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Discussion Starter · #1 ·
I have a 96 cobra with d1 etc. anyways It has been tuned with diablo chip, but I have drivability issues. When watching the scan tool I noticed the car never goes into closed loop and the o2 heaters are always on? There is no short term or long term fuel trim.
I have replaced the 02 and the temp sensor those were the 2 things I was told determined closed loop. Any ideas would be appreciated?

Also I have removed the chip from the car and it still never goes closed loop?
 

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Discussion Starter · #4 ·
Alot of Diablo dealers force the cars into open loop like that. For one it prevents the car from ever throwing 02 codes (rich/lean).

Are you positive, the PCM does not have an aftermarket tune flashed in?
Yes, stock I also had the computer reflashed today at the dealer same thing no change.

Some of those older cobra cars do weird things with closed loop (IE won't go into it) if the fuel trims are too far off.
What do you suggest I do. I have a wideband and when tunned corectly it missed really bad drivability wise wide open is always good. it is set up rich right now because it helped the missing but they told me without short terms they had to add fuel all the way across the map. right now A/F is 13.0 wide open 11.8 any help appreciate the reflash was the last thing I knew to do.
 

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Discussion Starter · #6 ·
All of the other sensors look ok when logging? Throttle Position, Coolant Temp, etc?
Yes I can watch all sensors - tp--- coolant climbs to 180-- the o2 even show up the short and long terms are just 0. there is no codes in the computer other than the normal egr rear o2's IMRC's(deleted) and these codes are only present with the chip removed.
 

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I have a 97 Cobra and some of the SCT logging data is incorrect. For example, my open loop flag does work or log correctly. The Load vs AFR table for open loop only works on about 3 loads and the other load values in the chart it just skips. There is a table for RPM VS LOAD at open loop that doesn't work right... etc... you just have to find out the bugs and work with them. I know there are a few Short Term Fuel logging items in the PCM and if your logging the wrong one it will show a "0". If your logging the correct one it will float around 1 or so in CL and when OL jump down to the commanded lamda value.... (.82, .78, etc)
 

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I have seen several 96-98 cobras fail to go closed loop because the thermactor system fails. If it is pumping air upstream, the PCM will leave the car open loop. For some reason, this usually will not throw a CEL. I will usually turn off the switch in the tune to confirm it, but you will probably just have to diag it old school.

The better way to datalog open closed loop is with Fuel Source. The open closed loop flag is not always active or accurate in a ford PCM, so we have become accustom to using fuel source. It will also let you know if you are running normal open loop or cold startup open loop (very useful).

James
 

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James is correct, if the termactor system has failed or has been removed, the EEC will stay in open loop. The thermactor can be turned off, have your tuner do so just for giggles, even if he's forced open loop.
 

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Discussion Starter · #11 ·
Sorry, for the delay car has been at paint. Thank You for the input I turned off the thermactor and instantly went to closed loop. Thanks again
 

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Also no closed loop

I have the same issue. I do have a tune on it as well, an SCT. I occasionally get a message saying it won't go into closed loop due to temperature not getting hot fast enough, or engine load issue. Tuner states that it's not in the tune but I know he did alter the fans on/off so wondering if that change to the computer has it freaking out. I do have a lower temp thermostat, maybe a 160 or a 170. New O2 sensors all around. It shows fuel trims for just a few seconds then cuts off and goes into open loop failure. I'm concerned that my fuel trims are off and may be lean or rich. I do also have a delayed warm start. 96 cobra bottom end with forged pistons/rods 9:5:1, 2003 Terminator heads, 2001 Cobra intake. Runs good but has a little miss about 3000 rpm. No other codes than the closed loop failure.
 
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