Skip the auto shop - Our mechanics make house calls

Q: Misfire wont go away

asked by on

Problem started with misfire codes on cylinder 8, then cylinder 5, then random misfire. Did full tune up, replaced iac, cleaned fuel tank, changed fuel pump and filter, had vaccuum and compression test done. Checked cat and oxygen sensors. Replaced injectors with 4 hole 21lbs, cleaned fuel rail, ran great for 130 miles. Now is even worse, stumbles, no engine light but stored codes say random misfire, plus misfire on all 8 cylinders. At a loss on what to check next.

My car has 188000 miles.
My car has an automatic transmission.

A: Hi there. From your description of all that...

Hi there. From your description of all that has been done. I suspect you may have a computer problem. The powertrain control module (PCM) is designed to store a fault code in pending codes, on the first drive cycle that it recognizes a malfunction. If, on the second drive cycle, the PCM recognizes the same malfunction, the check engine light should come on and stay illuminated. The check engine light typically flashes during misfires detected. This may also be a connection problem at the PCM. Programming may also be an issue. Try disconnecting the negative terminal of the battery. Disconnect and inspect the electrical connector(s) at the PCM for signs of corrosion or loose terminals. Repair as necessary. Reattach connector(s) and reconnect negative battery terminal. The computer will have a period of relearn, idle speed, etc. This should happen with a short road test. Something else to look at would be the ignition coil(s) output. If you are unable to resolve the misfire(s), a certified YourMechanic technician can come to your location and perform an engine misfire inspection on your vehicle to help diagnose this issue and suggest any service needed.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Save up to 30%

Get a quote

What others are asking

Q: I have 3 error codes, P1784, P0731, P0732. I need help knowing what it means and how to I can fix it

All three of these codes are for the transmission and indicate you have issues with shift solenoids and gear ratio problem. Each code is a problem with a different part of the transmission and would require separate diagnostics for each...

Q: Engine shuts down suddenly, battery red warning light on

I would say the tensioner was overlooked on the last repair and the oil pressure switch may have been damaged in the repair process. I would recommend having the repairs done, but ask for the old parts to see if...

Q: Loud bang when backing up only

If the only time the pop occurs is when you are backing up and turning, then this isn't necessarily something that must be fixed immediately. Many trucks will exhibit such noises and most of the time they don't have any...

Related articles

What Causes Hoses to Leak?
While the largest part of your engine is mechanical, hydraulics plays a significant role. You’ll find fluids at work in a number of different areas. Your car's fluids include: Engine oil Transmission...
How Long Does a Distributor O Ring Last?
The distributor is part of the ignition system in your vehicle and its purpose is to route high voltage from the ignition coil to the spark plug. The spark plug then...
How to Renew Your Car Registration in Oklahoma(DELETED)
Having your car registered with the Oklahoma Tax Commission is an important part of driving legally in this state. You will need to do this within 30 days of moving to Oklahoma...