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Boxster idle problem


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I've been using this board for a while searching for things but this is my first post. Glad to be here.

I've got a 2000 Boxster with 35k miles. It's been quite a rocky ride so far. I had the IMS bearing failure at 22k mile a few years ago (car doesn't get a lot of driving). Engine was replaced with a salvage yard one (2001) with about 10k more miles than mine and all was fine until last fall. I did the flat6inovations bearing replacement on the new engine and hoped I was good to go. Last fall the car started to idle rough and would eventually set the CEL with mixture out of range errors. I took it to my local independent (who did the engine swap) and he couldn't find anything wrong. Cleaned the MAF and told me if it didn't clear up to go ahead and replace the MAF. It would take days for the CEL to come back on but it always did. Replaced MAF, no improvement. Started doing research here and proceeded to replace spark plugs and AOS. Problem still persisted. Went back to the shop and they put it on a smoke machine and found a small vacuum leak from a hose that was chewed by a rodent. Things got a little better but still would set CEL and not idle smooth. Back again on the smoke, no more leaks found. At this point I think he was out of ideas and started shotgunning at my expense. Replaced both upstream O2 sensors, no improvement. Replaced MAF again.

The car runs great off idle, it just idles rough and will eventually set the light. I recently moved a few hours away from the old shop so I'm a bit on my own. What next?

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:welcome:

It would be really helpful if you told the current fault code(s).

FYI - the MAF has little if anything to do with idle. You can unplug the MAF and the idle will not change (of course you will get an MAF fault).

I just got it back yesterday and of course the codes were cleared. Drove it 150 miles yesterday and the light is not on yet. To make matters worse I still can't find my code reader after the move :(

I was thinking about upgrading to a pc based software package for OBD reading. Any suggestions?

Edited by CO_Steve
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  • 2 months later...

Steve,

Here's a follow on with everything I've tried becaue I have a similar problem but mine only manifests itself at high engine temps. I do all of my own work because I refuse to pay mechanic fees and I had 4 MG's when I was young and leanered alot about cars and motors from those expeiences. There was a problem with the first few years of Boxter with an air leak in the Oil filler tube from the rear trunk to the oil pan. This is said to cause the Check Eng light to come on and also a rough idle. There 's a couple of Press Fit conections I found on top by the intake manifolds. I wrapped them with gorilla tape to seal any potential leaks there. If your problem's at cold temps and you've replace the MAF and the engine side O2 sensors. I'm not sure what else you can do but seal those connections to see if that fixes or helps. The fault codes I see from my high temp probelm is that the fuel injector system seems to loose itself and change the air fuel mixture from lean to rich and then from rich to lean and finally seems to get lost. then the enigne starts to cough. I'm starting to think that it may be vapor locking when the engine gets hot which might be the cause of the air/fuel mixture fluctuations. I remember reading somewhere when I first got the car and vapor lock was mentioned but I can't find that article again. Has anyone heard about this and if you have, do you know what the solution might be?

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I've Seen all 4 1123, 1125, 1128 & 1130 Lean and Rich Mixture messages for both cylinders 1--3 abd 4--6. I haven't checkd to see if it's logged any lately because the check engine light hasn't come back on yet.

did you already replace the altenators?

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@ sliderr, code P1123: Oxygen sensing adaption area1 (cyl. 1-3) Lean Threshold means that cyl. bank 1 run too Rich !

A leaking or bad injector can cause this issue.

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RFM, thanks for the input. The Bentley Shop manual I have has all of the fault codes for every Boxster/Boxster S from 1997 to 2004 and I've seen all 4, so it seems as though when the engine gets hot (as it approaches the temp the cooling fan turns on) that the fuel injection computer for some reason starts swinging from lean to rich on all 6 cyclinders until it gets lost and then starts the cough like it's running out of gas and then when I come to a stop the idle fluctuates and the engine will sometimes stall. The car runs Awesome at high speeds on the California Freeways becasue it never reaches a tempt where the fan will come on but when I get on the city streets during hot summer days this problem shows up. I'm wondering if it could be vapor locking and when the fuel injection system starts to see vapor instead of liquid it tries to compensate and doesn't recover. Is that possible?

When you say leak where would that possibly be. I don't think it's a bad injector. If it was I think I would have the problem all of the time (correct)?

Sliderr,

As I suspected the Bentley shop manual describes Alternator as I always have. There's only 1 and it's teh main component of the battery charging system. Since you used Alternators referring to more than 1, when you say alternator what are you referring to?

Regards,

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I've been using this board for a while searching for things but this is my first post. Glad to be here.

I've got a 2000 Boxster with 35k miles. It's been quite a rocky ride so far. I had the IMS bearing failure at 22k mile a few years ago (car doesn't get a lot of driving). Engine was replaced with a salvage yard one (2001) with about 10k more miles than mine and all was fine until last fall. I did the flat6inovations bearing replacement on the new engine and hoped I was good to go. Last fall the car started to idle rough and would eventually set the CEL with mixture out of range errors. I took it to my local independent (who did the engine swap) and he couldn't find anything wrong. Cleaned the MAF and told me if it didn't clear up to go ahead and replace the MAF. It would take days for the CEL to come back on but it always did. Replaced MAF, no improvement. Started doing research here and proceeded to replace spark plugs and AOS. Problem still persisted. Went back to the shop and they put it on a smoke machine and found a small vacuum leak from a hose that was chewed by a rodent. Things got a little better but still would set CEL and not idle smooth. Back again on the smoke, no more leaks found. At this point I think he was out of ideas and started shotgunning at my expense. Replaced both upstream O2 sensors, no improvement. Replaced MAF again.

The car runs great off idle, it just idles rough and will eventually set the light. I recently moved a few hours away from the old shop so I'm a bit on my own. What next?

Rough idle is often caused by a dirty throttle body. I assume that you've already cleaned it but if not, it's worth a try.

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My response was directed to member "sliderr" because he only has code P1123 on one cylinder bank, what is clearly a different problem. Vapour lock is very rare under normal driving/temp. conditions, the problem will sit elsewhere i think.

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My response was directed to member "sliderr" because he only has code P1123 on one cylinder bank, what is clearly a different problem. Vapour lock is very rare under normal driving/temp. conditions, the problem will sit elsewhere i think.

RFM how can you tell a injector is bad or leaking? is it worth wile to buy this will it WORK?

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I've been using this board for a while searching for things but this is my first post. Glad to be here.

I've got a 2000 Boxster with 35k miles. It's been quite a rocky ride so far. I had the IMS bearing failure at 22k mile a few years ago (car doesn't get a lot of driving). Engine was replaced with a salvage yard one (2001) with about 10k more miles than mine and all was fine until last fall. I did the flat6inovations bearing replacement on the new engine and hoped I was good to go. Last fall the car started to idle rough and would eventually set the CEL with mixture out of range errors. I took it to my local independent (who did the engine swap) and he couldn't find anything wrong. Cleaned the MAF and told me if it didn't clear up to go ahead and replace the MAF. It would take days for the CEL to come back on but it always did. Replaced MAF, no improvement. Started doing research here and proceeded to replace spark plugs and AOS. Problem still persisted. Went back to the shop and they put it on a smoke machine and found a small vacuum leak from a hose that was chewed by a rodent. Things got a little better but still would set CEL and not idle smooth. Back again on the smoke, no more leaks found. At this point I think he was out of ideas and started shotgunning at my expense. Replaced both upstream O2 sensors, no improvement. Replaced MAF again.

The car runs great off idle, it just idles rough and will eventually set the light. I recently moved a few hours away from the old shop so I'm a bit on my own. What next?

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Steve,

I've posted here once already. Think I' have solved my problem and this may work for you as well. Check your oil level. Mine was above the MAX level on the daskboard uage so I tokk out a Qrt of oil (it's 1.6 Qrts between the min & max line on the guage. Problem solved. It appears that if your oil is overfull oil can get up into the combustion chamber and these engines like to run on high grade fuel not oil. 2 100 mile communtes to and from work and not even a hicup so far.

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