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Nov 27, 2012 | 04:09 PM

rusty84f-150

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Surge under load

I've got this surge while under little load that I've been trying to hunt down. I already put new rotor and cap on. The truck is a 94 f150 5 speed 4.9 no codes either. And also to see the timing on this truck what kind of mark is on the balancer.

Nov 27, 2012 | 04:11 PM

bashby

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From: Charles Town, W bygod Va

Could be a fuel delivery issue, try a new filter.

Nov 27, 2012 | 04:25 PM

rusty84f-150

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Duh I completely for got about it I guess I'll do that tomorrow. Do you know if I need any special clip tools to get the lines off?

Dec 1, 2012 | 02:16 AM

rusty84f-150

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Well changed the fuel filter. Helped very little. Still has a surge of some sort.

Dec 1, 2012 | 07:36 AM

bashby

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From: Charles Town, W bygod Va

I'd put a fuel pressure gauge on it and go for a ride, surging is usually a lean condition.

Dec 2, 2012 | 11:56 PM

rusty84f-150

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do you guys think it could be a malfunctioning o2 sensor. because now im getting crap gas mileage.

Dec 3, 2012 | 01:03 AM

billuptracyo

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Duh I completely for got about it I guess I'll do that tomorrow

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Dec 4, 2012 | 01:30 PM

rusty84f-150

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Does any one have any other ideas why I have a little surge and terrible gas mileage?

Dec 4, 2012 | 03:59 PM

#10

rla2005

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From: Kentucky

Fuel Injection Technical Library » How To Run a Self-Test

Did you verify the fuel pressure?

Did you check/replace the spark plugs?

Is there any exhaust leak upstream from the O2 sensor?

Dec 4, 2012 | 10:18 PM

#11

rusty84f-150

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Would a little exhaust leak make that big of a difference at the manifold to exhaust?

Dec 5, 2012 | 08:16 AM

#12

rla2005

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From: Kentucky

Quote:

Originally Posted by rusty84f-150

Would a little exhaust leak make that big of a difference at the manifold to exhaust?

Yes it does make a HUGE difference. The O2 sensor is measuring the oxygen content in the exhaust. An outside air source such as an exhaust manifold leak will definitely throw off those measurements. The PCM is basing the fuel needs based on the O2 sensor readings in closed loop operation. See the relationship here?

An exhaust leak lets exhaust out as well as air in....