Good day,
I have been having some trouble with Limp Mode on my 2007 Mustang GT California Special, 85k miles, manual transmission, no associated codes. Background: Bought from private seller who had the car in England when I was stationed there. Since it was an American car it had to be outfitted with English compliant lighting which they routed through the fuse box, the car ran fine during its time in England. When I was shipping it back and had the lighting work undone and it was shipped by the military. Since then the cooling fan shorted out and I took it to a shop who diagnosed a bad engine fuse box. I have since then replaced the engine fuse box with a used ebay part (no new OEM engine fuse boxes available) and the cooling fan now works but now have Limp Mode activation. Which brings me to the current situation. My car, upon start up, is not in Limp Mode but when rev'd past 3000 it turns on the Limp Mode. I am a DIYer and I am quickly at my wits end with what to do and am hoping to save an expensive trip to a dealership that will inevitably cost me an arm and a leg just to say they can't fix it due to part availability like they did with the fuse box.
Other relevant information;
1) Car has a BAMA tune initially was 87 Oct to account for exhaust and cold air intake mods. I have tried both stock and the 87 Oct tune to see if the issue was resolved, it did not.
2) The car's cooling fan problems did not throw codes or Limp Mode under the old engine fuse box but would overheat the engine cooling system. Engine Oil temp never reached the red line.
3) I put back in the old fuse box just to determine if the new fuse box was also bad and the problem returned.
4) Battery had died while car was being worked on in the garage. I had recharged it with a battery tender and it starts up fine.
5) With a partially charged battery the engine would start and some codes would end up being thrown. They have since not been thrown under a fully charged battery. I unfortunately do not have a pic of the previous codes but these are off the top of my head so take them with a grain of salt. Evap Control sensors 1 & 2, O2 Sensor 1 & 2, and two other codes that I do not remember.
6) I only drive this car on weekends but with the problems it has been extended to 2 weeks or more and now almost never.
Other, what I assume is not relevant info, but you are the expert;
1) Car A/C compressor clutch does not engage but I am unsure whether it is the electrics or a bad compressor, but at least I know how to diagnose and fix that.
2) I replaced the tie rod ends as well as the lower control arms and had a professional alignment done on the tires.
Any diagnostic tips or ways forward will greatly help.
2) The car's cooling fan problems did not throw codes or Limp Mode under the old engine fuse box but would overheat the engine cooling system. Engine Oil temp never reached the red line.
Does this mean your engine overheated? I'm a bit confused by this sentence.
The coolant overheated and began to burst out of the reservoir but I stopped driving the car immediately. The engine oil temp never left the normal range.
Your cooling system has some kind of problem. I've never heard of coolant bursting out of an overflow. Localized overheating of the engine is a real possibility.
Your cooling system and your oil are totally different systems, did your coolant overheat?
Thanks for the insight I will test that immediately.
https://m.youtube.com/watch?v=v0U8Iyf0kk4 Watch this. You can rent a head gasket tester at AutoZone. If your coolant overheated, especially to the point where the overflow tank burst, I can guarantee that you blew your head gasket. Oil and coolant are completely different systems, unless your car is literally on fire, your oil temperature will be normal.
I was able to test for combustion leaks in accordance with the video you posted. Thankfully, I do not have a blown head gasket, the fluid remained blue, and the coolant is clear of debris. For further clarification the overflow pressure relief valve worked as intended and spewed out coolant, the tank didn't burst. I am beginning to worry that the problem is electrical. I will reinstall the previous fuse box and see if it still throws the car into limp mode with the understanding that I will not have the cooling fan being able to run. Thank you for your help in this I really appreciate it and if you have any other suggestions let me know.
I have been giving some wrong information in the assumptions given in my original post. I swapped back to the original fuse box and found that the Limp Mode did not occur. However, under the old fuse box my car will almost certainly begin to overheat again. Long story short it seems as though there might be some hiccup that is happening within the "new" fuse box.
I will double check the relays but the fuses seem to be in order. If you know of something else that would possibly put the car into Limp Mode with the new fuse box installed, I am all ears.