Got the Z out last weekend after it's winter hibernation and it fires up fine and drives ok under light to moderate load. However, when asking for more power it judders and runs rough, seemingly misfires and does not boost.  I do tend to let it turn over and drive up the road every now and then on dry days in winter to avoid it being stood completely for several  months.

I have been very lucky  with the car as I have owned it 17 years and had only one major failure, ECU.  My first thought was the turbos but there is no smoking or obvious leak from what I can see. Seems more like a misfire related issue.  Looking for a bit of a 'checklist' to run through some obvious things at home.  

I fear a rodent or two may have taken up residence in the car over winter and got at something!

It is due a trip to Jimmer for some TLC but I'd like to see if it's something obvious first so I can drive it there.

Thanks.

Wow Andy 17 years of ownership is a long time ? You might have a boost leak  its the first thing I would try and check.

Could also look at injector wires, coil pack, PTU and MAF connectors for corrosion. My car did that.

Check for any moist/wet connections, I think it is the temperature sensor that I had to sort after every winter on my car, with these sorts of issues.

Update. I’ve got datascan running and it seems cylinder 4 is not firing properly. With the car idling, I’ve shut off each cylinder one at a time and there seems no notable difference to the Lumpy idle when shutting off cylinder 4. I guess next step is check coil packs ? Is it worth posting the data scan file for someone who knows the details to look at?

Ive also got a boost leak detector now but I can’t get pressure above about 4 psi with the foot pump or electric tyre pump. So either it’s a case of simply not being able to get the pressure up with those pumps or the gauge is not working(doubtful as it does move and is brand new from CZP, what pressure I do get in does release smoothly), or  I have a major leak as well.  Not entirely sure where I should be checking.

My aim is to make sure it’s not something easily fixable and if not that it’s ok to drive carefully c 50 miles to Bristol to get Jimmer to give it some TLC.

17 years of largely trouble free ownership means I’ve never had to learn to fix anything other than a temp sensor and plug in a new ECU!  I should be thankful I guess. 
 

Any input welcome. Thanks.

2 hours ago, andyb said:

Update. I’ve got datascan running and it seems cylinder 4 is not firing properly. With the car idling, I’ve shut off each cylinder one at a time and there seems no notable difference to the Lumpy idle when shutting off cylinder 4. I guess next step is check coil packs ? Is it worth posting the data scan file for someone who knows the details to look at?

To start these are the things to check from a Power Balance Check (right hand list below):

Check the ignition and injector connections for cylinder 4 for corrosion/continuity. Then:

and:

Check the PTU connectors for corrosion/continuity.

Edited June 12, 20205 yr by AndrewG

Thanks Andrew. Appreciate the details. I’ve had the coil pack and plug out on cylinder 4. Checked both with multimeter and both ok. Checked spark was getting to plug using a spare plug, ok. Can’t seem  to gain access to injector, not aided by the strut brace.  Spark Plug from Z is a little bit more carbon coated than I’d expected and probably due a change. Connectors all look good and clean. I only use the car on dry days and it’s garaged. 

I have  checked other connections and all seem ok. 
 

disconnected o2 sensors and MAF and didn’t seem to make any difference. Left battery disconnected and tried again, no change. just idles very rough and still seems like misfire. Ran data’s an again and dropped cylinder 4 out and it was not as notable this time. So I wonder if my cleaning the plug to get a multimeter test on it might have helped. I’ll change the plug and see.

Whilst having a good poke around I found a coolant leak at the back of the plenum. The hole is very small and actually in a metal part just above what I think is the EGR. All looking a bit wet and rusty back there(can’t remember how to post pictures).   I’ve topped up coolant and put a bit of epoxy over hole to seal it temporarily. Has stopped leak but still runs rough. 

I can hear what seems to be a hissing /air escaping noise around where cylinder 4 is. Could  not pin point it. This plus fact I couldn’t get boost leak tester to read higher than 4 psi makes me think boost leak? Does that affect it at idle? where should I be checking for boost leaks other than the major pipes on show at the front?

Thanks for the help so far.