil pack was over £200 and the 6 leads ran from £20 each. So, taking a gamble a bought a second hand coil pack with leads attached from a breaker on e-bay, which looked identical. Turned out it was! I fitted it and it has run sweet as a nut since - and all for less than £30 incl P&P

[chriscole]

thanks for ur responses. What controls the idling of the car? it doesnt idle properly when its cold! Does the MAF control the idling when it is cold?

I have changed the MFTS and the idle control valve and it stil idles unevenly when its cold!

Where do I plug in the Diagnostics for the 7A 20v engine?

[scotty33]

Suggest you check for vacuum leaks on the intake side. Common one is the corrugated rubber hose on the throttle body, these split on the underside. Another is the crankcase breather hose which originally is rubber and will be mushy/split if original. the new part is steel tube with rubber connecting hoses.
It's worth checking that the vacuum pipe to the fuel pressure regulator is connected properly, another poss vac leak but also causes the higher fuel pressure setting at all times, which would cause a too rich condition especially when cold.
As stated by jp paul the temp sender on the back of the head is the one for the ECU to control cold enrichment, if this is showing a warm engine at all times, you have no cold enrichment.
the maf is pretty robust on these cars, could be worth removing the electrical part and cleaning the elements with electrical cleaning solvent. excess oil fumes from the crankcase breather can find their way back to this area so worth checking. And yes it does affect cold running.
There is a whole 'industry' around 7A injectors. They are reputed to be quite poor as injectors go, even when in good condition. There are replacements available which are said to improve mid range performance and pick up a few hp, might be worth considering, or see about getting yours ultrasionically cleaned.
Also worthwhile cleaning out the throttle body internals. A build up of gunge, causes reduced 'natural' airflow, the ISV then becomes overworked. There is an idle air screw that can also be adjusted to help out the ISV. It has an O ring seal which can crack/perish and becomes yet another vacuum leak!


http://www.034motorsport.com/fuel-injection-solutions-audi-7a-efi-injector-adapter-kit-improved-p-329.html

diagnostics in the other thread