Rough idle issue,someone help please!
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Joined: Oct 2005
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From: MI
Originally Posted by R1Jester
I haven't had my issues since it has been relatively warm around here, but I would still lean towards a vacuum leak, even a small one. It only happens to you at idle, so I'd try to exhaust this fix next. I think Chester recommended in another thread somewhere, getting a can of starting fluid and spraying it at connections for the vacuum lines one at a time. If you hear the sound of the engine smooth out/go up....you found a leak. It's entirely possible that the hoses are in need of replacement.
In the 98's, the drivers side upstream is most common, passengers upstreams fail as well, just not as much..Hope you got her fixed..
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Sounds like you guys have the same problem as I do....my 98 f150 has a real rough idle in park or in gear. If you are sitting at a stop light while in "drive" sometimes the idle will drop so low the engine dies. But if I put it in park or neutral (sp) at the stop light it will not die, but just rev wildly. My check engine light is on too
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I've got an '04 5.4 that has been in the shop 8 times for several problems. Every time I complained about rough idle since it was new w/o ac, in gear. If I slightly press the pedal to increase the rpms approx 30 to 50 more the rough spot goes away. Turn on the ac and it goes away. Dealer has always said that it's normal for this 3v engine. Unfortunately, I finally blew it off and decided to live with it. If anyone has any ideas of how to increase the idle speed, I'll give it a try.
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I have the same problem, 00' 5.4, anyone find a fix? i'm gonna check the vacume leak, it would make sense to me that when your brake booster is sucking vacuum as you brake to a stop that the idle would dip if there is a leak bleeding more than the brakes normally would. however, i also have the problem in park... maybe it's the upper intake gasket, gonna check that next... oh also, i have No check engine lights on.
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Joined: Apr 2007
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From: Hawaii
maybe i can help....
Originally Posted by Josh98xlt
I have a 98 f-150 with the 4.6L . In the past few weeks I have been dealing with a issue that I cant solve! When its idling it shakes ,not alot but enough to notice.Almost like a misfire but throws no misfire codes. I replaced the plugs and wires with motorcraft plugs and 9mm motercraft wires and 1 coil pack. I replaced just one because weeks ago I got a cylinder 6 misfire code.Also replaced both downstream O2 sensors and cleaned out the IAC valve and throttle body.Also replaced map sensor with OE replacement. The damn thing still does it.The cylinder 6 misfire came up once after about 500 miles or so again.I ohmed the injectors,all 8 at .013. # 6 came at .014 but went to .013 after about 1/2 a second,so I think the injectors are good. What the hell can it be? The only code it ever had was cylinder 6 misfire,it came up 3 times in the past.HELP!!! I like my trucks to run perfect,so this is driving me crazy
this happened to me with 3rd cyl. I though it was injectors, O2 sensor and fuel pump. NO. Get a diagnostic on your valve coil(s). They regulat how much fuel goes to the injectors, too much or too little could cause a rough idle. If you've also noticed a change in mpg, that is a sign too. especially if codes haven't been brought up via the injectors. maybe this will work
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Joined: Apr 2007
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From: Southwest, Georgia
will help some
I had the same problem where I would come to a stop in gear and the RPM's would get so low the engine would die. I put some carb. cleaner on a rag opened up so I could get to the TB. and cleaned where the flap works. It seems there was a build up around it not letting it open and close correctly. I also run Lucas fuel injector cleaner thru it. It did help,My truck isn't dying at stop signs or when I slow down.I'm about to change my coil packs, plugs and wires because I have a slight miss up to about 50-60mph
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From: MA
Well just to follow up. I've ran seafoam...didn't help, maybe a little. cleaned MAF....didn't help. Had the TB cleaned about 1 1/2 ago....that didn't help either.....aldo I think the trans is slipping too....getting on the interestate ramp, it would downshift and the rpm would go to about 4-5000rpm then it'll upshift....any ideas on this?
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Same problem here. 00 XLT 5.4 with a rough idle whether its in park or in gear. Drives just fine otherwise. I haven't begun investigating, but watching this thread to see what others have tried. Hopefully someone comes up with a fix!
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Joined: Oct 2005
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From: MI
Brett , your EGR port is plugged up - BAD . You have to manually clean it out, they get carboned up . 
http://www.fordf150.net/howto/throttlebodyclean.php
http://www.fordf150.net/howto/throttlebodyclean.php
Last edited by jbrew; May 17, 2007 at 04:09 PM.
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From: L.A. County
Originally Posted by Josh98xlt
Ok so last night I used the wideband O2 on this pain in the a$$ and my air fuel is premo! 14.7:1. So that rules out fuel issues and valve/cylinder issues. Now what? Also check engine light has not gone on since I did my fuel system cleaning. Someone has to have some insight! Im too stubbron to go to the dealer. Besides it seems anyone that did go to the dealer still has the problem. I bet half of the shake/misfire issues on this forum are related to this same issue.
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Been a while, but issue still there.I get code (cyl 6 misfire) Last thing I checked was a comp test.All ok with 245000 mi. Someone mentioned the crank position sensor. Any thoughts on that? Anyone find a fix yet?
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From: Belgium
Hi all,
I'm from belgium and also drive with a F150 4.6 .
Now i have the same prob , engine runs rough and no check engine light goes on .
on the scan i have 2 dtc codes , bank 1 and bank 2 oxigen sensor .
I have replaced those but still the same prob .
Now im thinking after i have changed the spark plugs that it maybe is a leaking injector what gives me those misfires . Anyone have already had a defect injector on a 4.6 liter?
thx , regards
I'm from belgium and also drive with a F150 4.6 .
Now i have the same prob , engine runs rough and no check engine light goes on .
on the scan i have 2 dtc codes , bank 1 and bank 2 oxigen sensor .
I have replaced those but still the same prob .
Now im thinking after i have changed the spark plugs that it maybe is a leaking injector what gives me those misfires . Anyone have already had a defect injector on a 4.6 liter?
thx , regards
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Joined: Oct 2009
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From: Belgium
hi glc,
i have erased those codes , now after again rechanging the spark plugs i have recieved again a backfire , now on the snap onn scan tool i have code P1409 .
Now the intake air case has exploded :-( .
My E-mail is r.dewit@telenet.be
thx
Witte
i have erased those codes , now after again rechanging the spark plugs i have recieved again a backfire , now on the snap onn scan tool i have code P1409 .
Now the intake air case has exploded :-( .
My E-mail is r.dewit@telenet.be
thx
Witte