dorkman52000

Hi everybody, I just did a header install on my 88 N/A. It runs super sweet above 2K or so RPM, but if I don't give it constant throttle the RPMs drop and it dies really quickly. This was a header I had on my 87 a couple of years ago, and all I did today was take off the exhaust manifold and the two pre-cats. The main cat is still attached. I'm thinking maybe the O2 sensor, but why would it go bad in between? I checked and re-checked to make sure the O2 wire was connected, as well as everything else I disconnected, including the two wires from the ACV. I never disconnected my AFM, but I tapped on it anyway to see if there was a jump in RPMs while my friend gave it some throttle, and it seems okay.

I already did a search, and I found a thread where someone was having the same type of problem, but his car never died, and he had a steet-ported motor. Aaron put down in that thread that it was possible the TPS might be off a bit. Would this be the same for me? Again, the car runs perfectly smooth above 2-2.5K RPM, but below it shakes and just dies if you don't give it gas. Also, my car ran perfectly fine before I did the install today, so any help would be great. Thanks a lot everyone for checking this out. Please put down any suggestions if you can think of anything!

dorkman52000

bump, thanks

dorkman52000

Okay, I figured it out all by myself. I'm posting this so that in case someone has the same problem in the future, maybe it will help. I decided after much thought that the only possible thing that could be causing a problem was the ACV (air control valve). Last night after posting my initial question, I took off the ACV and realized that the gasket was not as perfect as it seemed. I think when I installed that after placing my header on, the gasket got crooked somehow and was partially blocking some of the holes for air passages.

I took off the gasket entirely and put the ACV back on the engine. Shazam! It runs, but still pretty crappy. At least it runs, though. So, since it was running around 4-6 hundred RPM, I used a piece of wire to ground that green connector to itself (by putting one end of the wire in one side and the other end in the other side), and marked with a sharpie pen the relationship between my Crank Angle Sensor and the front front engine cover. I then rotated the Crank Angle Sensor enough so that it was idling a little better. (I needed the car to get home, I knew it wasn't going to be up to par)

Today I went to the Auto Zone and bought some material for a new gasket, since I don't want to wait two days for the Mazda parts dept. to obtain one for me, and I made a new gasket based off of what was left of my old one. I just re-installed the ACV, and the car runs so much better. I adjusted the timing back to OEM specs using a timing light and now she runs just as well as before! Anyway, just thought I'd post this because apparently a little difference with that ACV and it makes a huge problem for the engine to run correctly. I'm going to get block-off plates and remove it entirely, but not right now.

Hope this helps anyone who has the same problem!

gordonrick

Thanks Dorkman. I replaced my ACV with a different one since it wasn't getting air back to the cat, but I did use a new gasket. It ran for a bit then started dying on me (similar symptoms). I'm going to double check it to make sure it is on good tomorrow. Maybe that's part of my problem.