Hi,

 

I changed the plugs on the my 91 Jap TT today and I seem to have cocked something up. I've been Googling for an hour or so now trying to make a plan for tomorrow and I'd appreciate any input from the veteran owners out there!

 

After swapping the plugs the car ran for a while but seemed to be missing occasionally - nothing too dramatic, but worse than before. Also if I touched the throttle gently the revs would die a little before climbing (car didn't stall). I shut it off and started it a few times with no change. I shut it off and went to start it about 10 minutes later and it wouldn't start at all. Lots and lots of cranking but it didn't catch at all. Plugs were (very) wet and I checked 1 cylindrt and it did have a spark. Someone else tried to a method for trying to start a flooded car (slowly pushing the throttle to floor and then releasing it as you crank) and we managed to get the car started. Ran rough to start with an then started to clean up, still running rich. Once it was fully warmed up it started hunting, idling OK, then dropping, catching itself and returning to normal. This was happening about every 5 seconds. Rev'ed fine and seemed better at high RPM. I turned it off and disconnected the battery for 15 minutes, and it's now back to not starting - same as before.

 

Sorry, I know that's a bit of jumbled information but hopefully someone can make sense of it!

 

My plan for tomorrow is:

 

- Check ECU for codes

- Check for spark on all 6 (not just the 1 I did tonight)

- Double check for vacuum leaks around balance bar and connections

 

I'm guess the most likely thing I'd done is related the balance bar, I've checked all 3 o-rings and they are in place and look OK-ish. I'm wondering if I've damaged the pipe to the IACV and bits, but I'm not sure that would cause this issue - any ideas?

 

I've checked all coil pack connectors (some were damaged) but I'm happy they are all making connections.

 

Really would appreciate some guidance as I'm having trouble seeing the wood for the trees!

 

Thanks,

 

Jynx

What plugs did you use?

What plugs did you use?

 

Gaz, NGK BKR7EIX - the iridium plug that most seem to use for the Z.

 

Also my car is stock, other than air filter and exhaust.

You haven't mixed up your connections or made poor connections have you?

 

What part of Hampshire are you in?

Pretty happy all connection are good, and didn't move any coil pack wires far enough that they would reach another cylinder.

 

- - - Updated - - -

 

Oh sorry, the car is in Fareham at the moment.

Possibly disturbed some brittle wiring to the point it's only making sporadic connections.

Start checking your loom

I know its a pain but put the old plugs back in to see if its still missing or if it runs better.

I know its a pain but put the old plugs back in to see if its still missing or if it runs better.

 

Yeah it's a good call. I did put the old ones back in the 4 easy cylinders, didn't change anything but I should do it properly to give me a true frame of reference. Will do that first tomorrow.

Trued to start this morning with new plugs in, caught on one cylinder but then nothing. Put old plugs back in and it started right away. Deliberately didn't change anything else, put all back as it was.

 

Driving round OK, might still be a little rich.

 

Thoughts?

 

Also my electric fan is on constantly now, any idea what might have caused that?

Trued to start this morning with new plugs in, caught on one cylinder but then nothing. Put old plugs back in and it started right away. Deliberately didn't change anything else, put all back as it was.

 

Driving round OK, might still be a little rich.

 

Thoughts?

 

Also my electric fan is on constantly now, any idea what might have caused that?

 

The problem is simple, the temp sensor cable at the front has been disturbed when you did the plug change, this now is been seen and a fault by the ecu and hence fuelling for a cold engine flooding the plugs and triggering the electric fan, so check the connection, clean and reseat. Oh and do not put those iridium back in, they do not suit the V6 engine well as they tend to not self clean enough, the original platinum NGK PFR6B-11C are the ones to stay with.

 

Jeff

 

Edited November 8, 201510 yr by JeffTT

Trued to start this morning with new plugs in, caught on one cylinder but then nothing. Put old plugs back in and it started right away. Deliberately didn't change anything else, put all back as it was.

 

Driving round OK, might still be a little rich.

 

Thoughts?

 

Also my electric fan is on constantly now, any idea what might have caused that?

 

Yes I had this problem once with new plugs then I put the old ones back in and it drove perfect. As Jeff says stick to the NGK PFR6B-11C and check your temp sensor.

Thanks guys, I'd been reading through this http://www.twinturbo.net/nissan/300zx/tech/auxfan/auxfan.html and had come to the same conclusion!

 

I've just been out and reseated the connector, spades were very green and now the fan is off and the car seems much happier, thanks guys! I have recently replaced the drive belts and I think I probably knocked it then.

 

Jeff, what an I told-you-so moment. You said the same thing to me just over a year ago when you did my timing belt and I still have the piece of paper you gave me with PFR6B-11C written on it. I ordered the iridiums from a different Z specialist by mistake and got talked into using them (although he did say I could return them). Should have followed your instructions more closely! Congratulations on your retirement :)

 

For those who might find this thread with similar problems this is interesting reading: http://www.twinturbo.net/nissan/300zx/forums/main/view/906698/Iridium-Vs-Platinum-Plugs-Answer-from-NGKs-tech-Guy.html

 

I compared both the old platinums and the new iridiums for spark, the iridiums were MUCH better. So this issue is either the projection or down to how the different plugs react to too much fuel.

 

Thanks again everyone for the help.

So which plugs are you now using?

I'm running the old platinums. I haven't tried the iriduims since fixing the CTS but given the advice they won't be going back in. If anyone wants a cheap set of iriduims let me know! Only used once and as black as coal!

Well I've never had a problem BKR7EIX-11's. Yours are black from the over fueling fault that you have now fixed.

Well I've never had a problem BKR7EIX-11's. Yours are black from the over fueling fault that you have now fixed.

 

Yep know what you're saying, but even with the over fuelling fault the old platinums ran the car fine, the iridiums (which were brand new) couldn't start it. I know there seems to be a bit of a division on which plug is favourable but for me old platinums allowed the car to run in conditions where the new iriduims didn't. While those aren't exactly ideal operating conditions it is an interesting outcome, especially given how much brighter the spark from the iridiums was.