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Discussion Starter · #1 ·
Hello All, and than you for having me. The good news is that I've been turning wrenches on cars for decades. The bad news is they were all 60-70 era cars. New ones may be beyond my capabilities.

Some time ago, my 2012 Fiat 500 sport began idling really rough and had no acceleration. As I was taking care of my ill Dad, I didn't have time to mess with it. Things have settled down, and with Gas prices being what they are my ole' Fiat is looking like a really good option again.

The really bad news is that the window mechanism and AC have also died (Really bad for Texas summer).

One thing at at time. The diagnostics module informed me of misfiring on cylinder 4. I replaced all four spark-plugs and all four ignition coils (low hanging fruit). While I was impressed with how smoothly this went, it did not help the rough idle. It was at this time time, I noticed that these wires in the image below had been broken.

OK.....

1) Having changed the coils and sparkplugs and still seeing cylinder four misfire, what would be a next diagnostics step?

2) What is this thing in the image? The image is near the passenger-side rear of the engine compartment. I'm thinking the line could either be AC or fuel.

Sorry if this has already been brought up. Any insights would be welcome.

Motor vehicle Hood Automotive fuel system Yellow Automotive exterior
 

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That's ac low pressure switch. That's probably the cause of the issue for the AC.

The misfire - what's the code? Are there other codes accompanying the #4 cylinder misfire? Does #4 cylinder has spark? If it does, time to crack open the compression tester.
 

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Check for other codes and get back to us. Sounds to me like maybe your multi air unit is getting clogged. The filter needs to be changed every 15k-30k miles. Is it turbo? When was the last time you changed the air filter?
 

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Discussion Starter · #4 ·
Hello All:

I'd like to thank you for your rapid reply, and apologize for the delay in getting back with you.

Short answer: I confirmed spark on all four cylinders. There were seven errors codes reported: P0304: cylinder 4 misfire, P0300: multiple cylinder misfire, P0351: ignition coil 1 circuit, and P0354: ignition coil 4 circuit.

Long answer: In addition to the motor not running, the driver's side window regulator also broke. I had to replace the plastic clamp that holds the glass before I could proceed with the engine. While is seems counter-intuitive to prioritize the window over the engine, I have learned the hard way about the necessity of ventilation while working on your car during the Texas summer. While the window does work, the front part still sticks a little. I have added a little white-lithium grease in hopes of fixing that.

I also had to figure out how to test for spark on a Fiat engine. Back in my day, this was done by pulling a wire off a plug, and putting it about 1/2 a cm from the engine block. I you were feeling sadistic, you could also have your little brother hold it. That method wont work on a car with recessed spark plugs. I purchased a test kit from amazon, and figured out how to use it. As mentioned, I am seeing spark on all four cylinders. Too bad it still runs really bad. I am also smelling un-burnt gasoline when I first fire it up.

Having replaced all four spark plugs and coils (in addition to the window clamp), I am at a loss of what to check next. :(

Thanks for your input.
Respectfully
 

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Check that your harmonic balancer is tight and running straight. When i threw those codes it was a broken crank position sensor which if your car is manual is not a hard thing to change (if its automatic it requires engine removal to my knowledge as it runs off the flywheel in an auto) my harmonic balancer had lost 2 of 3 bolts and ran off track and hit the crank sensor thus rendering it useless. Not a common case but it happened to mine so check yours.
 

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Discussion Starter · #6 ·
Check that your harmonic balancer is tight and running straight. When i threw those codes it was a broken crank position sensor which if your car is manual is not a hard thing to change (if its automatic it requires engine removal to my knowledge as it runs off the flywheel in an auto) my harmonic balancer had lost 2 of 3 bolts and ran off track and hit the crank sensor thus rendering it useless. Not a common case but it happened to mine so check yours.
Thanks much. It sounds like the crank position sensor might be my last option for an 'easy fix' and I have to bring her into a mechanic.
 

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Discussion Starter · #7 ·
That's ac low pressure switch. That's probably the cause of the issue for the AC.

The misfire - what's the code? Are there other codes accompanying the #4 cylinder misfire? Does #4 cylinder has spark? If it does, time to crack open the compression tester.
I've got four codes; P0304: cylinder 4 misfire, P0300: multiple cylinder misfire, P0351: ignition coil 1 circuit, and P0354. Replacing all spark plugs and coils didnt help. :(
 
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