Mystery Shudder

[xhomerjayx]

Hi guys, I am perplexed in my pursue for a smooth running truck. So when I am at a stop light on the brake, the engine shudders in no pattern what so ever. It runs smooth, the suddenly shudders. it is a mystery to me. Here is what I have done thus far:

Engine was rebuilt 20,000 miles ago.
New MAF
K&N air filter
New Coil (Motorcraft)
New Plugs (Motorcraft)
New Wires (Motorcraft)
Computer Flashed last week by Ford

The odd thing is that I am getting no codes at all and there is no check engine light.

I have no idea what is going on at all. When the truck is in park, it idles great, then shudders, then goes back to running smooth.

I just got back from a 300 mile trip last weekend, and the truck ran with no problems, had plenty of power, and ran like a beast.

I hate that the only problem I have at all is that damn shudder. I would appreciate any feedback and am happy to answer questions.

I have a weird feeling that it may just be a vacuum hose or something silly.

 

[Number4]

To me, a shudder is a symptom of something binding, or slipping / catching / slipping.
I believe your saying its a rough idle all of a sudden. Have you sprayed carb cleaner around the engine to see if the idle picks up.
Wait, is it carb cleaner....

 

[Joe in NY]

Nope, you want to use starter fluid, ether...

 

[swshawaii]

A leaking PCV elbow does not always throw a CEL or trouble codes, and can sometimes be intermittent. Easy enough to check. GL

http://www.explorerforum.com/forums/showthread.php?t=217062&highlight=pcv+elbow

 

[swshawaii]

IAC checked? :scratch:

http://www.explorerforum.com/forums/showthread.php?t=320337

 

[grandfunk]

I have the same issue (2000 xlt 4wd though). Buuuuuut, not sure what it is either. Usually more sever when engine is cold. When it happens I put it in neutral for a few seconds and it usually stops. I've decided to live with it for now.

 

[xhomerjayx]

Hey guys
I checked the PCV elbow and it looked fine. The IAC was next on my list, but I took it to a mechanic. He said it looked fine. He did an injector cleaning and vacuum thing to get carbon deposits. But same problem. So, I made an appointment for the dealer. One mechanic said my torque converter may be out of balance, but I don't see how that would cause the idle to be rough in park.

It may be the EGR, but who knows? I'll post against after dealer inspection.

 

[xhomerjayx]

Problem found...
Seems as though it was a bad plug. I actually checked the plug twice, but could find no fault, however the Ford tech pulled it, tested it and it was "broken" whatever that means. I re-replaced all plugs, and now Big Red runs like a champ.

 

[SergeJr]

My mustang those it to Every mechanic can't find it but the car a 03 Mach 1 with lots of up grade 450hp. I have a long block new in the box and does it.. I drive it hard and shudder come and goes. On the mustang forum said most engine ruibuilt it because of the heads I got my engine lifters change and does still chudder but not as loud.