Shandley Posted December 1, 2009 Share Posted December 1, 2009 I best start a new thread. My situation has changed quite a bit. I have a 1990 Jeep Comanche 2.5L RWD I rebuilt the engine because of major blow by. That fixed the problem. It was sitting around for a while but before you jump to fuel filter as my solution, I pumped all of the fuel out (it took hours to do) and I replaced the fuel filter again. Also I had the injector cleaned and tested. The trouble I am having now is a misfiring at idle and a hesitation when tapping on the gas. I will try to get a video of it... actually, I have one. It's hard to figure it but you can hear what it does during idle. BTW, it starts right up every time. How I checked the TPS: There are 3 wires. From the top down, they are A B C. A - Signal Voltage B - Ground C - Reference Voltage When I plugged my voltmeter leads into A & B and turned the key to ON, I got a voltage of 63mV. I pulled the throttle just off of the plunger it sits on and I got a voltage of 100mV. Just before wide open throttle, I get a voltage of 360mV. With the throttle wide open, I get a voltage of 14mV. I checked continuity between B and ground and it is quite good. When I checked the voltage between C & ground, I get a voltage of 4.972V I am wondering if anyone can tell me what this means. I have read up on this sensor and how to adjust but I get many mixed messages. 17%, 8%, 33%... If its less than THIS voltage then THIS is wrong... it's endless. Has anyone done this test with this engine, this year, and this sensor? O2 Sensor Now, when I went to check the oxygen sensor, in my Haynes manual it tells me to check the lead on the sensor to ground. My trouble is there are 3 leads coming off that sensor. I checked them all to ground and got infinite resistance. I started the truck and ran it for about 10 min. I checked again and 2 of the leads were infinite but the other one seemed to jump all over the place. This led me to believe that there was a voltage that was coming on and off over and over. I checked that but the meter I had would not show fast enough and didn't have a 'max' option to read the peak of any voltage. Any clues here? MAP Sensor Checked vacuum and it holds the correct voltages. Vacuum Hoses When I got to the hoses, a few were out of order but none of them were damaged or looking bad. Actually most looked brand new. I replaced a few that didn't look new and put all of them back to where they belong. I know a lot of you are wanting to throw me links to other places. Believe me when I say I have read them all. Every one of them. I have learned more about the Renix engine and the wiring than I have of anything else. While I really do appreciate the links, I would like to hear from someone who can really point me in the right direction and has has a 1990 2.5L (or relative). It seems the 1991 and later were all different. Many thanks and happy trucking! Link to comment Share on other sites More sharing options...
redneck23ms Posted December 1, 2009 Share Posted December 1, 2009 have you cleaned the iac? a dirty one can cause some strange idle issues Link to comment Share on other sites More sharing options...
dasbulliwagen Posted December 1, 2009 Share Posted December 1, 2009 Replace the O2 sensor, mine did something similar to this and once I replaced the o2 sensor, it cleared right up, and has yet to return. An o2 sensor is a sensor that creates voltage depending on the amount of o2 in the exhaust stream, the other 2 lines may just be for the heater if its a heated o2 sensor, you should have 12 volts on one of them, those 2 wires are the same color right? O2 sensors are very hard to test, so just get a new one, youll probably need one anyways. Link to comment Share on other sites More sharing options...
Shandley Posted December 1, 2009 Author Share Posted December 1, 2009 Hmm. Where is the IAC located on mine. Here is a photo of a top view of my throttle body. Link to comment Share on other sites More sharing options...
dasbulliwagen Posted December 1, 2009 Share Posted December 1, 2009 The 2.5 doesnt have IAC, It has an idle control solenoid, it is on the left of the TB in the pic, is a rod with a pluger on the end that pushes the throttle arm to where it wants it. Link to comment Share on other sites More sharing options...
Shandley Posted December 1, 2009 Author Share Posted December 1, 2009 Replace the O2 sensor, mine did something similar to this and once I replaced the o2 sensor, it cleared right up, and has yet to return. An o2 sensor is a sensor that creates voltage depending on the amount of o2 in the exhaust stream, the other 2 lines may just be for the heater if its a heated o2 sensor, you should have 12 volts on one of them, those 2 wires are the same colour right? O2 sensors are very hard to test, so just get a new one, you'll probably need one anyways. Thanks. They are so bloody expensive! I would hit up the wreckers here but they are expensive just the same! If I can test it, I am going to have to before spending a hundred :Canadaflag: on a sensor. Link to comment Share on other sites More sharing options...
dasbulliwagen Posted December 1, 2009 Share Posted December 1, 2009 Price them out, even at the dealer, I bought mine from the dealer for 45 bucks a couple years ago. Link to comment Share on other sites More sharing options...
Shandley Posted December 1, 2009 Author Share Posted December 1, 2009 The 2.5 doesn't have IAC, It has an idle control solenoid, it is on the left of the TB in the pic, is a rod with a plunger on the end that pushes the throttle arm to where it wants it. Is this the Idle Control Solenoid? Link to comment Share on other sites More sharing options...
dasbulliwagen Posted December 1, 2009 Share Posted December 1, 2009 Yes it is. Link to comment Share on other sites More sharing options...
Shandley Posted December 1, 2009 Author Share Posted December 1, 2009 Price them out, even at the dealer, I bought mine from the dealer for 45 bucks a couple years ago. I did. I cannot believe how much more they are up here in Canada. Link to comment Share on other sites More sharing options...
jmderyke Posted December 1, 2009 Share Posted December 1, 2009 your o2 sensor is a heated type so those wires getting high ground numbers are the heating coils, and the third is the actual sensor its self i believe its the white one(not 100%) that one should be with in spec so if not change it (but I'm not sure if a bad o2 sensor would make it run this badly) vacuum leaks will make it run this bad (i know you checked), check your emissions equipment, like the egr valve they go bad quite often. did you ensure timing was correct since a fresh rebuild? I will check in later I'm curious good luck Link to comment Share on other sites More sharing options...
Shandley Posted December 1, 2009 Author Share Posted December 1, 2009 Ok, good to know about the heated sensor. Now, I KNOW my Haynes manual is VERRRRY general. Can someone tell me what the readings (spec) are for the O2 sensor and how I can check it? How would I check the EGR valve. The Haynes manual, again, is very ill mentioned. The timing was never changed. It was a short block rebuild without balancing. Essentially, it was a ring replacement... which of course means bearings, head gasket, etc etc etc. It also says the timing is not changeable. I assume you are referring to the timing chain slipping. I have no idea what the timing is suppose to be on mine. On the sticker on the firewall, it says Not Adjustable. Here's a pic: I like photos.... :D Link to comment Share on other sites More sharing options...
mjeff87 Posted December 1, 2009 Share Posted December 1, 2009 disconnect the O2 sensor and run it, see if the problems go away. I chased a random stumble/misfire on my 2.5 for several weeks, couldn't figure it out. Then one time when it was acting up I started disconnecting things one by one to see what happened. When I unplugged the O2 it cleared right up. Ran with it disconnected for a few months and then one day I decided to plug it back in. Ran perfect from that point forward..... Jeff Link to comment Share on other sites More sharing options...
Shandley Posted December 1, 2009 Author Share Posted December 1, 2009 Alrighty. I will give that a shot when I get home. Link to comment Share on other sites More sharing options...
HOrnbrod Posted December 1, 2009 Share Posted December 1, 2009 It also says the timing is not changeable. I assume you are referring to the timing chain slipping. I have no idea what the timing is suppose to be on mine. Correct, you can not adjust the timing w. the stock distributor. But you can check it with a timing light off #1 cylinder. I ASSume there are marks on the harmonic balancer and the timing cover like the 4.0 has that should align with the timing light w. the engine at about 2K RPM. You can see if the timing advances as you increase the revs from idle and it should remain steady, not jumping around. If it jumps around it usually indicates a worn timing chain and/or a sloppy distributor shaft. Link to comment Share on other sites More sharing options...
Shandley Posted December 1, 2009 Author Share Posted December 1, 2009 Do you know what the timing should be at? Would it be zero if everything is ok? Link to comment Share on other sites More sharing options...
dasbulliwagen Posted December 1, 2009 Share Posted December 1, 2009 I still think th O2 sensor is it. Mine did just what your is doing, missing, running bad, hesitating. I know you don't want to spend anything until youre 100% sure, but this is almost guranteed, because you arent going to get satisfactory readings from an o2 sensor without an oscilliscope. Just try unplugging it like the other poster said, if it changes, bite the bullit and buy a new sensor! Link to comment Share on other sites More sharing options...
jmderyke Posted December 1, 2009 Share Posted December 1, 2009 hopefully its the o2 yeah try that test. you test the egr by applying vacuum to the top (see where that vacuum line connects at the top) use a mity vac if you have one if not use a piece of vac hose and suck on it if it holds its good, if air just passes through it, then the diaphram in it is bad. to check the timing get a timing light and connect it to the plug wire leading to the number one cylinder and battery, direct the light to bottom engine pulley timing should be around 10-12 degrees before tdc look at your manual for more info. it will have it under maintenance. even though the timing cannot be adjusted electronically it can be off mechanically. Link to comment Share on other sites More sharing options...
Shandley Posted December 2, 2009 Author Share Posted December 2, 2009 Well, I unplugged the O2 sensor and there was no change (nothing noticeable). I might have gotten a little rougher but I don't think so. I have pulled out the O2 sensor but is there any way to test it while it is out? Link to comment Share on other sites More sharing options...
jmderyke Posted December 2, 2009 Share Posted December 2, 2009 mmm I'm not sure...........did you get to check the egv and timing yet? Link to comment Share on other sites More sharing options...
Shandley Posted December 2, 2009 Author Share Posted December 2, 2009 Timing is tomorrow... but how do I check the EVG? Link to comment Share on other sites More sharing options...
jmderyke Posted December 2, 2009 Share Posted December 2, 2009 I wrote how to a few post back how to test the Exhaust Gas Recirculation valve but here's a video on testing it off of you tube to give you a hand. If you don't have a mityvac use a piece of vacuum tube and your mouth http://www.youtube.com/watch?v=IIUFw2KR6rU It might not be the egr valve but its has some of the signs, most likely your problem is in the items you just replaced or had worked on. But this is a very easy test worth a look at. Link to comment Share on other sites More sharing options...
jmderyke Posted December 3, 2009 Share Posted December 3, 2009 well any head way today? Link to comment Share on other sites More sharing options...
Shandley Posted December 3, 2009 Author Share Posted December 3, 2009 Yesterday, I pulled out my O2 sensor to get it all ready for the new one. As I got out from under my truck, I pulled a muscle in my leg... so I called it quits. Not to worry, I will post my results. :) Link to comment Share on other sites More sharing options...
Shandley Posted December 3, 2009 Author Share Posted December 3, 2009 Say, is my distributor suppose to have a sensor to detect the position of the camshaft? I've heard it called many things. Camshaft Position Sensor, Sync Signal Generator, Distributor Sensor.... Remember: My engine is the 2.5L from 1990 which suggests that it's a Renix. Link to comment Share on other sites More sharing options...
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