Renix idle issues...

1989 Cherokee, AX-15, 4.0L


I have probably done over 6 hours of research on this one, but yet i still can't seem to figure it out. When my cherokee first starts up, it idles pretty rough for a minute or so, then it smooths out and idles fine other then the idle is pretty jumpy and it idles a little low. When the jeep is warm it idles smoother (still a little jumpy), but it idles around 850-1000 rpm (I replaced the CCV orifice with just a grommet so that could be why it idles higher). Now what confuses me is when i turn on my A/C it doesn't seem that my IAC works right, It doesn't compensate for the extra load. Also for whatever reason my idle is jumpy, and it can't maintain a constant idle. I have a brand new IAC, CPS, MAP, and TPS. My TPS is adjusted to roughly .82 volts. I have checked my CTS and MAT, and O2 sensors and they check out fine. My engine is brand new, and my intake manifold and throttle body is completely clean. My ground wire is brand new, and all my grounds are clean and making good contact. My EGR is new, and i have tested everywhere for VAC leaks. Otherwise my jeep runs great, its just this problem really bothers me.

you are on the right trail.is the cts for the gauge or the ecu.the timing might be out a bit or something to do with the knock sensorhard to really say with out more details

Could be injectors. You say the engine is new. Was it just overhauled? If so, pulling the injectors while overhauling lets them dry out and gum up. I recommend running a can of BG44k. Don't bother with the cheap brands. BG44k is the best. If you absolutely can't find it at NAPA or parts house, give Lucas a try. It isn't as good but it is much better than all the rest.

Oh i forgot to mention that... haha i have new neon 703's (which were ultrasonically cleaned)... And my engine is rebuilt (only 10,000 miles on it), not new. Sorry, i didn't clarify. Oh... and the knock sensor is new also. The CTS sensor i checked is for the ECU.... So i really am baffled on this one.

Also on my O2 sensor, when i tested it alldata said it needs to be 5-7 ohms, and it tested to be around 8.5 ohms. It didn't give a infinity reading, nonetheless its not between 5-7. Should i be worried about that, or is it probably just fine?

How old is the O2 sensor? The testing procedure for the Renix O2 sensors is vague. If you don't knolw it's age, replace it.

You really need to get your CCV system back into shape before going much further. That being compromised could cloud future diagnostics.

You say it has 10,000 miles on the engine. Has it had this problem during the 10,000 miles, or is the problem new? What changes make, new parts did you replace before the problem started????

The CCV orifice is critical to having a stable idle!!!!! Fix that first!!!

The O2 data on the ohms is fine, but all that tested was the internal resistance heater. It did not test the O2 sensor. See:

http://www.naxja.org/forum/showthread.php?t=1012701&highlight=sensor+renix+test&page=5

I also suggest checking the entire system with a vacuum gauge and fuel pressure gauge if the problem gets worse.

Its had this problem ever since i had the jeep. It use to idle really low, and much worse before i upgraded my injectors. The 703's helped a whole lot as far as performance and the idle is concerned. My O2 sensor was new when i bought the jeep in 2009. I have checked the entire system with a vacuum gauge. My engine is producing around 16-17 psi of vac at idle. I don't have any leaks, i'm curtain of that. I couldn't find a CCV orifice in the local auto parts stores, they ordered in a "CCV orifice" that is supposedly for this jeep, and it looks exactly like the old orifice grommet, but inside this new one its open with no orifice if that makes sense. I figured that was better then having no grommet and a open hole in the valve cover and intake manifold. Where can i purchase a CCV orifice? Ill go check the O2 sensor sometime this afternoon.

I just used a multipurpose vacuum hose mender that had went from 1/8 OD to 1/4 or 3/8" OD on the plastic hose mender, then cut the 1/4" ID vac hose in half and slipped it in between, the ID of the hose mender is about 2 mm.

NAPA has an OEM style CCV tubing kit which includes the orifice IIRC.

Have you checked the cranking voltage of the CPS, and its connections?

Disconnect the CPS, and test the cranking volatge using 0-5 volt AC range on DMMeter. You wan to see at least .5 Volts.

No CCV orifice may be a lot of the problem!!!