Limp Mode

MikeS

have u checked fuel pressure ?

ad172

Hi Mike

Not checked the fuel pressure. Is there an easy way to do this? Tech 2??

I was reading a thread last night where the symtoms were very similar to mine and the end result was a knackered ECU :o

I'm fairly sure it's not the chain as this was changed a few months ago and it has been fine for about 8k miles.

Thinking back I had an EML for a Lambda sensor that seems to have gone away. I'm guessing the Lambda can control fueling so I really am hoping the Lambda could be the cause of my problems.

Got one on order so will keep you posted.

Adam

ad172

Just a very quick update. I inspected the spark plugs today and 3 of the 4 were showing to be quite white. The fourth was fairly brown. That would suggest the engine is running quite lean right? Going to change the spark plugs as a matter of course but have a feeling changing the plugs won't solve the problem. 🙁

I think the next step following that will be changing the Lambda sensors.

Adam

MikeS

keep us updated

out of interest u done a compression check ?

ad172

Will do Mike.

Not done a compression test. Don't have the means at home so it would be a garage job. Speaking to JG (.org) earlier he had a similar problem and it turned out the be the pre Cat Lambda. I just want it sorted now.

ad172

OK changed the plugs which hasn't solved it although I think the old plugs needed changing as a matter of course.

As said previously another VX owner discovered that by replacing the front lambda solved the problem. I have a spare rear Lambda so was going to fit this into the front location. Would this cause any problems save for a slightly longer cable?

Adam

MikeS

unplug the lambda

take her for a spin

takes about 5 mins before the eml light appears

ad172

EML is already on Mike. Will unplugging the Lambda just stop the car going into the full limp mode (Reduced revs)

When the original EGR valve was insitu, by unplugging the EGR, the EML would be on but it would not go into the Limp mode.

Adam

MikeS

clear down codes and unplug lambda

and take it for a spin

ad172

will do Mike. Is the plug for the Lambda just under the coolant expansion tank?? (VX)

MikeS

just follow it back off the downpipe m8 🙂

ad172

Ok some interesting results from unplugging the lambda sensor. Essentially the car was responding in exactly the same way as if it were plugged in. In other words going into a limp mode when the car was put under load.

To me this would suggest that the Lambda is not working as it should when plugged in. I've got a spare rear lambda sensor so will this be OK to fit into the front location (pre cat)? I'll do this tomorrow morning so fingers crossed!!

ad172

OK so just an update; changed the rear Lambda and although the car seems to drive a lot smoother, it's still reverting to limp mode under load. The final thing I can think of changing is the Fuel Filter. If that doesn't work then I think I will need to bite the bullet and get a replacement ECU :thumbdown:

ad172

Managed to collar someone with a Tech II this afternoon to do a detailed read into what is happening. He's downloading the results and will send them to me shortly but one thing that was apparent is there was a drop in voltage just before the ECU 'trips' into a limp mode. Could this be a loose connection somewhere or a dodgy earth??

ad172

OK so here are the results from the recent logging. There are three different conditions:
Normal (EML Off)
EML (On)
Limp Mode (EML Flashing)

So here's the Normal driving with no EML on and all fault codes reset

EML Flashing - So car is about to go into the limp mode. This happens after putting the car under load (look at the engine rev) The one thing that stands out here is the Dwell measurement. It appears to drop off and then throw the ECU into panic.

EML ON and car in Limp mode

So can anyone point me in the direction of what the problem might be. Also can anyone explain what the Dwell is.

Cheers

Adam

MikeS

ignition dwell angle

what code is being thrown up

ad172

P0300 - Random engine misfire

MikeS

u had timing checked ?

ad172

Timing Chain was done about 15000 miles ago and it was fine for 14500 miles afterwards. It's just recently where the car has started doing this.

Thinking logically the car was in the garage for a few months over Christmas and probably left standing for a while. I'm wondering if the car has been jump started and caused the chain to jump?? notsure.gif :thumbdown:

MikeS

you practically done everything

get the chain checked

if that turns out oki then look at loom / ecu

it is uncommon for these ecu's to go down but it has happened before with another member concerning the p0300 code

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