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peterpete190, Technician
Category: Audi
Satisfied Customers: 24199
Experience:  Auto Technician with more then 17 years ecperience.Past ASE and other certifications.
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Audi Misfire with Cyl 4 And Car Shaking Badly.

Customer Question

Audi has misfire with cylinder 4. I changed the spark plug, ignition coil and fuel injector, but the car is still shaking badly between 1500 and 2000 RPM's.
The car has completed 200,000 miles. Cleared codes but number 4 keeps coming back. Pressure test 120 lbs.
What has to be done?
Submitted: 9 days ago.
Category: Audi
Expert:  peterpete190 replied 9 days ago.

Hi my name is ***** ***** I will be happy to assist with this today.In some cases I may need more info to assist better.I apologize for any delay.

Did you do a compression test on all cylinders and if so were all at 120 psi?

Let me know so we can continue,thanks Pete.

Customer: replied 9 days ago.
Not at this time
Expert:  peterpete190 replied 9 days ago.

O.k.,if your compression is 15 psi lower or more then the rest on cylinder 4 this can indicate a compression issue.I have seen 15 psi difference cause a misfire and had seen that the cylinder head valves were the issue.Let me know what you come up with here.

Thanks Pete

Customer: replied 9 days ago.
All the rest of the cylenders at the same psi, but 4 plug is wet.
Expert:  peterpete190 replied 9 days ago.

Have you tested to see if the #4 injector is being held open.It should have a pulse signal to operate it.Usually the injector will have power with the key on and then a ground pulse (off/on signal) when cranking over or when running.If it has a solid power and ground signal with the key on this is holding the injector open causing the cylinder to flood out causing this issue.This can be caused by a fault with damaged or shorted injector wiring leading from the computer to the injector or an issue with the computer itself needing replaced.

If this is o.k. let me know.

If more help is needed, use the reply tab to continue our conversation. If no further assistance is needed, kindly rate my service,your 5 star rating is appreciated.You can rate at any time and we can continue to work on your question as this will not close out your question.Keep in mind in some cases it can be difficult to fully diagnose or help repair your vehicle without seeing it and I work on delivering the best possible answer from what I see to work with.

Thanks Pete

Customer: replied 9 days ago.
Ok, Pete. Thanks for the FYI. I know at 200,000 rounds many vehicles are ready for help or junk. I appreciate your time.

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