Shaking after 15 mins.... | Ford Explorer - Ford Ranger Forums - Serious Explorations

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Shaking after 15 mins....

not turbo

Well-Known Member
July 29, 2006
Reaction score
City, State
Everett WA
Year, Model & Trim Level
87 Bronco 2
Hey all....

So I have an 87 Bronco 2, 2.9, which until recently ran great. Lots of miles (around 300,000), has had some work done a couple years ago, but nothing recent.

Problem is this: After running for about 20 minutes, the whole truck shakes like it's misfiring, the power brake pedal seem to become quite hard to press, and the truck can't exceed about 50mph.

If I slow down to about 30, the shaking mostly goes away, but the brake pedal stays stiff until the engine cools off. eta: It's been doing this for about a month (that goodness my commute is only 12 minutes!)....but the past week the time has dropped to about 15 before failure.

Engine code says "31", which is the EGR valve sensor...changed it, and the valve, and the other thing in the system (effectively "shotgunning" it; I did each item and then test-drove and checked the codes, no fix)

Looking around here with the search, it would appear that there may be a vacuum leak...but everything looks good (but I don't know if I'm checking every vacuum port). So what part of the vacuum system engages/disengages after 20 minutes of engine running?

Any ideas?