problem with 7A

[Mikemul]

Ahh! but there can be a leak(s). We are not saying there are, but we must know (and this is the whole point, don't assume), prove it, is / are there?

Why simple vacuum hose replacement alone is not enough?

Because the humble vacuum hoses are foundational to proper engine function, we must get very good hose. One must avoid hose that is not good purpose-built vacuum hose. One must avoid the cheap, often shiney, thin-walled, often made in Asia hose which is vacuum hose; in name only. One must understand what good vacuum hose consists of. It is so inexpensive and easy to get really superior hose for this, that there are no excuses to not do this just once and properly. After proper hose replacement, testing must follow.

What is good purpose-built vacuum hose?

While it may have been entirely necessary to replace all your vacuum hoses (it is usually just soft lines that go bad BTW), the hard plastic (nylon?) ones may have been fine for years to come. It is also quite important what you replaced the soft vacuum hoses with (the originals we are most concerned with are those fabric-covered rubber ones that become all cracked, brittle and loose-fitting), the best replacement hose is perhaps BMW silicone hose shown below (there is a newer version than this I have not tried, no need so far). Important because our small vacuum hose needs to have a particular ID to remain leak-free everywhere it attaches, but also that the wall-thickness must be more than usual to reliably transmit full vacuum in use longer-term; without narrowing or collapsing.

https://www.audiworld.com/forums/12v.../#post22438034

Why testing the vacuum system is required?

Testing is necessary to ensure we have captured sufficient engine vacuum to then utilize throughout all the tentacles of the vacuum system; and that we can reliably transmit full vacuum without loss to all vacuum customers. We test because there are no in-car gauges for vacuum, no warning lights, no fault-codes for this, just poor engine performance, drive-ability, fuel mileage and because this is some of the most cost-effective work you can do yourself on your car most easily.

What does vacuum testing involve?

There are two types testing, dynamic testing for what the peak engine vacuum is at warm idle; and static leak-down testing (over a period of time) of the many branches of the vacuum system; to ensure there are no leaks. We need a vacuum gauge, a vacuum pump, and some simple fittings such as in the basic Mityvac kit described earlier. You can read about vacuum testing in the Mityvac catalog.


Fuel Injectors

The O-ring on the bottom of the injectors is really only a necessary vacuum seal between the injector and the I/M to prevent air (and dirt) from leaking in. You will not see fuel leaking there, even if your injectors are leaking fuel. You may see fuel leaking from the top O-ring or any other connection upstream in the fuel supply; and you should check everywhere to.

Because you have found fuel laying in your I/M (and your spark-plugs are black) it would be a good idea to ensure your injectors are at least closing properly when not being activated.

Injector servicing is a more complex procedure which would require you send yours away to get done. What follows is not servicing, just a simple leak check.

The fuel system will stay pressurized hopefully at least briefly after the fuel-pump is off. With a stone-cold engine, cycle just the fuel-pump alone with the ignition-key in the mid-position (of which you can hear running) then turn the key off. With those injector clips on I mentioned before, you can then safely pull all the injectors off at once while still attached to the fuel- rail (like you may have done already, correct?) and see if they leak (perhaps squirting, dribbling, or dripping fuel?). They should not be. If need be and you are careful, (don't attempt to start the engine) if you still have those clips on, and are prepared to capture the fuel, you could try to cycle the pump on again to re pressurize the fuel rail to see them at full pressure; without replacing them back into the I/M (see bottles photo).

injectors spray caught in bottles.png

Short-term goals:
- to have 18 inHg engine vacuum at warm idle;
- to have leak-down tested the vacuum system to prove no leaks; (start with the vac line from the I/M through to and including the FPR) and
- to have 5 injectors that close properly under full fuel pressure; and do not leak.

To a couple of your questions:

"Is there a P/N for the sensor?" Yes, find at link.

https://audi.7zap.com/en/rdw/audi+co.../9/919-919065/

"What's next if no vac leaks and sensor is good?" I suggest "pulling fault codes" is next. Please read up on that at 20v.org

To other readers, please feel free to pipe in if you've something to add, or if I messed this up or missed something, thanks in advance.

Thanks in advance for youre response, i check the injectors, when I crank first all the injectors spray together 1 time than 1 per time and really Good Closing. The rings at the bottom of the injectors looks Good and clean. I have place the injectors back. I order a new coolant temp sensor and 5 new bosch sparkplugs. I also order a vacuüm meter so i can test the vacuüm system. I let you know if I have test it.

[Lago Blue]

Meanwhile, you may want to pursue the ability to access DTC's.

(When considering whether to do this task, it may be encouraging to take some time to read through some of the faults that having access to these warning codes may give you towards engine trouble-shooting)

see at:http://20v.org/fault.htm

This will involve reading about and building an attachable light detailed at bottom of page here:

http://20v.org/tools.htm#VAG1115

or

finding an available attachable light that would substitute for the above (such as a small LED electrical test light)

or

Absorbing the relevant material from here applicable to your Euro spec car to make a functional "MIL" malfunction indicator light (a.k.a.: CEL or check engine light) right in your instrument cluster, (as opposed to the above temporary and perhaps necessarily self-constructed light):

http://s2central.com/main_frame.html

and

locating the "2x2" connectors (see drwg,), loose wires whose ends resemble those in the drwg., often tucked away in the driver's foot-well detailed at 20v.org

audi 90 2x2 connectors for DTCs.png

[Mikemul]

Meanwhile, you may want to pursue the ability to access DTC's.

(When considering whether to do this task, it may be encouraging to take some time to read through some of the faults that having access to these warning codes may give you towards engine trouble-shooting)

see at:http://20v.org/fault.htm

This will involve reading about and building an attachable light detailed at bottom of page here:

http://20v.org/tools.htm#VAG1115

or

finding an available attachable light that would substitute for the above (such as a small LED electrical test light)

or

Absorbing the relevant material from here applicable to your Euro spec car to make a functional "MIL" malfunction indicator light (a.k.a.: CEL or check engine light) right in your instrument cluster, (as opposed to the above temporary and perhaps necessarily self-constructed light):

http://s2central.com/main_frame.html

and

locating the "2x2" connectors (see drwg,), loose wires whose ends resemble those in the drwg., often tucked away in the driver's foot-well detailed at 20v.org

audi 90 2x2 connectors for DTCs.png

Thanks you, i have check the fault codes and there is one code: 2232 that means there is a problem with the air mass sensor. I also checked the vacuum system it has -0,20bar that means 5,91 INHG this is at cold engine I can’t test it with warm engine right now. But I think it’s not much higher

[Lago Blue]

Very good sir!

Old fault, still valid?
One of the first things you can try with a fault code is to (perhaps write it down and) erase it and see if it comes back later on, as perhaps it won't.

If your vacuum sort of sucks:
If you think your warm idle vac reading won't be much different, perhaps:
- ensure your throttles are getting fully closed (have you a tiny bit of slack in the cable?);
- did you put new O-rings on the injector bottoms?
- is your air-filter box free of squirrels and the air-filter stock and clean?
- other typical vac leaks are if you re-used the old gasket between the throttle-body and I/M; and the I/M to cylinder head gasket needs to be leak-free also.
- you can suck on the FPR by its' hose and then plug it / clamp it and see if it holds vacuum for over-night - that is leak-down testing!

I have also blown cigarette-smoke into the I/M to see where it may leak out from, but this is not quite the same (its the opposite!) as vac testing.

Some have directed an un-lit hand-held tank-type propane torch gas stream around the injectors' I/M O-rings with the engine running; to see if that fuel gets sucked in and possibly changes the engine rpm, and indicating a vac leak.

Q's: Later, when you can do warm idle, what rpm are you idling at; and is it now steady / steadier?

[Lago Blue]

Engine vacuum testing cont'd., some component variations, possible vacuum leak-points and some specs...

As I find the previously mentioned vacuum testing description in the Mityvac catalog is somewhat lacking, and I can't immediately find anything better, here are some points to possibly help you re-capture your missing inHG.

What may need to take place is that each branch of the vac system that can be made temporarily separate, from the I/M with the throttle-body attached, to the FPR, and all other branches all the way back to the rear diff and possibly the fuel tank (which although for unmetered air leaks (not eng. vac.), and may even involve the fill-cap seal!), can be and may have to be; disconnected and "leak-down" tested separately.

If you can measure (capture / recover) 18 - 20 inHg at warm idle (this is the other of the two types of vac. testing) before doing (vacuum leak-down testing on) all of them, bonus! Each branch to be tested will need to be plugged as required (perhaps only with the Mityvac and its' attachments), plumbed to that vac pump/gauge combi-tool, all sealed up, evacuated (to 18 -20 inHg on the gauge) with the vac pump; and left to sit overnight to confirm that each branch contains; -no- leaks. The vac. system drwg. below should help you visualize what's involved in this process. Yes it is tedious. Did no one warn you? Think of it as a possible entry barrier to the less determined.

Because this can be quite a process, it may now have become apparent, the reason for the previous emphasis on best quality, purpose-built and properly sized vac. hose. I bought three yards of the BMW hose.

The 7A engine compartment vac. system lay-out (Note: this is of an early car, but even if yours is early, it may be different from this):

Audi 7A engine compartment vacuum system lay-out drwg.png

Below are listed the fuel system performance checks. One can perhaps appreciate the importance of having the full (within these specs) vacuum made available to the FPR, when one recognizes that the fuel injection design requirement is to have provided the necessary (approx. 25%!) change in fuel pressure during that very brief interval between fully closed and slightly open throttles (between zero and 18 - 20 inHg vacuum). When this has been tested and found to be true, this will have a good affect on the character of the car's drive-ability, as well as the other consequences (on the idle etc.) mentioned already.

Audi 7A engine performance checks fuel pressure specs.png

Note the fragility of the throttle-body's (T/B's) gasket at its' narrowest points here, a common leak area (I used an aircraft grade traditional gasket sealant for paper gaskets (-Not- silicone sealant!) on mine):

Audi 7A throttle body two vac ports and fragile gasket.png

Not all the I/M's and T/B's are the same, some have extra ports to attend to (all vac. sys. connections and the components themselves are possible leak-points):

Two small vac. ports (one is rubber-capped?) of a three - port T/B (some have but two) Third port may be for EGR equip'd cars (and could be a possible un-metered air leak, (as opposed to a vac. leak) as IIRC, the port emerges up-stream of the T/B blade) here:

Audi 7A 2 vac ports of a 3 port throttle body.png

I/M with three big vac. ports (some have but two):

Audi 7A IM with 3 vac ports.png
Enroute to the rear diff (under the rear seat, yet more possible vac system leak points, but also as before, more connections where the system can be taken apart and possibly tested to isolate leaks; if found (through testing to be) necessary:

Audi eng vac sys enroute to the rear diff.png

At the rear diff., a possible actuator vac leak (thanks to Mk2i) and what that might cause:

https://www.s2forum.com/forum/member...00#post2040300

Audi B3 rear diff vac actuator cracked.png

Further, here are some spec. numbers to perhaps help answer some of your previous questions:

Audi early 7A electronic specs.png

[Mikemul]

Very good sir!

Old fault, still valid?
One of the first things you can try with a fault code is to (perhaps write it down and) erase it and see if it comes back later on, as perhaps it won't.

If your vacuum sort of sucks:
If you think your warm idle vac reading won't be much different, perhaps:
- ensure your throttles are getting fully closed (have you a tiny bit of slack in the cable?);
- did you put new O-rings on the injector bottoms?
- is your air-filter box free of squirrels and the air-filter stock and clean?
- other typical vac leaks are if you re-used the old gasket between the throttle-body and I/M; and the I/M to cylinder head gasket needs to be leak-free also.
- you can suck on the FPR by its' hose and then plug it / clamp it and see if it holds vacuum for over-night - that is leak-down testing!

I have also blown cigarette-smoke into the I/M to see where it may leak out from, but this is not quite the same (its the opposite!) as vac testing.

Some have directed an un-lit hand-held tank-type propane torch gas stream around the injectors' I/M O-rings with the engine running; to see if that fuel gets sucked in and possibly changes the engine rpm, and indicating a vac leak.

Q's: Later, when you can do warm idle, what rpm are you idling at; and is it now steady / steadier?

Hello,

I have check the fault codes and delete the 2232 code. after that the code is back again. when i checked the cable and the MAF i saw this: https://ibb.co/gtPjr5j the tube on the MAF is broken down. i dont know or the MAF works fine if its cracked? i think not because there is a fault code and is this the problem about the fuel ??

The throttle close good and the cable not stuck.

I change the injector rings at the bottom and use some vaseline to protect for drying.

there is no airbox on the car. there is a powerfilter mounted on it. this is not the stock one. there is a new gasket on the car a year ago, and a new intake gasket to the cylinderhead 2 months ago. when the car is warmed up its is not steady its fluctuating about the 600 to 750 rpm.

i wait for my new sparkplugs and temp sensor. I go and test the vac system and at first disconnect all the components only the intake line and check if it is about the 18InHG. there are no vacuum hoses to the gastank and to the diff.(because the gastank is removed) and the diff is always on. only the vac is go to the carterbreather and to the fuel pressure regulator. and the other line go to the Idle Switch.

I will let you know what the test results are about the vacuum system. can you say me what i need to check about the MAF?

Greetings Mike

[Mikes2]

All a waste of time. If you have a fault code for your maf and the wiring is all good, you should replace it.

[Lago Blue]

I see your cracked MAF in the photo. Its' reliability would therefore be doubtful. As there would be an electrical connection inside that broken area (between that CO adjustment in the small black tube; and the rest of the MAF circuitry. So as the unit's performance would likely be unstable, it is probably best to find a replacement. You will be able to find both a used 7A MAF and a factory air-filter box on Ebay for cheap.

If your vac lines only go to the FPR and the crank-case breather line, it may be easier to find your vacuum leak(s) because the "what to check" list is shorter!

To your MAF question:

Yes I can, MAF outputs are usually between one and five volts, like this:

From 1.35v at cold idle, 1.65v at warm idle, 3.35 at WOT blips (of throttle) while in neutral and 4.85v at load.

Pull back the electrical connector boot and see the connectors are numbered. No. 1 is the MAF sensor output

However...

the first two rules of trying to diagnose a MAF successfully are:

1) Eliminate all the vacuum leaks (air leaks into intake tract downstream of throttle-plates) and un-metered (by the MAF) air leaks (air leaks into intact tract upstream of throttle-plates) first; and
2) Make sure the crankcase vent system is also similarly faultless second.

Your MAF best needs replacing and...

As you have very little warm idle inHg, you must have vac. leaks well worth chasing; beforehand.

So it may not make too much sense to put the cart before the horse.

Chase down a MAF and get the original air-filter box (and all the stock air-guides) too, as the motor is just breathing in hot air from the rad and exhaust header -not a good thing to allow to continue. The stock cold air intake arrangement is by far the best for most folks.

[mcandmar]

Just looking at the image in your first post, that looks like a broken joint to me?

[Mikemul]

Just looking at the image in your first post, that looks like a broken joint to me?

Oh Yes i see it too, i replace it for a other one. Is there a different between the 054 133 471 for the Audi 7a and the 2,8 V6 AAH? There are much of those AAH for sale and it’s the same number on it?

[Bowie69]

That break is just a shadow from the flash, you can see the same effect the other end of the wire, that pokes beyond the post.

[mcandmar]

Could be i suppose, but worth double checking anyway. I have a couple of spare MAFs and other bits for a 7A if your stuck for anything. All for the later 1990 onwards 7A engine..

[Mikemul]

Could be i suppose, but worth double checking anyway. I have a couple of spare MAFs and other bits for a 7A if your stuck for anything. All for the later 1990 onwards 7A engine..

Does this fit? https://shop.autopartsveghel.nl/0565...iolet-bj-87-00 It had the same number

[Lago Blue]

Mike,

Yes, that (MAF in that ad) should be identical to what you have (all the details: P/N, 4-pin connector, casting should have the same small outlet diameter to fit the ninety-degree rubber hose to the T/B, CO pot). Many of the V6's shared this part with the 20V's.

Mcandmar has made you a very kind offer also!

[Mikemul]

Sorry for the long waitings, the other MAF sensor is arived today. I have install it and now its with cold engine as you can see in the video. https://m.youtube.com/watch?v=r8XuLfz48a4


i waiting for the temp sensor and the sparkplugs and that i can test the vacuüm system. Do you think the car runs rich? Or is it better than it was?

I let you know if i have test the systeem and find the leaks.

greetings Mike