Originally Posted by Ranger97bc
Hi, I am having the same problem. I have never changed the pintle caps or injectors. I have replaced the IAC, MAF sensor, EGR pressure sensor, Spark plugs & Wires. And I still have that Idle problem, so did you use that kit you were talking about. Would you think that if I had that seal kit done, it would do the trick. Or do I have to change the Injectors & stuff also? Thanks, Randy
I couldn't say for sure. If you've never done anything with the injectors, I would say that your problem isn't the same one I was having. This problem was my own doing from installing the wrong pintle caps when replacing an intake gasket set.
I will say that I don't generally throw parts at the problem, though. If you test a part and it passes then it's on to the next one. Most electronic components can be tested with a multimeter.
I would start by checking for vacuum leaks. If you don't find any, it couldn't hurt to voltage check the DPFE sensor and (although unlikely) the TPS. My problem appeared to be an IAC issue, and I replaced that sensor a couple of times (in spite of it testing good) because I just couldn't figure out what the problem was.
After I had the idle problem under control (after finally settling on an OEM Hitachi IAC), the CEL came on with P0171 and P0174 codes. I discovered also that the 1997 4.0L is bad for fuel manifold gaskets going out. I went through and replaced the VC gaskets, upper and lower IM gaskets, fuel manifold gasket, every gasket and o-ring on the intake side, went through about 8 cans of parts cleaner, cleaned the injectors and replaced the o-rings and retainers (because my retainers were cracked), then put it all back together I finally had it running right again.
One problem with the lower intake on the 4.0L is that the sides tuck up under the valve covers. If the lower IM is taking in air under the valve covers you may never know it because it is undetectable with starter fluid and I would imagine it would be undetectable with a smoke machine as well.
And now... I have a lower end knock I have to figure out... it never ends!!!