7A engine slow throttle response query?

[Stick Insect]

Dear all, I have an early 1990 coupe Quattro 20V. It has a 7A engine 2309cc.
25K miles from new.
It has the standard Hitachi parts on it and the bag of snakes exhaust manifold.
The catalytic converter has been removed and replaced with a straight through section.
I had a rolling road run last year to try to improve running.

It is currently still running lean and the throttle is slow to respond. I stick my foot down and it takes a while to get going. I've had this car for 23 years and it has always been like this.
The MAF is from a 2WD coupe Quattro 20V.
there are no air leaks.
The cam belt has recently once again been changed and the timing marks are correct.
The MAF has been carefully cleaned
it has a K+N air filter on it. could this be a problem?
I'm off to the French alps on a classic car rally in a month and would like the car to run better.
MPG seems to be about 22mpg.
Any helpful suggestions appreciated...

[SA BOY]

There's definitely a problem as it should go like a scolded cat check fault codes? Could be fuel filter, air flow meter, lambda sensor or fuel reg?

[John.]

Lambda sensor could be an issue, have you checked the Multi-Function-Temp-Sensor for corrosion at the connectors/plug?

Any pictures of your car would be nice......25k from new

[mike74]

Has the spark plugs ever been replaced?

[Stick Insect]

Thanks for the replies, last year before recomissioning I fitted a new fuel filter, thoroughly cleaned the MAF. the car develops a lot of power and revs really well, it's just slow to respond.

I have two connecters, think they are black and brown to play with no white connecter. I'll have to get my finger out and read them. may help fixing the ABS fault...

I like the idea of the fuel pressure regulator. I will have to check that out.
If anyone has more ideas I'd love to hear them.

I'll post photos after a good clean up.

Hoping to post pictures from the event now I've got a working account again.

David

[Greg_S]

Drop me details of email you had on other account and will get it reactivated for you

[nribs]

I've had this car for 23 years and it has always been like this.

I think there is your problem...the 7A 20V NA

[Mikes2]

Running lean is probably the root of the problem.

Check that the vacuum line from the pressure regulator to the inlet manifold is complete and that the rubber end pieces are intact and not holed. Same for the throttle body breather hose which goes to the carbon canister. The small elbow on the throttle body is particularly prone to splitting.

You may want to consider fitting the Bosch injectors to replace the Hitachi ones.

[Stick Insect]

Thanks all,

The car had a very good service last year. all oils and fluids changed, new fuel filter, new top quality NGK plugs.

Lambda sensor was replaced with an expensive new Bosch unit.

Mikes2:
I did find that the small diameter pipe had come of the rear of the manifold. this kept popping off, It now has a proper clamp on it. All other hoses are in 'reasonable' leak free condition.

I am strongly considering changing to different injectors. It should be ok with the hitachi injectors though. I'm not after lots of power ( this comment should see me being thrown off the forum!) I need a smooth running responsive car for the alpine rally next month. lots of Hairpins...

The car runs and cruises fine but even when not In gear is slow to respond.
Over 4,000 rpm it really gets going but is plain dead below. I know the 7A is cammy but this is not correct...

Nribs, thanks for your comment. the 7A sounds better than the turbo engine and I like to be different

The car is going to Mikeanics in Congleton next week for investigation on the rolling road. Just trying to sort as much as possible myself...


David

[John.]

Wonder if timing could be retarded or maybe knock-sensor issue??

looking forward to pics.

[macspring]

Is 25k miles a typo, or correct, just curious to see photos if not typo.

Post what it is when you find the cause of the 'lag'.

and maybe some photos of your Alpine trip in due course.

Regards.

[steve briance]

Have you done a code read using the LED technique? counting flash sequence gives you any stored problems and it may tell you where to look...
20v.org has good info and a search of the googleweb will find you lists of codes.

I recently did this job after developing a judder on mine. It wasn't all the time, just a 'burping/hiccup' and only every now and then though perhaps more when cold.

The code that came up said the Throttle Position Sensor was out of range / not functioning.

A quick bit of investigation later and i found the 3 way bosch plug connecting to the TPS had crumbled away and was barely holding the wires in place! I ordered a new connector (search for Junior power timer), fitted it with a short length of new loom soldered in and all is now well. Yours being an early model will have the 4 pin connection to the TPS. In your case I doubt your plug will have crumbled as at only 25,000miles it won't have got hot that often!

Either way, get a 12V LED (so you don't need to sort out a resistor) unfold a paperclip and get them codes read!

[Balnas]

I had the same issue with mine 20V, some years ago, the problem was faulty maf sensor. I do suggest you try another one.

[Ryss]

Make sure the TPS throttle position sensor is working as it should.

Also check the ignition timing. The plastic gear on the bottom of the distributor is a weak point. Can be replaced with a brass one that works well.

[Stick Insect]

I think it may be fixed...

Dear all, thanks for the comments and suggestions,
I knew there wasn't an air leak. The earth is flat and the moon is made from green cheese...
There is a large pipe fitted in the underside of the MAF sensor to throttle body. this pipe was not in place at all. bit like having a 12mm hole in your induction. The pipe was fitted in with great effort and the car now ticks over for the first time in 22 years.

I have bought some red bosch injectors and adapters from Germany to replace the Hitachi injectors.
once I have got the car back on the road after a failed door lock I will do the modification.

Thanks once again for the comments.
P.S. sorry for the slow response. Greg_s has managed to het me back on line. Thanks Greg!