some running problems and MAF sensor 7A

[djpeck]

You have certainly sorted a lot of potential problems.

A garage i went to once had a good piece of kit for checking leaks - removed MAF and it pushed smoke into the hose the MAF fits in. The idea is the very fine smoke finds its way out of leaks and is visible...

One other observation from my own problem solving is that by 30 years of age most plastic connectors have become brittle and cracked which caused problems on mine. The throttle pot plug and idle switch plug had both broken so badly that the electrical connection was lost.

Has the mixture control been set properly?... I would make 100% sure there are no leaks first but setting mixture can be done but it needs a fuse to be put into the fuel pump relay to allow changes. Not many garages know that!

Im afraid i can't help re MAF as mine is the later type.

Throttle potentiometer ok? They get very hot!

You can swap the early and later MAF without issues, you just unbolt it from the aluminium housing.

Hello again, I did some checks before answer again.

- I Checked leaks with a smoke machine and all pipes and hoses are perfect. There are no leaks.
- The throttle potentiometer seems to be good, and it is on parameters ( Resistance). Anyway, I have another throttle and I changed the potentiometer to check it.
- I removed the vacuum intake for calister with a plug but without differences.
- ISV was cleaned days ago.


Now the dubs.

Lectures are ok, CO is low and seems to burn correctly.
Regarding regulation, Autodata says that vehicles before 88 have to been regulated with the picture method(attached). In my case, my car is February 90, so you can regulate CO and iddle as normal... but I am not sure. Depending on the documentation you read.

Something I don´t understand is the fuse on the fuel pump relay.

At this moment, there is no fuse on it.

But In one ocassion, when I put a fuse there when the car is running, the iddle becomes more stable, it works better and in neutral the revs going down as normal.
After switched off the engine and turn on again, the engine worked as before, with iddle revs over 1800 on hit, and revs going down with difficulty.

Otherwise, I tried to use some vagcom machines but it doesn´t work. I don´t know if I can connect with one apart of the official vag1551.

Maybe all parts are good but the main problem is the basic adjust....

[jp_paul]

I had similar issues with my 7A. After many hours of trying everything like MAF, lambda, throttle pot and idle switches, I moved on to ignition. It turned out that my distributor was (and still is) passing some oil through to the hall sender, then oil pools in the sender connector block and and affects the circuit. After cleaning out the oil, everything went back to normal. So I now just clean this out as a routine until one day I'll have to strip the cooling system down to get at it and do something with the distributor seals (my LPG vaporiser makes it very difficult to get to the clamp bolt).
So I'd suggest having a look in the dizzy cap and hall sensor plug for traces of oil.

[Bowie69]

You can swap the early and later MAF without issues, you just unbolt it from the aluminium housing.

[steve briance]

You have certainly sorted a lot of potential problems.

A garage i went to once had a good piece of kit for checking leaks - removed MAF and it pushed smoke into the hose the MAF fits in. The idea is the very fine smoke finds its way out of leaks and is visible...

One other observation from my own problem solving is that by 30 years of age most plastic connectors have become brittle and cracked which caused problems on mine. The throttle pot plug and idle switch plug had both broken so badly that the electrical connection was lost.

Has the mixture control been set properly?... I would make 100% sure there are no leaks first but setting mixture can be done but it needs a fuse to be put into the fuel pump relay to allow changes. Not many garages know that!

Im afraid i can't help re MAF as mine is the later type.

Throttle potentiometer ok? They get very hot!

[djpeck]

Idle issue is likely a vacuum leak, examine the hose between the MAF and the throttle body, they often crack underneath where the breather goes in.

Then check all the other hoses, of which there are many, any air leak the wrong side of the MAF that lets in unmetered air is BAD.

The kicking at 3k may be knock sensors, but fix the vacuum leak first, as it may be related.

Also, have you checked for codes? Common failure is the lambda probe.

I checked for vacuum leaks in all pipes arround MAF, ICV, carbon canister pipes, presure regulator vacuum pipe and I didn´t see anything. My engine was rebuilded years ago and I'm afraid that maybe there is some air leak in IM, EM etc...

Both knock sensors are new (Bosch), less than 1 year. Lambda sensor is a a new one ( bosch with less than a year).

Beware swapping MAFs with part numbers which do not match the original. They have outputs designed to suit an engine ecu, air and fuel needs. These are not the same on every engine so, even if it fits: any other MAF may well also cause problems.

As above, vacuum leaks are a common cause of high idle, it is the opposite of turning the idle speed screw down after all! It wont take much of a leak so take your time looking.

Id also check your injectors are spraying nicely especially if they are the original hitachi parts.

They are old now and may well be leaking more fuel in than needed...

Ultrasonic clean or replace with the bosch upgrade to be sure.

I did the conversion to red bosch inyectors (new ones) months ago (https://store.034motorsport.com/audi...-improved.html) and it doesnt exist any diferences about this issues. So I came back to the original ones to try to fix this problems before making "updates".

I asked about MAFs versions because I don´t know what version is the correct one, I have the early 7A engine ( 2 ecu connectors) and I have in 3 MAFs, 2 AFH50-12A and 1 AFH50-01B. I don´t know if it exists differents between those.

Thans for both answers, it is appreciated to have some help

[steve briance]

Beware swapping MAFs with part numbers which do not match the original. They have outputs designed to suit an engine ecu, air and fuel needs. These are not the same on every engine so, even if it fits: any other MAF may well also cause problems.

As above, vacuum leaks are a common cause of high idle, it is the opposite of turning the idle speed screw down after all! It wont take much of a leak so take your time looking.

Id also check your injectors are spraying nicely especially if they are the original hitachi parts.

They are old now and may well be leaking more fuel in than needed...

Ultrasonic clean or replace with the bosch upgrade to be sure.

[Bowie69]

Also, have you checked for codes? Common failure is the lambda probe.

[Bowie69]

Idle issue is likely a vacuum leak, examine the hose between the MAF and the throttle body, they often crack underneath where the breather goes in.

Then check all the other hoses, of which there are many, any air leak the wrong side of the MAF that lets in unmetered air is BAD.

The kicking at 3k may be knock sensors, but fix the vacuum leak first, as it may be related.

[djpeck]

Hello everyone,

I have an early 7A engine with some running isues.

1. It consumes 15 liters per 100km, so something is not runing properly. But I think that the engine is not lossing power.
2. Iddle rev are jerking. I openned and cleaned the ISV like this web sais ( http://20v.infinityfreeapp.com/engprob.htm#isv )
3. The Throttle Body screw is at minimum and when the car is over 95ºC, the rev increase to over 1200rev or more
4. Whe I run at 3000revs without charge, the car makes some jerks. Only in that revs and when the revs are going down, when you are speeding up it isnt a problem.

Does anyone know what could be the problem? I am thinking that probably the problem comes from the MAF, I want to buy a new one or only the sensor, because I tried with 2 more that i have and I didnt see the difference.

Does anyone know whats the difference between AFH50-01B, AFH50-12A etc?

And if it is possible to put a AFH50-11 for example