Hi, ive posted about losing boost previously and ordered new dv. My car is hesitating between 1500-2000 rpm and occasionly misfires at these revs. When it was recently servixed i had race plugs fitted and needed a new coil pack, i was told i may have a faulty lambda sensor, would that cause this misfire? I have also been told by pals that lambda sensors rarely fail unless the catalyst is pooped, any help would very much apprexiated, thanks

 

mehhh...who need them anyway ? LOL

 

When you say lambda sensor is that the same as O2 sensor? I have heard of alot of O2 sensors failing without cat failure. In fact the only cat failure I heard of was on some aftermarket exhausts had faulty cats from factory.

 

Im not overly technicaly minded but i know their are two before the cats and two after, would they vause this issue do you think??

 

I dont think O2 sensor would cause misfire. They usually just throw a nuisance CEL and that's about it. If its missing its usually an ignition problem. You said plugs and a coil pack were recently changed. Did they change all coil packs or just one they thought was bad?
A code reader like a Durametric can be a lifesaver for chasing down misfires.

 

"race plugs"??? Specifically WHAT plugs (manufacturer and part number) were installed?

(If the reply is "I don't know, the shop said these are race plugs", we have a problem...)

This same shop said you MAY have a faulty lambda sensor ???(O2 sensor here in the US)

"MAY"???? On what do they base this assessment?

Lambda sensors fail all the time- they are a maintenance item. They do not fail as a result of the cat failing- indeed, the post cat o2 sensor is there precisely to monitor the cat health... and the pre-cat o2 sensor is BEFORE the cat, so it cannot be 'hurt' by the cat. And the pre-cat sensor is the one that drives the air/fuel...

One single coil pack? Not all 6? When you get misfires any codes??

 

Good questions ARD. I flagged on the "race plugs" too....???

 

Hi, i believe the plugs are bosch items designed for more boost. Only one coil as swapped as it was cracked, after the service the car was put on diagnostics, it registered faulty lambda sensor, the fault was cleared and didnt re-appear after short test drive. Could it be other coils causing problem?? Thanks

 

Plugs are probably ok. I suspect lamda code was a red herring or maybe an O2 sensor is starting to go but I dont think that is the cause of the misfire problem. I suspect other bad coils which is a shame because it would have been easy to change all of them when the plugs were changed. If one coil is bad chances are more or all of them are bad.

 

Ok thankyou for your help, how hard is it to change the coil packs? I did that job on an m3 i used to have and it was simple, hopefully same sort of job

 

Not simple at all unfortunately. It is just as hard as changing the plugs since the coil is over each plug. The exposure is the problem. There is just not much room there. It will take as resonably experianced tech about 5 hours to change coils.

 

Oh dear! Thats gonna be £300 labour and 1000 dollars for coils. Betta get it posted to santa!!

 

Coil packs are US$50 ish...

Unfortunately the prevailing wisdom here is to replace the coil packs at one of your regular plug changes, since they have a propensity for cracking and causing...well, your issues.

If one has cracked, the others may have cracks that are not visible.

Given that the coil pack comes off to change the plug, a responsible shop should have said "for another £150 we can change the other 5 packs, and avoid a likely future fault".

If all they charged for labor to remove the bumper, intercoolers, shields and change plugs was 300, you are doing good....

GL

A

PS Would be good to find out exactly what plugs are in the car....

 

Stock coils should run about $200-250US for five. I would complain about them not changing all at once when they did plugs and try to get a break on the labor.

 

Ok, i was considering the uprated ones offered on the forum at 1000 dollars, would they be worth that extra?
Also the labour is 300 pounds not dollars. I think thats around 500 dollars