Cayman S 987.2 - 2009 CODE P1026 - P1023

Hi All, My Cayman S 987.2 - 2009 - 80000KM has issue which I can`t solve since 1 year. Hard to start in cold and the car cuts off over 4000RPM and i get message engine reduce power. CODES are P1026 - P1023 Changed so far all are brand new 1. fuel pump in the tank 99762014201 genuine 2. HIGH PRESSURE fuel PUMP 9A111031507 genuine 3. High-pressure injector 9A111012810 Only 1 is changed new and the rest 5 where cleaned. 4. Fuel Pressure Sensor Porsche 94860623003 genuine 5. Ignition Coil Porsche 6 pcs Pack 9A160210407 genuine 6. Porsche 100% original Spark Plugs 6 pcs genuine 7. Mass Air Flow Sensor 98760616502 genuine 8. OIL SEPARATOR 9A110704201 genuine 9. Crankcase Breather Tube 9A110752001 genuine 10. Vent line 99720125106 genuine 11. New Battery Any advice for someone with knowledge please. thank you

I didn't see any mention of a new battery ... I would have started there first. It may be too old or just worn out. Low battery voltage causes all kinds of weird errors. Hard to start implies battery as well.

I did change the battery too.

Ok, I see you edited the first post to reflect this as well... Is the new battery known-good, or could it also be bad? This happens sometimes... Check the battery cables and grounds as well, to ensure those are clean and well connected to the frame, etc. Again, hard-to-crank means there may be an issue here as well. Was the battery brand new, and charged before installation? Sometimes, a battery that sits on a shelf will discharge, and may cause damage to the alternator if its not fully charged before installation (I've seen this happen myself). P1023 and P1026 are usually fuel system related... typically due to the high pressure fuel pump . You said these were replaced, so that's good, but what about any filters on the lines? Fuel issues aren't "common" on these cars, so it sounds like a problem specific to your car, which means you may just need to get into it more deeply, unfortunately. Are you using a Porsche capable code reader, or just a generic OBD reader? The former may provide better information, if there is anything more to be seen. For that matter, it might be helpful to look at the readings to see what's happening (eg, fuel pressure reading, is it valid? Is it glitching? Etc) I admit, there's no easy answer here... just have to keep looking, unfortunately.

thanks for the reply. The battery is VARTA BRAND , I will check the battery and the cables grounds again tomorrow and see if it has any issues. Cayman 987.2 does not come with separate fuel filter , the filter is built in the Fuel pump in the tank. Piwis 4 is the reader used for the issue. what is the best battery in case it need to be replaced again ?

I went chasing the codes you posted: "CODES are P1026 - P1023" - but apparently those are specific to the high-pressure fuel system with direct injection. My AllData subscription doesn't cover the S model, just the 2.9 with port injection. It might be worth getting a 1 month subscription to AllDataDIY (around $30/USD) and do some research on those codes. Usually AllData not only explains the codes, it has instructions on how to test for what's wrong, and how to fix it. Right now - you're doing diagnostics by part-replacment. That can get quite expensive rather quickly, and often doesn't lead to the actual problem resolution. A question - has anyone looked at the piston tops to see how they look? If they're white and crusty that may be a sign of faulty injectors or a lean mixture. What do the plugs look like when removed? White and burned = too hot a plug or a weak mixture. What do the fuel trim numbers tell you? Is the car fighting to get more fuel into the engine (fuel trim will give the level the ECU wants the engine to have, and then it will give the level the engine IS having. These should be the same or VERY close in value.) Has anyone looked at the catalytic converters to make sure the inside mesh hasn't broken up and plugged up the exhaust ? Since you're in Europe (Bulgaria?) - Varta is probably the best battery to get. Keep us up to date on this.. and once it's fixed - please go to our New Users forum and make a post telling us about you, the car and anything else you think we might like to know. And post some photos of your car..

thank you for the reply A question - has anyone looked at the piston tops to see how they look? One of the injectors has been changed at Porsche dealer here and they have checked all the piston and piston walls as I paid for that. they said all looks perfect. I will remove the plugs and check the exhaust catalytic converters and update here. the mechanic thinks maybe the new High pressure fuel pump is defective . I will first check the above then replace again the pump.

Test of the high-pressure fuel pump shows the pressure is not stable.

Excellent... thanks for continuing to reply here! I figured there not be another filter, but I had to ask (I have a non-S motor as well, so I don't know!) Sounds like the fuel pump still has issues... so it needs to be replaced again, or it could be that the lower pressure pump is bad as well, maybe? If the high pressure one is "starved" then that could cause issues as well. It might be nice to put a pressure gauge on the input side of the HP pump, if possible, to see if that's the case. Or, if the shop is willing, I'd just replace both again and see if that helps the situation... if that's easier. While checking these, take a look at the wires (or maybe even check voltages at the pumps) to ensure they aren't losing voltage for some reason? For example, if the wires were damaged or corroded along the way, they may not be able to provide enough current to the motors to work properly. Rats, mice, etc like to eat wires, and corrosion is a problem as well, of course. Might want to check the relays for these pumps as well - maybe they have weakened? Good work getting into this... you're on the right track I think... just need to find the problem!

Thank you again for the help. They are almost done with replacement of the high-pressure fuel pump to make sure if the first one we put is not defective. I will update later. Thank you