Ok vehicle experts, what's wrong with my car...
Long story short, here were the original issues...
1: Check engine light was on.
2: Got messages for "check fuel cap" (I couldn't completely fill the car up with fuel) and "check charging system".
3: Sometimes the AC would blow cold air, sometimes not. It was random.
4: Car would have hesitations and stalls at low RPM, like when I was turning, or accelerating after being stopped at a light. Almost felt like there was no fuel getting to the engine, or maybe there was an air flow issue. One day it stalled out completely going to the office, and I had to turn it off and turn it back on in the middle of the road.
So, I went and got it checked out, and as it turned out, the alternator was overcharging the battery. So, I got a new alternator. That seemed to fix everything, and it has turned out to completely fix the "check fuel cap" and "check charging system" issues. But not the others. The next day, I was having some of the same issues again...
1: Check engine light is on.
2: Slight hesitations, though nowhere near as bad as with the bad alternator. No more complete stalls.
3: AC sometimes blows cold air, sometimes it doesn't.
So, I took it back, and they ran another diagnostics check, and it said I needed new O2 sensors and a new mass air flow sensor. Sounds right...I thought an air flow issue might be the trouble anyway. Also, recharged the AC, filled with Freon, also got the radiator cleaned out totally with brand new fluid (I know that part of it needed to be done). Another $700, after $400 for the alternator.
So I get that done, and everything seems to be working fine. The check engine light is not on. The AC is blowing really cold air. Don't notice any hesitation. Sweet! It's fixed.
NOT! The next day, the check engine light is back on, the AC is sometimes working and sometimes not working, and there is still a very slight hesitation sometimes when I hit the accelerator after I slow down to turn. Not all the time, but sometimes. Nothing major, but enough to be annoying. Doesn't happen when I'm rolling at 75 on the interstate. Only when I'm changing speeds a lot around town, and even then not all the time.
I feel like I wasted money on new O2 and mass air flow sensors. I know I needed the work on the radiator and new Freon, etc. Clearly the new alternator was needed, since it knocked off the "check charging system" and "check fuel cap" warnings.
Any ideas? I feel like it's something electrical. Somebody told me it could be the smart junction box (which I think would be another grand, sheesh). I guess I'll call Shelor later and get a Ford specialist to look at it and run a more specific diagnostics test, but apparently I'm looking at a 1.5 week wait right now. Thought I'd run it by yall to see if you have any ideas.
60 Replies
E
EDGEMAN
2y
...a free (or inexpensive ~$5%) software programs for your smart phone. Have it read the codes and get back to us with the list of what it finds.
Or you can go to an Advance Auto (or Auto Zone) and ask if they give free code readings for your car.
I like having the device so if anything starts acting up, I can run the codes than search the internet for a solution.
(In response to this post by Chris Coleman)
2y
including bad O2 sensor, bad or dirty MAF, bag spark plug(s), bad ignition wire(s), bad coil(s) and last but not least, break in the air intake lines....which was the answer. Luckily I had a guy who was a true mechanic, not just a read the codes and start replacing stuff guy. He found it in twenty minutes, replaces a couple pieces of hose and boom...done.
Bottom line, none of the sensors read correctly when the air isn't flowing over them properly, and when they don't read correctly they send bad instructions to all the other parts.
(In response to this post by EDGEMAN)
2y
(In response to this post by EDGEMAN)
E
EDGEMAN
2y
...it will only do 2008 and earlier vehicles. Buy a newer vehicle and you'll need to buy another cheap code scanner.
Next I went with the Bluetooth OBD II dongle and an iPhone app because whoever does the software will continue to update it. (Not to mention the dongle and the software together were half the cost of my original code reader.
(In response to this post by Major Kong)
2y
Granted, yours is an older vehicle and there certainly could be a leak in the system somewhere that isn't worth the cost to chase down and fix. But A/C is a closed system and theoretically shouldn't need topping off.
Beerlady's A/C was being wonky this past spring. Sometimes it worked. Sometimes it didn't. No obvious trigger and I couldn't find any problems poking around. Turns out the problem was TOO MUCH Freon. Now, I've done all of the service on her car so I know I didn't do that. Near as I can tell a "helpful" dealer mechanic must have done something when she'd taken her car in for a recall replacement a year or so ago. But too much Freon means too much pressure in the system, and that can cause it to behave erratically.
(In response to this post by Chris Coleman)
2y
stalling. Part of the evap system
(In response to this post by Chris Coleman)
2y
Seat it and a couple of fillups would turn it off; until it was 5 problems.
My AC got warm and it was the radiator that needed replacing.
Go figure!
(In response to this post by Chris Coleman)
E
EDGEMAN
2y
Hard to get a good seal if the gasket is worn.
(In response to this post by TomTurkey)
2y
Haven't gotten that notice in years. 🤦♂️
(In response to this post by EDGEMAN)
E
EDGEMAN
2y
...it solved the problem. It got to the point where I would get the fault almost every time I refueled. I would have to remove the gas cap, then screw it back down even harder to get it to go away. A new gas cap was the answer.
(In response to this post by TomTurkey)
Spit on them spark plug thangs!
(In response to this post by Chris Coleman)
2y
The they are really problematic on Asian vehicles especially Infiniti. Best to just ignore if you can.
(In response to this post by Chris Coleman)
2y
...fuel efficiency, as they help the PCM adjust fuel trims. But I believe the post-cat O2 sensors, however, really only help monitor catalyst efficiency. A bad catalytic converter won't affect engine performance (unless it's clogged), so replacing the downstream O2 sensors probably doesn't really provide much "bang for your buck".
(In response to this post by GreenvilleVT)
2y
(In response to this post by BobG)
Depends why the check engine light is on. That’s easy to determine with a
cheap code reader. That’s why modern cars have 1000 sensors.
Hesitation is possibly a vacuum leak, or maybe the throttle body controller (maybe even the throttle body sticking).
A/C on and off is either a compressor clutch not engaging due to a short or other intermittent failure, or the lines leaking. If it worked fine after charging and then didn’t, it maybe a leak. If it seems like it’s working at 80 degrees but not at 90, that just seems like low Freon.
Another remote possibility is your AC compressor or pulley going bad and it’s putting an extra load on your engine to turn. It doesn’t matter when your opened up at 75 mph, but when your idling it takes a little extra hp to get the engine rpm up because of the drag of the AC.
(In response to this post by Chris Coleman)
2y
...the check engine code(s)? Knowing that information is paramount to being able to troubleshoot this on your own. If you don't know the codes, I'd highly recommend purchasing your own OBD II reader...there are tons of inexpensive options that allow you to pair the reader with a smartphone using a Bluetooth connection and a number of free apps available. You plug the reader into your OBD II port (usually located somewhere under the dash) and pair it with your phone, and you should be able to see/clear codes. I would not clear any codes until you have made repairs.
I think vatechcowpatty is on the right track. My first thought was vacuum leak...I'm not a Ford guy, so I don't know how that era Mustang is set up, but I do know that I once had a vacuum leak on my '01 Ram truck that played havoc with the HVAC system. The control that changes the airflow from floor to vent to defrost is controlled by engine vacuum, so depending on the engine RPMs and load, the vacuum would change and would randomly cause the HVAC air to start blowing out of different vents (i.e. - it would switch from the dash vents to the defrost vents or vice versa). I don't know if that type of issue would cause the AC compressor to shut off, but I do think that's a possibility, particularly if the hot/cold air blend door is actuated by engine vacuum, also. Otherwise, I suspect a refrigerant leak as vatechcowpatty suggested. Also, it would be good to verify whether the AC compressor is turning when you are experiencing a lack of cold air. The compressor is operated by a magnetic clutch that allows the compressor pulley to "freewheel" when the AC is not in use, so if the AC is set to "On" at the dash, you should see both the compressor pulley and the compressor clutch spinning together. Sometimes the magnetic mechanism can wear out and you can smack the clutch with a hammer/screwdriver and it will engage, but you have to be careful that whatever tool you use does not get snagged by the accessory belt in the process.
As for the lack of power/acceleration, that could also be explained by a vacuum leak. If you want to try to troubleshoot that yourself, you can use a aerosol can of a flammable substance like carb/choke cleaner and spray around the intake manifold and vacuum hoses with the engine idle...if there is a vacuum leak, it will "suck" in some of the aerosol spray and should cause the engine speed to increase, which should be noticeable. Just be careful not to spray directly on something really hot like your exhaust manifolds or it could get a little bit exciting.
Good luck...let us know if you/the mechanic are able to figure it out.
(In response to this post by vatechcowpatty)
2y
of check engine lights.
Call the local Catholic church and tell them your car needs an exorcism.
(In response to this post by Chris Coleman)
2y
gives all the same codes as O2 sensors or MAF issues (rough idle, stalling, hesitation). Nothing wrong with the sensors, they are just not getting proper airflow to do their job.
(In response to this post by Chris Coleman)
2y
which is causing the other things to not operate properly... perhaps broken or ate through wires? What year is it? A lot of cars are "talking" to all of the various systems together... even my 05 Grand Cherokee does which has caused a lot of electrical gremlins that hasn't been pinpointed for years.
(In response to this post by Chris Coleman)
2y
Could even be something as simple as a messed up/broken ground.
(In response to this post by Chris Coleman)
2y
twist it back on
(In response to this post by Guy LeDouche)
N
No Clue
2y
(In response to this post by Chris Coleman)
2y
sounds like bad fuel honestly - the check engine lights come on just to let you know they still light up if there is any age on the car
(In response to this post by Chris Coleman)
2y
I'm guessing the two issues are linked somehow, but I could be wrong.
(In response to this post by bigbadbird)
2y
(In response to this post by Chris Coleman)
J
jdkhokie
2y
just on and stays on probably not the plug or coil.
(In response to this post by Chris Coleman)
2y
could do without getting reamed... we have a 12 silverado that had similar and they changed spark plugs and it fixed some things... also had a oil foul on one of the cylinders- which sounds catastrophic except they used a non fouler for 7 dollars - and it drives fine... only a guess
(In response to this post by Chris Coleman)
2y
fuel injector cleaner like Seafoam with your next tank of gas. It works for my older cars & boats. Your AC may draw from the same as the spark plug cables, which might have been eaten by the racoons under your hood. ;)
(In response to this post by bigbadbird)
2y
the horror
(In response to this post by Vtskier1)
2y
I've read about quotes of $1,000 or more. Apparently some of them are hard to get to and it's very labor intensive, which drives up the cost.
That said, I don't remember the last time I had mine replaced, haha. So it's something that needs to be done anyway.
(In response to this post by bigbadbird)
2y
(In response to this post by Chris Coleman)
2y
Granted you need a deep socket wrench to reach them, but in my car you just have to take the valve cover off.
(In response to this post by Chris Coleman)
E
EDGEMAN
2y
The front three plugs are a piece of cake, but you have to remove the intake manifold to reach the back three.
That's why if you buy a car with a transverse engine (FWD style), recommend stick with a 4-banger...lol Longitudinal engines are so much easier to service...for everything.
(In response to this post by IV_Hokie12)
2y
(In response to this post by IV_Hokie12)
2y
(In response to this post by Chris Coleman)