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Discussion Starter · #1 ·
I recently bought a used 2004 honda pilot with 59000 miles from a private owner. She mentioned that at some point she had trouble with the car because it would stall at stops once in a while. It looks like her mechanic replaced the idle valve and I though the problem had been fixed.

About a month after I bought the car the engine would rev up and down at idle and sometimes stall. this problem continued intermittently. Then the car started to hesitate or studder at low and then higher speeds. I brought it to my mechanic and he cleaned the idle valve. Unfortunately at that time I did not look through the the old records which show that the idle valve was already replaced. Anyway after I picked the car up it continued to do the same thing.

Next the check engine light and the VTM light came on. The VTM light eventually turned off but the engine light stayed on. Brought it to the dealer who said the car was fine and the previous mechanic did not reset something afte the idle valve was cleaned. Picked up the car and the check engine light was on. Drove fine for about 10 minutes then it started hesitating again on the freeway.

Brought it back to the dealer and they said the honda techline reccomended a valve adjustment. The wanted 380 and my mechanic would do it for 250 so I took my car to my mechanic. When I picked up my car from the dealer the check engine light was on again. They said it was because it needed a valve adjustment. My mechanic talked me into getting a new thermostat, coolant and spark plugs before getting a vlave adjustment. I guess the spark plugs looked pretty bad. He drove it after the repair and said it was doing the same thing. So he reccomended a valve adjustment and said he would do it for 150. The codes he pulled up when I brought it to him had to do with the engine running too rich but Im not sure of the exact codes., I guess I could get those and post them.

If looked at a number of forums and it seems like other owners have had similar problems. At first I thought it was the tranny because of the studdering but there is no associated noise and the dealer said its not the tranny. My model was recalled because of the tranny and they put in the oil heat shield at 2200 miles.

If anyone can shed some light on this problem I would greatly appreciate it. Right now I have a car that I bought for about 12000 dollars and it doesn't work right. And the mechanics don't seem to know what it is.

Thanks!
 

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What code(s) is the Check engine light producing?

Kind of a shot in the dark, but with previous (non-honda) vehicles I've experienced similar strange idle up and down and hesitation symptoms when the Oxygen Sensor was failing. But I would have expected it to throw a code for that.

Something to think about anyway.

Good luck!
-Brightdog
 

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2016 CRV Touring AWD, 2005 Pilot RIP.
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Normally the iac is the cause of those issues.
Its clean and I sure hope it's working correctly,
Have you checked the EGR? Pull and clean.
Does this happen hot and cold?
Have you checked battery and alternator outputs? Weird things happen when they are bad.
 

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Discussion Starter · #4 ·
Not sure what the codes are.

The problem happens when the car is warm and when it is cold.
I'll ask my mechanic to see what the exact codes are. If the valve adjustment doesn't fix the problem I'll try the oxygen sensor and the EGR valve. I'll look into the battery and alternator outputs as well.

I really appreciate your help. I hope this doesn't go to far because every repair seems to cost a couple of hundred dollars.
 

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idle problems are usually from vacuum leaks. Unmetered air enters the system and the O2 picks up a lean condition. The computer starts dumping in more fuel to compensate.

How is your gas mileage?
 

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Robs I think you've got it.
That makes perfect sense ESP on an 03 where perishable rubber is involved
 

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Discussion Starter · #7 ·
The codes are P1129 Map sensor and P0170 Rich mixture. My mechanic adjusted the valves, replaced the map sensor and cleaned the EGR valve. I'm going to pick it up on Monday. He says he test drove it and the idling and shuddering problems are resolved. I hope so.
 

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Mixture richness has nothing to do with the valves. So they are taking you for a ride there. Its all to do with the IAC, MAF and vacuum lines.
 

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Idle bypass valve, almost every time.
 

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Discussion Starter · #10 ·
Still same problem

Hi guys,
I was out of town for a couple of weeks and picked up my car from the mechanic about 4 days ago now. The car was driving fine for the first couple of days. On the third day it did the same thing: Idiling up and down until the engine died. Over the next day or so it did the same thing with it even dying right after start up one day. It also started to do the funky studdering or not responding to gas while driving. Doesn't seem to matter if the engine is hot or cold.
So far I've had the idle valve cleaned and it was replaced a few years ago. Had the EGR cleaned. Replaced Map sensor and had valve adjustment since there were codes for Map sensor and engine running too rich. My mechanic also replaced spark plugs, thermostat and coolant. Also had transmission fluid drained and replaced. At the moment there are no codes. My mechanic also told me he didn't see any vacuum leaks. Any other ideas. Do you think it could be a fuel injector problem? I'm also wondering if it has anything to do with the transmission since it was recalled and had oil heat shield replaced at 2200 miles.
Any help would be greatly appreciated.

Thank You!
 

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Discussion Starter · #12 ·
Even if Idle air control valve was replaced at 50000 miles?

The Idle Air Control valve was replaced at 50,00 miles and it was just recently cleaned which didn't fix the problem. Would you still replace it?
 

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The IAC valve is only $140 or so at the online parts places, and it seems like about the only part that you haven't replaced that would deal with the idle. As N-Jay said, it is also the most likely part to cause your problems. It sounds like you only have records that say that it was changed earlier and your mechanic has cleaned it, but maybe it has some defect or is somehow otherwise not functioning properly. I would get that changed (and make sure it's a new genuine Honda part) and then go from there...
 

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The chances of a replacement iac being bad is slim. However it can happen.
After all the work you have done, I doubt going down the iac road again will help.
I'd turn my attention to fuel. Drop a 20oz bottle of techron into your tank. If that doesn't solve it, you'll know dirty injectors are not the problem.
Then it's time to test fuel pump pressure and replace the fuel filter.
 

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Check Fuel pressure regulator, if the Pilot has one. It relies on vacuum to regulate the fuel pressure. Easy to test with vacuum pump.

Fuel filter? Fuel pump? Pumps can be erratic before total failure. Have pump pressure checked and change the filter.

What is the engine vacuum at idle hot and cold?

Engine computer could be intermittently bad. Chip or transistor could be on the way out. They act up before total failure.

TPS on the intake throttle is suspect.

Mass air flow regulator is highly suspect.

A poor or open ground in the wiring (the shield replacement) will create all kinds of havoc.
Mechanic should inspect previous work for damage.

As suggested, poor Battery voltage and current can create havoc.

Find you a willing Mechanic that will logically work these suggestions. I have little faith in your dealer at this point. A good independent Honda shop would be my choice.

Keep us posted.
 

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Discussion Starter · #18 ·
Had battery and alternator tested.

Apparently one cell of the battery is dead. This wouldn't contribute to the cars problems would it?

Also, yesterday the check oil light started flashing. I checked the oil and the level was fine. It turns off after I turn the car off and turn it back on.

I also put in some injector cleaner but it hasn't made a difference.

Thanks for your suggestions. I think I'm going to replace the fuel filter next.
 

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A bad battery will cause all kinds of erratic behavior.
 
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