What vacuum and RPM do you get on your gen3 at idle?

[tj90]

Some of you may be seeing that I sometimes have a stall or instantaneous loss of power when the truck is cold. Attempting to diagonse, Ive been watching real time monitors using OBD and Torque app. I havent seen anything abnormal except for my vacuum. The most Ive been able to achieve is 13 inHg vacuum. That seems low to me and I can only achieve that going down a hill or intermittently at a light idling. Most times idling its anywhere between 11-13. My idle is right at 590 RPM which is just outside the spec of 700+/- 100 RPM at idle.

For anyone that monitored their vacuum and RPM, can you please comment on if this is normal? This may indicate a problem with vacuum leak or clogged cats, This could be my problem with low idle?

 

[MoabRefugee]

Dollars to donuts, I’ll bet you have a cracked manifold. My ‘01 has a cracked DS and it has a loping idle and sounds on the verge of stalling when cold. I suspect that this is due to the EGR circuit( on the DS) “sucking” through the manifold. Once throughly warmed, no problem.

If you have an 03-06 your EGR is on the PS, and you have the additional likely vac leak location of the manifold butterfly linkage. Might as well remove the “piston eaters”and fix the vac leak at the same time. Just did this to our company’s ‘06 today.



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The bad
news...OEM manifolds are spendy.