If you look back at some of my other posts you will get a better idea of this problem that I have with my car. In a nutshell, my car refuses to advance timing beyond 6 or so degress until it randomly decides to kick in. I have datalogger logs to prove this weird ass symptom. The car also idles real rough, rough enough to shake my seat back and head rest so much that it vibrates loudly.

For the last two days, us central Floridians have been experiencing some nice cool dry air (thanks Canada) and as a result, my car problems have fixed themselves or at least have improved. On the first day of cool dry ~70 degree weather I found myself waiting inline at the bank drive thru teller idling perfectly. In fact, my car has idled great for everyday of this cool weather. On the datalogger, my timing looks good too. I get about 10 degrees advance, then it pops up to 20 from 3500 to redline, drops to about 15 at the beginning of the next gear and is back to 20 at redline. The car feels fast and I can finally enjoy every mod I have done.

The real question is, what is broken in my car that can be affected by this temperature change. I know our cars do not normally drive like complete crap on a hot 100 degree humid day. I have a drastic drivability inprovment with a simple 20 degree weather change. I have checked every sensor and they all check out within spec. I feel that one sensor intermittently fails randomly while driving. I have my money on the MAP sensor, but before I shell out $120 I want to know what you guys think.

-Jared
Melbourne, FL

Iceman CAI | RS*R Cat-Back | AFX Pully | Milled Head 10:1 CR | MP 60mm TB

IAT sensor might cause a problem like that. Have you checked it?

I edited to the wiki!

I checked the resistance of the sensor at several different temps and according to my Chiltons manual it is fine. The datalogger shows that the air temp is 105 degrees while cruising and about 125 while idling. If I go WOT then the air temp drops to about 95. I do have an Iceman cold air setup. I have checked every sensor according to threads that I have found by searching and according to several manuals. I think that whatever it is that is bad only decides to screw up when I am driving the car. It shows up on the datalogger as a timing problem. Another funny thing I saw this morning is while cruising at 45 mph, my timing value will just drop to -5 or -7 for a split sec, then go back to normal. Normal is around 30 degrees advance. I dont feel anything, but the datalogger shows this.

Also, when my car plateaus the timing at 6 degrees under WOT, the O2 sensor output is lean under .3 volts. When it kicks in and timing goes up, the O2 ouput goes back to normal. The sensor is new from the dealer, along with plugs, wire, and coilpack. Since I have 10:1 compression should I gap my plugs smaller? I have NGK standard heat range v-groove plugs gapped at 0.045; is there any reason to go to 0.040?

It is a little warmer today and the bad idle is coming back a little.

-Jared
Melbourne, FL

Iceman CAI | RS*R Cat-Back | AFX Pully | Milled Head 10:1 CR | MP 60mm TB

Did you test the map sensor? That could cause troubles like this with the timing and all. Or the 02 sensor could be bad, but I wouldn't think it would make the timing do that. Even new sensors can be bad out of the box.

I edited to the wiki!