old_man
NAXJA Forum User
- Location
- Loveland, Colorado
More likely the leak is the intake/exhaust manifold gasket.
More likely the leak is the intake/exhaust manifold gasket.
All of the above along with 20 years diagnosing 4.0L's and 50 years of wrenching. When the rpms start to go up, spray some carb cleaner around the intake area and if you see a sudden rpm fluctuation, bingo. Careful of flash back.oh ... can i ask why you say that? just because it's more likely to deform when expanded due to heat (not as massive as a head)? or because it happens more commonly?
incidentally i didn't do this until i had the new IAT - I wanted to test one thing at a time you know... anyway- with the IAC disconnected it behaves nicely and the idle doesn't climb ... hmmm... maybe i should drive it around with the IAC off for the time being ... at least it should be able to get me to the post office without having to turn off my vehicle in the middle of busy intersections!
Did anyone check the manifolds to see if they were flat, parallel, true and not warped?
If you hear a sucking sound the same time the idle ramps up, its obviously a vacuum leak. I hear water trigger spray bottle at possible vac leak locations can be informative?
Do not get the TPS wet!!!
If you suspect fuel injection controls, disconnect the IAC, and or TPS and O2 sensor right after cold start up and then see what happens.
All of the above along with 20 years diagnosing 4.0L's and 50 years of wrenching. When the rpms start to go up, spray some carb cleaner around the intake area and if you see a sudden rpm fluctuation, bingo. Careful of flash back.
Are you using Bellville washers on the intake? If not, do it.
In that case it is not a vacuum leak, the ECU is opening the IAC valve to add air. Bad IAT (even if it is new), wrong IAT, bad ground on the IAT sensor???
A pro could figure it out in 1-2 hours for $50 or less in parts. Based on what he said I would have hopped in the jeep and left. I never had any luck with pros, and always had troubling sitting down for weeks after trying them, even when I brought a tube of my own Vaseline.
And they always broke more than they fixed.
It has to be a Vacuum leak or excess fuel. Only so many places that can happen. I don't by a head issue, not all. Warped intake or loose manifold bolts yes. It does not cost $$$$$$$$$s to find and tighten loose bolts.
Did you check the fuel injector to intake port spots for Vacuum leaks???? Could be a bad O'ring on the fuel injector ports?
A pro could figure it out in 1-2 hours for $50 or less in parts. Based on what he said I would have hopped in the jeep and left. I never had any luck with pros, and always had troubling sitting down for weeks after trying them, even when I brought a tube of my own Vaseline.
And they always broke more than they fixed.
It has to be a Vacuum leak or excess fuel. Only so many places that can happen. I don't by a head issue, not all. Warped intake or loose manifold bolts yes. It does not cost $$$$$$$$$s to find and tighten loose bolts.
Did you check the fuel injector to intake port spots for Vacuum leaks???? Could be a bad O'ring on the fuel injector ports?
I'd guess intake manifold leak due to loose bolts or failed gasket. Both very easy to troubleshoot and fix.
well we'll see - it's been one week and still not even an estimate - if it's too high and makes no sense then maybe i'll seek greener repair pastures ... though i was reticent to go somewhere else after paying the $120 flatbed fee