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misfire strange happening

pabr639

New member
Joined
18 Jun 2021
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46
Hi I have a 996 1998 3.4 Carrera, weird thing is happening, When I turn on the ignition and start the engine, it seems to misfire pop and all sorts, but if I turn off the ignition and turn it on again and start the car it seems to clear, I drove it yesterday and it drove fine until I had a misfire and the engine light came on, I put my snap on verus on it and came up with misfire on 4 5 and 6 so one bank. It also had 2 unidentified codes, with ne explanation, not sure what that is all about.


Any help please


Paul
 
Others more knowledgeable will probably be along shortly but something to check would be cracked ignition coils.
They go through a great many heat cycles and crack with age. Eventually moisture gets in causing misfires. Obviously spark plugs would be another thing to check. Both are more likely to show symptoms the colder and wetter it is
 
The issue seems to be just bank 2. I'd have thought a coil/plug problem would be more sporadic. The fact it's just bank 2 would lean me toward thinking variocam solenoid, lamdba sensor or something else specifically related to that bank.
 
Thanks, Good shout, I have seen a Lamda sensor fault a few days ago but it did not come back again, would this make it misfire on all 3off that bank?


Paul
 
Hi,

It could be so many things.

Firstly check the coil packs but ultimately, it could be one things or several.

In my case, a suspected fuel pump was an eaten wire by a rat.

I was worst cares, so engine and box out, fixed, every part changed whilst there and £6.5k later, car is the best it's ever been.

Take it to an Indy and they'll investigate and fix
 
Only being 1 bank means it can't be so many things and makes the problem a hell of a lot easier to diagnose.
 
The unidentified codes should have a P code with a number .. if you can post those it might help .

You have an issue from cold on first startup i take it .. as such lambda sensors are not active at that point as they have to be preheated .. about 2 mins before they are active and the control unit actually takes notice of them so thats an unlikely issue unless problems after that heating period .
.

Most obvious is as been mentioned .. some sort of issue with the cam timing solenoid . normally they just pack up but its not unreasonable to say yours on that banks has an oil restriction issue when cold .. cam timing is in essence in the wrong position which will cause a misfire or rough running on 1 bank .

It's not the cheapest or easiest job to replace the cam solenoid on an early model im afraid .
 

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