engine missfire

[bulletprooflestat]

Hi,

I wonder if anyone could shed any light on my problem. I have a 1998 V8 se non egr with a PUK stage 2 chip conversion (approx 450 bhp) with K&N filters and a lotus sports back box the car has done approx 16k miles. I have owned it for aprox 4 years with no major problems until now. Due to me not having a weather shield on the underside of the rear deck lid i have a problem with water getting into the plug pots which I thought was causing the missfire. I know am able to keep the car engine bay dry and have put new plugs in new coil packs and plenum gaskets injector cleaner. the missfire occures once the car has warmed up no matter how you drive the car and it pops on tickover when warm. it drives fine when cold. I have used a scan tool which states the throttle position sensor is working and the o2 sensors are working fine.I removed the cats to see if anything was wrong to fine that there weren't any!! due to them being eaten!! apparently this happens when they are chipped. So I have removed the post cat o2 sensors and put shields over the ends of the sensors and taped them up above the gearbox. I have put blanks in the hoes where the post cat sensors were The missfire is still there. I put new leads on the car last year so dont think there is anything wrong with these. I have been told to get the car warm until it is missfiring then take off the plenum to get to both ends of the leads then test them via ohms to measure the reistance to see if there is any difference between them. If nothing my next idea was to get the ecu tested by blue streak to see if there was any issues here. Oh I have also done a compression test when warm which was fine. any ideas as \i am getting desparate as its summer and need to use it!!

[mike_sekinger]

You have investigated all of the

[neal]

One of the injectors could be over or under flowing. Not only would that cylinder start misfiring but the oxygen sensor for that bank would pick up that it is running too rich or lean respectively and compensate by adjusting the flow rate to all the injectors in that bank. So you'd end up with one cylinder running rich and the other three lean or vice versa.

[Zhastaph]

I had a missfire when warm up once due to a dodgy solder joint on one of the big trannys in the ECU.

[bulletprooflestat]

Thanks for your help chaps, Mike unfortunatley I dont have a stock or other type of ecu to try in its place as i dont know anyone local with any form of esprit let alone a V8!! I will test the leads this week one evening then if nothing will send off the ecu to Blue streak has anyone used them ?they were good last time I had to have my chips re glued in .Also if I do have to change the leads I have been told that the magnecor ones are cheaper than Lotus ones and are also "better" but wether this meant more performance or more resistant to braking down under heat do any of you use them. Hopefully one of these will sort out the problem and I wont have to change the injectors as this will be expensive!!

will keep you posted sorry for the delay in replies as I have no tinternet acess at home so only get online a couple of times a week

Liam,

[mike_sekinger]

Hi Liam,

I can

[bulletprooflestat]

Thanks for the help Mike let me know how much you want for the Rochester injectors are they brand new? sorry being a bit thick what is the dirrerence between the 2 sets I presume the RC ones are uprated will they be able to be fitted straight in or will they need to be set up eg rolling road?. Can you recommend someone for the ECU checking in UK ? I only was going to use Blue streak as I had before and I read that someone on esprit world had used them for triage think its about

[mike_sekinger]

Liam,

The standard primaries are sized for 235cc/min at approx 50psi. The RC injectors flow 257cc/min at the same fuel pressure. They are matched as a set (very close flow rates) and also have a better spray pattern than the standard ones. They are a direct physical replacement.

The ECU will automatically compensate in Closed Loop mode to the larger flow rate.

The standard ones I have are brand new and we can sort out a very generous deal if you need them.

On the ECU front, I

[bulletprooflestat]

Hi All Checked my leads when the car was warm and missfiring last night set the meter to ohms 20k and readings for all leads were between 8.7 and 10.1 after switching the car off i dismantled the plenum as quickly as poss and lifted upp to get to the base end of the leads so this was around 15 mins then the test took around 20 mins to do so it was coolling as i did it. Does this sound unusual to any of you? I am not convinced it is leads as they were a new set last year and the car has run fine with them for around 500 miles. I have rang blue streak re the ecu,

[bulletprooflestat]

Hi Chaps update as below can anyone help

I have had the injectors re conditioned and tested 2 in particlar were bad which seemed to be the bank that was missfiring so I thought i had cracked it!! Oh me of little faith. Put it back together last night cracked up and thought i had cured it went for a run and after about 8 miles once fully warm it slightly did it again but not as bad as before My only thought it that the car was low on fuel and the warning light did come on and it now misses slightly around 3k-3.5k revs on full bore acceleration once you shut off throttle it pops back a little Does anyone know if fuel starvation is an issue as i was going through twisty bends at the time i will put some fuel in tonight and give it another run to try again also i have had the ecu back from Blue streak who have found no fault so i know it isnt this so now i am clutching at straws should i change the fuel filter also now the injectors have been done and also uprate to the magnecor leads which i have been told are less prone to breaking down under heat ??

Please help !!! yd

[mike_sekinger]

Hi Liam,

It sounds as though a fuel filter change might not be a bad idea at all. Your car is about 10 years old and if this hasn

Edited July 29, 2008 by mike_sekinger

[bulletprooflestat]

tried it again tonight with half a tank of fuel and it still does it BUT it is a lot better than before it seems to be down on performance around 3k revs when you floor it generally after pottering around at low speed where it runs perfect so i think next on the agenda will be fuel filter and magnecor leads has anyone tried them are they any different that std ones ??

its either this or sell it via classifieds as its driving me insane now as i want to be using it and cant!!!!