CEL from HEL

[986Rick]

Well, I've scanned the forums for specific help on this, and while I've found some topics that were close, nothing really has lead to a conclusive "AH-HA!"

I have a MY 2000 3.2 Boxster S, which is exhibiting the following behavior.

Symptoms:

1. Rough “starting idle” – Car occasionally has a “bouncing idle” on cold start (650-1100 RPM)

2. Throttle hesitation – Push the pedal, you get a kick, then a brief fade, then another kick that stays there. It’s like the throttle fades for a fraction of a second, then kicks back in.

3. Persistant CEL (no surprise there)

Diagnostics:

I hooked up the car to my Durametric several times. I consistently get

P1126 Porsche fault code 356 - Multiplic. mixture adapt. lower load range B.1:

P1133 Porsche fault code 358 - Multiplic. mixture adapt.lower load range B.2:

Along with the above codes, I usually get one of the following two codes, but *never both at the same time*:

P0102 Porsche fault code 115 – Mass air flow sensor below limit value

P0107 Porsche fault code 299 - Ambient pressure sensor below limit value

What is happening feels like a vacuum leak. Last night I ran the engine and probed around with propane which should increase RPMs if it’s sucked into anything on the inlet side. I probed the vacuum line, oil separator, and all the major lines on the inlet manifolds.

Nothing.

I’ve also disconnected battery, and cleaned the MAF. Seemed better for a while, but the behavior came back.

The only thing I haven’t done yet is to disconnect the MAF, reset the DME, and drive the car around for a while to see if it behaves better. I intend on doing that on my lunch break today.

The question is, has anyone else ever seen this? Any suggestions on direction?

I don’t mind buying a MAF, but I don’t want to buy it and find that I never needed it to begin with…

If my understanding of what others have done here is right, I most likely have a bad MAF. The oddball is that P0107 code that the bad MAF code alternates with, which, so I’m told, may mean my DME is bad.

The car definitely acts like there is an issue with getting too much air (similar to when my vacuum bleeder line had a hole worn in it by the airbox), but I’ll be damned if I can find a leak anywhere…

Thanks guys.

-Rick

[Chris_in_NH]

"The only thing I haven’t done yet is to disconnect the MAF, reset the DME, and drive the car around for a while to see if it behaves better. I intend on doing that on my lunch break today."

yeah, give that a try and let us know how it goes. when i did this to my car, the rough running/bucking/misfiring stopped instantly. it was like the car was brand new. i hope it goes as well for you.

[RFM]

I agree with Chris in NH.

[986Rick]

yeah, give that a try and let us know how it goes. when i did this to my car, the rough running/bucking/misfiring stopped instantly. it was like the car was brand new. i hope it goes as well for you.

Just out of curiosity, what did you end up doing to fix it permanently?

Thanks,

-Rick

[986Rick]

Unplugged the MAF, reset the DME, and drove it like I stole it.

She runs like a whipped horse (fast and furious--like she should).

The ODB codes that came back after the drive (predictably) were:

P0102 Porsche fault code 115 - Mass air flow sensor below limit value

P0112 Porsche fault code 124 - Intake air temp. sensor below limit value

Sounds about right for an unplugged MAF.

Sitting in the car now. she's idling at a steady 600-650.

Sounds like MAF or wiring then, I take it?

-Rick

Edited February 27, 2008 by 986Rick

[wvicary]

Replace the mass air flow sensor, I've cleaned loads of them and never had any long lasting results. Let us know how it all turns out.

[tXster]

I had similar symtoms on my '01 S without your CELs, I replaced my air filter, MAF, and cleaned the throttle body, would run okay for a awhile, then right back to irratic idle. Tried to find any sign of a vaccum leak using a similar method as you with no success. Car would run rough and idle would bounce between 650 - 1100 RPMs. Just by chance I was hunting for a buried leak when I bumped one of the rubber sleeves ahead of the throttle body. I heard a gaping inhale, come to find my leak was a slit under the clamp that was holding the sleeve on. Ordered a replacement sleeve, installed, and problem solved. Keep searching, could be buried like mine was.

[Chris_in_NH]

yeah, give that a try and let us know how it goes. when i did this to my car, the rough running/bucking/misfiring stopped instantly. it was like the car was brand new. i hope it goes as well for you.

Just out of curiosity, what did you end up doing to fix it permanently?

Thanks,

-Rick

i bought a new MAF. no problems since replacing it.

glad to hear that your car ran well after de-MAFing. just pick up a new MAF and you'll be all set.

i think http://www.autohausaz.com has the lowest MAF prices these days.

[986Rick]

yeah, give that a try and let us know how it goes. when i did this to my car, the rough running/bucking/misfiring stopped instantly. it was like the car was brand new. i hope it goes as well for you.

Just out of curiosity, what did you end up doing to fix it permanently?

Thanks,

-Rick

i bought a new MAF. no problems since replacing it.

glad to hear that your car ran well after de-MAFing. just pick up a new MAF and you'll be all set.

i think http://www.autohausaz.com has the lowest MAF prices these days.

Thanks, Chris...it does indeed look like the MAF was it. Expensive part with easy access vs. a cheap part with harder access...oh well :-)

Autohaus does indeed seem to have the best price. I just scoped it out this evening...$247 for the eGas version. Glad that it looks like I finally will have it resolved.

I'll close out this thread once I install the new MAF and verify that it fixes the problem.

-Rick

Edited February 28, 2008 by 986Rick

[986Rick]

I had similar symtoms on my '01 S without your CELs, I replaced my air filter, MAF, and cleaned the throttle body, would run okay for a awhile, then right back to irratic idle. Tried to find any sign of a vaccum leak using a similar method as you with no success. Car would run rough and idle would bounce between 650 - 1100 RPMs. Just by chance I was hunting for a buried leak when I bumped one of the rubber sleeves ahead of the throttle body. I heard a gaping inhale, come to find my leak was a slit under the clamp that was holding the sleeve on. Ordered a replacement sleeve, installed, and problem solved. Keep searching, could be buried like mine was.

Thanks tXster...

I flooded that engine compartment with as much Propane as I felt comfortable with (read: If the car sparked, it and I would have been spread about a 1 block radius).

Ok, well, not QUITE that much, but there was a clear propane smell all about the driveway.

Revved the engine, thinking the same thing you did---higher revs might open the hole--but nothing happened.

I'm going to go for the MAF for now, and see where that goes. I highly suspect it will fix it. I graphed my pre-cat o2 sensors against each other...they seem to be behaving linearly with respect to each other...at least at the extreme points of operation, so that problem went the way of the dodo (thank God). all that is left is fixing this air mixture issue. As I have *zero* hesitation on the throttle with the MAF unplugged through the entire RPM spectrum, so I'm guessing that we're on to something in that area.

I'll post what happens after I get the MAF.

Thanks again!

-Rick

PS-- There is nothing quite as fun as blowing down the freeway in your Porsche with all the carpeting and rear console gone, and only the heatshield between you and the engine. Love to hear that 3.2 scream....if nothing else, this MAF test was a blast by that experience alone...

Edited February 28, 2008 by 986Rick

[986Rick]

looks like the MAF was it. replaced it with a new one from AutohausAZ, reset the DME, and she runs like a charm. 75 miles, no CELs or pending codes.

Has a slightly erratic idle, but I haven't cleaned the Throttle body yet, so it may not be an issue.

I'll update if there are any changes.

Thanks guys.

-Rick

[tXster]

Has a slightly erratic idle, but I haven't cleaned the Throttle body yet, so it may not be an issue.

That's great Rick, glad you got it figured out. From what I understand from my dealer and experience, eGas throttles will have a slight bounce at idle, mine bounces sightly between 650 - 680 rpms. Nothing to worry about. Good Luck!

[986Rick]

Has a slightly erratic idle, but I haven't cleaned the Throttle body yet, so it may not be an issue.

That's great Rick, glad you got it figured out. From what I understand from my dealer and experience, eGas throttles will have a slight bounce at idle, mine bounces sightly between 650 - 680 rpms. Nothing to worry about. Good Luck!

Thanks, xSter. She runs like a champ. Shifts better too, now that I replaced the *totally sheared" front engine mount on Sunday. I'll have to post a picture. I'm amazed I wasn't having bigger issues than the occasional missed shift.

Downer is I now get a CEL for P0430 (Cat conversion bank 2 - exceeds limit value)

Could be bad gas, I suppose. I also looked at the seal on my Gas cap and the o-ring does look like it needs replacing, so I'll try that first. Can't think of what else it could be other than the cat actually being bad...but I never saw that cell until after replacing the MAF and the B2 pre-cat O2 sensor.

If it needs a cat I just hope that I'll just squeak in under that 8-year warrantee.

All said and done, I'm happy....she does, after all, have 100K miles as of 3 weeks ago....

-Rick

[986Rick]

Consider it solved. Today, I took Gretta down to the SMOG shop, and she passed with flying colors.

I think I can now access the engine compartment faster than a NASCAR pit crew does a tire change.

To recap, I ended up:

--Replacing the MAF (Thanks, AutohausAZ)

--Replacing the left Pre-Cat O2 sensor

--Replacing the gas cap

Can't stress enough the advice that disconnecting the MAF and resetting the car really assisted in the troubleshooting. Saved me from going down the path of chasing for a vacuum leak that wasn't there.

Chris, Loren, Xster--Thanks.

Now on to bigger, better pcar projects...

-Rick