Z3 will not start

[Jasn]

I also gently resolved this problem while I was scanning for the DME line thingy.

 

[TrevD66]

When did you spot that.....I’d have had a big decision at that point.... how much do I love my Zed?
I hate snakes with a passion

 

[t-tony]

Did you use a good quality sensor?

Tony.

 

[Jasn]

Did you use a good quality sensor?

Tony.

It is a VEMO. I think it’s meant to be decent.

Jasn

 

[Jasn]

When did you spot that.....I’d have had a big decision at that point.... how much do I love my Zed?
I hate snakes with a passion

I put the bonnet up, looked down and there he was. Just a tree snake - quite docile.
Jasn.

 

[Jasn]

I looked into towing costs to my usually mechanic and got a quote for $300 so I want to persist a bit longer. I unplugged the MAF connector and tried again — and the engine started and kept going. Does this point towards a broken MAF or something else? I have read that unplugging the MAF actually disables various other sensors as well, though I don't know that for sure. A new MAF is expensive enough I don't want to replace it unnecessarily.

Any suggestions?
Jasn

 

[colb]

Maf's dont always sets codes when they go wrong in my experience, they either work or mis report what they are seeing passing through them or fail completly. Had an issue with mine on the Z3 1.9, car ran but felt restricted when driving it and fuel trims high, unplugging it made a slight difference. Also had a camshaft sensor code, that was changed but in the end I shelled out on an oem Maf, put that on and the car was transformed, no problems since. Its very easy to throw parts at a car that hurts your wallet without fixing the problem, since you got it to start with the Maf unplugged it will revert to default settings instead of reading what the sensors are picking up hence the better running as its ignoring out of kilter readings from bad sensors. Always good to view live data in diagnostics if you can, view what the Maf is seeing going through it at different revs and look at the fuel trims to see what they are doing, high trims are usually down to air leaks in the vaccum system between Maf and exhaust. A visual check of all rubber hoses between the Maf and exhaust side of the engine for splits or holes should be the first thing to check for. Unmetered air not seen by the Maf will cause it to think its running lean and add fuel to richen the mixture hence the high fuel trims. This is picked up by the O2 sensors in the exhaust a mismatch between what the Maf has seen and what the exhaust sees affects the fuel trims. Seems replacing the Maf on yours is the way to go, cleaning the old one with Maf cleaner didn't work for me, it killed the Maf completly.
Do not be tempted to replace the Maf with cheap ebay ones, they rarely work or work for long only buy Bosch or Seimens brands that were oem parts, been there done that paid twice bu got my money back on the cheap part thank goodness.

 

[NZ00Z3]

You have got he engine running with the MAF disconnected. That's good its running. Do the below test to see if you have any vacuum leaks causing you problems. As @colb says, you're now on a richer mixture, which can mask lean conditions.

Do you have a vacuum Leak?

The proportion of unmetered air from a vacuum leak to metered air is higher at idle and lower at revs. Do this test.

With a hot engine at idle, check the 4 fuel trims, 2 short-term and 2 long-term. If any are > 8% then you likely have a vacuum leak. Rev the engine to 3,000 rpm for 30 seconds and watch the short-term fuel trims. If they reduce significantly, might even go negative, then it is confirmed that you have a vacuum leak. Smoke test the engine to find the leaks.

If the short-term fuel trims do not reduce significantly, then it’s something else.

 

[Jasn]

Alrighty, I took the air filter and MAF off to clean the MAF and figured I would take the rubber boots off to have a really good look for any splits or holes. I found a split along the underside of the rubber boot closest to the throttle body. I have a new one coming in the mail, hopefully before the weekend. I have fingers crossed that will solve the issue — I could not see or feel the split until I took the rubber boot off the car, but I assume it is the problem and not something I have just done while removing it.

Jasn

 

[t-tony]

Very common aliment on the Z3 Jasn.

Tony.

 

[colb]

I think you found the cause of your problem, these engines must have a sealed vaccum system, the smallest leak in the system will play havoc with the sensors often sending you off in the wrong direction to replace parts that don't need changing. Certainly hold off replacing the Maf now you found the split rubber, fit the new one and clear any codes before starting the engine with the new rubber fitted. See what difference that makes and view the fuel trims with diagnostic live data if your scanner can do that. See if you get a engine management light on the dash and scan for codes again after running it.

 

[ktnez99]

Hi I recently had this on my M. Battery shows charged and holding 14v ish but wouldn't start the car, same issues as yours. I can only assume the voltage is OK but the amperage is down? Anyway I got a new battery and its fine now. Id say you may need a new battery.

Agree. This happened to my car about 18 months ago and it turned out to need a new battery.

 

[Jasn]

So I have replaced the split boot and getting exactly the same problem so I will now look at the fuel trims to see if I have a vacuum leak somewhere else.

I had expected the replacement boot to resolve this — very frustrating.
Jasn

 

[colb]

I feel your pain, ensure you have a good battery and an air tight vaccum system, a smoke test will pinpoint any further leaks you may have, check out what Murray advised in his earlier post. If you get the car running and view the fuel trims in diagnostics it should show you what the sensors are making the engine do, high fuel trims would indicate the exhaust is seeing a weak mixture and adding fuel to richen it up. Common cause is a vaccum leak, since you replaced that split hose you may have another leak elsewhere, smoke should find any you can't see. Last resort would be to pay out on a new Maf, only use Bosch or Siemens brands don't be tempted to use cheap ebay parts.

 

[Jasn]

I feel your pain, ensure you have a good battery and an air tight vaccum system, a smoke test will pinpoint any further leaks you may have, check out what Murray advised in his earlier post. If you get the car running and view the fuel trims in diagnostics it should show you what the sensors are making the engine do, high fuel trims would indicate the exhaust is seeing a weak mixture and adding fuel to richen it up. Common cause is a vaccum leak, since you replaced that split hose you may have another leak elsewhere, smoke should find any you can't see. Last resort would be to pay out on a new Maf, only use Bosch or Siemens brands don't be tempted to use cheap ebay parts.

Thanks. I tried to check the fuel trims this morning, but I am not getting any values. I am guessing now that I would only get values with the MAF sensor plugged in (but the engine won't run with it plugged in). Is that right?

I had a quick look at all the data I could see and saw that I was not getting a value for true running values for cylinders 2, 3 and 6. Would that just be because the MAF sensor is not plugged in or is that pointing to another problem?

With the MAF sensor plugged in I am not getting any codes (but the engine isn't running). With the MAF sensor unplugged the only code I am getting is that there is no signal from the MAF sensor.

Jasn

 

[colb]

With the maf unplugged it will run on default settings and you should see fuel trim activity

 

[Jasn]

With the maf unplugged it will run on default settings and you should see fuel trim activity

OK, thanks. I am running out of options I think.

 

[Jasn]

Just revisiting this in case anyone stumbles across this thread in future. It turned out simply to be the MAF sensor. We now have a new one and the car is back to normal. It is a bit frustrating to have resorted to paying a mechanic when it was just a matter of swapping the sensor, but when replacing the torn intake boot didn't fix the problem I suspected it was going to be something more sinister.

Thanks everyone for the suggestions.

Jasn

 

[ktnez99]

I’m glad you’ve got your car back in working order @Jasn

 

[Joss]

Sorry to hijack a thread, but is the symptom of a MAF failure the car turning over, nearly starting but not quite catching?

EDIT: I've got the pipe off, and it has the cracks all around the T connection - so I've ordered one of those to start.

EDIT 2: just tried again with the pipe "fixed" using electrical tape, it starts, but isn't running quite, so ordered a MAF now too