Mike J

Thanks for the input everybody!

I think this is actually a true misfire since you can hear it at the exhaust. In my case its not having a vibration with a smooth idle tone....unless all Porsches go **phut**phut** ;-). I am trying not to "shot gun" it but since I have 13,000 miles on the caps/rotors I figure I can change them out anyways. If the problem does not go away then I can always change them back and shelf the new ones for the next service. The next step, if its the plug wires, is more costly. I am likey to look at some of the resistance values of the wires before dropping the money...hopefully I have time before going away for two weeks over spring break (leaving on thursday...Yah!!)

Cheers,

Mike

Mike J

Well, here's an update as of April 10, 2005:

1 - I replaced the caps/rotors with no change at all. Looks like I have a spare set now..

2 - I found the #6 lower plug wire was in rough shape and a few others were a little cooked. I opted to replace the whole harness...which I just finished yesterday. (I would like to have a little talk with some of the Porsche engineers...what the hell were they thinking when they ran these wires and positioned the screws that hold them down?). Anyways I think there was a slight change...the idle seems to be smoother.

The kicker is that I threw another msfire code...a general one and then for some random cylinders. I still get a little bit of the **phut**phut** sound on the exhaust, its not at a steady beat but irregular. Appears to be less than before I changed the wires. If the AC is on it almost dissapears...only once in a while I get a **phut**phut** in that case.

Not sure where to go from here. I have not touched the coils yet but don't want to go there if I can avoid it. I am still ruling out the DMF since that would not produce the exhaust tone. I will do the selective coil unplug test to see if the **Phut** noise is caused by one specific ignition circuit.

This car is starting to grind my energy down......the enjoyment goes out of it when you get persistant problems like this... ;-(


Mike

cabrio993

I am gld to hear that your efforts has gotten it better. Now that you know you got good ignition components...what is next? Vacum leaks? Intake leaks? O2 sensors? temperature sensors? Air Mass flow sensor? With any ODBII car if any of the sensor is sending wrong reading to the computer, the computer is "fooled" with wrong data.

However changing each component to see which one is the faulty part can be costly. Now that you have a good ignition system in place, it will be probably a good idea to get the car to a shop that has a really good scanner and that can read all the sensors data in real time and see if any of the sensors are bad.

Please keep us posted on what you find. My car went from relly poor to much better after I changed all the ignition components minus the coils. My idle still is not perfect but I am suspecting a vacum leak or sensor could be the culprit.

Mike J

I have been using my ODB-II scanner to check what parameters I can get to. Not having many ODB-II cars I am not sure what is the normal range for values.

The O2 sensors are working but the primary ones are all over the map (i.e. 0.07, 0.68, 0.18, etc). The secondary ones (after the cat) are much steadier which means the cat is working. There does not appear to be any "dead" sensors that I can find by scanning through all the parameters.

BTW, I noticed the **phut** noise, when it occurs (which seems to be always when the engine is cold), actually can be felt in the exhaust flow by the tips. If you put your hand by the tips every time you hear a **phut** you can feel a little puff of extra exhaust. Oh it appears the exhaust noise does not occur when the engine is cold.

Since I do almost all of my own servicing I don't really have a "steady" mechanic. I have been trying to avoid going in because these kinds of diagnostics can cost a lot of hours and thus $$$. I will phone up a few on Monday to see if I can bring the car by a shop and look for opinions.

Cheers,

Mike

cabrio993

Funny that you mention about the cold engine. Mine is steady without the AC ona s long as the engine is cold or just warm. After 15 minutes or so and the engine gets to good op. temp, then my idle goes a bit rough if my AC is not on. Mostly I keep the AC on so it doesn't bother me much. But I am very interested on what you find out. I may be suffering from the same thing and considering that others are posting the same symptoms, there may be a common part here that just goes "weak" with age and makes it idle this way.

Do you notice any difference during Cold vs Hot days? Or ambience temperature doesn't really makes a difference?

JasonAndreas

The normal range values are given in the technical workshop manuals, if you don't have them PM me.

JasonAndreas

Have you tried to isolate the problem to a specific cylinder? With the car idling pull the electrical connectors off the fuel injectors individually and see what effect that has on the "phut" sound. In a proper running car the idle speed should drop for about a second and then return to normal everytime you disconnect an injector.

Mike J

Thanks Jason,

I have not tried that yet. I don't have access to the car at the moment....its getting some window seals looked at. When it gets back I will try that. Are you sure you can disconnect the fuel injectors while its running? It would seem safer to disconnect them while the engine is off, and then start it up.

I was thinking maybe I have a bad injector too...the car has 120,000 km ( 75,000 miles). They could be worn and spraying a bad pattern.

Thanks!

Mike

Mike J

I have started another thread on this. Please see https://rennlist.com/forums/showthre...28#post2113428

Cheers,

Mike