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  #1  
Old 11-25-2010, 01:58 PM
gshockxc gshockxc is offline
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Default Idle fluctuates low

I'm going to give some background in case it's useful.

I have a '99 Ranger 2WD, 5 Spd, 2.5, 4 cyl. This truck was given to me, so I don't have any input or history with the PM's on this truck. I've mentioned in other posts that the EGR tube was bad. The power steering was REALLY dirty, and hadn't been changed in years. I also cleaned the MAF.

So I replaced the EGR tube, cleaned the MAF, and flushed all the PS fluid.

But, after the engine is warm, if I come to a stop at a light, or just let the engine idle, the rpms will drop down to about 500. It's smoother than it was with the MAF cleaned and the EGR tube replaced. But the rpms just drop erratically, and then they will come back up after a few seconds. Sometimes it stays at about 500 rpms until the light changes, or I give it more gas. But I'm not sure what's causing it to drop like this. Normally, it will idle at about 750-800 rpms. I'm assuming this is normal idle speed.

Could it be the distributor? As it gets warm, it drops the rpms?

Any thoughts on this?
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Last edited by gshockxc; 11-25-2010 at 02:00 PM.
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  #2  
Old 11-26-2010, 05:33 AM
whitesonj whitesonj is offline
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Default Re: Idle fluctuates low

Shouldn't your engine not have a distributor? I thought they went distributorless.

I'd check the PCV valve, it can cause a drop in RPM's at idle. They're only a few bucks and they take seconds to change.

Maybe think about changing the fuel filter also.

If it's been a while or you're not sure of the last time it was done, a full tune up certainly wouldn't hurt if neither of those help. Cleaning the EGR valve itself is also a good idea.

Do you have a CEL?
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  #3  
Old 11-26-2010, 06:15 AM
terryduanemiller terryduanemiller is offline
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Default Re: Idle fluctuates low

no distributor...
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  #4  
Old 11-26-2010, 10:17 AM
ekandresen ekandresen is offline
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Default Re: Idle fluctuates low

Sound like the same problem a lot of us are dealing

withhttp://www.fordrangerforum.com/4-cylinder-tech/20168-2-5l-major-issues-please-somebody-help-me.html
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  #5  
Old 11-26-2010, 12:22 PM
terryduanemiller terryduanemiller is offline
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Default Re: Idle fluctuates low

never exp' it, I had High idle flux, it was EGR
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  #6  
Old 11-26-2010, 03:32 PM
FFSHOKE FFSHOKE is offline
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Default Re: Idle fluctuates low

ive got a 2005 and it does the same thing...mine is when it goes to stop and i hit the breaks and you can almost feel it like the rps just plummit close to stalling out but it only does it every once in a while like maybe twice a week asked my dad and he said drive the shit til it breaks lol
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  #7  
Old 11-27-2010, 08:53 AM
gshockxc gshockxc is offline
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Default Re: Idle fluctuates low

Quote:
Originally Posted by whitesonj View Post
Shouldn't your engine not have a distributor? I thought they went distributorless.

I'd check the PCV valve, it can cause a drop in RPM's at idle. They're only a few bucks and they take seconds to change.

Maybe think about changing the fuel filter also.

If it's been a while or you're not sure of the last time it was done, a full tune up certainly wouldn't hurt if neither of those help. Cleaning the EGR valve itself is also a good idea.

Do you have a CEL?
Originally, the CEL was on before I replaced the EGR tube, and the code read "bank 1 lean." I don't remember what the number was. I reset it and it came back on about 6 weeks later. After replacing the EGR tube, I wanted to leave it alone and see if the ECM would reset itself. It hasn't yet. Since I've replaced the EGR tube, the erratic idle hasn't been as bad, but it's still noticeable.

As I stated above, it will idle at about 750-800 rpms, drop to about 500 for a few seconds, maybe as much as a half a minute. But it never goes below 500, and then it comes back up. Before I replaced the tube, it was more severe. Sometimes it would drop below 500, almost stalling, and then come back up normal idle speed.

I haven't replaced anything else. All I've done is change the oil. The truck has sat for several winters over the last few years.

My next step is to unplug the battery and clear the codes, drive it and see if the CEL comes back on. If the idle still drops erratically, then I'll clean the EGR valve and see if that helps.

Thanks to everyone for the comments and the links. I'm sure we can figure this thing out.
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  #8  
Old 11-27-2010, 09:09 AM
gshockxc gshockxc is offline
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Default Re: Idle fluctuates low

Quote:
Originally Posted by ekandresen View Post
Sound like the same problem a lot of us are dealing with http://www.fordrangerforum.com/4-cyl...y-help-me.html
I read through all the posts, and the OP (Ranger153) is having a more severe issue than I am, but I'm beginning to wonder if this is tied to the EGR somehow. I'm not sure how it gets tied in with cylinder 2, but here's my theory:

The EGR works in two ways, one is to recover unburned gases, and the other is to add positive pressure to the intake, kind of like a turbo but on a much smaller level. By opening and closing the EGR valve, the intake uses the exhaust pressure to drive air into the combustion chambers and improve performance. It's small, but disconnect the EGR tube and see how rough it runs.

At highway speed, the higher rpms provide enough driving head to force some of the exhaust into the EGR tube as long as the EGR valve is open. When the engine slows down, and the exhaust pressure decreases (like at idle), the EGR valve may close partially or completely, and that takes the exhaust pressure away from the intake side. If there's a leak in the EGR system, the engine struggles to get more air because it's lost some of the pressure from the intake side. So it might seem like it's choking, and the rpms would drop. When you tap the throttle, it would dump fuel into the intake, but the system wouldn't have enough air to combust and it would smother the ignition, i.e. causing it to stall. I still don't know how this could be tied to cylinder 2, or why the code would isolate that cylinder only.

I noticed that after cleaning the MAF on my truck, the idle condition wasn't as bad, but still present. So if the MAF is dirty, and the EGR system has a leak, this could result in more severe idle problems like what Ranger153 is having.

Any thoughts? Let me know if you guys think this is reasonable or if I'm just way off base.
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Last edited by gshockxc; 11-27-2010 at 09:11 AM.
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  #9  
Old 11-27-2010, 11:00 AM
terryduanemiller terryduanemiller is offline
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Default Re: Idle fluctuates low

I questioning a vacuum leak? grab a can of starting fluid, spray round the vacuum lines see if she jumps up in rpm's.. just be careful. it is very flammable, lol
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  #10  
Old 11-27-2010, 12:56 PM
modelageek modelageek is offline
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Default Re: Idle fluctuates low

I dont think anyone has mentioned the IACV.......the IACV is the first thing to clean/replace for an idle issue..........and as suggested vacuum leaks......
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  #11  
Old 11-28-2010, 04:37 AM
whitesonj whitesonj is offline
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Default Re: Idle fluctuates low

Quote:
Originally Posted by modelageek View Post
I dont think anyone has mentioned the IACV.......the IACV is the first thing to clean/replace for an idle issue..........and as suggested vacuum leaks......
Good point.

It's looking like cleaning the IACV, EGR valve, cleaning/replacing the PCV, and checking for vacuum leaks would be your best next step.

But I say definitely clear the code and see if anything new comes up as well.
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  #12  
Old 11-28-2010, 08:21 AM
ekandresen ekandresen is offline
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Default Re: Idle fluctuates low

Ranger153 says he found his problem. He says he has a bad valve. I don't think we have the same problem, but it is possible. Your theory on erg pressure at idle is flawed because the erg valve is closed a idle and on deceleration. The erg valve adds exhaust gas to combustion to lower NOx by lowering combustion temperatures. That's why blocking it off on some cars will cause detonation.
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  #13  
Old 11-28-2010, 08:34 AM
modelageek modelageek is offline
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Default Re: Idle fluctuates low

Ekanderson. I take it you have anidle issue haveyou

-cleaned/replaced IACV
-cleanedthe MAf, TB
-changed air filter and looked for blockage inintake
-checked ECT sensor

Do you have codes and what year is your truck?
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2004 Ext Cab, 4WD, 4.0, Auto, 154k. (4.0 engine is out of a 2009 Ranger w/96k) ( as of 7/1/2017)

2004 Ranger, Ext Cab, 2WD, 3.0, 5 speed , 4WABS, crank windows, no cruise, Edge 116k.(6/5,2014) (SOLD).
1999 Ford Ranger, Reg Cab, 2.5, 5 speed, 2WD, no AC, 150k (SOLD).
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  #14  
Old 11-29-2010, 03:32 PM
ekandresen ekandresen is offline
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Default Re: Idle fluctuates low

Quote:
Originally Posted by modelageek View Post
Ekanderson. I take it you have anidle issue haveyou

-cleaned/replaced IACV
-cleanedthe MAf, TB
-changed air filter and looked for blockage inintake
-checked ECT sensor

Do you have codes and what year is your truck?
Yes, yes, and yes. The ect is new. there are no codes. Everyone i run this by seems to think there is a vacuum leak somewhere, but i can't find one. I am going to run a propane enrichment test as soon as i get some time. This is my 3rd vehicle so it is low on the priority scale, but any insights are appreciated.

----------

Quote:
Originally Posted by modelageek View Post
Ekanderson. I take it you have anidle issue haveyou

-cleaned/replaced IACV
-cleanedthe MAf, TB
-changed air filter and looked for blockage inintake
-checked ECT sensor

Do you have codes and what year is your truck?
Oh, and it's a 2001
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  #15  
Old 11-29-2010, 03:36 PM
findiit findiit is offline
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Talking Re: Idle fluctuates low

My 2005, 2.3 ranger is having similar issues. MOST of the time, it works great. Sometimes, it dips to about 500 RPMs and is idling roughly when there. Other times, it idles at 1000-1100 and seems to be very smooth and no shaking at all.

Can someone please advise?

NOTES:

Happens mostly when the truck has been driven for a bit, but this is not always the case. It has never stalled, and does not seem like it wants to. But it is bothersome and worrysome that this issue exists.
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