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96 ranger 3L idle irratic


98v70dad

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I've been trying to bring back a slightly neglected truck to good repair. The idle is a little erratic. So far I've replaced the cam shaft position sensor, synchro, epfe sensor and tubing, plug wires and plugs and cleaned the EGR and mass airflow sensor. I currently don't have any codes.

The rpms at idle sort of wander all over the place. When the engine is cold it idles at about 1000 rpm and then drops into the 900 range after a while. When its thoroughly warmed up the rpms vary from low 800's to just under 900. It varies 100 rpm within a few seconds. So I have a couple of questions.

1) what is the idle speed supposed to be?

2) I suspect that I have a vacuum leak - are there any typical leak spots to suspect first?

3) Is there some other sensor that may not be working right that I could clean or replace that will settle down my idle?
 


rangerenthiusiast

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Hey, ‘dad. I have a similar problem but worse on my ’92 with a 4.0, so I’ll be following your thread closely. I replaced the MAF and IAC, with little change. Idle races like a b@tch. The only thing that made a difference on mine was when I completely disconnected the IAC, which dropped it down to a nice 800-900 (instead of 1100, 1300, or 1700, depending on godknowswhat). But after the computer caught up a few days later, the check engine light came on and she sounded like she might stall a few times. So much better than a darn racing idle, though.

I suspect vacuum leaks as well, but don’t really know where to start. I really hope folks here can help us both!
 

98v70dad

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Hey, ‘dad. I have a similar problem but worse on my ’92 with a 4.0, so I’ll be following your thread closely. I replaced the MAF and IAC, with little change. Idle races like a b@tch. The only thing that made a difference on mine was when I completely disconnected the IAC, which dropped it down to a nice 800-900 (instead of 1100, 1300, or 1700, depending on godknowswhat). But after the computer caught up a few days later, the check engine light came on and she sounded like she might stall a few times. So much better than a darn racing idle, though.

I suspect vacuum leaks as well, but don’t really know where to start. I really hope folks here can help us both!
Yeah, hopefully we can get some good ideas. FYI, I used to live in the Hudson valley - way up in Troy. Atlanta winters are better. Atlanta traffic is worse.
 

cbxer55

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Hey, ‘dad. I have a similar problem but worse on my ’92 with a 4.0, so I’ll be following your thread closely. I replaced the MAF and IAC, with little change. Idle races like a b@tch. The only thing that made a difference on mine was when I completely disconnected the IAC, which dropped it down to a nice 800-900 (instead of 1100, 1300, or 1700, depending on godknowswhat). But after the computer caught up a few days later, the check engine light came on and she sounded like she might stall a few times. So much better than a darn racing idle, though.

I suspect vacuum leaks as well, but don’t really know where to start. I really hope folks here can help us both!
Sounds like you have a vacuum leak somewhere. When you disconnect the IAC, the engine should either stall, or idle very very low, close to stalling. That is the test that is used to determine a vacuum leak.
 

98v70dad

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Anybody? So far I've got someone with the same problem hoping for help and someone who agrees I might have a vacuum leak. Does anyone have any suggestions? So far I've done these things and the car still lopes at idle. I've sprayed carb cleaner everywhere I thought there may be a vacuum leak - no results. These things below managed to clear all the codes which is good but the loping idle is driving me crazy.

1) new plug wires
2) new plugs
3) cleaned egr
4) cleaned IAC
5) cleaned throttle body
6) cleaned MAF
7) replaced dpfe
8) replaced dpfe tubes
9) cleaned all eletrical connections for above with contact cleaner
10) replaced air filter
11) new camshaft position sensor
12) new cam shaft synchro
13) new PCV valve - wrapped in hvac aluminum tape to increase valve diameter so it will to seal tight
14) cleaned the crude from the PCV valve rubber grommet for a tight seal
 
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So, did you do the test that cbxer recommended? What was the result?

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98v70dad

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So, did you do the test that cbxer recommended? What was the result?

Sent from my SM-G960U using Tapatalk
Yes, I did. Idle dropped from mid 800's rpm to mid 500's rpm. Don't know what that indicates. cbxer's post tells me two possibilities but doesn't say what either of them indicate.
 
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98v70dad

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Thanks for the comments so far, any other ideas?
 

cbxer55

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Yes, I did. Idle dropped from mid 800's rpm to mid 500's rpm. Don't know what that indicates. cbxer's post tells me two possibilities but doesn't say what either of them indicate.
I thought I explained it pretty well. If the engine quits, or idles very low, almost to the point of quitting, when you pull the IAC connector, it indicates there are no vacuum leaks.

If the idle doesn't change, there is a vacuum leak somewhere allowing unmetered air (didn't go through the MAF) into the system.

Looking back at my last post, guess I didn't elaborate on it. Sorry bout that.
 

98v70dad

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I thought I explained it pretty well. If the engine quits, or idles very low, almost to the point of quitting, when you pull the IAC connector, it indicates there are no vacuum leaks.

If the idle doesn't change, there is a vacuum leak somewhere allowing unmetered air (didn't go through the MAF) into the system.

Looking back at my last post, guess I didn't elaborate on it. Sorry bout that.
Thanks. So, idling in the low 500's with the IAC disconnected I don't have a vacuum leak. That's surprising considering the car is 21 years old but if I don't have a leak that's great since they are a pain to trace down.

I wonder what else could be causing the stumbles in my idle. Its not continuous and its not big. Just an occasional (like every 30 seconds or so) slight bump in an otherwise smooth idle. I have no idea what to check next. I've been meaning to replace the fuel filter (original ) BUT I don't have the special tool(s) and the ranger is my daily driver. I don't want to mess with it without some spare clips if its held together with plastic. I have a 40 mile commute and can't be without my ride.
 

cbxer55

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Well, mine is a 98, so it's 20 years old. Only problem I've had with leaks is the old worm gear clamps on my aftermarket intake would not stay tight. They'd get loose, and next thing ya know, I get the damn lean codes. Also had the hose from the intake to the oil filler neck go bad and throw those codes. Made a new one from clear tubing and attached it with worm clamps, fixed.

But I have no idea what would cause your problem, never happened to me. My truck has eaten a lot of Vato Zone made in Mejico IAC's over the years, which when they go, cause a bad idle. I replaced it with a Made in Japan Hitachi IAC two years ago, not another problem since.
 

98v70dad

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Well, mine is a 98, so it's 20 years old. Only problem I've had with leaks is the old worm gear clamps on my aftermarket intake would not stay tight. They'd get loose, and next thing ya know, I get the damn lean codes. Also had the hose from the intake to the oil filler neck go bad and throw those codes. Made a new one from clear tubing and attached it with worm clamps, fixed.

But I have no idea what would cause your problem, never happened to me. My truck has eaten a lot of Vato Zone made in Mejico IAC's over the years, which when they go, cause a bad idle. I replaced it with a Made in Japan Hitachi IAC two years ago, not another problem since.
Thanks. Mine runs OK but a constant idle would be less annoying. For some reason the blimps annoy me. I finally came up with a good way to describe it - I'd call it an occasional mild tremor in the idle. My rule of thumb on old cars ... if you don't know what the problem is it will eventually reveal itself.
 

cbxer55

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Now that you put it that way, I'll agree with you. Mine has that as well. Doesn't bother me none, so i just leave it be. Check Engine light is off, and that's all I care about with this 20 year old truck.
 

rangerenthiusiast

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We’re having somewhat different problems then, in that when I disconnect the new Hitachi IAC, there is no change in the idle whatsoever. One would think that this is indicative of a vacuum leak (which I may well have), but the 26 year-old Motorcraft IAC did drop the idle when disconnected. If possible, I’d try to loop in a member here named RonD. He seems to be a wiz with this kind of thing and has given me a lot of good advice (that I’ve had little time to implement, due to my work schedule).

Good luck with it. I’ll be checking back from time-to-time to see how you’re making out.
 

98v70dad

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Replaced the 21 year old fuel filter Saturday. Not really any better.
 

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