rough idle ... checked everything what can it be?
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Elder User
Joined: Mar 2003
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From: Villa Rica, GA
rough idle ... checked everything what can it be?
My '99 V-10 has been idling horribly for the last couple weeks. My check engine light has been on .. the codes are P0171 and P0174, both say "system too lean". I posted all the symptoms and everyone recommended getting a new IAC. I first cleaned the old one, unplugged the battery, put everything back together ... the check engine light went off but the truck still ran like crap. So I got a new IAC, put it on and the check engine light is back off after unplugging the battery but the truck is still running like crap. I have made sure all the vac hoses are connected, made sure all the electrical connections are together, and cleaned the MAF sensor. I also put a brand new air filter, pcv valve, and fuel filter on it.
Does anyone know what is next? new O2 sensors? new MAF sensor? this thing is driving me nuts.
Thanks, Jason
Does anyone know what is next? new O2 sensors? new MAF sensor? this thing is driving me nuts.
Thanks, Jason
Post Fiend
Joined: Jan 2002
Posts: 5,859
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From: USA
You chkd the hose that goes to the pcv valve ? There is a elbow in that hose that likes to split and cause a vacum leak .
Also in 99 there were case where the intake gasket o-rings leaked and caused a vacum leak .
What you have is un-metered air entering the system causing a lean condition .
most of the time.
Then there is a condition where yor running rich and the pcm tries to compensate by adjusting fuel trims to most oposite (lean)
This is the downfall of OBDII ssystem.
But yours sounds like a vacum leak.
Don't forget the hose going to the brake booster also
Rich
Also in 99 there were case where the intake gasket o-rings leaked and caused a vacum leak .
What you have is un-metered air entering the system causing a lean condition .
most of the time.
Then there is a condition where yor running rich and the pcm tries to compensate by adjusting fuel trims to most oposite (lean)
This is the downfall of OBDII ssystem.
But yours sounds like a vacum leak.
Don't forget the hose going to the brake booster also
Rich
Post Fiend
Joined: Jun 2003
Posts: 5,643
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From: NE Texas
Could be the EGR valve, too.
Also, something to look at - is the battery good? It might just crank the truck, but if it's going south it could cause some problems like that. Simple but...well, you know.
Also, something to look at - is the battery good? It might just crank the truck, but if it's going south it could cause some problems like that. Simple but...well, you know.
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Elder User
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From: Villa Rica, GA
Battery was brand new a couple months ago.
I did read the codes and they are both O2 sensor codes, I highly doubt both O2 sensors went at once, they are just both reading a lean condition.
I will check the PCV and brake booster hose again when I get home tonight. I am pretty sure they are both good but I may have missed something. Come to think of it, I remember wiping some grease/oil off the PCV hose, I wonder if that had been covering up a crack I didn't notice. That is probably where that grease came from.
I did read the codes and they are both O2 sensor codes, I highly doubt both O2 sensors went at once, they are just both reading a lean condition.
I will check the PCV and brake booster hose again when I get home tonight. I am pretty sure they are both good but I may have missed something. Come to think of it, I remember wiping some grease/oil off the PCV hose, I wonder if that had been covering up a crack I didn't notice. That is probably where that grease came from.
Senior User
Joined: Dec 2001
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From: Mason, Ohio
Does the truck run better once it warms up? If so, it is likely the intake manifold gaskets leaking. That was what was going on with my son's explorer. It has a plastic intake manifold. As the weather got colder, the worse it ran because the thermal expansion was taking longer to seal up the leaking gaskets. A cracked intake manifold will do the same thing. If the crack or leak is bad enough, it may not seal itself as the engine warms.
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Joined: Jul 2002
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From: Long Island USA
Originally Posted by Keith Smith
Does the truck run better once it warms up? If so, it is likely the intake manifold gaskets leaking. That was what was going on with my son's explorer. It has a plastic intake manifold.
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Elder User
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From: Villa Rica, GA
PROBLEM FIXED!! Thank you FORTYFORDS and everyone else for your ideas.
It ended up being the hose that goes to the PCV valve, it was cracked in 3 spots right below the throttle body where it has a tight bend in the hose ... which happens to be right where I wiped up the oil from, I can't believe I didn't notice the cracks at that point. Anyway, I slipped on a new chunk of 5/8" rubber hose and she is runnin better than ever.
Thanks again, Jason
It ended up being the hose that goes to the PCV valve, it was cracked in 3 spots right below the throttle body where it has a tight bend in the hose ... which happens to be right where I wiped up the oil from, I can't believe I didn't notice the cracks at that point. Anyway, I slipped on a new chunk of 5/8" rubber hose and she is runnin better than ever.
Thanks again, Jason
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Post Fiend
Joined: Jun 2003
Posts: 5,643
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From: NE Texas
Chuck - get that OEM elbow when you get a chance. On some engines, just a regular hose will fail with all the rubbing going on in there.
Sometimes you have to buy the entire hose assembly, but surely a parts house has just the elbow...
OBTW - good for Old Forty - the old fart needs kudos now and them to keep his pumper going....
Sometimes you have to buy the entire hose assembly, but surely a parts house has just the elbow...
OBTW - good for Old Forty - the old fart needs kudos now and them to keep his pumper going....
Last edited by Big Orn; Feb 1, 2007 at 05:03 PM.
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Elder User
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From: Villa Rica, GA
I will get the right one when I get a chance, but I had the piece of hose so I just used it. The piece I used is about a foot long and I routed it out and around the throttle linkage then attached it to that smaller hose so I wouldn't have that sharp bend in a hose that wasn't meant for it. Thank you all.
Jason
Jason
Post Fiend
Joined: Jan 2002
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From: USA
Originally Posted by chuck641
PROBLEM FIXED!! Thank you FORTYFORDS and everyone else for your ideas.
It ended up being the hose that goes to the PCV valve, it was cracked in 3 spots right below the throttle body where it has a tight bend in the hose ... which happens to be right where I wiped up the oil from, I can't believe I didn't notice the cracks at that point. Anyway, I slipped on a new chunk of 5/8" rubber hose and she is runnin better than ever.
Thanks again, Jason
It ended up being the hose that goes to the PCV valve, it was cracked in 3 spots right below the throttle body where it has a tight bend in the hose ... which happens to be right where I wiped up the oil from, I can't believe I didn't notice the cracks at that point. Anyway, I slipped on a new chunk of 5/8" rubber hose and she is runnin better than ever.
Thanks again, Jason
Rich