I've got problems at the moment with the zed with it's idle keeps going just keeps varying from about 400 to 1200rpm in cycles (if you know what I mean), seems to be running rich (coked plugs and used £30 of fuel on the drive) and won't rev about 2400rpm. As I understand it - the 2400rpm limit is from the ECU being in some sort of safe mode? I am suspecting the MAF/AFM to be the cause of the safe mode but wondered if I could have such a big boost leak that it's causing a dodgy reading from the MAF and fooling the ECU into thinking the MAF is knackered? I've not ran any diagnostics on the car yet but I'm looking into buying conZult. Is there anyone near Stoke-on-Trent with conZult I could borrow the use of? :rolleyes:

 

Do you think I've got a knackered MAF and a boost leak or just the boost leak throwing the MAF reading out?

 

Cheers,

Vern

Could just have some water in the maf itself.

 

Disconnect the battery live.

 

Take the nose panel off and take the MAF off. Give it a good clean (do not directly touch the sensor itself) Carb cleaner is good for this.

 

If you have a cone filter, heat the oven on gas mark 200 for 5 mins and then switch off, place the cone filter in the oven 5 mins after switch off for 5 - 10 mins to dry out any moisture in it.

 

Clean the connector on the MAF and the connection to the MAF.

 

Depending on how long it's taken you to do that lot, you want to have left the battery disconnected for about an hour at least. If the hour is past reconnect the battery (ECU shoudl now have reset and will be in learning mode).

 

Test to see if the problem is sorted. If it still continues to play up then you need to try a replacement MAF to see if it's the MAF itself. Worth borrowing one to test first before buying a new / 2nd hand one.

...heat the oven on gas mark 200 for 5 mins...

 

Or alternatively use a blast furnace ;)

 

I think ya mean gas mark 6 or 200 degrees C :nelson:

I think ya mean gas mark 6 or 200 degrees C :nelson:

 

oops lol.

 

Yeah, gas mark 200 may be a little high. 200 degrees is what I meant :)

Lol - I'll try gas mark 200 I think ;) Cheers SMW1. I've checked the MAF for water and it's bone dry but I haven't got any carb cleaner or anything similar so I haven't actually cleaned it. I will try disconnecting the battery and keep you all updated :)

 

CheerZ,

Vern

A quick 10 minute ECU diagnostic should show up if the MAF is not registering correctly. You can also unplug the MAF with engine running to see if the engine behaves differently, if MAF is faulty then with plug off it should remain the same same, if MAF not faulty the engine respnce should change.

smithy

May well be worth grabbing a can of carb cleaner as the sensor may be covered in dust and crap that has squeezed though the filter and built up.

 

Resetting the ECU alone will not solve your problem. If it does it will only be a tempoary fix until you try and drive it again and then what ever is causing the fault will continue to do so.

 

Get yourself down to halfords and grab some carb cleaner. Give the MAF and it's connections a good clean and see how you go.

 

If you eliminate one thing at a time, sooner or later you will find the problem.

A big boost leak wouldnt affect the actual MAF reading as its before the turbos. However a dead maf would cause it to only run up to 2400rpm ish. I would say the maf is toast and you need a new one, now from memory if no maf is connected it should actually run better than with one that doesnt work at all.

 

I have experienced this on a 320d, was quite scarily slow, unplugged the maf and it was a different animal, gave it a new maf and it was better again. But no maf seems to go into a preset mode which allows at least some power where as dead maf seems to cripple them!

I've already tried cleanin the MAF connections. But like I said I didn't have any carb cleaner at the time and didn't want to attempt to clean it with anything else :) I tried disconnecting the MAF while it was running and there was no change but I didn't know if this may be because I have such a big leak somewhere that it's pulling the air from the leak in the intake and not through the air filters and past the MAF - just a thought. Looks like the next step is an ECU diagnostic when I next get a spare half hour :)

 

As I understand it after reading the service manual - if the ECU detects erratic readings from the MAF (or any sensors) it goes into a kind of 'limp-home' mode and physically limits the revs to 2400 and limits boost as well :)

 

CheerZ,

Vern

Vern, if you mean it's as though the engine is 'revving itself' every time the revs drop then I would expect a BIG boost leak - probably around the intercooler hoses. I had the same thing, pretty sure that's what it was (although I also corrected some other stuff at the same time)

By disconnecting the MAF it will go into limp mode, will probably run nicely at idle but will not rev much past 2000, if it feels bad in a different way with the MAF disconnected then this isn't your problem. Mine would rev higher (though very badly) with the MAF connected, revs hit a 'brick wall' with MAF disconnected.

 

Might also be worth checking the vent from the carbon can is not blocked, could have been that that was my issue - I can't be sure without blocking it up again!

 

HTH

 

H

Vern, if you mean it's as though the engine is 'revving itself' every time the revs drop then I would expect a BIG boost leak - probably around the intercooler hoses.

 

This is exactly what it's doing mate. I thought it pointed to a boost leak as well and it seems the boost leak is so big that I can't get any pressure into the system at all - but since I've tried to do a boost leak test it's the 2400rpm limp mode limit has come on. Wondering if I've dislodged the already leaking hose whilst messing with stuff trying to find the leak and made it even worse???

 

Something I've noticed - when the revs drop and the engine 'revs itself' the boost guage up to 0 then back to the left as the revs rise. Does this indicate anything? Confirmation of big boost leak?

 

CheerZ,

Vern

At Idle the boost gauge will never go above 0.

 

You should be sitting at about -20 (not sure what this would be on the stock gauge) when at idle and you can rev till your hearts content but it will nto go into boost until you are actually moving.

So it should sit as far left as possible when not moving? -7mmHg*100 or whatever it is? Is the fact that it moves to 0 when I rev it indicative of dodgey boost guage or big boost leak? Is there anyone in the Stoke area with a known to work boost leak tester setup? Ideally with compressor cause I don't think I've got any chance of hearing a hiss otherwise :) I've tried a cheap 12V compressor I've found in the garage but that can't get any pressure into the system either - then again I think it's designed to pump up push bike tyres :D

 

CheerZ,

Vern

This is getting all confusing now mate, so to start a fresh so we can work things out, when you last drove the car did you get lots of smoke coming out of the zorsts ? did the car stall at halt signs etc ? these indicate a major boost leak.

If you unplugged the MAF and the symtoms remained entirely the same, then that generally indicates the MAF is faulty.

Have you any other symptoms, like warning lights constantly lit up on the dash or is the electric sub fan constantly on when the ignituion is on or engine running ? if not, then it's not in limp mode and indicates a duff MAF.

there is another member quite close to you, will see if i can see when he was last on.

smithy

Don't I know it mate. To make things clearer then - there was no smoke out of the zorsts that I can remember but it would stall at stop signs if you didn't keep the revs up yourself. No other symptoms i.e. warning lights, sub fan on etc. Like I say - it wasn't in limp mode before I tried to do a boost leak test (it would rev the whole range) so I'm wondering if I've dislodged a hose or sumthing.

 

EDIT: I've just had a thought that perhaps I have dislodged the MAF wiring - my engine wiring loom is known not to be exactly reliable so possibly a wiring related issue? Think I'll get the multimeter out and check the MAF readings :)

 

CheerZ,

Vern

Okay then, with no lights and fan on all the time, it can't be in limp mode.

The guy who i know is neaer you hasn't been on since June, so that's out.

Zedworld in Tamworth is what 45 mins from you ? if you think you can drive that far then it would save all the messing around and maybe save getting worse ?

Oh has the car got aftermarket dump valves on ?

smithy

Lol cheerz for all the help Smithy. Cars not MOTd, taxed etc at the moment or I would have already been lol :) And nope - not got any dump valves - can't stand the things to be honest :D

 

CheerZ,

Vern

You won't be able to pressurise the system if the leak is anything bigger than one of the small hoses (and it sounds like it is). Best you can do is break down the intake into smaller sections (start off by taking each side in turn and checking up to the intake pape which runs to the throttle body), gradually add new sections as you prove each section as 'good'. I use a surgical glove over the end of the hoses with an elastic band to hold it secure, if it inflates to the point of expanding then you know it's ok. You may also need to plug up the front PCV's to keep some pressure in...

 

FWIW I'd be tempted to check all your large IC hoses

Cheerz RobH. I tried breaking it down into left and right but still didn't really get anywhere (although I was running out of time at this point so is probably worth doing again without rushing) and cut up and old Vespa tyre inner tube to clamp round the end of the pipe that goes to the throttle body. Again - have had a quick look at the IC hoses in the IC's themselves but the car's not really high enough off the ground to get underneath for a proper look (just driven onto 2 stacked paving slabs at the mo). Will have to jack it up and get it on axle stands to investigate properly methinks :)

 

CheerZ,

Vern

You prob need to get the front bumper off to have a proper look. The inner tube will be a bit strong to give you a good indication, a surgical glove or condom :P will give you a better indication as they will actually inflate when the leak(s) have been bypassed...

 

Other prime failure locations are the large, flexible plastic pipes that run from the intake 'T' to the turbo compressor intake hardpipe, very difficult to see without removing some other stuff, may have come adrift at the join or can split (I had a split one a few years ago).

 

It's an unfortunate fact that to eliminate a boost leak you have to make yourself familiar with the whole intake circuit and get an idea of the route that incoming air takes through the turbo compressors, intercoolers and ultimately to the throttle bodies. It's made particularly difficult on the Z32 thanks to the lack of space in the engine bay but you will feel a better person for understanding how the system works and it will make future investigation much easier.

 

Cheers

 

H

Cheerz again for the reply RobH. I've already downloaded diagrams of the intake system so I've got a bit of an understanding about the routing of the major pipes :) I'm able to get at the intercoolers and pipes a little easier that most because my car came without wheelarch linings lol.

 

The inner tube will be a bit strong to give you a good indication, a surgical glove or condom :P will give you a better indication as they will actually inflate when the leak(s) have been bypassed...

 

Lol good idea. Will be interesting explaning to the girlfriend where all the condoms have gone missing to :rofl:

 

CheerZ,

Vern