Engine dies with AC on?????

[JakeWens]

I have a bone stock 2010 Explorer with the 4.6 in it. I recently put all new lifters, rockers, cams, timing chain and all the other associates goodies on it as a rocker froze and wore the cam out. Since getting it done, I’ve had an intermittent problem that has now turned into a regular problem. When I drive it with the AC off no issue, but when I turn the AC on it will kill it/stall it. At first it only did it if the AC was on and I stopped whether it was at a red light or in a parking lot. Now it does it any time the AC is on, I was just driving down the interstate and it shook the whole truck like i hit a wall and then shut the engine off. Any ideas as to what this could be? I tested it 3 times the other night with my snap on scanner hooked up and it doesn’t throw any codes or put any in the memory banks. I’m super confused! TIA!!

 

[J_C]

First guess would be that your A/C compressor has failed, either seized now or getting nearer to doing so. I'd carefully examine the belt too, in case it's been shredded as a result.

Having done all that work to the engine is a variable I'm not taking into account, because it seems to run, drive and idle okay without A/C on, right?

My '98 4.0L SOHC had an issue where it idled rough when the A/C compressor kicked on, due to a dirty/sticking IAC valve, but it never killed the engine and that was only noticeable at idle. I'm only mentioning it in case someone else has the same problem and finds your topic... even though that's not likely to be your issue.

 

[Mbrooks420]

I agree, check the compressor clutch. You can get a short belt to bypass for the time being (ac usually works with the heat in most settings).

 

[Josh P]

I was just driving down the interstate and it shook the whole truck like i hit a wall and then shut the engine off.

I've never had a belt that would not slip when an A/C clutch, alternator or mechanical engine fan clutch failed and the engine was spinning faster than an idle. I'm probably the lone nut way out in left field but it sounds electrical to me and the issue/short etc shows when the A/C is on.

 

[J_C]

^ Guess he could unplug the clutch (in case it's shorted) to see if the issue still occurs, but I would expect the fuse on it to blow before anything else happened.

 

[Josh P]

^ Guess he could unplug the clutch (in case it's shorted) to see if the issue still occurs, but I would expect the fuse on it to blow before anything else happened.

If the A/C circuit energized something in the pcm, it may not draw enough current to blow a fuse. The top end of the engine was worked on, so the wiring was disturbed. It may take hitting a rough bump in the road or a specific song to come on the radio to replicate.

 

[J_C]

It's worth checking the wiring for sure, but I'm doubting that energizing the A/C would cause the PCM to change any parameters, except to kick up throttle at idle to keep it smooth, and the A/C clutch cutout at startup and at full throttle for max power (both of which would just keep the clutch from engaging during that event). If the pressure sensor wires were disturbed, it should only affect A/C operation.

Then again it's a 2010, Ford has had a few years to work on mucking things up, but if it were some A/C pressure sensor wiring fault, I doubt that would kill the engine... in a way that seems more like it's excessively bogging down, and has gotten worse. IMO if the compressor isn't seized, it will very soon.

 

[Josh P]

It's worth checking the wiring for sure, but I'm doubting that energizing the A/C would cause the PCM to change any parameters, except to kick up throttle at idle to keep it smooth, and the A/C clutch cutout at startup and at full throttle for max power (both of which would just keep the clutch from engaging during that event). If the pressure sensor wires were disturbed, it should only affect A/C operation.

Then again it's a 2010, Ford has had a few years to work on mucking things up, but if it were some A/C pressure sensor wiring fault, I doubt that would kill the engine... in a way that seems more like it's excessively bogging down, and has gotten worse. IMO if the compressor isn't seized, it will very soon.

It's just a theory. I wonder what the serpentine belt looks like? Repeated sudden lock ups would leave some indication on the rubber.

 

[J_C]

This should be easy enough to watch under the hood, with a helper engaging the AC. Put a spot of paint on the pulley if necessary and see if it spins much, if at all.

 

[JakeWens]

Thank you everyone for all the responses, I’ll be sure to check this all out and try some of your ideas tonight and report back with any findings!!

 

[JakeWens]

So I’ve checked some things with it sitting in the driveway, 1. The compressor operates as it should and the clutch isn’t locked up, 2. The belt is in great shape, no tears or shreds or bad wear spots, and 3. It won’t do it while I’m under the hood looking it at

 

[J_C]

Intermittent faults can be a pain to find. Next I'd try unplugging the compressor clutch and driving it a while to see if you can replicate the fault. In this state, the PCM will think the A/C is running and do the same thing it's been doing when you try to turn A/C on, then you see if the fault happens.

If it doesn't happen, seems like the only things remaining are the clutch coil has an intermittent short in it, or the compressor only seizes up at certain temperature ranges. I suppose there's some chance that it begins energizing the radiator fan, but I would have thought you would notice a fault with the fan independent of whether the A/C was turned on.

If it does happen with the clutch unplugged, I'd want a scan tool hooked up that is capable of showing and logging live data.

To clarify, this now happens every time you turn the A/C on while driving, or every time you slow to an idle in drive (or then park?), or only once in a while?

 

[illogical]

Did you ever figure out what was causing this? My 2010 is doing the exact same thing. Intermittent stalls but only if Im running the A/C

 

[J_C]

Did you ever figure out what was causing this? My 2010 is doing the exact same thing. Intermittent stalls but only if Im running the A/C

Check the things already mentioned in the topic. There's more than one possibility even if the end result is the same stalling of the engine.

 

[rotero8513]

Exactly the same problem on a 2009 expedition. The air conditioner shuts off the engine, even on the highway at speed. Looks like a short circuit affecting the PCM. If I remove the A/C fuses the vehicle runs perfect with no faults.