1990 Renix 4.0 Fixed blow by - now low idle

The P.O. had an open element air filter and ran the big hose off the valve cover to a coke bottle catch can. As you can imagine, it was a big mess. I put it back to stock with new hose assemblies, all the open vac ports are accounted for, the EGR is hooked back up...but now I have a Low Idle. It is low enough to stall out. Gotta goose it to keep it going at stop lights.

New plugs, cap, rotor wires, filters....

I suspect that I need to fiddle with the TPS, but having done that on a previous XJ and screwing it up to the point of actually having to take it in to the dealer, is there somewhere else to check first?

The temp gauge never gets up to the usual 210. It's way low. Should I suspect the sending unit in the radiator (closed system) or is there some other temp sending unit that might be affecting the computer?

Check the line from the MAP sensor to the throttle body. I broke it on both my Comanche's when I replaced the CCV lines on them and caused a low idle,like you described, until I replaced/repaired the line. Worth a check.

Try this easy upgrade to get away from "plastic" vacuum lines. I did this to my 87 Wagoneer and it works great. Also when they get clogged you can clean them up really easy with some carb cleaner. Since this pic I have completed the rest of them. Probubly cost me $10.00.

Looks nice. Is that silicone? A few more details, please!

I would bet serious change you have a stuck EGR valve, or atleast an EGR problem somewhere, especially since it started after you put it back in the mix. I bet that may have been why the PO bypassed it.

Looks nice. Is that silicone? A few more details, please!
Cherokee89


For the heater hoses? I think so. I dont know I "found" a bunch of it and thought it would look good. So I tried it and it works great. It is also rated at like 1500 psi so it will not give out on me. I may have some left. I will check and maybe we can work something out. If you are interested. It is a tight fit but with some effort it works fine. I could really use some tan front seat belts for my Jeep.

I replaced all my vacuum lines with rubber lines as well. Except I put a Chevy valve cover breather on the front hole in the valve cover. No more blow by.
I think you need to clean out your TB and air intake controller. (AIC or IAC) I would do a quick seafoam treatment on it and make sure you get some down the hole in the top of the TB for the IAC. It usually clears it up. Good Luck.
Big Black , is probabl right , check to make sure your EGR valve rod on the manifold goes up and down. and that it has vacuum to it. Good Luck

All good suggestions. I'll get to work (again).




I might wait 'till after dark for the Seafoam:laugh:

kevin s said:

All good suggestions. I'll get to work (again).

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My 90 had a stuck EGR valve, it would completely die at stop lights. A quick test...pull the vac line from just the EGR valve...that will temporarily fix it if that's the problem...or it should anyway.

kevin s said:

I might wait 'till after dark for the Seafoam:laugh:

Click to expand...

Good idea, that way your neighbors will have to change their underwear.

RenixPower is the winner!!
I finally got around to replacing the EGR valve and that did it. The PO also had a 180 degree T-Stat in there. Replaced that with a 195 and now my temp gauge is where it should be. Me happy now.

I replaced all my vacuum lines with rubber lines as well. Except I put a Chevy valve cover breather on the front hole in the valve cover. No more blow by.

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I just did the same only I used a "MR. Gasket #2057" Valve cover breather. But I have oil leaking out of the breather now.
Has anyone done anything inside the valve cover to stop the oil from pushing out of the front hole? I see a baffle in there but it doesnt seem to be doing any good. I heard or read on here that just cleaning it out will help. And what about the alum cover in the quadratec and 4wd.com catalogs?