ismith

Have you had a diagnostics readout? It really is useful. If you are doing 85-90 on the motorway, then 30 is about right. 65-70 would get you 35-37mpg.

kevhaywire - Thanks for your tips. I could do this inspection, but the car was performing well for many years and then badly with nobody touching the chain. It performed exactly the same after chain replacement and same again after the cyclinder head valves were replaced, so I think it's probably ok. From what you say, I could have three suspect MAFs, or lambda/MAF wiring with an intermittent fault I can't find. Oh to find a car technician old enough to remember how to find these problems!

I've had my 1993 VR6 for 12 years and when she was young (under 150k), a motorway journey keeping under 75mph would give me 35mpg. A mixed commute of 10 miles would get me 30mpg. I'd have to be urban and under 5 miles to get 25mpg. Now 23mph on 10 miles :-( and the diagnostics show it is not happy.

Injectors have been out, overhauled by an agent and back in. Not them sadly. I even tried a second set just to be sure.

Compressions spot on. When the head was off, the bore wear was bearly discernable. The bore expert said he couldn't charge me for anything! I just wonder if there's a hard-to-spot air leak. I need some flammable liquid to spray around the intake.

190k miles. New chains and valve guides. That didn't make huge difference, but is smoother at some revs. I suspect thererfore that the garage got the sprocket on the right way! Were your MAF wire or film types? I've tried three (6-pin) replacements in total: two scrap and one from VW dealer, to no effect. Performance off - it's like a 2 litre. I get 23mpg on a 10 mile commute which is 60% country lanes and 30% urban. When she was working properly, I'd get 30mpg.

Well I got a new MAF today, reset the ECU, and no difference :-( I remember once when I had the throttle body off to clean it and the ISV, the car was back to normal for the drive in to work and then horrible from then on, but I tried that again for luck and no joy. Any bright ideas?

Brilliant list of suggestion, folks. Thanks! Cam sensor was replaced, even though it was not faulty. TPS dig go a couple of years back. VAG-COM shows correct operation. Car gets nice and hot. (Been through a couple of temp senders in her life.) VAG-COM diags show correct temperature too. VAG-COM logger shows the lambda probe switching at idle and when driving. (The lambda on the VR6 is different from the other models in that it has four-wires and does not rely on a local ground.) VAG-COM adaptation at idle varies from 0.4-0.8, depending on when I've checked it. It should be pretty close to 1.00 from what I can rememeber. Last year I had the valve guides replaced, as a valve was sticking, but that didn't fix the fuel consumption. It made a huge difference to the oil consumption! The ECU was dodgy. The fuel-pump relay started clicking rapidly just before I started. A scope showed the ECU driving it 200ms on, 1ms off. Sounds like a reset watchdog going off in the software. Ebay got me a good replacement one. Still didn't impact the mpg. I just wonder if the old ECU could have damaged the MAF. I have two of them, but there's a chance they both could be damaged I guess. I'll see if I can get them tested. Otherwise I can only thing of an obscure air leak. I did find one before when a garage didn't replace the injectors properly and damamaged their seals. That still didn't make a significant difference.

All brakes are fine. They have needed maintenance in the past year. Tyres unchanged. We're talking about a lot of fuel here and the lambda does have a film of black soot, so the car is definitely deciding to over-fuel. Performance is significantly off.

Thanks for your suggestions. The MAF on this vehicle is the wire, not film type, so generally give few problems. I actually replaced it with a new one from the dealer. The hall sender is brand new new too, as the last one fell apart. Any other clues? This is beyond the dealer's ability.

I've had the car 10+ years. It used to do 30+mpg, now 25mpg over same journeys. Performance off. Lambda adaptation values look bad on VAG-COM. Lambda probe switching ok at idle. Lambda probe, MAF, ECU, temperature senders, distributor, injectors all been changed. Fuel pressure measured and ok. Any ideas?

Looking for ABS valve module thing next to the brake master cylinder. Also sun visors.

Finally got some ECU errors come through with my long-standing poor mpg. Any ideas? The plugs are a little black, not normal. I've tried an ECU reset and training procedure. The blue sensor was replaced a couple of years ago. With logging on VAG COM, it warms up beautifully in a sensible ramp from cold to 85C. The lamda readings start changing at 60. The lambda was faulty once before and replaced and appears fine now - 0.95-1.05 on VAG COM when idling. The weird thing is the range of ADAPTATION values for idle, mid and full throttle (group 6). This previously was 0.9xx-1.0xx, but now anything from 0.400 to 0.999. (Today 0.415 0.992 0.922) I also checked the wiring from ECU to lambda and MAF and the supply to the lambda heater is good. The injectors have been overhauled and I've tried a new MAF. The fuel pressure is spot on (3.5 bar idling, 4.0 bar on throttle blip.) Compressions cold and hot are well within spec, although there is some oil consumption (around 0.5 l /100 miles). I also checked the evap purge valve closes after start. Is my ECU failing? --------------------------- VAG-COM Version: Release 311.2-N Control Module Part Number: 021 906 258 B Component and/or Version: MOTOR PMC 1 Software Coding: 0261200494 Work Shop Code: 1267357207 2 Faults Found: 00537 - Lambda (Oxygen Sensor) Regulation 11-10 - Control Limit Not Reached - Intermittent 00561 - Mixture Adaptation 15-00 - Adaptation Limit (Add) Not Reached

When I turn off my ignition, the fan will come on if the engine is a little on the hot side, even if it wasn't on previously. In traffic, the temp gauge has to go over 100 and nearly up to 110 before the fan kicks in. You should be okay to test up to 110. Above that, steam may fly!

Just disconnecting the power for a few minutes and then doing the training sequence will get you close enough. The basic settings mode of the pay version of VAG-COM didn't seem to affect my economy, just ran things a bit smoother. Even if you don't do a reset, the ECU will re-learn most of the way within a few hundred miles. If you're not seeing an improvement, we could be in the same boat!

Anybody any updates?

Yes I did the reset and relearn.

Yes, the lambda readings fluctuate correctly. The ECU values go from 0.95-1.05, which corresponds to a sensible voltage. The weird thing is the range of ADAPTATION values for idle, mid and full throttle. This previously was 0.9xx-1.0xx, but now anything from 0.6 to 1.4. What upsets this? Bad ECU, bad MAF wiring?

My 10 mile commute to work is only getting 25mpg (UK). I'd expect 30mpg from past experience of 10 years of being together now. Long distance is down some too. The plugs are black but there are no ECU error codes logged. The blue sensor was replaced a couple of years ago. With logging on VAG COM, it warms up beautifully in a sensible ramp from cold to 85C. The lamda readings start changing at 60. The lambda was faulty once before and replaced and appears fine now - 0.95-1.05 on VAG COM when idling. The adaptation values seem to be weird though and change a lot: 0.626, 0.735, 0.891. The injectors have been overhauled and I've tried a new MAF. The fuel pressure is spot on (3.5 bar idling, 4.0 bar on throttle blip.) My last track day left me behind a standard 2.0 litre mk2, so performance is way off. Help!!!!!!!

The problem has been for a while on, yes, my VR6. Never failed the emissions test. I had hoped the local "expert" garage had found the cause when the injectors were found to be spraying badly, but that has had no effect. The calipers and handbrake are all fine (above freezing anyway :? ) and the tyres have been changed with no effect during this period. The lambda wire broke and made things obviously worse and with the appropriate fault code, which has been since fixed. I got chased by a new Golf GTi yesterday, who couldn't catch me, so I know the max performance is ok. It's just the around-town economy and gas-guzzling warm-up that seem to be way off. Only thing I don't know how to check is the fuel pressure. Could that do it?

Thanks for the reply. The blue sensor was replaced a couple of years ago. With logging on VAG COM today, it warms up beautifully in a sensible ramp from cold to 85C. The lamda readings start changing at 60.

My 10 mile commute to work is only getting 25mpg (UK). I'd expect 30mpg from past experience of 10 years of being together now. Long distance is down some too. The plugs are black and there are no ECU error codes logged. The lambda was faulty once before, but it is fine now - 0.95-1.05 on VAG COM when idling. The adaptation values seem to have changed since I remember some years ago. They are now: 0.626, 0.735, 0.891. I tried a new MAF, which got the adaptation values close to 1.0, but the mpg was still the same. The injectors have been overhauled - they were in a bad way - but that has not made a difference to the mpg. The inlet system seems well sealed. The fuel pressure regulator is new. Any ideas?

Thanks for your tips, guys. Strange how the car runs reasonably ok and passed the emissions when it's over-fuelling! Anyways, ideas on the oscilloscope stuff? I am an electronics engineer and have access to a lab full of stuff.

I can see inside that it's a hot wire one. Mine is a 93 VR6 with 170k miles. I wonder if it's testable or repairable? Euro Car parts want £200. A scrappy will probably sell one for half that (i.e. still a rip-off).

Thanks for your support. There are no ECU errors in the log. What would you recommend I do to test the MAF?