Misfires + Rough Idle
 

Hello All,

I have a 99 Boxster 2.5L runnin 0w 40 Mobil1 that recently started giving me some trouble.
Has about 187k miles, aside from just recently. its ran like a dream and never had any issues prior

Got a check engine light with codes:

STORED:
P0300 - Random/Multiple Misfires detected
P0306 - Misfire Cyl 6
P0304 - Misfire Cyl 4
P0305 - Misfire Cyl 5

PENDING:
P1319 - Misfire Emission Related
P1318 - Misfire Cyl 6 Emission
P1316 - Misfire Cyl 4 Emission
P1317 - Misfire Cyl 5 Emission

P1524 - Camshaft Adjustment Bank 2

Cars been taken care of and maintained since Ive owned it. The Misfires for 4,5,6 came first initially with noticeable fluctuations in RPM below 1500 RPM. Decided to do all plugs, coils, and plug tubes first to see if that would fix it. Codes came back some time later and i noticed a consistent small drop and raise of RPM just below 1000. Before this, ive already changed the MAF and O2 sensors just for ensuring other basic maintenance things were up to date. This all came out of nowhere so i doubt its anything critical. Ive test driven the car a bit and it runs amazing aside from those idle misfires at a light or stop sign.

Im thinking it could be AOS related ? or idle actuator related. Not sure as the Misfires have only come from 4,5,6 and never 1,2,3. Any assistance or recommendations would be much appreciated

P1524 is telling you that there is an issue with the cam shaft adjuster on bank 2.
It has an effect on cam shaft timing. It is most likely why your having miss-fires on all cylinders on that bank. You need to fix the P1524 issue first.

looked a good bit into it online, just wondering what you would recommend a starting point would be for a diag on this case. does this automatically mean the adjuster is bad and i'd need to swap said ~$800 part out or something to be cleaned and potentially fixed

Could be that adjusters chain guides (betweekn the cams) are worn out very badly and the adjuster does no more do it's job well.
If chain guiders on the adjuster have never been changed, those are already in need for that. Chain guides are very cheap, but best to change engine out (jes, some have changed those engine in...).

The starting point is to determine if the adjuster functions or not.
It is an electrical devise so the electrical circuit portion can be tested with a volt meter.
It can be made to "test" actuate with the proper type of OBDII reader such as a Durametric or some of the Foxwell brand readers.

The second thing to consider is the high mileage ...there is very possibly high wear issues.
Access to things like the cams is very limited unless you pull the engine.
With these type of engine designs repairs can get costly.

have a visit to a local porsche shop scheduled later this week. However i wanted to do some
light testing myself before hand so i could see the full behavior of my car.

Update: car runs fine generally above 1500 rpm. anything at idle or below typically will misfire and cause the CEL to start flashing. Ticking noise mustve been from the old-ish oil, as after i did an oil change, noise went away after a few miles. The oil itself had no fragments or anything of the sort in the filter or oil itself so the engine isnt blown, thats a good sign. I did notice a faint rattle upon accelerating ? not sure if that could be the timing chain however it doesnt seem to be something catastrophic compared to what ive heard on cars before.

Saw a thread where ppl mention cleaning the throttle body, MAF, checking AOS or any leaks to see if that fixes anything, havent done it yet but might need to check live data again due to seeing MAF have 0 readings at one point. Sensor was replaced less than a year ago with OE so not sure about that. Aside from the low RPM misfires, the car still runs just as great. Saw someone else mention giving a car a spirited drive to see if new oil can unclog the actuators or vane adjusters, did one drive today and didnt seem to change much, might try again tomorrow.

Just throwing this out there... already you may have considered it...

Have you disconnected the MAF to see if the problem persists?

hello, yes i did try, unfortunately the symptoms persisted and the only difference it made was throw a pending MAF code. MAF itself had no oil on it or anything that could make it look bad. Perhaps i read it wrong on the scanner.

This sounds like a problem with the variocam system. The variocam system is active above 1500 rpm. You need to check the cam deviation angles and fuel trims to tell if this is chain stretch or more likely cam pad wear. You really shouldn’t drive the car until you get it properly diagnosed because if it is a problem with the variocam system you do not want the chains to jump time.

noted, since this issue has persisted its been driven only 3 total times and none more than 5 miles so hopefully if this is the case, nothing has happened to worsen it. ill go ahead and check your recommendation and follow up

small update - car did not end up going to shop as they tried to change my estimate the day i wanted to take it in. decided to just get a TopDon AD600s to read cam deviation and do further testing in my garage. I have no problem with it though id rather spend $200 on a scanner than 200+ to be lied to at a shop potentially. anyways i did drive the car around my neighborhood not exceeding 25mph though just enough to warm up the car and idle. plugged in the scanner and the codes did come back as well as cam deviations reading at -6. ill be looking into values shortly to understand what values i SHOULD expect however both banks sat there even once warmed up and on idle.
I have a buddy of mine that has worked on porsches before who will come over this weekend to further diag variocam / adjusters. i want to go through every possibility first before concluding a full timing job + adjusters

http://986forum.com/forums/uploads02...1734126733.jpg
http://986forum.com/forums/uploads02...1734126743.jpg