fbacungan

Hi fellow Porsche-ites.

I'm new to the forum. I've done a search on this forum, as well as others, and didn't see a fix for this. I thought I'd throw it out to you all.


I'm getting a p0650 along withn p0300, 301, 302 and 303. I took it to a local dealer who charged me $175 to tell me that all cylinders are misfiring. I already knew that. They want an extra 2 hours and $325 for further diagnosis. What!?!?

I thought I'd ask the forum for a fix.

I have recently done the following:
- a major tune up (replaced spark plugs, fuel filter, air filter, oil and tranny fluid change, etc)
- replaced AOS
- replaced MAF
- checked for vaccum leaks and didn't find any. HOWEVER, I didn't see smoke coming out of the oil dipstick. (a little concerning?).

Anyone have any ideas for a fix?

I have a 2000 Boxster.

Macster

The P0650 is a "new" code to me so here you go:

P0650 Check Engine Malfunction Indicator Light (MIL) – Open Circuit
P0650 Check Engine Malfunction Indicator Light (MIL) – Below Limit
P0650 Check Engine Malfunction Indicator Light (MIL) – Above Limit
Check wiring from DME control module, pin IV/31, to instrument cluster for continuity.
1. Connect special tool 9637 to wiring harness (DME control module connector).
2. Remove connector X 2/3.
3. Connect ohmmeter to special tool 9637, pin IV/31, and to X 2/3 on pin side, pin 11.
Display: 0 - 5 ohms
If infinite ohms is displayed, check wiring harness for chafing and pinching damage.
4. Remove connector III of instrument cluster.
5. Connect ohmmeter to X 2/3, sleeve side, and to connector III of instrument cluster, pin 2.
Display: 0 - 5 ohms
If infinite ohms is displayed, check wiring harness for chafing and pinching damage.
Check wiring from DME control module, pin IV/31, to instrument cluster for short to ground.
1. Connect special tool 9637 to wiring harness (DME control module connector).
2. Remove connector III of instrument cluster.
3. Connect ohmmeter to special tool 9637, pin IV/31, and ground.
Display: infinite ohms
If 0 - 5 ohms is displayed, check wiring harness for chafing and pinching damage.
Check wiring from DME control module, pin IV/31, to instrument cluster for short to B+.
1. Connect special tool 9637 to wiring harness (DME control module connector).
2. Remove connector III of instrument cluster.
3. Switch on the ignition.
4. Connect voltmeter to special tool 9637, pin IV/31, and ground.
Display: 0 V
If battery voltage is displayed, check wiring harness for chafing and pinching damage.


Given the presence of the P0650 code and the misfires I'm going with you disturbed something (make that damaged something) while serivcing the car or replacing the AOS.

You'll have to check your "work" and look carefully at all wiring and wring connections for any signs of any damage.

Without knowing the car's history if you tell me the car has sat a while this raises the possibilty of rodents having been at the car's wiring system.

fbacungan

Thanks Macster,

That makes some sense. I puchased the car recently and the previous owner made a mess of the car. The serpentine belt was installed improperly for starters. The code 650 was always there, even before the work I did to it..

With the codes 301, 302 and 303 also, is it safe to say I should start looking on cylinder 1to3, driver side, for loose connections?

Macster

Well, "previous owner made a mess of the car" opens up a can of worms. But lets assume the mess as it were is limited to the immediate vicinity of the engine. However, you are at the car and need to keep your eyes open for any signs of the previous owner's handiwork. Also, keep an eye peeled for signs of rodent damage. Gnaw marks on plastic tubes/hoses, wiring harness insulation. Patches of carpet fuzz missing. Rodent litter on top of the underbody plastic panels, on top the the engine.

Misfires confined to one bank of course suggest you start your investigation with things related to that bank. Fuel supply/pressure. Injector connections. Coils and plugs and of course the connection of each coil to its plug and to the engine wiring harness. The coils should all be the same and look the same, have the same patina.

Given I trust your assessment and with the low confidence you have in the previous owner's work on the car you might consider pulling all the plugs and verifying they are the correct plugs and all are gapped correctly.

Misifres confined to one bank can be misleading. In one case I know of an owner who's Boxster was misfiring on one cylinder and it proved to be a bad MAF. The bank it seems was a bit more sensitive to incorrect fueling than the other bank.

But in other cases one bank can misfire while other bank is ok. The bad bank misfires because the fuel supply to its fuel rail is affected. Massively positive fuel trims can be a clue. Can be a clue too of an intake air leak. Or a VarioCam solenoid connection is bad. (This can have the fuel trims way off the mark as the DME tries with fueling to get the #2 O2 sensor reading it expects by adjusting the fueling to the cylinders of that bank but if the adjustment goes too far...) Or the actuator is bad. This has no electrical connector but is activated by the solenoid.

The freeze frame error code and freeze frame data, which is a snapshot so to speak of some of the engine telemetry when the error that triggered the freeze frame data snapshot occurred, can sometimes shed some light on what's going wrong.

O2 sensors can play a role in misfires confined to one bank. You don't need to remove these there is no cleaning you can do that can help and worse is you can damage them if you clean them. O2 sensors are sensitive to handling too. But at least look them over carefully -- in situ -- for any signs they have been disturbed.

Might add be sure you give the O2 sensor wiring a good going over. You want to be sure the sensor wiring leads are routed properly, properly secured. This goes for any and all wiring. If you spot wiring -- or hoses/lines -- lying loose, or mis-routed, that can be because the previous owner was there or nearby.

Likewise check the exhaust manifolds are secure with no leaks or cracks/split seams.

At the other end be sure the intake system is intact. Customized/aftermarket air boxes or damaged/broken stock air boxes can affect air flow through the MAF which can have the engine misfiring. Be sure the air filter is installed and in reasonably good condition.

In some ways you are tasked with finding the needle in the haystack so you want to keep your eyes peeled for anything out of the ordinary.

RennPart

You're on the right track, check your coils and spark plugs, they are common to go bad and cause mis-fires. The MAF is a common failure too.

We have a bum 2.5L Long block and can give you a good deal on a set of used coils and MAF if interested and of course we can also supply all new parts.