Rough Idle
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New User
Joined: Dec 2000
Posts: 6
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From: California
Rough Idle
I have a 1990 full size Bronco 351. The truck just passed smog with great results. However the truck has a rough idle. Seems like there is a miss, I have changed the plugs and wires, cap and rotor. California smog requires the check of all smog equipment, EGR, O2 etc. The compression checked good on all cylinders too. I still have good power off of idle and the truck runs strong no missing. Any suggestions?
Junior User
Joined: Oct 2000
Posts: 65
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Rough Idle
I hope your problem has a different cause than mine. About 10 years ago I had a 460 with the same thing. I checked everything I could think of and never found it. It kept getting worse and finally I found metal shavings in the oil. Turned out to be a lobe on the cam going flat. I installed a new cam and set of lifters and got another 70K from it before finally selling it.
Good luck.
Alan
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95 C350-4x4,PSD,4-Door Bronco(Huh?),49K,auto,AIC,switched glow plugs,switched TC lock-up,4.10,Banks PowerPack,straight piped,Mobile-1 gearboxes,Rotella,BFG AT's 295/75/16
Good luck.
Alan
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95 C350-4x4,PSD,4-Door Bronco(Huh?),49K,auto,AIC,switched glow plugs,switched TC lock-up,4.10,Banks PowerPack,straight piped,Mobile-1 gearboxes,Rotella,BFG AT's 295/75/16
Posting Guru
Joined: Mar 2000
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Rough Idle
[font size="1" color="#FF0000"]LAST EDITED ON 21-Dec-00 AT 10:48 PM (EST)[/font][p]has the tps been checked for correct voltage and resistance yet? that is a cause of rough idle...all you need is a voltmeter........and is the timing ok?
Freshman User
Joined: May 2000
Posts: 29
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Rough Idle
I beleive there is a throttle position sensor that takes part in regulating the idle. It is a problem I have read about in the past. Also check the vacuum lines although passing emissions is a good sign they are ok.
I too have a 90 with a semi rough idle but not bad enough to replace the part.
I too have a 90 with a semi rough idle but not bad enough to replace the part.
