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

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

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: Potential differential problem.

It is not uncommon for the rear differential to fail on this vehicle. If you see metal in the oil then that is an indication of a bearing problem. Most of the time the differential will need to be rebuilt,...

Q: We are replacing break lines and having a hard time removing the break line clips and need to know how to remove these

The clips are removed easily by using a long set of needle nose pliers. If they are still not coming loose then use along punch and hammer to tap the corners to loosen the tab and then finish using the...

Q: Van dropping out of gear

Hi, before you replace the ECU, make sure all the related fuses are still intact and that the wires haven't been damaged. You can try resetting the computer by disconnecting the negative terminal of the battery for a few minutes....

Related articles

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...
P0052 OBD-II Trouble Code: HO2S Heater Control Circuit High (Bank 2 Sensor 1)
P0052 code definition HO2S Heater Control Circuit High (Bank 2 Sensor 1) What the P0052 code means This code is seen when the Engine Control Module (ECM) tries to control the...
P2103 OBD-II Trouble Code: Throttle Actuator Control Motor Circuit High
P2103 means there is a fault with the throttle actuator control motor circuit, likely due to a defective electrical component or part.