Engine runs bad when cold

[kskertchly]

I'm extremely frustrated with my 2001 Boxster S. It’s a long story but I’ll try to make it short.

I bought the car 2 years ago for a decent price knowing it had a few issues, thinking I would be able to fix them. One of these issues is the engine running very rough when cold. From a stand still, if I press on the accelerator more than half-way during the first 10 minutes of turning the car on, it will lose power and backfire. It does this even in neutral. When the engine is warm, all of these issues go away.

I took the car to several different shops, and none of them could fix it. They ran smoke tests to check for vacuum leaks, checked fuel pressure, replaced the MAF, temp sensor, AOS, spark plugs, ignition coils (most of the parts from Pelican Parts ). One of the shops discovered it had hollow catalytic converters, and that the ECU might have been tampered with. I sent the unit to ecudoctors.com and they replaced it with a new one. After I installed the replacement, the car runs better than ever when the engine is warm, but still stalls when cold.

I don’t know what else to do. Could the hollow catalytic converters be causing this? Anything else I should check? I have spent what I would consider an inordinate amount of time and money trying to fix this and I still can't get it to work properly. My excitement about having this car has almost disappeared now that it's turned into a money pit

[stealthn]

Could the hollow catalytic converters be causing this?

Yes, get some donors from a junk yard and throw them in to see if it goes away

[bell]

Its not necessarily the hollow cats but the signals the 02 sensors are sending to the dme, on some of the exhausts I've done we installed ”mini-cats” which essentially are tubes which the 02 mounts into...... There is some info out there on them....

Do you have any info as to what the adaption numbers are doing at idle range?
It sounds out running too rich at startup (assuming its backfiring out of the exhaust), this could be a result of the 02s, secondary air valve stuck open (or closed)......

Are you getting any misfire codes when it ” runs rough”?

[kskertchly]

I don't have the adaptation numbers, but I'm not getting any codes.

I told the ECU guys about the hollow cat issue so I think the programmed it accordingly. According to them: "We did what we call a ROW conversion on your ECU where the 2ndary Air Injection is turned off and the 2post cat O2 sensors are ignored".

It may be important to add that I bought the car in Mexico, so I guess it's a ROW version. I looked under the car, and if I'm not mistaken, it only has what would be considered the secondary cats in the US version. Is this expected or did the previous owner do something shoddy? If this is normal, would it be a valid test to remove the catalytic converters and the remaining part of the exhaust to see if the issue persists?

[faverymi]

Im running catless with no issues. Possible.....

I had the secondary air valve going on my bmw and was behaving just like the way you describe with no codes. Simple fix. And I cleaned the throttle assembly while there.

It seems that you are getting close to the problem. Good luck