Big problem after header install...Please help!!

Ok guys,

I just finished installing my MAC headers. I put new NGK TR55s in gapped at .059 and used the stock wires. I plugged the O2 simms in the rear because I am using a dual exhaust setup. We did not put the exhaust on yet, just the headers. Ok, we get everything back on EGR , etc. I fire the car up, great. Ran it for about a minute with open headers. It idled at 900rpm smooth as silk. I wanted to run it a little longer so I backed it out of the garage and ran it for about 5 minutes with a few small revs here and there. She threw an SES. So I kill it, look everything over and make sure no wires are touching. I fire it up for the third time and blah, will not turn over!! Just keeps cranking and sounding like it wants to turn over but will not. I can hear my fuel pump come on and smell gas in the front of the engine. What could it be???? I used the rear driver's side O2 sensor as the new front drivers side and kept the passenger side 02 the same. I let it sit for 15 min, reset the PCM, and tried to start it. After 10 seconds of cranking it idles at a put put rate, like 100 rpm and does not get any higher. Please help me!!!!

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'98 Silver Z28
Whisper Lid, MAC headers, Custom H-pipe/Dual exhaust, Free mods, BMR Strut brace

I wonder if the PCM is thinking that there isn't enough back pressure with no exhaust after the headers. Did you try putting the rest of the exhaust on, resetting the PCM and try starting it?? Sounds like a PITA but it might work.

[This message has been edited by RobertoZ28 (edited July 27, 2002).]

I just realized, if you arent using the Y pipe, and the O2 sensor is close to the header exit, you can get some air into there and the O2 will read very lean, causing the PCM to dump fuel, which would account for both the hard starting and and the fuel smell you get.

By the way usualy the terms cranking and turning over refer to the same thing, the engine spining when the key is turned. Im assuming that you mean the car will turn over but is hard to start. if thats not what you meant, you can probalby ignore everythign I said

[This message has been edited by Freak (edited July 28, 2002).]