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Old 11-14-2008, 04:45 PM   #1
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Help. CEL won't go away after Engine Swap

I did an engine swap to a 3.4L (from a 99') after my 2002' 2.7 died.
After the mechanical was done, it drives fine, but the Check Engine Light came on. I then got the softronic software to flash my DME and it drives better, but the CEL still won't go away. I used the intake, injectors, and MAF from my boxster. Does anyone know if I should be using the ones from the 996 and is it possible?

Does anyone else know what I can do to get rid of the CEL?

Thanks,

Eric
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Old 11-14-2008, 05:51 PM   #2
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What codes are being presented?
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Old 11-14-2008, 10:22 PM   #3
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What codes are being presented?
It's reporting P1128 and P1130.
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Old 11-15-2008, 04:24 AM   #4
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I believe those codes are for the pre-cat O2 sensors on both sides of the car. Usually both O2 sensors won't go bad at the same time. I've heard this could indicate a MAF sensor problem, but I'd search through some archives to confirm that.
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Old 11-15-2008, 08:15 AM   #5
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Your car is running lean. Most often from an intake vacuum leak, bad AOS, or bad MAF.
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Old 11-15-2008, 02:44 PM   #6
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Can also be low fuel pressure or open evap canister purge valve.
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Old 11-15-2008, 04:12 PM   #7
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Originally Posted by Topless
Your car is running lean. Most often from an intake vacuum leak, bad AOS, or bad MAF.
I've checked for intake leak and we're suspecting the MAF right now. What does AOS stand for?

Does anyone know if I need to use the 996 MAF if I did the swap? I'm using the old one from my boxster right now.
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Old 11-15-2008, 04:14 PM   #8
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Can also be low fuel pressure or open evap canister purge valve.
Excuse my ignorance, but what do I do to check if its these 2 things?

Thanks.
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Old 11-15-2008, 05:48 PM   #9
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What size MAF Housing are you running. The 2.7L and 3.4L MAF's are the same part but the inner diameter of the MAF Housing is different between the two.

The 3.4L has a 3.5" MAF Housing. Get a 996 Airbox lid, cut out the MAF housing and you should be good to go.

Last edited by VRsyncro; 11-15-2008 at 05:50 PM.
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Old 11-15-2008, 08:20 PM   #10
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Originally Posted by VRsyncro
What size MAF Housing are you running. The 2.7L and 3.4L MAF's are the same part but the inner diameter of the MAF Housing is different between the two.

The 3.4L has a 3.5" MAF Housing. Get a 996 Airbox lid, cut out the MAF housing and you should be good to go.
Thanks for that. If the 2.7 and the 3.4 is the same part, then it shouldn't matter which one I use after the swap?
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Old 11-16-2008, 07:49 AM   #11
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Check the part numbers to make sure, but I believe the MAF is the same part from 2002 and up on both 986s and 996s.

Are you running a 7.8 DME?
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Old 11-16-2008, 08:01 AM   #12
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Why aren't you using the 996 injectors? Are you running the DME as a 996?
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Old 11-16-2008, 08:05 AM   #13
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Originally Posted by victoreric
Thanks for that. If the 2.7 and the 3.4 is the same part, then it shouldn't matter which one I use after the swap?
I don't know if it's true that the housings are different sizes between the 2.7 and 3.4, but if it is, that may be part of the problem. The MAF only measures air speed, to convert that into mass flow, the DME needs to know the size of the tube that the MAF is sitting in. If the 2.7 and 3.4 use different diameter housings, and you don't have the DME software matched with the right housing, it will be mismanaging fuel flow.

If the DME is programmed for the smaller housing and you are using the larger one, the computer is calculating a lower mass flow than you are actually getting and the car will run lean.
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Old 11-16-2008, 08:09 AM   #14
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Quote:
Originally Posted by victoreric
Excuse my ignorance, but what do I do to check if its these 2 things?

Thanks.
PM sent.............
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Old 11-16-2008, 09:49 AM   #15
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Why aren't you using the 996 injectors? Are you running the DME as a 996?
I don't know why, but I guess I should be using the 996 injectors then? The DME was the original one from a 2002 boxster, (7.2?) but then I flashed it with Softronics conversion file so I don't know what it is now.
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Old 11-17-2008, 07:51 AM   #16
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Caveat- ( I have never made this swap before) but it seems to me that if you have 996 displacement you also need a 996 MAF housing, 996 injectors and 996 DME software so everyone is on the same page.

I have more questions than answers at this point. Tholyoak is our resident motor swap expert as he has done many 996 conversions. Probably need to inventory all things on your car and look him up to sort this all out. Custom DME programming is probably the way to go on your car since the intake/displacement/exhaust no longer match any stock setup.
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Old 11-17-2008, 10:30 AM   #17
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As I stated on Renntech, you need to contact Scott Slauson at softronic and find out how the mapping was done. This will dictate what MAF is needed. The 996 injectors are the same as the boxster. Without knowing how the 7.2 was remapped to run the earlier motor, everything else is just guessing. My only recommendation would be to ditch the 986 intake manifolds as this will restrict the breathing of the 996 motor.

-Todd
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Old 11-17-2008, 09:50 PM   #18
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Originally Posted by tholyoak
As I stated on Renntech, you need to contact Scott Slauson at softronic and find out how the mapping was done. This will dictate what MAF is needed. The 996 injectors are the same as the boxster. Without knowing how the 7.2 was remapped to run the earlier motor, everything else is just guessing. My only recommendation would be to ditch the 986 intake manifolds as this will restrict the breathing of the 996 motor.

-Todd
Ok. So when you say ditch the 986 manifold, then does that mean to use the manifold from the 996?
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Old 11-19-2008, 01:24 PM   #19
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Yes, that is correct.
It isn't just swapping the plastic part either. The 996 manifold consists of the upper plastic component that bolts to the aluminum intermediate manifolds that in turn mount to the cylinder heads. The boxster plastic intake bolts directly to the cylinder head. To use the 986 fuel rails with the 996 manifold the mounting tabs for the fuel rails to the manifold need to be modified in position and height.
In order for the taller 996 intake to fit, both ends of the engine/trans system need to be lowered by ~1".

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Old 04-06-2009, 10:36 AM   #20
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Where can I find a 996 sized MAF housing?

Quote:
Originally Posted by victoreric
Thanks for that. If the 2.7 and the 3.4 is the same part, then it shouldn't matter which one I use after the swap?

I'm wrestling with the same problem right now. Does anyone know the exact inside diameter of the 996 MAF housing? I believe it is 80mm or maybe 82mm?

Does anyone know of a source for a generic MAF housing that is the same size as the 996 or a 996 airbox lid that I can buy and cut the MAF housing off?

Thanks!

George
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