Disco2 Thor V8 no power

Zaphod · Post by **Zaphod** » Sat Jan 03, 2015 12:19 am

Hi, I finally have my D2 V8 back together, and it is running.. but not well
It idles nicely, and seems to have reasonable low down power in that I can move it about with very little throttle, however it has almost zero performance when driving and seems very reluctant to go much beyond 2.5K (revs fine in neutral). One thing that did happen was I initially had bank 2 connected upside down on the coil, this resulted in some interesting noises. Would this have resulted in any significant issues? Is my MAF dead or have the cats died, or have I possibly got the cam a tooth out? (the chain was a bit slack when I put the pulleys on). It feels like my old LPG 827 did when I had the LPG valve screwed in too far

I should add that the engine has been apart to the level that only the crank, pistons and rods remained in the block, and that this is the late THOR engine that means nothing is easy to get at!

Zaphod · Post by **Zaphod** » Sat Jan 03, 2015 1:51 pm

Well I finally found my blue tooth ELM dongle and found it has P0130 DTC which is 'Lambda Circuit Bank 1 Sensor 1' it did have some other but in light of the attempts to start with the coil connected wrongly I cleared them and then ran it for a while to see what came up, this was the only one to return.

However this would normally not result in a loss of driveability surely? I can see that this sensor stays low and seems dead, the other one is switching as normal

ChrisJC · Post by **ChrisJC** » Sat Jan 03, 2015 4:26 pm

If the lambda sensor is broken, then the ECU has no idea whether the mixture is right. So I am not surprised it isn't happy.

The two lambda sensors are the same, so I would swap them over and see if the fault moves with them. If it does, get a new one. Otherwise the plot thickens......

Chris.

Zaphod · Post by **Zaphod** » Sat Jan 03, 2015 10:49 pm

A little more observation reveals this..
left idling the offending sensor starts to behave as normal and the engine goes into closed loop mode, however the reading goes to 0.1v and stays there till left idling. For a short while the ECU remains in closed loop mode and during this time the dico is drivable, the second it drops out to opeb loop it becomes horrible again

New sensor ordered anyway as looks like its not hard to change

Zaphod · Post by **Zaphod** » Sat Jan 10, 2015 6:44 pm

Hi I have just put my engine back together after sorting out a slipped liner on number 4 (everything has been off). It runs and idles nicely but has no power and off idle seems to be fuel starved and has a few pops from the exhaust when revved (this might just be the pin holes in it) on connecting a code reader I find it has an error code P0130 and that's it. This appears to be a fault in the lambda sensor circuit. The lambda sensor has been changed for a new on on bank 1 and there's no change. The fault returns, using a blue tooth obdii device I see that if cleared and started I can see both probes working normally and left to idle they seem normal and the engine goes into closed loop mode. If you apply any throttle to raise the revs sensor 1 drops to .1v and stays there shortly followed by sensor 2. The engine then goes to 'open loop mode (Sys fault)' and when read the P0130 fault has returned.

This was not an issue before the engine was taken apart, so it's quiet probable something has not been connected correctly or the MAF has been damaged but I can't see that doing this?

unstable load · Post by **unstable load** » Sun Jan 11, 2015 6:18 am

Swap the sensors over and see if the problem follows. If so, then it's likely a duff sensor.

Zaphod · Post by **Zaphod** » Sun Jan 11, 2015 8:39 am

It's already had the sensor changed, Once for a known good one, once for a new one, no change. I don't think the sensor or the wiring has a fault, I think they are just fine as at idle it all looks normal and the lambda signals look perfectly normal, it all goes wrong and throws the code as soon as you open the throttle

ChrisJC · Post by **ChrisJC** » Sun Jan 11, 2015 12:58 pm

Have you got another MAF?

Have you got any way to look at live data when the engine is running to see if the MAF looks sensible?

Chris.

unstable load · Post by **unstable load** » Mon Jan 12, 2015 5:18 am

I don't know if the same trick will work on the petrol engines, but on the diesel you can unplug the MAF and go for a drive to see if anything changes, then use that as part of your troubleshooting.

Zaphod · Post by **Zaphod** » Mon Jan 12, 2015 7:14 am

I have an obdii device and have some other observations. When at idke the affected bank has a very low voltsge wave form it seems to switch bewtten .2 and .3 v. On opening yhe trottle it drops off the bottom at 0 and flat lines (and then logs the p0139 fault) the other bank looks normal. Looking at the fuel trims the long term ones are tge sane accross both banks, however thevshort term trims are wildly different 1.6% is the latgest figure I hsvecseen for the bank with no fault, however the troubksome one is at +25% occasionsll drops to 24.8 but solidly at 25 when held above idle. Is this consistant with an sir leak?

If the MAF was at fault woikd that not affect both banks?

ChrisJC · Post by **ChrisJC** » Mon Jan 12, 2015 6:48 pm

You can't unplug the MAF on a petrol, that only works on Diesels.

I agree that a MAF fault would affect both banks........

Is the inlet manifold fitted correctly? Can you check for air leaks?

Chris.

Zaphod · Post by **Zaphod** » Mon Jan 12, 2015 7:18 pm

Unfortunately the wonderful inlet manifold that BMW saddled this thing with make it very difficult to check anything. (I am not a fan of this iteration of the V8 nearly every job starts with 'remove top half of the inlet manifold') however I am becoming convinced there is a leak in that side that needs attending to so I have bought the gaskets and the o-rings for the injectors..

ChrisJC · Post by **ChrisJC** » Tue Jan 13, 2015 9:26 pm

I know what a pain it is, particularly at the rear where you have to tilt back the coil packs to allow it to lift off.

I also recall there is one connector on the right hand side (I forget what for), that can go to two places. All the other connectors you can't get wrong, but one of them fits two things. I am thinking that little emissions black jobby behind the throttle body, and maybe one of the connectors on the rear of the head that you can't see. I know when I put the wiring loom on my engine I scratched my head about this one for a bit, it is just a shame I can't be more specific!!

Chris.

Zaphod · Post by **Zaphod** » Wed Jan 14, 2015 9:01 pm

It's the coil and idle valve connectors you are thinking of! (don't ask how I know!)