jmayzurk

I just finished buttoning up the car after replacing plug wires, cap and rotor, diverter valves, boost sensor, and MAF.

Started it up and...well, the car runs well...for a five cylinder. The idle is rough and the left side exhaust is sputtering compared to the right.

My only guess is that I damaged one of the right side (cyl 4-6) plug wires during installation. Cylinder four was a real pain due to the turbo pressure hose. With the turbo hose installed it was easy to install the plug wire, but then I couldn't get the turbo hose back on. Ultimately I had to use a lot of pressure on the turbo hose to deflect it enough to install the plug wire.

Any tips?

On most other cars I would disconnect one plug wire at a time until I found the one that didn't cause the engine to run worse. With our cars this is not really practical because of the amount of disassembly required to get to the plug wires.

I plan to take it apart again tomorrow and check continuity on the plug wires. I may just drop the engine as I am planning turbo replacement in the near future anyway. If anyone has any other ideas, please let me know.

Thanks,

-Jeff

Basal Skull

Hi, not sure if I'm missing something but it seems to me that you could disconnect the plug wires at the distributor end to see which one doesn't make a difference in the way the engine is running...

jmayzurk

Indeed...I am tired and frustrated...thanks for pointing out what should have been obvious!

911/Q45

Get a good night's sleep, then check to be sure you didn't swap two plug wires at the distributor. It's easy to do when changing the cap and rotor.(guess how I know) Also, it isn't necessary to drop the engine to change turbos.

viperbob

What spark plug wires did you use?

jmayzurk

Beru. They were identical to OE except that the Porsche part number on the wire blocks had been ground off. Also the coil wire was too short, so I didn't use it...

Acropora

Sometimes it's just not worth the hassel IMO. Maybe a reasonable and reliable mechanic is the answer.

Kevin

If your wire up job is correct, make sure that your MAF connection is sound.. Otherwise you might have a bad set of wires??

jmayzurk

OK...stupid mistake and easy fix.

The wire for cyl #5 was not on the plug; it was wedged in between the head and the plug. This one is a pain to install because it's basically under the hydraulic pump and it's difficult to get your hand in there. After cursing at it in German and approaching from a different angle I was able to get it on.

After everything--new MAF, plug wires, diverter valves, cap & rotor--the car definitely runs better. The idle is smoother and throttle response is better. Since I did MAF and plug wires at the same time, I'm not sure what to attribute the change to, but my bet is on the wires (I was not throwing any codes from the MAF, in case you're wondering).

My car has 70k miles on it. Some of the wires were starting show cracks in the rubber sheathing.

Acropora, I know the feeling...but I prefer to do jobs like this myself. It's a good opportunity to get to know the car, a chance to inspect various components (especially rubber parts in a 10 year-old car), look for leaks, etc. I also like to do some cleaning while I'm in there.

-Jeff
'97 993TT
'02 BMW M3

911/Q45

There is an enormous satisfaction in doing the work yourself and you know exactly what has been done. Congrats.

chris walrod

This plus the fact that I dont like paying someone else to screw-up my car, I do just fine on my own