Coupe Quattro running problems (7A)

[mcandmar]

No its a real dodgy one i bought on ebay, i was surprised it worked at all

Likewise i would have bought one if any reputable tuners had them available. The only one i ever found was this http://www.tap1.com/catalog/index.php?cPath=96_60_67. Dont know anything about them, but i dont think they had one for the later ECU's. There does seem to be fundamental difference in the two versions as 9/10 i have seen were all for the early version.

[S2central.net]

That eBay chip does help find some things - but I can't trust it at all - annoying really as it could be a perfectly good chip. I will get a look at this... Someone else has offered an ECU for evaluation, but yours is closer Mark so that might work better... Plus I should be in that Dublin for a day or two next week. They post from UK to NI ten times faster than from IE...

Your idea about running Motronic on 7A is a funky one... guess it could be done with 3B ECU relatively easily... But we'd need to check the location of crank sensors - may need 3B flywheel instead of 7A for example. Guess you could a step further with full DI setup on ABY if you use the AAN tunacan dissy to house the camshaft sensor. Would be easy enough to have the turbo chip do nothing. The more I think about it - its a great idea... Are you serious about trying it ?

Requires a bit of wiring hell, but nothing horrendous. Give me the weekend to check for any other gotchas between MPI & Motronic.

[mcandmar]

I was really only thinking out loud, at some stage over the next few months i plan to take the car off the road and start the conversion, i wouldn't mind trying it then out of interest. The cam sensor is a point i hadn't thought of, i am almost sure there is a suitable sensor inside the dizzy that could be used for that purpose, i.e. fit an ABY cam cover and coil packs and leave the dizzy in place to drive the cam sensor. Everything else should work fine provided i use the aby intake for the TB, MAF, and IAT sensors. The 7A has the same two sensors on the flywheel, however we would need to check the pins are in the same positions.

The more i think about the easier i think it will be, i have to change out the wiring loom and re-route the fuel lines anyway for the ABY engine. I might as well do all that with the 7A lump still in the engine bay, then connect it all up and see does it run.

Sorry Toby, your thread has gone waaay off topic now

[stiglet]

The only bit that worries me is having to change the throttle body if you change the loom. I want to keep mine NA so I think the 7A inlet manifold would be the better manifold to use. The 3B one is great for a turbo, but I'm not so sure that it would work very well with an NA motor.

Toby any progress with your problem?

[S2central.net]

Agreed that 7A IM is best for that application... Dunno if the throttle pot in that is compatible with Motronic - but a simple conversion circuit could sort that out.

Fuggit - if the Hitachi is such a hard ECU to tweak well, then Motronic is a cool alternative. I'll look into it some more. Interaction between turbo and motor chips is far from clear so I don't yet know how much of a pickle the ECU would get into if it wasn't seeing boost.

Oh and sorry Toby. This is very interesting stuff, but not helping you at all.

[stiglet]

If you want to move this to a different thread for the purpose of future searches that would be fine by me, I get the feeling this could go on for a while!

[Toby_Unna]

Oh and sorry Toby. This is very interesting stuff, but not helping you at all.

No probs, it's all worth reading.

RE the original post - I'm aware of the throttle-closed switch's presence, it works correctly and the wires back to the ECU show no resistance; it's certainly doing something because the engine makes a noticable change in running when the switch closes.

However, the ECU is not operating the ICV at all, so I'm wondering why. perhaps another sensor input that's not right or something? or maybe the ICV is fused somewhere, or the driver transistor in the ECU is fried or something.

[mcandmar]

I dont like the 7A intake personally, i came from a world of high revving Honda engines and they always have IM's with short runners and a single choke throttle bodys. If it were a japanese car it would have an IM very similar in size to 3B/ABY items. Besides attempting to tune these engines for torque is futile, i would rather turn it into a high revving screamer.

@Toby, have you tried the ECU output tests, one of which will test the ISV and verify if you have an electrical problem?

[S2central.net]

I had a dicky ISV/ICV on the 7A that I owned about 12yrs ago - strewth...

Should indeed be a fused item - but not uniquely so - I'll hit the schematics later.

[Toby_Unna]

Thanks. Does anyone know where I might get hold of a circuit diagram for the engine loom?

As for ECU output tests, if you mean read the codes then no I haven't but it's on my list! assuming that's what you meant?

[mcandmar]

The output tests let you trigger fuel injectors, ISV, and evap valve one at a time to verify ECU control. Output test are performed the same was as reading fault codes. If you dont have access to vagcom you can still do it with a paper clip and LED.

Follow this page http://www.20v.org/fault.htm and get the fault code outputs working. Then follow the below link for the output tests. Note its converted from German.

http://translate.google.com/translat...lr%3D%26sa%3DG (go into tips and tricks / actuator diagnostics)

If you know anybody with vagcom it will make life a lot easier

Mark.

[Toby_Unna]

Thanks, that looks very useful - I'll have a play with it!

[Toby_Unna]

Are the Bosch injectors mentioned above a straight swap for the Hitachi ones, in terms of impedance and the fuel rail connection?

I haven't taken the Hitachi recirculating rail off to see whether the injector tops are the standard Bosch fitment or not, as the car is in daily use, but I could certainly do with knocking this ridiculous fuel consumption on the head before the sump fills with petrol and the bores wear out!

[stiglet]

The Bosch swap comes as a kit from 034motorsport, and it includes adaptors for the fuel rail. The Hitachi units are low impedance but the Bosch units are high imp, so you need to bypass the resistor pack. Again, the kit comes with a bypass harness which is basically just two plugs and a wire! Very easy job if you get the kit.