Can anybody give me any reason why my car could be missfiring?

 

Im getting very bad missfiring at high rpm and a noticable missfire at low/idle.

 

All the injectors are firing and connections seem ok

All Coilpacks seem to be working and the connections are ok on all but one.

 

This prolem is driving me mad and i need any help you guys can throw out.

 

Note to john300zx, my idle problem has reappeared!

Hey mate

 

Air leak? Also have you tried cleaning all your connectors? Make sure your coil packs are working well as they can with age break down. Sounds like an air leak somewhere spray some aerosol around the engine and see if you have some going the wrong way.

I cannot hear an air leak of any sort and the boost gauge (aftermarket) is saying its boosting good. Ive looked at all the pins on the coilpack connectors and none even have any of that green poop on them

i know its a daft question but your not hitting the limiter high up are you and thinking its missing...dont laugh as its been known:o

no, sometimes it starts missing from 5-7000rpm, sometimes it just misses and wont accelerate further, other times it will change gear without any missfire.

 

It happens in all gears but is worse during full throttle, if im very light on the pedel then i get good boost untill missfire, if hard on the pedal then it feels sluggish and i get poor boost

 

The missfire feel is unmistakable and sounds like a dumping noise from the exhaust.

bad plug or plugs or even a cracked plug cap which is earthing..easy to spot in the dark (darker the better),take the car into a road with no lights and lift the hood then wind it up and look for the blue arcing

the dumping noise in zorst will be unburnt fuel which makes me think its ignition probs

didnt think you could get arching on coil packs, infact i thought that was the hole point in them, where would i be looking?

I'll just throw this out there as it caused my car to miss. My rocker cover gasket had gone and was leaking oil into the spark plug 'reservoir' (number 6 i think) and the rubber bit on the coilpack was in bad shape. This caused the 6th plug not to fire and therefore it missed.

 

Just another thing to check, make sure there aint a load of oil leaking into where your spark plug goes.

ive had them all off but havent checked the sparkplugs themselves yet so i may have missed that...

 

And only one connector is broken and thats number one and still fits ok.

 

Will check first thing, ta

didnt think you could get arching on coil packs, infact i thought that was the hole point in them, where would i be looking?

 

when i first bought my car over 4 years ago i could hear the "cracking" of the spark and it turned out to be oil and shite in the plug recesses and they where arcing on the under side of the boot,cleaned them but i could still hear it ocasionaly so i took off my coil packs one by one and low and behold after resting it on the cam cover the spark was jumping from the outside of the cap..replaced and been fine for years;)

i remember the last time i removed a HT lead to check for the same thing i got electrocuted! hehe funny times

 

I will check znut, but because i will have to have them all unbolted in preperation so i can just pop them off (with engine off) i will check them tommorow so i can see what im doing.

 

Please everyone keep throwing ideas out there

Have you got a series one ptu? might be worth checking the cables etc?

yep, still a series one, but... normal driving is fine, would that matter?

My RS turbo did this ( i know its a different car, but same symptoms ), on boost it would suddenly misfire and splutter until the revs came down then it would be fine again.

 

Turned out to be a dodgy dizzy cap, no obvious signs either, just some very minor cracking.

 

Changed it, worked perfect after that.

 

I would defo do the arcing test on the coil packs mate, when i first bought my z, it also had the same problem, that turned out to be a 'split' coilpack, the rubber / plastic bit near the tip. Again, replaced the dodgy one and all was fine.

 

Hope this helps point you in the right direction.

i hope so

I had a similar sounding problem, turned out that although the connectors on the coil packs fitted ok, the clips were all broken.

 

Under hardish acceleration the engine moved just enough to pull the connectors off some of the coil packs just enough to cause a miss fire.....And when I checked them they had dropped down and looked good again.

how did you fix?

Hi mate I had this problem when I first got my car. I bought a new loom and replaced it over a weekend. didn't stop the engine lunching itself 100 miles later though!!!

 

Anyhow, if your loom is looking a bit crust and brittle and your connectors are brittle etc and you can afford it the I would recommend a new loom. It will remove about 100 different options of what might be wrong next time you have a problem.

I made some little brackets that pushed down on the connectors and kept them firmly in place. Using the coil pack bolts to secure.

 

Its true a new loom or new connectors would be better but I wanted to see if this really was the problem.

 

I will probably make some nice brackets in the spring.

I have got oil in the intake plenum, lots of oil! what could this mean?

 

Rocker cover gasket?

I have got oil in the intake plenum, lots of oil! what could this mean?

 

Rocker cover gasket?

 

Thats what my problem was matey. Once i replaced that - sorted.

damn it!

How much would that be izzac?

 

Could it not also mean i need new pcv valves? It cant be turbo related because the actuator pipes are clear... and could this be the cause of the missfire?

 

Im going crazy!

 

ps. All the Coilpacks are in top condition and all the clips are bob on too, no gunk and seal very nicely

And no oil or shite in any off the spark plug resovoirs

I can't give you an exact price i'm afraid as i had quite a few other things done at the same time. So really you need to look into it with a zed specialist or something. Its more a case of how long it takes and how much per hour.

 

I did replace my PCV valves and hoses while i was it at.

ok, so this might not be as bad as it seems then. ill get in touch with jeff, so back to my missfire problem...

Yep Jeff would be top of my list for a chat if i had to do it over :)

Pete, i swear, you must be working on my car, lots of similar problems, popped off my balance tube yesterday, lots of oil inside the plenum (and fuel). I have a known pcv issue though, no restrictor OR wire brush in the drivers side of the pcv system. Some dick has replaced the drivers side with just a long hose. Apparently that allows a lot of oil to get sucked in on vacuum, i.e. after throttle.