I was in the parking lot the other day sitting there and my seat started shaking. I thought it was my subs but then i turned off the music and the whole truck was shaking. I opened my door and could hear the truck sputtering. The RPMs would go up and down slightly. It is starting to happen more often. Any ideas of what is happening? Thx Josh

 

Engine? Miles? CEL on? CEL blinking? What has been maintenanced recently? What hasn't? What type plugs are in it? Any mods? Warm Idle RPMS, what are they when the truck is ruuning normally?

Need More Info.

 

My bad forgot the specs. it has got a 5.4. has around 130k on it. CEL has been on for awhile because of exhaust but it hasn't been blinking. I don't have any engine mods. We have not changed the plugs so they should be motorcraft. We changed oil and filter about 1000 miles ago. I will post RPMs and specific parts in the morning.

 

Go get the codes read and post them. If those plugs have 130k on them, they are WAY overdue for replacement. Might need some COP's too.

 

Went and had the codes read. It's a major vacuum leak.

 

The codes were 1151 0174 0171

 

Yep, that will do it

 

Probably the PCV elbow behind the intake manifold. You may also have a dying O2 sensor. Clear the P0171 and P0174 first and see if the P1151 also goes away. If not, get new front O2's, it's best to replace them both when one starts going out.

 

I would think so as well, but the 1151 (Lack Of HO2S21 Switch - Sensor Indicates Lean) ~ lack of switching could be caused by fuel trim shifts as well as a sensor malfunction -"Lean Switch" may be the result of that vac leak. The PCM had adjusted trims to parameter stop.

You might want to locate the leak, fix that, -re-boot the KAM and see if that takes care of the O2 code as well. If the 1151 isn't fixed at that point, it will re-appear after Entry Conditions are met. The test will be carried out when the engine load is between 20 and 60%, when the exhaust temperature is assumed to be 800° C. FYI -It may take 180 minutes after re-boot for it to re-appear IF there's still a prob with the sensor.

 

We checked all the vacuum hoses we could find. The leak is still there. Still runs like crap at idle. My dad said we should take it somewhere where they could check the hoses with smooke or something like that. We couldn't find anything wrong.

 

This is where they leak most of the time Josh -



This is the part that glc is referring to - "The PCV elbow behind the intake manifold"

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That elbow connects to the manifold here -



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Yea, they either tear or develop pin holes.




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Smoke testing is a cool way to check for leaks. They started selling smoke test kits @ Auto Zone as well. I haven't tried one out yet,-I guess I need a reason first.

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I'll try this again, - What's your warm idle RPMS ?

 

Idle is 700 - 800 RPM

 

- How about this, is it above 750 RPM or below ? Idle should hold steady somewhere. If you don't know how, post how many little lines past 700 the needle is

 

Right now there is no steady idle. The needle is jumping all over the place. If I had to make an educated guess before it goes wild it it around 750 or 800.

 

So did you replace or atleast check the elbow where they leak most of the time ?

A hole in that elbow will make her idle like that. You give up on it?

Here's another pic, or diagram of it. -



You and I have the same truck. I can take a long screw driver and pop that elbow off without removing ANY other parts on the truck. Theres NO clamps, it's a Push on /Push off.- Takes about 5 minutes to yank the PCV system - It's a easy fix!

So fix it man..