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2003 Honda Pilot rough idling

izmatt234izmatt234 Member Posts: 1
edited June 2022 in Honda
About two months ago my 2003 Honda Pilot with 185K miles on it surged and stopped in the middle of the road. Figured my timing belt skipped but it is perfectly lined up. Ran codes and had P1129 (MAP sensor pressure higher than expected) and P0401 (EGR system insufficient flow detected) but no engine light. I had replaced my EGR and cleaned all ports and intake manifold a couple months prior to this happening but the code only went away for a short while. After a couple tries the car did eventually start with low RPM's but the RMP's would jump like crazy and smell very bad and then die. I have replaced idle control valve, cleaned my throttle body and replaced throttle body position sensor, replaced my MAP sensor, and did a smoke test to see if there was a vacuum leak (didn't see anything). I then noticed that I had a coolant leak in my thermostat housing so I replaced the gasket (and thermostat just because) and that was no longer and issue. I took off my intake manifold and there seemed to be small puddles of oil and water inside, so I also replaced my PVC valve. After all of that the car didn't run any better, after running out of ideas I took it to a mechanic. They told me it had been running rich for awhile now pouring fuel into the engine (which was hard on the catalytic converter possibly causing the smell) and that they figured the fuel injectors were possibly stuck open. Took the car home and replaced all 6 injectors, now the car still starts but has below 1 RPM's and the RPM's don't seem to raise when stepping on the gas or manually raising RPM's on the throttle body. Now I have a check engine light that flashes when the car is running after a little bit, all my previous codes are gone and then I got 7 new ones! P0131 (heated oxygen sensor bank 1 - low voltage), P0113 (intake air temperature sensor - high impact), P1519 (Idle air control valve - circuit malfunction), P0303 (Cylinder 3 misfire), P0305 (Cylinder 5 misfire), P0300 (Random/multiple cylinder misfires), and P1399 (A:Misfire-temporary malfunction B: Random misfire). There is a possibility I need to check my spark plugs and such but last time I tried to take one out it was stuck in there and there was no getting it out in one piece.
I ended up replacing the fuel pump and for now all codes have gone away. although, it still runs the exact same, I also keep having backfires in my manifold as well, couple fire balls here and there! I made sure I was getting power to my fuel injectors, checked for damaged wires and hoses, made sure all sensor were hooked up properly yet every time I step on the gas pedal nothing happens. The really strange thing is when I spray carb/choke clearer into the manifold the RPM's raiser right up (without stepping on the gas) and it seems to run decent but only when carb/choke cleaner is being sprayed into it.


  • thecardoc3thecardoc3 Member Posts: 5,745
    Have you tried to measure the exhaust back-pressure?

    You have a long list of what you have done, but my first question now is why did you do all of these things? It's not uncommon for me to see a list like this where repairs were tried on hunches without real testing being performed. In many of those cases problems were added to the vehicle during the repair attempts resulting in being further away from repairing the vehicle than they were before they started. For example, where did you get the injectors? Part of your description suggests the engine is too rich, but then contradicts itself and makes it appear that it is now too lean. So I am left wondering what is it right now, too rich or too lean and did replacing the injectors somehow result in an undesirable change?

    Being a speed density system (MAP sensor) it isn't affected by a vacuum leak the way a MAF sensor system is. Essentially a vacuum leak lowers the intake manifold vacuum level and the MAP sensor signal reflects that. The result is the engine control module commands a longer injection pulse and delivers more fuel to the engine automatically correcting the air/fuel ratio for the vacuum leak.

    At 185K miles has the timing belt been replaced when it was due at approximately 105K miles? Were the valves adjusted then and how much clearance is there right now?
    I saw that you said that the timing marks line up, imagine a situation where one of the camshafts has rotated out of time with the camshaft gear. The result is the gears and their marks are in-time, but one or both camshafts are not.

    What is the fuel pressure (via a gage)?
    Have you checked compression?
    Have you tested the alcohol content?

    What kind of a scan tool do you have? (Be very specific)

    Depending on what tooling you have and your ability to do proper testing I can lead you to the answer.
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