Rough Idle

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May 30, 2005 | 08:12 PM

nmaranto

Thread Starter

New User

Joined: May 2004

Posts: 15

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Rough Idle

First, let me start by saying that I have gained a wealth of information from reading the old posts. I think the information I saw on the old posts in regards to slow starter when engine warm may have solved a problem that has plagued my truck for years.

My truck is a 77 Ranger XLT F150. 400 CID engine, C6 Auto. Trans is rebuilt, engine is a rebuilt engine and has about 80,000 on the engine. Suddenly started idling rough. Accelerated normally and performance at speed seems normal.

Replaced rotor, cap, plugs, and plug wires and saw an incremental improvment, but still rough. The rough idle seem to be intermittent. I'm thinking it is something with the ignition system. Distributor and ignition control box are original and have a total of about 300,000 on them

Anyone have any wisdom to share

May 30, 2005 | 09:12 PM

Matts72

Post Fiend

Joined: Jan 2003

Posts: 10,323

Likes: 2

From: Montana Territory

You should try adjusting your idle set screws on the base of your carburetor. You should turn them all the way in, not tight, then back out. Starting at 1 1/2 turns try to start your truck, it should start easily. If not, turn them out 1/4 turn at a time.

Otherwise, you probably need to replace your needle and seat in the carburetor.

May 30, 2005 | 09:16 PM

savage066

Mountain Pass

Joined: Dec 2004

Posts: 123

Likes: 1

From: Maryland

you might look for a vacuum leak...a suddenly rough idle could indicate a disconnected line...also, check and see if the carb is tight.

May 31, 2005 | 09:51 AM

beartracks

Lead Driver

Joined: Nov 2000

Posts: 6,635

Likes: 349

From: Albuquerque

The EGR plate under the carb is famous for warping and burning through. Causes the idle to change/surge as it warms up. Also the EGR itself could be the cause.