Cold Start Misfire 2004 Honda Pilot

[pew]

Hello,

I am getting a cold start misfire on my 04 honda pilot for several months. After it warms up, it seems to run fine. I do not get a blinking engine light. I got this car with 180K on it. It started at about 220k. I have replaced coils/plugs, replaced the TB/Valve adjustment (105k service since it was due),cleaned egr passages, fuel injectors(i know this is becoming swaptonics). I agree.. this is looking insane. Thankfully, i did this over a period of time and not one shot.

My next direction (thanks to Matt’s videos) is:

1.Test Fuel pressure(waiting for the honda fuel pressure dampener adapter):
2.Smoke Test or Propane(carb cleaner..etc):
3.Timing
4.Exhaust

I feel to get a proper diagnoses I would have to spend some $$$ on more tools. Timing light, proper smoke machine, and maybe pico scope.

Is it just worth to take it someone who is honda competent?

Fuel trim look normal ST -10% LT 0–1%.
O2 pre cat oscillates.
02 post cat stable.

I have tested intake vacuum pressure and it is holding at 20in of Hg at operating temp 206F.
730 rpm at idle
10 degree at operating temp idle

I have gone thru the service manual of all the tests that I can do myself.

The more extensive tests would cost more $$ pico scope and a good vacuum leak tester.

Are there any other thoughts or ideas I can go?

Thanks

Patrick

[Importech]

Hi there, Your short term fuel trim is a little bit high. Can you monitor the pre cat o2 sensor during cold start warmup? Maybe the sensor is tired and sending false info to the PCM until it warms up good, making the engine run too rich and skippy for a minute or two. Does it high idle ok when cold? See if you can make the engine smooth out if you give it a little throttle.
Your fuel pressure is probably ok because it starts and runs ok. You probably don’t need a smoke test, though you might have a clogged vacuum hose (how old is that pcv valve?). Don’t worry about timing because it runs ok otherwise, but if you have any kind of exhaust leak near the o2 sensor that will definitely mess things up.

[pew]

Thanks for the reply. I checked the exhaust. I did not see any holes and felt the exhaust pipe coming from both sides and it was all intact. I did not see any leaks by the pre cat o2 sensor.

My STFT is -10 or less.
Mt LTFT is around 0.

I will try and get better cold start data. The HDS is more comprehensive which is something i do not have. I have a generic elm 127 software and connection.

Thanks

[lrpasni]

Anyone have advice on best way to check for an exhaust leak?
On the 3.5l pilot engine, bank one exhaust (cat) is difficult to see, at best.

I have an 05 pilot. Replaced a burnt exchaust valve on bank 1, and now am trying to figure out what caused it. Fuel trims look good at idle, but under throttle, I get a negative STFT on bank 1 only. While rebuilding the head, I bench tested the injectors using an arduino microcontroller, and graduated cylinders….all look good. Swapped bank 1/2 wideband O2 sensors, and still bank 1 shows same symptoms. I’m Still scratching my head. An older version of AutoEnginuity is really buggy on honda’s, which is making it difficult to observe equivalence ratio’s response.

[logans08]

My initial thought is that if you are running rich on one bank then that rules out fuel regulator and delivery. A leaking injector would flood the cylinder so it’s a no go there unless of course there is a misfire. I would say that unburned fuel is passing through on that bank and you need to start looking for a weak cylinder. Low compression or weak ignition spark.

[frankiedon]

Hi A vacuum leak could cause it because when the engine gets hot, the manifold expands and closes the leak. Leaks in the manifold need to be checked for w/cold engine and smoke-machine. Or apply some water or propane around the manifold gasket area and listen for sucking noise w/water or watch fuel trims w/propane,or listen for engine revs change around the manifold gasket area w/engine running. Frankiedon

[Author]

Posts