996 w/997.1 transplant; can't pass smog...

Hey All, I'm at my wits end, maybe someone can think of some avenue I haven't explored yet... CA SFBay Area car...2002 996 C4, 70k miles when the IMS blew, 81k on her now. We really love the car... 996 motor died - IMS Failure - so I finally sourced a 2007 997.1, took me almost two years to win a car at CoParts auction... $12k. My daughter and I transferred over the motor. Had some teething problems, we both learned a whole lot about Porsche cars during the project... (997 injectors are different than 996...) We got it running fairly well in June. Definitely runs a little rich but runs strong with no rattles, hiccups etc. Took it out of state and racked up almost 10k on it. CEL popped on the initial cold start but diagnostics showed an SAI failure so didn't really sweat it. If I reset the CEL when the motor is hot, it sometimes might not come on for several hundred miles or until I do a cold start again. Anyway, now back in sunny CA and I cannot figure out how to keep the CEL from turning on. I need to get it smogged and it won't pass with an active CEL. I've done the recommended drive cycle many times but no luck, can't get it clear for long enough to get the smog test completed. 997 has an onboard-the-engine SAI pump whereas 996 has a separate one. I hotwired a 40Amp fused ground for the SAI from pin 20 on the engine loom and the pump can be fired up by computer but it won't turn on as part of the normal cold start process. I had it at BRRacing earlier this year for help, they were the ones who told me about the injectors being different...great help but I'm hoping to find an indy closer to home - mid peninsula or SF possibly. Anyone got a lead on a good dependable indy shop around here? I've pulled the alternator, looked at the onboard pump and it's connections and as far as I can tell (without pulling the motor again), all of the smog hoses are connected where they should be. So, here's where I'm at... And I have to say, pulling the motor is not at the top of my list. These cars are a pain to work on and pulling the motor in a home garage was quite the challenge, although I do now own all of the specialty tools to do the job... Option One : Pull the motor, disassemble all of the 2007 smog crap and put all of the 2002 smog crap on this 2007 motor, then re-install the motor and hope for the best... I did pull the alternator to check but it'd be much easier to strip and see all of the smog crap if I take the inlet manifolds off...and easier to modify whatever to go back to the 2002 setup... Option Two : Pull the motor and sell it (~$10k), buy a Chevy V-8 (~$10k), buy basic Renegade parts (~$5k), put it all back together and hope for the best... I know there's a group on here who are shaking their heads at the thought of the V8 but the car is already an "outlaw" so maybe why not?... Option Three : Sell the car out of state - KBB says its worth $18k to $20k. Add more $$ and look for another (much younger) one with no IMS issues. I do have a ton of 2007 parts I'll be putting up for sale here soon so that'll also help to offset some of the costs involved. I also intend to go to an active suspension setup as part of this process if we keep her. Any leads on a mid-peninsula or SF shop that might want to help me negotiate this next part of the project? Be nice please, I'm a tad tender at the moment... I could use some constructive help rather than opinions...

About two years ago Dundon motorsports did a 997.1 3.8 swap into my 996.1. this is even harder than your upgrade and I have not had any CELs. I would contact Charles Dundon and see what he thinks....he is super helpful. ​​​

Have you pulled the codes that you are getting? If you post them here, it might help us help you. Also, I read in this thread and your other one that you swapped 996 injectors into your 997 engine. Why? Did you move the DME (engine computer) from your 997 into the 996?

Are you running an 996 engine management on a 997 engine? Any of the 996 accessories and sub systems made it onto the 997 engine?

Dundon can help...Any parts like seats left from the 997?

From my reading, to be confirmed by the poster, he swapped a 997 engine into the 996 body and kept the 996 engine management system. The swap for the 996 injectors is because they 996 ECU is probably controlling its injectors differently than the 997 injectors especially if the flowrate is different. He is getting a Secondary Air Pump malfunction CEL every time he does a cold start or if he keeps driving it all day and it will come up at the end of the day when the ECU does its routine self-test while the engine is hot. There is something I don't understand about the 40 amp fused ground thing. If this were my experiment, I would pull the engine and swap ALL the secondary air injection hoses and pump from the 996 to the 997 engine. The 996 ECU is expecting that, and is operating under that expectation and the 997 SAI components are not the same at all. That would be the easy thing to do.

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I think yelcab is exactly right and where similar issues we ran into and had to correct. I vaguely remember we had to do something with fuel injectors as well and that maybe even the ECU had to be swapped but I may be remembering wrong which is why I would call Dundon...he has been there and done that successfully.

I'd want to run the engine with the injectors and DME from the donor, and have it operate as designed in the 997. You're in the best possible place having both the donor and recipient vehicles. Can you please share the codes that it is throwing?

I had BRRacing look at the car awhile back and that was one recommendation they had. The 997 injectors deliver about 30% more fuel than the 996 ones. Since I’m using the 996 ECU with no changes, the car was running rich... It did smooth it out a lot although they’re a pain to replace with the motor still in the car... I have no current plans to move the 997 ECU into the 996 unless that becomes a viable solution. I do still have the 997 donor vehicle and it’s parts...

@Imo000 yes, running the original car as is, the only real part I changed was the 997 motor complete with all of it’s stock parts...

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Seems to me, you should be prepared to contact the group that helped Lowpue with his installation. But if I'm not mistaken, Dundon Motorsports had to install the M97 ECU, gauge cluster, and update wiring. That meant matching the correct engine management software as others have noted. You're running ME7.8 at the moment which as we all know is incompatible with the engine. If you still have the 997 donor car, I don't see why you couldn't use the ECU and wiring like Lowpue's install. Now, if you decide to throw in the towel, then you have two more options: Option 4: Sell the M97 engine and part out every square inch of the savaged 997 and then with that money, you can purchase a nice M96 engine for the 996. Option 5: Move out of California

@808Bill Thanks, I’ll reach out. Yes, I have all of the useable parts from the 997. The 997 seats are heated, the 996 are not, kinda planning on replacing the 996 ones at a later stage altho’ 997 seats have side airbags 996 does not so will have to figure out wiring. The connectors are different too...

@lowpue @yelcab Yes to both of you; I’m thinking that might be the best solution at the moment. I’ve been kind of dreading pulling the motor again tho... :-) I will reach out to Dundon and see if that’s what he did for you...

@NuttyProfessor My thinking is that the basic motors are the same; there’s not much physical difference between the two if any at all... The only difference in the engine wiring is that Pin 20 on the 996 is a spare; On the 997, it supplies a fused ground to turn on the SAI pump. On the 996, the connector for the SAI is wired separately from the engine loom. So the 997 motor should run fine with the 996 electronics controlling it. Option 4 is in process; I’ve stripped almost everything off it that I could and have it sitting. I haven’t started trying to sell any of it in case I need something for the 996. I should probably start selling the parts I know I won’t be using - Lobster claw wheels, radio, nav, doors, trim, etc... Option 5 was a non starter 30 years ago. I dragged my much better half here all the way from Ireland and she’s never gonna leave!!

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LOL on option 5

@lowpue email sent to Dundon. I’ll post up when I hear back... Thanks!!

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I'm not an engine builder and so maybe someone here that has taken Jake Raby's engine class can chime in, but while it may seem they're very close in design, inside on these engines is another story. For example, Porsche increased the displacement to 3.8L for the Carreras. That meant a larger bore and stroke which translated to higher HP numbers. While the two engines used similar "VarioCam+" systems, timing on the newer M97 was modified to support the increased HP and torque requirements. Seems to me the engine management software was working overtime to keep this engine running. I'm surprised you didn't get more codes.

Another option would be to run a custom tune. Put the car on a dyno and tune to the correct AFR. Even lean it out a little to get you through smog. I came from the world of custom tuned ECUs for Japanese cars years ago. I'm honestly not sure what's available in the Porsche world, but if this is an option it would be a heck of a lot easier than pulling the engine again.

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If CA is also scanning the ECU during the emission test then it needs to have a working OBD2 port with the Check engine light off and the drive cycle complete or else it will fail. That's how it was up here until last April when then finally got rid of the emission testing.

California does not require tail pipe testing for 2000 or later models anymore. All they do is plug in an OBD2 scanner and if everything is good, you pass.

@NuttyProfessor my 07 motor is a 3.6l and is pretty identical to the 02 at least on the outside. Ancillary parts are all identical. I don’t believe the 997.1 motor is all that different mechanically to the 02 996 motor. A ton of the parts on the 997 have 996 part numbers...

@z driver 88t @Imo000 @yelcab Yes, CA is simply a plug in now, no sniffing... they do a visual of the engine bay to make sure nothing looks amiss, check the dash to make sure the CEL is not on and that’s pretty much it. Pass or don’t pass... While in this particular case it’s a pain, I do think our relatively clean air is worth having ...

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They are supposed to check your timing, the presence of a correct cat converter and any exhaust modification. Anything weird and you fail the visual inspection.

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We've already determined your M97 has a different SAI pump, right? And, we already determined the fuel injectors are different, right? Are the scavenge pumps different? Does one of them have a brake booster on them? The M96 doesn't have that. Thanks for clarifying what M97 engine you're implanting. I still think there are some notable mechanical differences between the two engines even though they share a lot of the same parts and have the same displacement. There wasn't a tremendous amount of power jump between the M96 3.6L and the M97 3.6L, but enough of a difference in engine management to cause the issues that you're experiencing. Seems like you got some good advice here on the forum. Hope you find a solution.

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That's what I did! Mike

@NuttyProfessor I don't believe the oil pumps are different between the two motors but to be honest, I didn't really look hard at them. I will tho... Yes, got some great info here and have done throughout my swap process so thank y'all for that... I'll try to get in and under the car tomorrow and look for those differences you mention...

@Rdrcr as I said earlier, the much better half is glued into where we're at so no chance of that...

In my opinion, you are just shooting in the dark unless you use a code reader to pull the specific codes and systematically troubleshoot them. Everything else here is just a guess. A CEL could even be for some unrelated reason, but you won't know until you pull the codes.

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lowpue, in my opinion, you are in a slightly different boat going from the 996.1 to the 997.1. There is a lot more work involved in that swap, as I understand it. The 996.2 and 997.1 are much closer from a wiring, engine management, and fuel system perspective. No doubt Dundon can help, but are they likely to share this information with someone who isn't a paying customer?

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You never know unless you ask. It's worked for me although I did offer upfront to pay for a little "tech advice" and was given (not Dundon) it for free.

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You are absolutely right....my car was a much bigger job since I also had to move to .2 cluster, HVAC, ABS, etc....so the way I figure, if Charles Dundon can figure my car out, colmfmurphy's car should be a piece of cake for him. And knowing Charles, I am sure he would be willing to help regardless of whether you are a customer or not, since that is exactly how I became a customer...I will say email though is not the best way to communicate. :-) I will ping him.

Check your combi valve. If this is faulty it will throw a sai code. I can not tell on my engine if there is a vac port but if there is you can test it with a mighty-vac to see if it can hold vacuum. The porsche dme is very adaptive. However, if I recall correctly, Charles mentioned to me it would be harder to swap a 997 motor into a 996 3.6 car bc of the differences in the vario-ram. I would try to find a 996.2 3.4 Ecu to swap in if the combi valve isn’t your issue.

Any other problems to swapping a 997 engine into the 996? Is it a good option after the M96 engine blows up?

I don�t think I saw it suggested yet. I think if you get the ROW tune on your car it will ignore SAI codes and not trigger a CEL.