problem with 7A

[Mikemul]

Just a thought I had wandering idle problems for a number of years on my 90 quattro with 7a engine, having gone thru the usual suspects (stable valve, maf, relays etc.) I finally sorted it by replacing the temp sensor on the rear of the cylinder head.

how can i test the temp sensor, put it in cooking water and look to the recistence? how many Ohm is normal?

[Mikes2]

it's 2000 ohms when cold typically. It usually throws a fault code

[quattrodave]

it's 2000 ohms when cold typically. It usually throws a fault code

From memory replacement temp sensor cost about a tenner so just replaced it with a quality non OE part back in the day, never did check codes on that 7A car has it was before I owned the correct tool and connectors,never had much luck flashing codes using an led either.

[Lago Blue]

You are getting some very good help here!

Yes sir, a pot of water on the stove, a thermometer and an Ohm-meter.

You may get some further ideas here:
https://www.audiworld.com/forums/aud...-rich-2810651/

Do you know if you have a functional "Check Engine Light"?

Perhaps you have the original fuel injectors?

[Lago Blue]

Yes, your MAF appears sooty. You understand how delicate these are and that you should not touch the wires, correct? See my post (#4) regarding MAF sensor cleaning here:

https://www.audiworld.com/forums/aud...aning-2795712/

Article with a very good graph showing VAG coolant temp sensor (CTS) test value ranges (see fig. 6-26):

http://eva2.homeip.net/eva2/FU01/ch6.2.html

[Mikemul]

Yes, your MAF appears sooty. You understand how delicate these are and that you should not touch the wires, correct? See my post (#4) regarding MAF sensor cleaning here:

https://www.audiworld.com/forums/aud...aning-2795712/

Article with a very good graph showing VAG coolant temp sensor (CTS) test value ranges (see fig. 6-26):

http://eva2.homeip.net/eva2/FU01/ch6.2.html

i have change all the vacuum tubes and the inlet tube had some cracks. i have use some rubberfix on it and now its better. i clean the inlet manifold, the Maf and the idle valve. and connected the carter breather with the inlet tube. now the idle is better but is this how it supposed to be?

https://www.youtube.com/watch?v=TUcko0W67WI

[PeterS]

Just a thought I had wandering idle problems for a number of years on my 90 quattro with 7a engine, having gone thru the usual suspects (stable valve, maf, relays etc.) I finally sorted it by replacing the temp sensor on the rear of the cylinder head.

Also suggest checking the actual connector to the sensor. I had a troublesome idling issue that ended up being a broken connector shell which resulted in intermittent contact with the temp sender in the head. Pull the boot back and make sure that the connector is in sound shape

[Lago Blue]

I saw your video, yes, I think you are going to be able to make it smoother and steadier on both de-acceleration and idle.

Some ideas to think about:

- Do you have a functional CEL (check engine light)?

- Did you re-use the original Audi / Hitachi fuel-injectors?

- There is an O-ring (mentioned in "Wandering Idle @ 20v.org) that is often found degraded (and leaking vacuum) under the adjustment screw on the throttle body. See idle speed adjustment screw labelled on the 2nd throttle-body here:

http://20v.org/throttle.htm

Count the above adjustment screw turns out on removal (so as to put it back exactly as found afterwards), clean the passage itself, and check the O-ring.

- At warm idle, how much vacuum does you intake system pull (on a measuring gauge, in inches of mercury, a.k.a.: inHg) in the manifold, downstream of the closed throttles. Tip: a "Mityvac" gauge is very handy / inexpensive tool for checking out all the branches of your vac system as well (as long as you don't also use it to bleed your brakes! Yuk, what a mess that makes!).

One reason to get a handle on what the vacuum is at warm idle, is because you are going to want to know you can use it to sufficiently lower your fuel pressure at idle, as much as that vacuum will allow, via the fuel pressure regulator. The ECU also expects this function to be working very well, to ensure it can then best do it's fuel delivery volume work on top of that variable fuel pressure delivery, as you transition away from (and / or back to) idle.

[PeterS]

I saw your video, yes, I think you are going to be able to make it smoother and steadier on both de-acceleration and idle.

Some ideas to think about:

- Do you have a functional CEL (check engine light)?

- Did you re-use the original Audi / Hitachi fuel-injectors?

- There is an O-ring (mentioned in "Wandering Idle @ 20v.org) that is often found degraded (and leaking vacuum) under the adjustment screw on the throttle body. See idle speed adjustment screw labelled on the 2nd throttle-body here:

http://20v.org/throttle.htm

Count the screw turns out and back in, clean the passage itself, and check the O-ring.

- At warm idle, how much vacuum does you intake system pull (on a measuring gauge, in inches of mercury, a.k.a.: inHg) in the manifold, downstream of the closed throttles. Tip: a "Mityvac" gauge is very handy / inexpensive tool for checking out all the branches of your vac system as well (as long as you don't also use it to bleed your brakes! Yuk, what a mess that makes!).

One reason to get a handle on what the vacuum is at warm idle, is because you are going to want to know you can use it to sufficiently lower your fuel pressure at idle, as much as that vacuum will allow, via the fuel pressure regulator. The ECU also expects this function to be working very well, to ensure it can then best do it's fuel delivery volume work on top of that variable fuel pressure delivery, as you transition away from idle.

a damaged or rotted o ring under the throttle body adjustment screw will definitely cause idle issues, and you will drive yourself crazy checking elsewhere for vacuum leaks or sticking idle stabilizer valve. The car should idle without the idle stabilizer valve electrically connected, its role is a damper to throttle changes.

[steve briance]

As above.

The o ring is only small and doesn't look like it would admit much air but, if it has crumbled or even is missing then you would be surprised how much can suck past the idle screw...

While chasing Idle faults in mine, I temporarily blocked off that Idle screw by putting modelling clay over the recess while I ordered o rings. The vacuum almost sucked it past the screw and into the thread.

[Lago Blue]

I think I've got the following correctly (it's been a while since I looked at this), however if not and you have other info, please feel free to point out my misunderstanding. Here are the drawings of the Crank-case Vent (a.k.a.: CCV) (or "Breather") arrangement for the early production 7A's I was trying to upload previously. This should help if you are trying to confirm or re-establish the original plumbing configuration and / or improve your idle stability and the ability of the engine to best return to smooth idle upon release of the throttle.

Early 7As Breather & Intake Basic System Drwg 1b.png

1) Even amongst these early cars, there is a possible variation one may find in the CCV system, that small vent line shown connecting the interior air space (above the cam-shafts) of the cylinder head to the larger vent line near the crank-case connection.

2) Separately, note at the top center of that 1st drwg., there is a part labelled "restrictor" in the vent line attached to the intake manifold (I/M) which Tee's into the larger vent tube connecting the crank-case to the "Intake Air Boot".

That factory restrictor provides a small regulated and constant source of engine vacuum to the CCV system when the throttles are closed, which is how the crank-case is vented at idle.

Audi early 7A CCV hose connection to intake boot and cam box.png

3) Because the void under the cam-cover is plumbed to the crank-case (2nd drwg.), and the crank-case to the I/M's vacuum at idle, even the rubber gasket and plugs sealing the cam-box shut (including the perimeter and the five spark-plug access holes in the cylinder-head) can affect engine vacuum and idle performance. On the top-side of the cam-cover, the oil fill cap's replaceable rubber seal (a common VAG part) may also become too old (heat-cycled) and inflexible to best seal shut that opening to the cam-box cavity, allowing this aspect of the oil fill-cap's role in the CCV system to best function, the cap's seal alone can be easily obtained and replaced.

Audi 20v Cam Cover Intake Manifold and Seal.png

The above explanation is really just a start at examining how engine vacuum (critical to both proper lowered fuel pressure at idle, fuel economy, emissions; and the best co-ordination with both the digital ignition advance at idle, and idle air stabilization) needs to best function. High warm idle vacuum, critical to getting the most favourable and smooth transitional throttle response at zero to low throttle settings (which is very much used under most street-driving conditions), also permeates throughout various other linked engine systems and components (the entire idle stabilization system plumbing, same for the FPR, (perhaps even fuel tank venting (may be this one is more of a possible un-metered air leak than vacuum) and vacuum for the rear diff IIRC (correct?)), EGR if present, and not to forget the 13(?) places the I/M can leak come to mind), all of which should be viewed as having possible locations where inadvertent vacuum loss might take place.

[Mikemul]

I saw your video, yes, I think you are going to be able to make it smoother and steadier on both de-acceleration and idle.

Some ideas to think about:

- Do you have a functional CEL (check engine light)?

- Did you re-use the original Audi / Hitachi fuel-injectors?

- There is an O-ring (mentioned in "Wandering Idle @ 20v.org) that is often found degraded (and leaking vacuum) under the adjustment screw on the throttle body. See idle speed adjustment screw labelled on the 2nd throttle-body here:

http://20v.org/throttle.htm

Count the screw turns out and back in, clean the passage itself, and check the O-ring.

- At warm idle, how much vacuum does you intake system pull (on a measuring gauge, in inches of mercury, a.k.a.: inHg) in the manifold, downstream of the closed throttles. Tip: a "Mityvac" gauge is very handy / inexpensive tool for checking out all the branches of your vac system as well (as long as you don't also use it to bleed your brakes! Yuk, what a mess that makes!).

One reason to get a handle on what the vacuum is at warm idle, is because you are going to want to know you can use it to sufficiently lower your fuel pressure at idle, as much as that vacuum will allow, via the fuel pressure regulator. The ECU also expects this function to be working very well, to ensure it can then best do it's fuel delivery volume work on top of that variable fuel pressure delivery, as you transition away from (and / or back to) idle.

thanks for youre comment, i have change the o ring it was really hard. i doesnt have a vacuum meter im sorry, the injectors are the stock ones and i place it back. there is no engine light. while the engine is warmed up the car has a bad idle and smokes alot. (because to much fuel) i dont know or the ignition is correct set. how much engine speed does it take to check the ignition?

[Lago Blue]

Very good. Hard, that O-ring won't have been sealing well. One less thing to need be wondering about.

At a certain point it will in my view, be more difficult to continue to trouble-shoot most effectively without both:
a) Engine vacuum measurement capability. I have a most basic plastic-handled MV8000 Mityvac kit (see on page 6 of catalog in link below) that can be had for (see link to ad below) online.

Mityvac is an SKF company! Who knew?

https://www.skf.com/mityvac/about-mityvac

Catalog:
https://www.skf.com/binaries/pub299/...pdf#cid-525294

A current ad:
https://www.ebay.ca/itm/Mityvac-MV80...0AAOSw4stfAwqe

...and
b) Access to possible current (and future) stored Diagnostic Trouble-shooting Codes (DTC's) from your cars computer (ECM). While a functional in-car CEL is not a necessity, making your car's CEL functional is not difficult and will make "pulling codes" so much easier.

See all about DTC's at good old 20v.org again...

Other issues:
1) Injectors.
a) Did you use new O-rings both ends of the injectors?
b) Did you replace the small clips labelled in the attached drwg? They will serve to keep your injectors attached during the partial removal and test below.
c) It may be that a 2nd part (1st reason is possibly low delivered vacuum to the FPR, detailed previously) of the reason for the fuel you are finding inside the I / M is that 30-some years on, the original injectors do not now really ever close properly in between the individual timed injections they are tasked with. The other 2 common faults that develop with any kind of injector with long service are degradation of the design spray pattern and flow rate variation (between the individual injectors, compared to each other, both of which also hinder good performance. Injectors, (and unfortunately only other than the Hitachi's AFAIK, can be professionally serviced to correct all the preceding.

You could pull yours while still connected and test them (are they constanly leaking?), taking precautions to prevent fire, like disabiling the ignition and catching and collecting the fuel that will otherwise spill during some short period of cranking of the engine with the starter-motor. For over a decade now, many owners (myself included) have replaced those Hitachi's with a newer type of Bosch units, and been happy with the results both short and longer-term.

2) Coolant Temperature Sensor (CTS or G62). This may also be part of the reason (3rd part) for excess fueling, if the ECM is being told (by a faulty G62) that the engine is not warmed up. Some folks have had better success with genuine VAG sensors here. It is also one of the inputs to the ECM for ignition timing, fuel enrichment and engine idle speed.

If it's close to its' original position (is it where you first found it?), the exact rotational position of the distributor may not be so critical, as the ECM will sort that out, given good inputs.

As the G62 provides info to the ECM used for cold engine fuel enrichment, idle speed control, cold engine ignition adjustment and the operation of deceleration fuel shut-off, you can see that this component must always be affecting the behaviour your engine is displaying in your video.

3) Did you test your coolant thermostat before installation? Does your comment "while the engine is warmed up..." mean before or after the engine is warmed up? What does your engine warm up to?

Audi 20v 7A fuel rail IM and injectors drwg.png

[Mikemul]

Very good. Hard, that O-ring won't have been sealing well. One less thing to need be wondering about.

At a certain point it will in my view, be more difficult to continue to trouble-shoot most effectively without both:
a) Engine vacuum measurement capability:I have a most basic plastic-handled MV8000 Mityvac kit (see on page 6 of catalog in link below) that can be had for (see link to ad below) online.

Mityvac is an SKF company! Who knew?

https://www.skf.com/mityvac/about-mityvac

Catalog:
https://www.skf.com/binaries/pub299/...pdf#cid-525294

A current ad:
https://www.ebay.ca/itm/Mityvac-MV80...0AAOSw4stfAwqe

...and
b) Access to possible current (and future) stored Diagnostic Trouble-shooting Codes (DTC's) from your cars computer (ECM). While a functional in-car CEL is not a necessity, making your car's CEL functional is not difficult and will make "pulling codes" so much easier.

See all about DTC's at good old 20v.org again...

Other issues:
1) Injectors.
a) Did you use new O-rings both ends of the injectors?
b) Did you replace the small clips labelled in the attached drwg? They will serve to keep your injectors attached during the partial removal and test below.
c) It may be that a 2nd part (1st reason is possibly low delivered vacuum to the FPR, detailed previously) of the reason for the fuel you are finding inside the I / M is that 30-some years on, the original injectors do not now really ever close properly in between the individual timed injections they are tasked with. The other 2 common faults that develop with any kind of injector with long service are degradation of the design spray pattern and flow rate variation (between the individual injectors, compared to each other, both of which also hinder good performance. Injectors, (and unfortunately only other than the Hitachi's AFAIK, can be professionally serviced to correct all the preceding.

You could pull yours while still connected and test them (are they constanly leaking?), taking precautions to prevent fire, like dis-abiling the ignition and catching and collecting the fuel that will otherwise spill during some short period of cranking of the engine with the starter-motor. For over a decade now, many owners (myself included) have replaced those Hitachi's with a newer type of Bosch units, and been happy with the results both short and longer-term.

2) Coolant Temperature Sensor (CTS or G62). This may also be part of the reason (3rd part) for excess fueling, if the ECM is being told (by a faulty G62) that the engine is not warmed up. Some folks have had better success with genuine VAG sensors here. It is also one of the inputs to the ECM for ignition timing, fuel enrichment and engine idle speed.

If it's close to its' original position (is it where you first found it?), the exact rotational position of the distributor may not be so critical, as the ECM will sort that out, given good inputs.

As the G62 provides info to the ECM used for cold engine fuel enrichment, idle speed control, cold engine ignition adjustment and the operation of deceleration fuel shut-off, you can see that this component must always be affecting the behaviour your engine is displaying in your video.

3) Did you test your coolant thermostat before installation? Does your comment "while the engine is warmed up..." mean before or after the engine is warmed up? What does your engine warm up to?

Audi 20v 7A fuel rail IM and injectors drwg.png

I have replace all the vacuüm hoses there can be a leak in there. Also replace the o ring on the throttlebody. I removed the injectors in one time. Only the o ring on the bottom side can be damaged but when that is they leak I think?? When I am home i wil test the injectors. Is there a number to order the temp sensor? I have read some about a fuse for the injectors?? What if there are no vacuüm leuks and the sensor is okay ? The labda is replaced for new and the airmassmeter is cleaned. Can i test the airmassmeter if hé Works? I dont know or the idle valve Works. I have mensure the connector and i got 12 volt on each pin with the car is only on contact.

[Lago Blue]

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 significantly more than usual hose 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.