sn95 Closed loop/Open loop

[RogerStout]

Alright I am going to get in a little over my head here but I have been getting some conflicting information..

What is the process the sn95 ECC uses from start up to normal operations and at WOT. I have been looking into this just to chase down a minor miss I have when cold..

is this correct..

when the car is first started, running on open loop. Reads fron MAF and Coolant sensor to get AFR. When conditions met (dont know what they are) the car switches to open loop and reads from the o2 sensors for AFR..

I have also read it quite the opposite..

My car when cold, been running 5-10min will get a miss POP POP POP on the top end.. Its will only do it once and never does it again. Idles fine and runs fine. After the first time I go WOT it quits.. will run smooth to redline from there on out..

[SK360]

Unless fords EFI systems are dramatically different from the GM systems I am used to, Open loop references the same MAF calibration as closed loop its just once the car switches to closed loop (Time or ECT based) it uses feedback from the front O2 sensors to adjust AFR via +/- fuel trims.

WOT = open loop no matter what.

[RogerStout]

That is consistent with what I was thinking, un aware of the WOT situation.. The car is untuned and has a good bit of mods so I am really lucky this is the only issue I have and really not an issue cause for the most part I dont go WOT when it cold anyway.. after its warm it does not do it..

[SAC81]

If it's definitely a misfire, take a look at your plugs. Plug related problems often show themselves worst when the car is cold, and go away after it heats up.

The EEC in the 94/95 5.0s is a bit sensitive compared to the earlier fox unit (but not as bad as it's reputation would lead to believe). You'll want tuning software if you want to get into "serious" mods for it.

[RogerStout]

I put NGK Iridium plugs in it and everyone told be they would/could cause problems. Really a minor issue but it bugs me. I will swap out the plugs with motorcraft plugs and see if that takes care of it..

[stanggt94]

For what its worth I put 8 dollar plugs in my 94 dont remember the brand. Ran good for a week then same problem your having missing when cold ran fine when up to temp. Talk to some guys on here told me to get some motorcraft plugs 2 bucks a piece never had a issue again. An ran better than ever.....