99 2.5L Tip running on 5 cyl - 986 Forum - The Community for Porsche Boxster & Cayman Owners

Quick history. I've had the car 12 years, put 50K miles on it. Had the trans rebuilt, security module replaced, etc. over the years. It's been running perfectly with nothing but gas, oil, tires and pads for the last few years. So after being fine for ages, I had some stalling and non restarting when hot. New CPS and MAF element, and everything was perfect. After this work, I cleared all codes so I'd know if anything happened. Then I left the car parked outside, just once, and it rained. Now it's only running on 5 cylinders, and I need help with diagnosis. Full disclosure. Years ago the soft top drains blocked, water got into the cabin and the first I knew was when there was so much water I get wet shoes through 1 1/2" foam and carpet. That cost big time for a used (old one was not repairable) security module, and I seem to recall the DME had to be repaird, but I"m not sure now. So, the misfire starts. As I'd recently done the CPS and MAF, I checked those connections and anything in the vicinity, since I figured maybe I hadn't fully clicked something home and it had now partially come loose. Nope. I read the codes with my Foxwell knock off Duramtric tool and had: P0300 - Misfire detected P1301 - Misfire cyl 1 P1319 - Refer to service manual - emission-relevant cylinder misfire P1313 - Refer to service manual - Misfire Cylinder 1 (Emission Relevant) In the past, I think I had DME code 22, which I think is incorrect load from DME to the tiptronic DME. I assumed this was related to the MAF, but I'm mentioning it here for completeness. So I did the normal things. Swap the coil pack between 1 and 2. Nope, still on cyl 1. I also swapped spark plugs between 1 and 2 just in case. Nope. At the same time, I was obviously checking for moisture anywhere and cleaning things. Nothing. I have pulled up the carpet under/behing the seat, and there's no moisture or evidence of any having been there. So I don't think it's that. Note. I know the drains are blocked again, possibly permanently, as we have a magnolia tree and those effing leaves have got in there and I can't clear them with air or trying to use stainless steel wire in a drill as a snake - hence I always park it inside... except this once. So, I need diagnosis help from those who know these brilliant little infuriating pieces of poopoo!

Quick update. You know, lying underneath a car to reach the plugs and coils obviously does something to my brain. A friend called and suggested pulling the coil and plug and cranking it while grounded to see if there’s spark. I have no idea why I didn’t think about that before. It’s the first thing I would’ve done working on any car from the top side! Anyway, I’ve done that. The car will start and run just like it did with that coil and plug in. Nothing, no spark. So it’s definitely electrical unplugged one. Now I have to start working my way back through and see if I can find it. Any ideas on where to look?

I'd be following and inspecting that plug wire in its entirety, top to bottom. Maybe a rodent got to it. Do you have a Durametric? Do you have a local mechanic who could diagnose it?

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Trying to trace it back. Next step is to uncover the DME under the seat and start pinning out wires. I need to look for a pin out diagram for the DME connector. I have a Foxwell knock off Durametric which is how I got these codes. Asking here, GRM, and a friend in the service dept of the local Porsche dealer. Consensus everywhere is starting pinning things out. Damn I hate electrons!!! I’m a damn mechanical engineer not a sparky!!

Quotes source post: 670818

The DME is in the trunk on the bulkhead, under the carpet.

Thanks for the tips, and sorry for the delay. I had to work on other things, not the toys. So, does anyone have the pinout for the 1999 986 DME so I can start tracing wires and checking for individual connectivity? Also, someone said the DME is in the trunk, on the bulkhead. What's the DME under the driver's seat? Is that just the security module? Thanks

Yes, the one under the seat is the immobilizer module. For the diagrams search for this file: 986 Group 9 Circuit Diagrams To 99.pdf