OK, way back when I got the car its had this problem about how when it gets hot in traffic (235* or so) it misses and dies and won't start 'til it cools off. I have replaced within the past 10k miles: ECT, MAP, IAT, Fuel pump (Walbro), Opti (AC Delco), Coil, Ignition module, and the ECU got reflashed when I worked at a dealership back to a 'stock' tune, Cooling system backflushed and refilled with DexCool, new waterpump (new, not reman). When I went to reflash it it said "Unknown calibration" was currently installed so I thought some idiot put a Hypertech on it. It still misses and dies. A buddy of mine loaned me a ECU out of a '96 Caprice to try, car sounds worse and tach is off. I put mine back in. We got thinking about why its doing this and we think that the car is getting too hot. His '95 TA (Boltons, tune, and hotcam) runs at 180 all day long. We took my car for a spin and when we got back the fans were never on. I let it sit in my driveway for about 1/2 hour, the needle was a tad above the top white line almost to the red and the fans never came on. I jumped the fans on the relay and they work perfect. I jump the relay to a + source (not the bigger wire but the smaller one) and the fan turns on ONLY when the car is off, if the car is running the fan will not come on even when connected to the battery. I put everything back together and now when I start it it runs fine, then after a minute the SES light comes on and both fans run. This happens with both ECUs. I don't have a scanner that'll read a '95 but a shop that my friend owns does so I'm going to go grab it for a night to see whats going on. If any of you guys could throw some ideas out there I would greatly appreciate it.

 

Anybody?

 

Not an expert by any means, but the SES triggers the fans in a "protect mode" of sorts via the PCM. Here's a link to Shoebox's site for the schematic to trace it out. Also, LT1's are notorious for overheating if not bled properly. If it started happening after the waterpump install, that could be one reason for overheating.

http://shbox.com/1/fan_schematic_1995.jpg

HTH's

 

Bled it today, still same problem. Thanks for the schematics, definately helpful, gonna pull it into the garage in a few minutes to go over it.

 

Stock fan operation is 225* low speed and 235* high speed so 235 is not a problem if stopped in traffic. Stock t-stat starts to open at 180* and s/b fully opened by 195* or a little less. On open road air dam cools the radiator and temp should drop to 190 or so. With a/c on the PCM senses refigrant high pressure runs the fans at low speed and the temp should drop accordingly. No a/c in traffic 235 is normal. The temp control sensor on the WP feeds the PCM and controls the fans and engine operation. If your fans don't act like stated and the engine misses then it could be the temp sensor is bad (always seeing cool) . A scan of the engine temp in the PCM (not dash gauge should be done). Without a scan Shoebox has a good writeup on checking out the sensor with an ohmmeter. " http://shbox.com/1/4th_gen_tech2.html#cooling "

 

So running 180ish on the highway and 235ish in town is ok with a factory tune? My friend's TA runs 180* constantly, but he also has it tuned. So basically there's not 'running hot' problem, its just the misfire and SES light. I might change the O2s, they're original as far as I know. I haven't gotten ahold of a scantool yet unfortunately. I read that on OBD1.5 you jumper 5&6 to flash codes, I tried it and it just turns my fans on lol.

 

Jumper only works on '93 or lower with chips, You have ODB1 flash PCM. You need a scan tool or software setup to read the codes. Also your friend either has a tune or a low temp fan switch installed. Here is a manual switch setup from shoebox " http://shbox.com/1/fan_sw_diagram1.jpg "

 

http://img154.imageshack.us/img154/7666/dlcobd15lf0.jpg

Haynes books suck.

I'll just get tunercat and a cable to make em turn on lower, until then wire them so they run constantly with the key on. Don't feel like 'rigging' it to work on a switch when the ECU can do it lol.

 

Did I somehow set the computer to do this as sort of a limp-mode by connecting 5&6 on the ALDL?