Hello all.

Some of you may know I have a 99 986 that just received a 3.4l swap. It is still using the all the old parts except for the engine itself. (ecu, injectors, headers, exhaust are all from the 99 boxster)

I have been having check engine light issues. The fault code says there is a vaccuum leak at idle. The light takes about 100 miles to come on. We have checked for obvious leaks, and replaced the oil filler neck thinking that was the problem.

Have other cars had this issue? I feel like I have run out of leads to chase. Some are suggesting an ecu reflash, but that doesn't make sense to me.

Anyone else had this issue?
Matt

 

Did you reflash the ECU to the 3.4L file?

 

no. no reflash was done. I was told this wasn't required at this point?

oddly, I have been told by several people that an aggressive reflash sometimes throws a check engine light because of engine bay temps?

 

Start with what is obviously wrong, and running a 2.5L program on a 3.4L is a big one.

 

Doc-

I sent you a pm that you can disregard.

I just found out that the 99 cars do not have field reflashable ecus. only the 2000+ ones do. So what are my options? I know a 1999 996 ecu will plug into my harness, but don't know if it would actually run start the car.

Does someone have a new chip for this ecu that has the 996 fuel and timing tables?