300's Idle

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Jan 4, 2002 | 11:46 PM

fish462

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Joined: Oct 2001

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From: Tulsa

300's Idle

This is my 2nd late model F-150 with a 300 I6 and a manual trans; both of them seem to have a slightly rough idle...almost like a miss. You can really feel it in the gearshift. Is this something that is inherent to this engine?

Jan 5, 2002 | 05:46 AM

Hausladen

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Joined: Sep 2001

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From: Howard Lake USA

300's Idle

I am being to think so because we have had three trucks that do the same thing. It must be something about the 300 Inline 6.

Jan 5, 2002 | 09:13 AM

carlos57

Cross-Country

Joined: Sep 2000

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300's Idle

I had a '66 240, a '77 300, a '88 300 and now a '91 300. Only the '91 had missing problems. The wiring harnesses are made in Mexico on the '91. I really don't think the others were. I think that Ford would have found and cured the problem if it had been a component and not something related to the wiring harnesses. Poor grounds, shorted wires, power doorlocks and windows that work sometimes or poorly. Bad grounds and connections. All these problems we're haveing had been solved years ago. It's only since the extreme cost cutting that we are seeing this nonsence. My '91 has more rust on it than some '40 Fords. We should not be haveing these problems with poor quality materials, disimilar metals etc.

My 2cents
Carlos

Jan 5, 2002 | 11:21 AM

Vampiro

Cargo Master

Joined: Sep 2001

Posts: 3,135

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From: Canada

300's Idle

with my 300 6 at idle, it misses a little too. but it's not the timing, because it's set to 10 degreee tdc. you can kinda feel it miss, cause the engine will jerk aliitle. is this normal for the 300 or is there something wrong with mine?

Joseph

Jan 5, 2002 | 07:03 PM

inliner

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Joined: Jul 2001

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300's Idle

I have a 68 F100 with a 240 six and the factory sticker recommends an idle setting of 525rpm but if I set it there it rocks like a Chevelle with a really big cam in it, so I set it at about 650 to have a smoother idle.

Jan 21, 2002 | 02:28 PM

rustydog

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Joined: Jan 2002

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300's Idle

I have had my 86 f150 4x4 Shortbed Stepside with the 300 six since new.
it has never idled smooth and sounds like a small miss and the gear shifht ***** shakes a little. Just the trade off for a long stroke big bore motor. has 125k on it and always idled like this.

Jan 21, 2002 | 03:08 PM

wtroger

Cargo Master

Joined: May 2001

Posts: 3,208

Likes: 13

300's Idle

The ragged idle on these is from the emmision control systems especially the feed back systems used in the mid 80's. Ford leaned the idle circuits out to the point where 100% successful combustion was next to impossible. The use of platium plugs helps somewhat. If you have a 300 six and it has a feed back carb on it temporarely dis connect it and as the Ford shop manual will tell you the idle will improve that is how you test the feed back solenoids on the older 300 six trucks. The fuelies run there idles even leaner it is a wonder they will even idle at all. On the fuelies the o2 and map sensors are the real culprits. A slightly slow or fouled o2 sensor can really have an effect. A bad map sensor will usually cause them to run to rich.