I traced my misfire problem (or so I thought) to a dodgy coil pack connector and a dodgy injector connector. I also put a new battery in, and the car idles much better.

 

When I first start (cold), the revs sit at 1500 for a while, before dropping to 7 or 800 and staying there, with a very occasional "lumpy" sound through the exhaust (seems to be driver side).

 

Here's the problem(s) - driving cold seems fine and smooth, when it warms up, the acceleration and cruising is very slightly lumpy. I haven't accelerated hard yet (or gone into boost), but accelerating moderately, the acceleration gets lumpier over 3000, and starts misfiring badly at around 4000 - after which, the idle jumps about all over the place between 200 - 1000rpm.

 

If I turn the engine off and back on when it's doing this, the idle will hunt between about 400 and 1000 about 4 or 5 times before settling back, smoothly at about 800.

 

Something else which happened the other day was under cruising conditions, the engine suddenly started to misfire horrible, pressing the accelerator did nothing (aside from make horrible noises), lifting off seemed to help very slightly, but once I pulled over and left it for a bit, it fired up and drove without the misfire. It had been absolutely p'ssing down, so could this be water in the MAF or air filter? - the filter is an HKS btw.

I traced my misfire problem (or so I thought) to a dodgy coil pack connector and a dodgy injector connector. I also put a new battery in, and the car idles much better.

 

When I first start (cold), the revs sit at 1500 for a while, before dropping to 7 or 800 and staying there, with a very occasional "lumpy" sound through the exhaust (seems to be driver side).

 

Here's the problem(s) - driving cold seems fine and smooth, when it warms up, the acceleration and cruising is very slightly lumpy. I haven't accelerated hard yet (or gone into boost), but accelerating moderately, the acceleration gets lumpier over 3000, and starts misfiring badly at around 4000 - after which, the idle jumps about all over the place between 200 - 1000rpm.

 

If I turn the engine off and back on when it's doing this, the idle will hunt between about 400 and 1000 about 4 or 5 times before settling back, smoothly at about 800.

 

Something else which happened the other day was under cruising conditions, the engine suddenly started to misfire horrible, pressing the accelerator did nothing (aside from make horrible noises), lifting off seemed to help very slightly, but once I pulled over and left it for a bit, it fired up and drove without the misfire. It had been absolutely p'ssing down, so could this be water in the MAF or air filter? - the filter is an HKS btw.

 

The HKS filters are a bit prone to this, more than some of the other brands.

It could also be a faulty PTU unit.

I had same problem matey,

replaced the afm, yours may not need replacing but mine was intermittant and doing it in the dry too.

 

Have you got a splashguard fitted?

 

If not try cleaning up the conns but if it does it when its been lashing down it'll more than likely be wet AFM. No splashguard.

Yeah, I have a splashguard on there, but there is a gaping hole in the front bumper of the bodykit (supposed to be there ;) ) - would putting a fine mesh behind this help prevent further rain related mishaps?

 

The first part of my post, about the revs being rough under acceleration - any suggestions on this? The air filter was dry today when it was happening, as I took it off and into the house, along with the MAF to dry them out, just in case.

The HKS filters are a bit prone to this, more than some of the other brands.

It could also be a faulty PTU unit.

 

I have one in perfect working order if you want to try it?? But I'll need it back unless it cures you problem then you can buy it from me!! ;)

 

Matty.

Matty - that would be great, a most generous offer thanks! :)

 

If you could pm me your number, we could sort something out.

Update - must be water / MAF problem. Short downpour just before I left work, and it goes into massive misfire mode just before I got home.

 

Is this a knackered MAF? Or do I just need to find where the water is getting in and take measures to stop this? Would a different filter help?

You may have already posted this but, what type of filter do you have?

HKS filter - had a chat with Matty earlier this evening and following his advice, am going to place an order for an A'PEXi in the morning. :)

Good idea - I assume you mean the HKS mushroom. I had this and when it rained the car would stutter because my drip tray is gone. I now have a twin apexi. :D No Stutter!

Looks like the problems are finally sorted :hyper:

 

Replacing the ECU temp sensor sorted the idle out and replacing the MAF cured the hesitation and massive misfiring.

 

Just want to say thanks so much to everyone that offered help and advice - a special thanks (not like that :nelson: ) to Matty, for the reassuring talk on the phone, Zack for the replacement MAF, Danny from DTA for the A'PEXi kit and Mr. Feeney from MJP for the outstandingly quick delivery of the ECU temp sensor.

 

I dread to think how much I would have spent getting this sorted without your help. The £20 subscription fee is definitely the most essential mod you can get for a Z!

No problem fella, glad to hear you have it sorted :D

 

:hyper:

 

Good thing you followed it up too as I have the PTU boxed up and ready to send off to you tomorrow morning!!!

 

I'll leave it here now.... :)

 

Matty.

Glad to hear you still have the PTU there :) - I was concerned that you had sent it and our wonderful postal service had "misplaced it in transit".

 

Gutted I missed out on Billing, but there's always next year.