ok got a misfire when i boot it, plugs have only done 1000 miles i have checked all connectors, had a bad fuel fill 2 tanks ago, got some dett, went back to optimax, detonation then almost instantly went, have ran 2 tanks since. It feels for all the world like a plug or two giving in on full load, do i buy new plugs ???? could it be possible to have eaten them so quick??? Would the detting have shortened their life or am i barking up the wrong tree??? any help would be gratefully received

does it happen at a particular rpm? I had the same thing and it was the AFM.

 

Vijay

No only when you floor it, well not at low revs but as soon as it boosts if your foots down, otherwise if you feather the throttle it will go right up the revs smoothly?? need help me does

I have the same kinda thing at the moment.

I have replaced the AFM, TPS, fuel pump, got a new fuel pressure regulator, none of that has changed anything so am in the middle of fitting new injector and coilpack connectors and after that will be the fuel control unit................! Its the classic plug going down syptoms though...maybe I should have replaced those first. I will let you know how I get on. My hunch is on the old, corroded injector conectors.

I was reading a bit more this morning and now my suspicion has turned to the IAA valve. Does anyone know if this gives problems at the top of the rev range, under full load?

james u aint filled me full of hope, just been reading your posts jesus, anyone any ideas what to do

So can anyone tell me whether plugs will be destroyed so quickly ??

i had this on my previous car,(not a z by the way) it was a boost leak

Right, fitted new connectors on the injectors and that hasn't improved things. Still got the coilpacks to do-cos they are in a shit condition too. Then my attention will turn to plugs, fuel control unit and then to a boost leak as Scoops mentioned. Saying that, maybe boost leak check next as that will be free!

Idles spot on so can rule out the IAA I think, and as a pointer for anyone reading, it only seems to misfire after 1st gear which seems odd, but I guess there's more load up through the gears.

My hunch has now turned to the plugs!

It is possible that if you've been experiencing some detonation your plug electrodes or insulators could be damaged or have a 'hot spot' form - I guess this could then lead to a misfire. Might be worth checking the gaps.

 

I think most people on here go for 0.8-0.9mm with a standard platinum. Should be fine running up to 1.1mm with an Iridium. If the gaps to large you'll get a misfire - too small and you get a weak spark.

 

HTH!

 

RobH

Sounds like the fuel pump control unit TBH. Get a voltmeter on the fuel pump and make sure the voltage steps up when you floor it ;)

I had a similar problem with misfire when I floored it (coupled with odd autobox shifting) and it turned out to be the ECU connector in the pass footwell not connected properly. Cheap fix - worth a try...

 

Pete

You'd know all about "cheap fixes" eh Pete??

No, seriously, thanks for that.

 

Andy - you've known of these going before? I will test the fuel pump today! Cheers bud.

 

Do you mean do this test http://www.z32.org/html/fuelpumpdiagnostics.shtml and see if the voltage increases?

Or this one http://www.z32.org/html/fuelpumpcontrolunit.shtml dierctly on the control unit?

*************** we have fookin lift off ******************

 

Bought some plugs off of Mark (Topless) today and these have done the trick.

 

 

Oh yes.......I am grinning my head off. And with all my new injector connectors, fuel pump, AFM etc, its going better than ever.

Gonna try some plugs in the morning, really appreciate the help, i was speaking to a friend with a cosworth who reckoned he only used to get about a thou miles out of his plugs on both his rs escort and his sierra, gonna be expensive if this is the case eh

Well,

 

I'm a little confused now.

 

James has had 3 sets of plugs in about a year am I right ?.

 

What is causing the problem ?. These plugs are supposed to be good for 70k miles aren't they ?

so what was wrong with the old plugs, I think there's a pic somewhere which tells you how to diagnose engine problems from the discolouration of plugs.

 

Would be interesting to find out. Hopefully save you another set of plugs in a few months time too :D

Gavo..........funny you should say that as a mate of mine said exactly the same about his Sierra Cosworth and was convinced my problem was a plug(s) going down.

Going by the plugs section on this page http://www.twinturbo.net/ttnetfaq/FAQpages/hesitate2.html mine may have suffered from dry fouling. Will look again at them in the morning cos they're at work and I'm at home now. Just got in from a spin and I'm happy! :D

 

Might aswell put up for sale my AFM, TPS, and fuel pump!

I'll have yer TPS then!

 

Cleaned the contacts last night... now it seems to be OK when you first start it but after you've driven a while the vibration seems to lead to intermittent connection again. (Sometimes when I stop at lights idle is correct, sometimes it isn't.)

 

So I think it's time to put a known good one on!

It turned out to be plugs, well one in particular!!!, they were bosh platinum tips, one of them had disintegrated!, well the hooky bit on the end that goes over the electrode had, it was about a quarter of the length of the others. new plugs are now in and im back to missile like performance again, thanks for all the replies. Would it have been caused by the dettonation? or are bosch sh$te plugs, i mean only a thou miles is a bit hopeless ????