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Old 11-15-2014, 05:27 PM   #1
Join Date: May 2013
Location: Georgetown, SC
Posts: 210
3.4 motor swap into 1998 boxster

Anyone have any thoughts??

DME is 5.2.2 from the 2.5 Boxster

Intake and throttle body is from the 996 Carrera

Air filter box is from a 987 but converted to fit in the 986

3 1/2 inch silicon piping runs from air filter to throttle body

MAF is stock from the 996 with the 3 inch 987 tub that holds the 996 MAF

MAF is located approximately 6 inches from the throttle body opening.

oxygen sensors are the stock 2.5 oxygen sensors

Finally got the motor in the car and started it up today....major mile stone.

I had my DME re-flashed with a ROW flash. Am running CAT by pass pipes with no muffler as of yet.

Put the boxster 2.5 pre-CAT oxygen sensors on the by-pass pipes.

No seats in car yet.

Motor started right up...at idle ...NO FAULTS !!!

blipped the throttle a few times and got the following FAULT CODES:









I am only guessing......... I have a bad Oxygen sensor in bank 2 (4,5,6)

Cleared faults...and again at idle, it caused no fault code. gave it some revs. and same codes as above showed up.

Any thoughts?

Pictures and writ-up to follow.

Thanks, Bob

Last edited by Reebuck1; 11-16-2014 at 04:28 AM. Reason: More descriptive title
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Old 11-16-2014, 03:21 PM   #2
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Join Date: Sep 2009
Location: Iceland
Posts: 145
If I understand what you are saying correctly, you used ROW Boxster flash for the DME. It will make the car run awfully lean with the 3" 996 MAF housing. The DME will think the engine is getting much less air than it really is and will adjust the injection of gas accordingly, i.e. the car will be running lean. I haven't studied your codes in detail, but believe you have 3 options.
1. Run with an aftermarket DME-tune from some of the reputable tuner that understands these things.
2. Re-flash with ROW 996 tune. (appropriate for the MAF house that you have in the car)
3. Run with the Boxster DME-tune and the original Boxster MAF housing.

Options 1 and 2 will understandable give you a little more power than op 3.

I believe that if you disconnect the MAF wiring, reset the codes with Durametric or by disconnecting the battery for 20 sec, the DME will revert to a "standard" mapping that it has stored and the car will actually be running a little rich, which is a much better situation, but don't run it for to long that way.
If you search this forum you will find that Byprodriver has written something on the subject.
My advise is to start up with new O2 sensors and fresh injectors if you want a smooth running, powerful engine. Don't ask how I found this out....
Good luck

There is no replacement for displacement
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Old 11-16-2014, 06:40 PM   #3
Join Date: May 2013
Location: Georgetown, SC
Posts: 210
Thanks BF I am on it and will report back in a few days.

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