Coupe Quattro running problems (7A)

[Toby_Unna]

Hi all. I'm having some problems with a 1990 20v Coupe with Hitachi management, and would appreciate any help with this!

The car generally runs ok, albeit richly. It was bought with a faulty ICV, and the previous owner had fiddled with the throttle stop/throttle bypass screw/CO adjustment (!) to get it to idle acceptably.

However, the ICV seems to work fine when connected to a separate supply, but does nothing when connected to the car. I've reset the throttle stop so that the throttle closes properly, and checked the wires from both throttle switches and ICV plug back to the ECU with a mulitmeter which seem ok.

I have sorted several air leaks, replaced breather hose with metal version etc etc, checked air mass meter elements which are clean.

The other issue is that the engine will *only* idle if the throttle is cracked open a little - I would expect to be able to keep it running just using the idle bypass screw, but it won't, although the screw is clearly letting air in.

With regard to it running rich, I was going to look at the resistance of the coolant temp sender and change the O2 sensor, but a search here makes me think perhaps the injectors are the problem?

Thanks in advance!

[stiglet]

There is a throttle switch which tells the ECU when the throttle is completely closed. You can just here it click when you open the throttle. This tells the ECU to engage the ICV and keep the car idling. Could be this that is the source of your problems. It's on the bottom of the throttle body i think, and the plug for the switch is on the top.

Check all your fuses too, including the ECU ones. I had a similiar problem and it was a blown ECU fuse.

The rich running could be, as you say, lambda or temp sensor. Or it could be MAF.

[Acidburn]

also worth checking out

20v.org

[mcandmar]

Good advice from Stiglet there, if the idle switch is at fault you will have to bodge the throttle body adjustment to get it to idle again causing all sorts of issues. I have had a few of those switches fail on mine. There is a procedure for setting the throttle body plate stop, base idle adjustment, and idle switch adjustment. They are critical to get right or the car will never go properly. First thing to check is the throttle plate adjustment, the stop should have a dab of yellow paint on it. If its still intact, i.e. hasent been messed with move onto the idle switch adjustment.

Old/dirty injectors will cause idle problems and a rich mixture at low revs, usually when these crappy hitachi injectors fail (and they all do) they constantly leak. I had my original five put on a flow bench and the guy was doubled over with laughter at how bad they were. I would also advise you put a bottle of injector cleaner through every few tanks to help keep them clean.

[Flat on my back]

.

Dont bother with the injector cleaner...stick in a tank of V power once a month...unless you use it already?

Go for the throttle body first...clean it and check the TPS over properly as suggested.

[Error404]

You can adjust the idle switch so it just clicks open when you move the throttle just off closed. You can disconnect it and the car should still idle and run, but not perfectly and will take a long time for the revs to drop when blipped. This could tell you if the switch is not aligned properly with the throttle plate or broken.
The throttle potentiometer can also be adjusted to, and can also casue idle and running problems if not right. IIRC the later 7A had a throttle pot with an integral idle switch, so this is something to look at.

[panzerwagen]

As to the idle switch I agree with everyone on it, but....

for the injectors...DUMP THEM! They are POS. Do what most of the US guys have done. Go to 034 and get their uprated & modded injector setup. I have a set and they are by & far waaaaaaay better then those pieces of Jap ****. Why in Gods name Audi used Hitcahi is beyond me. The engineer who spec'd them should have been shot.

[stiglet]

Same with the ECU too!

Just as a side note, I run the 034 Bosch injectors and my car now runs rich as a result. Probably as a result of the ECU not tuned for the WOT open loop mode. If your car is running rich as is already, the Bosch units could make matters worse!

However, they are otherwise undoubtedly a better solution.

[panzerwagen]

034 injectors come in 2 types...

Ford and Bosch. The Ford ones have proven to help emissions while the Bosch are for performance. Most guys who have to take emissions testing go with the Fords as I have done. Those who have no testing will go with the Bosch.

[stiglet]

Cool, I didn't know they did two types. I have got the Bosch ones which would make sense.

[S2central.net]

Who has a running 7A that I can play with on an emulator - in Ireland ?

It can't be that hard an ECU to tweak - though it is some Jap crap alright - dunno why Herr Bosch lost that gig...

All it needs is the main fuel and timing maps tweaked (one for low and high octane) - then there be some sort of full throttle enrichment.

The same principle should be applicable to shitachi controlled V6 motors as well - though all the pointers there say that little gains are to be had on them. There must be some headroom in them though - no way Audi tuned that to the max.

[stiglet]

Paul, If you could get your head around the Hitachi ECU I would deffo pay money for that!

[S2central.net]

Just looking at it now... I have some different 7A chips here and there was at least two variations of the ECU to complicate things.
Some maps aren't too hard to find. A real-time session would prove things out nicely - needs an AFR guage though.

The checksum on these is a real nose bleed - gonna have to get into disassembler again - my poor tired brain...

[mcandmar]

Paul i have the perfect guinea pig here for you to test with. I even have a spare ECU with a socket. It would be nice to get to the bottom of that chip i sent you, it has a noticeable improvement in the midrange.

Call me crazy but i always wanted how it would run with ABY loom an intake manifold, provided you can make the ECU run without boost. Basically convert the engine to motronic

[stiglet]

mcandmar - I have wondered the same thing. I'm tempted by the idea of converting to a 3B loom, just to be a little less complicated with the dizzy and everything. However, it must require a remap still surely? If I needed a remap anyway, it would be better to stick with the original if Paul can crack it.

Just out of interest, was that chipped ECU you're talking about the one I sold? I can't remember who I sold it to... think it was Hibby actually. Would like to know if that chip was any good or not.

This thread has gone way off topic now...