Thread: Help with misfires

Originally Posted by s7000

In that case, I'll need to double check. They look like this though...

Those plug leads look like they sould be the correct type. Try some different plugs first, standard type not iridium or anything fancy just to see how it goes.

Originally Posted by Pedro_The_Swift

The O2 sensors are like the MAF, they just dont suddenly die, the performance just deteriorates slowly over time. (unlike the crank sensor)
unlike the MAF, the O2's are easy to judge electronically,
just plug in an OBD2 wifi dongle, download the free torque app onto your phone and bingo,,
Long Term Fuel Trims below double figures, same for STFT, and all four sensors semi- static,, maybe a touch of up and down on the STFT's and nearly even bank to bank.

OK, so the dongle arrived, and first off... It was a cheapish one at $20. It seems to be working though, and here's the read out.



While I was driving the Short term and long term stayed jammed at that minus position on bank 1, while the position on bank 2 seemed to stray between +5 and -5.

So does this mean my 02s on bank 1 are shot?

Swap them and see what happens.....

Originally Posted by ballbag

Swap them and see what happens.....

I swapped them over, and the problem didn't follow the sensor...

What's weird is there's a short/long fuel trim dial for each bank in the torque app, and then also one which is just "Fuel Trim Bank X Sensor X"

Both banks in that dial seem to be reading correctly, it's only the short term/long term dials which are faulting...

Anyone with any other ideas?

All your misfires listed above are on the RHS (driver's) ignition coil pack. You state the coils and leads were replaced, so check for loose ignition leads and loose signal wire (ensure retaining clip is in place).

While you're at it make sure the idle control valve signal wire is connected properly. Fuel pump is another possibility but given misfires seem confined to one coil I'd chase that first.

just some housekeeping,, depending on how unlucky a photographer you are,, the small green light in the ACCEL guage should be present in all--- not flashing green, not live data. Should be car symbol and wifi symbol as well, wait till they all stop flashing.
$20 is fine though it took me two replacements to receive a dongle that actually worked, so theres that as well.

It could be your OBD reader.
Bank 1 which is on the passenger side and contains the odd cylinders shows that the PCM is reducing fuel - a lean command. Bank 2 shows no action on the STFT, eventhough there are reported misfires there - cylinder 3?
A misfire allows extra O2 to travel past the O2 sensor. STFT will react accordingly. There are plenty of youtube videos showing this.

Start again.
What are the current misfire codes if any. Are they still on both banks?

Concentrate on the bank with the misfires.

Bring up the O2 readings again and this time pull off a vacuum hose to introduce an air leak - does the STFT react? They should react. If not then your O2 sensors are bad - or the OBD is bad( cheap OBD readers are notoriously unreliable). If they react then move onto the energy of the spark.

You can buy fairly cheap spark testers that show how strong the spark is on each cylinder. Dont just pull off the lead and hold it against the block as this is a DIS system and you can cause damage in the windings of the coil packs. Check each pot to see if the coils can create a 1/2 inch spark - about 10KV. If the spark is strong on every cylinder then you can start to look for other evidence.
Report back when you have time.

My mistake - Bank 2 shows no real action eventhough there are reported misfires there - cylinders 2 and 8 - not 3 as 3 is on Bank 1.