Macster

Well, first if you had asked me I would have advised against going to a hotter plug.

You are addressing the symptom of something amiss not the source of the symptom.

The stock plugs have an extended tip. This runs hot at slow engine speeds to keep the plug from loading up and yet at higher engine speeds the tip is exposed to the cooler incoming charge and thus doesn't run too hot.

IOWs, the plugs are not the problem.

A healthy engine just doesn't jump cam timing. The problem that allows this to occur is not a transient problem. And an engine with jumped timing doesn't run good then bad then good again.

However, a botched IMSB upgrade install can possibly get the timing goofed up and while I would not expect an engine to have suffered from this to run good, than bad, then good again, who knows?

I have not gone back and re-read the thread, so I do not recall if the engine behavior appeared after you did the IMSB upgrade or was present before, or showed up some time after. If it was present before, or showed up some time after then it is not related to the IMSB upgrade. But if it showed up concurrent with the upgrade, then of course a botched IMSB upgrade has to be suspected. But if you are sure you did this right then that is not likely the source of the problem.

The engine is spitting back through the intake that is a symptom of a lean engine and that could be due to an intake air leak. It can also be the result of a failing fuel pump or a bad fuel pressure regulator.

First an intake leak. You checked the hoses and found none leaking. That's good.

A botched AOS installation or a bad (out of the box) AOS or an AOS (or more likely one of its hoses) damaged during installation can of course result in an intake air leak.

You can possibly pinch off the hose from the AOS to the intake but I can think of no way you can eliminate the large hose that connects the AOS the crankcase to isolate the AOS to see if it is leaking or bad.

Based on what you have told me I do not think there is sufficient grounds to replace the AOS with a 2nd one. I would prefer more conclusive evidence and so far there is none at all.

The car is a 1999 2.5l model. Thus my recollection is it should have an idle air control (IAC) valve. Have you checked this for proper operation, cleaned it? Since I haven't owned a car with one of these in years and even then I never encountered a bad one I have no suggestions as to how to go about checking this out. Cleaning it is about all I can recommend and if the unit is suspected as being bad then replacing it. I do not think it is that expensive, but it is up to you if you want to go this route.

The spitting back through the intake behavior is what an engine does when it is running lean and it can run lean with an intake air leak, to (re)state the obvious.

The engine can also run lean if the fuel supply or pressure is lacking.

I'm reluctant to advise someone to attempt a fuel pressure flow test and fuel pressure test as these require the fuel lines be opened and there is always the risk of fire.

While I have done these tests myself before I have always moved the vehicle out from the garage and had a good fire extinguisher handy.

The problem is you are at a point where you will have to do some testing/diagnostics to make progress, unless you resort to throwing a IAC valve at the symptom, a new (2nd) AOS, or even a fuel pump.

Qmulus

Have you connected diagnostics to the car? I haven't seen any reference to checking for codes in the ECU. I would recommend a Durametric tool at a minimum. Generic OBDII tools won't show everything that the Porsche specific tools do. This will also give you real time data showing what is going on. The problem is without know what readings like MAF _should_ be it is difficult to see what is out of whack. Even the earliest 2.5l cars have comprehensive diagnostics built in. Might as well use them.

IME, I have seen a lot of defective MAF sensors on these engines, with symptoms like you are seeing. The key is you really need to do your due diligence starting with checking for faults and real time data to see what the ECU thinks is going on.

Macster

The MAF hasn't come up for direct consideration. I did touch upon a possible air intake temp sensor problem which is part of the MAF's function.

My thinking was it was something the OP did when working on the car.

But is could be the MAF. Since you brought it up the OP could try this: disconnect the MAF at the wiring harness and road test the vehicle. If the symptoms persist it is probably not the MAF. If the symptoms are gone, then reconnect the MAF and retest. If the symptoms return this it is probably the MAF.

After unplugging the MAF, or plugging it back in, I like to advise an OBD2 tool be used to clear error codes. Even though none are present this resets the fuel adaptation values among other things and the DME starts out with all these set to their defaults. This is in case the bad MAF has got these so far out of whack the engine acts up from the start and this has one thinking the symptoms are still present.

Oh the OP never mentioned anything about the CEL being on. There might be a pending code which if there is could be of some interest. (When my Boxster's VarioCam solenoid/actuator proved to be bad the engine ran poorly but there was no CEL, but there was a pending code which pointed to the solenoid/actuator.)

Qmulus

In my experience, a engine running too rich from start up usually is caused by a defective coolant temp sensor or MAF or the wiring to them. That assumes that you KNOW that it is running too rich, and are not just guessing. Vacuum leaks result in an engine that runs too lean, as air would be bypassing the MAF. You could also have a fuel pressure regulator or vacuum line to it that is off, so the fuel pressure would not be getting referenced to intake vacuum. That is not common though. Running too rich once it is warmed up points to O2 sensors, but that wouldn't cause this issue.

I still say connect a diagnostic tool like Durametric and see what it tells you. Check what the airflow reads at idle. Off the top of my head, I think it should be 6.5 g/s or so. SOMETHING will show up as out of spec. Perhaps something was disconnected or damaged when all the other work was done. Swapping parts or changing things without knowing what is really going just creates the possibility of causing more issues, which may be one of the problems you have now. Like Macster said, there are many faults that can be present in the ECU, but not set the CEL. Also know that there are many faults that will not show on a generic OBDII tool, but will show up on a tool that uses the manufacturer specific OBD protocols. So, a generic OBDII reader may show two faults, whereas a factory or Durametric, etc., tool might show four.

FWIW, my business is being the guy that shops call when they can't diagnose problem cars or need to have electronics repaired. I previously designed and built manufacturer specific diagnostic tools for VAG vehicles that are still being sold by one of the largest import car parts distributors in the US. Last month I helped out with a '99 986 2.5 that was also running way too rich. The owner claimed to have installed a new MAF, so the shop dismissed that as a possibility and spent five hours trying to diagnose it, ending with a call to me to repair the ECU. Guess what the actual problem was?

Duezzer

Have car up and running
With engine warm intermittently will stall out / turn off
On trying to restart have to go to full throttle - have to maintain above idle to keep running.
When out for a run - runs very strong - engine is smooth and lots of power.
Only issue is when at idle and on start up.
Looking to get hands on diagnostic reader.
Currently CEL is on.

Qmulus

Personally, I wouldn't recommend running it at all until you figure what the CEL is for.

Duezzer

Borrowed a OBD code reader from a buddy
Had 3 codes in - 2 were related to O2 sensors
1 was the crank sensor

Cleared codes - Ran car and let it quit a couple times - No CEL came on
Put OBD on again - Crank sensor failure code.

Did a little reading on Pelican site to see how tough it is to change and if it could be done with trany in - Seems it can be changed without trany removal - Just a bit of a crap job.

A few of the people who wrote in about the sensor failure seem to be having the same issues as I have - a couple were right after clutch changes also.

Will order in a new one tomorrow and may take a night this week and put it in.

Hope this is it.

Again - Thanks for all the help and the push to get a code reader.

Will be purchasing one of my own soon.

Macster

Was not aware the CEL was on. Whenever the CEL is on the codes need to be read. They often are very helpful when trying to determine what is going on.

A crankshaft position sensor can certainly explain the symptoms you have been reporting.

Do not forget about the hotter plugs. I think you are playing with fire -- no pun intended -- by running hotter plugs. My advice, being always wiling to err on the side of caution, would be you remove them and install the proper plugs.

Qmulus

Would you happen to have the exact codes? If you are using a generic OBDII reader it should give something like P0336 for the crank sensor. As for O2 faults, there could be a few failures depending on the fault description. It would be good to know what the actual codes are. Those other faults will likely come right back once it is run a couple of times.

While it probably doesn't matter anymore now that you have already ordered a sensor, I would pull the existing one, inspect and clean it. It wouldn't hurt to check the resistance (~1000 Ohms), but I bet it is OK as it "kind of" works. Sometimes the crank sensors can be damaged from careless installation of the flywheel when doing a clutch or rear main seal, but that is usually something you will see. You could just have a bunch of iron filings stuck to it. If you are lucky you could just clean them off and be good to go. The crank sensor is a VR sensor, pretty much a coil wrapped around a permanent magnet. When iron passes by it (flywheel teeth) a voltage "pulse" is induced proportional in amplitude to the speed of the teeth going by. If there is iron stuck to the magnet of the sensor, or if the sensor is too far from the crank, of if the magnet has just gotten weak, it will not properly pick up the teeth going by. That could explain why it would run at high RPM, but cut out at idle and give the fault you are seeing. If it is clean and the gap is correct and still gives the fault, the magnet has probably gotten weak and replacement is the only option. At least it is pretty easy to get at. You just have to take off the right rear wheel.

My guess is you have at least a couple of issues. The crank sensor issue, and a yet undefined mixture issue.

Duezzer

Once the CPS is installed I will test the car.
If all is good I will do a second check to see if any hidden codes are in. I will let you know what I find.
When we first ran into this no CEL had come on and we could not get the car to start and stay running.

Had I known about the hidden area of codes I would of sought out a code reader alot earlier to see what was in there - would of saved me alot of frustration.

Only went to the hotter plug to get it running. Now that we have had a run and got the codes I will change back to normal plugs - I was suprised to find out plugs need to be done every 10,000miles (15,000km) - The plugs we pulled were very dark brown - not the normal light brown.

This usually (other vehicles I have worked on) ment the heat range was to low - but does this darkening happed due to having to many miles on the plugs?

What plugs do people find they have had good success with in the Boxster of my vintage?

Beru 14 FGR-6 KQU Spark Plug?
NGK BKR6EKUB (7969) Spark Plug?
Bosch FGR-6-KQE (7413) Spark Plug ?
NGK BKR6EK (2288) Spark Plug ?
Bosch FR-7-LDC+ (7402) Spark Plug ?
Beru 14 FR-7 LUD Spark Plug ?
Spark Plug "PLATINUM+4" Bosch 4417 ?

Thanks

Duezzer

Qmulus

Unless you have a good reason to change heat ranges, I wouldn't. The safest option is to go with the stock plugs (Bosch or BERU) if you want to be sure that everything is as the factory intended it to be. Personally, I went with NGK BKR6EQUPs on my '03 S. They have the same heat range and four ground design as the very worn BERU 14FGR-6KQUs that I took out, but have a platinum center electrode so they should last longer. The center electrodes on the BERUs were really eroded. Performance won't be any different, but they should last longer. I might try the Laser Iridiums, as they will probably last 2x or more as long with the same performance. I have had Iridiums go 100k miles with no apparent wear. Porsche had no reason to put in super long lasting plugs, but as an owner it makes sense to spend a couple of bucks extra each to get something that will last.

I doubt you will find any real difference in the performance of any of the listed plugs in normal use.

Macster

My info is the early Boxsters get a plug change every 30K miles. Starting in 2000 the change interval went to 60K miles.

The plug color was what it was because the engine wasn't running right. Used to be to "read" the plugs one took a hard full throttle run up through the gears than shoved in the clutch and turned off the engine then stopped the car and pulled the plugs.

I wouldn't bother with trying to read the plugs. You have the symptoms and now I guess DTC (diagnostic trouble codes) to help you iD what's going on. When these go away from whatever you do and with the right plugs in the engine there's no reason to read the plugs.

For plugs for my 2002 Boxster I just use whatever the parts department manager shoves over the counter. Beru I think. I do not know the number, but FGR-6 rings a bell. It is a 4 ground electrode plug.

Duezzer

Installed the new Crank Position Sensor
Car still overfuels on start up.
Back to searching for a vacuum leak or something.
Double

Qmulus

What codes do you have now? Without checking codes and looking at the live data, you really don't know what is going on. Guessing and swapping parts can get expensive as you are finding out.

Duezzer

Before we changed out the Crank Position Sensor we had 3 codes. 2 for O2 sensors - Expected these due to the flooding. One for Crank Possition sensor. Cleared codes. Restarted car - Ran for a bit till it did a few stalls and the only code that came in was - Crank Position Sensor failure.
So I changed the Crank Position Sensor
Went for a start after the sensor replacement and the car would not fire up - Found the back 2 cylinders on each side had warm pipes leaving them. Pulled front cylindar plugs and they were soaked in fuel - cleaned and dried plugs - tried again - all cylinders cold this time.
Pulled plugs and cleaned - left plugs out so the cylinders could dry out.

Put the code reader on and - Crank Position sensor failure code is in again.

Left it like that.