JeepComanche89 Posted October 22, 2014 Share Posted October 22, 2014 OK so I have a 89 4.0 renix engine and AX-15, I thought I had gone through everything at least once but apparently not. Its pretty much always had intermittent problems with the engine. The issues have no real pattern and can sometimes go for a month without a single problem. Over the summer the truck would just stall, at random times whether idling or under power. And then not start back up again. If it sat for 5 to 20 min, it would start up no problem. I replaced the CPS with a new OEM one which did not help. I originally was running an 88 ECU that was original to the truck, not the 89 motor that is in it. In a attempt to solve the stalling issue, I installed the ECU from the 89, which was original to that motor, as far as I know. So both ECUs were from renix 4.0s, but currently I have the ECU that was original to the motor that is now in the trucki. Changing out the ECUs did not solve the issue either. I eventually replaced the CTS on the side of the block, with an autozone brand sensor (the dealer claimed they no longer made them). This solved the issues and ran great after that. About 2 months later I developed a bad fuel leak from the sending unit. The day I discovered the leak, the truck was loosing power randomly, and intermittently idling rough. However it would NOT stall, and I would eventually be able to correct it. I figured it was a fuel issue with the leaking sending unit. The truck sat for about 5 days while I was fixing the sending unit, and when I started it for the first time after that it started hard and was still ideling rough/loosing power. After a 5 mile drive, things had worked out and it was running perfect, fuel leak fixed. One day had passed and it began to loose power again. I noticed it was far worse when towing a trailer or under a load. So i checked fuel pressure and it was around 31 to 33 range, and did not fluctuate at all when loosing power. I ordered an O2 sensor from napa but it did not come in yet. I then discovered something that I think may be the cause. There is a port in the back of the intake manifold behind the TB, that is currently plugged off on my manifold. I just discovered that there is a IAT sensor that is meant to be installed in that port, but speculation on where to buy one. If anyone has any idea where to get one/ what ones will work or any info at all on that that would be great. Link to comment Share on other sites More sharing options...
88ComancheMitch Posted October 22, 2014 Share Posted October 22, 2014 Have you done Crusier's Renix Tips? Link to comment Share on other sites More sharing options...
big66440 Posted October 22, 2014 Share Posted October 22, 2014 As far as your question for the IAT sensor it is no longer available anywhere, not even aftermarket manufacturers ( at least that none that I know of) its a junkyard only part,I clean mine with Mass air flow sensor cleaner every oil change, your running issue could very well be caused by the missing sensor. Link to comment Share on other sites More sharing options...
big66440 Posted October 22, 2014 Share Posted October 22, 2014 Have you done Crusier's Renix Tips? This to, even the most insignificant thing can make a difference and if it doesn't you can at least cross it off the "Renix owner to do list" Link to comment Share on other sites More sharing options...
ParadiseMJ Posted October 22, 2014 Share Posted October 22, 2014 I had a bizotch of a time getting my MJ to start after I replaced the engine harness. It turned out to be just ONE of the sensor grounds, the CPS ground, being detached (not securely attached). When I found it and attached it (soldered it) it fired right up, every time. So I then learned the importance of grounds. Cruiser spent some time and energy learning and putting the list together and nothing on it should be discounted. Unless you have a 91+. Link to comment Share on other sites More sharing options...
JeepComanche89 Posted October 23, 2014 Author Share Posted October 23, 2014 Thanks guys. Yes I'm familiar with Cruisers tips. I still have not found time to eliminate the firewall pin connector (name escapes me), but I did clean it thoroughly. But yes I will double check the grounds again. However earlier today I had a second to look under the hood, and I DO have the sensor :doh: . For some reason I thought I didn't, too much other stuff on my mind lol. But behind that sensor, there is a fitting for a vaccum line. And that is indeed plugged off, I forgot to mention that in the original post. I know I researched it before, but could anyone refresh my memory on what that port is for? I will clean the IAT sensor, throw in the new o2 sensor just for kicks, and I'm going to order a MAP sensor from the dealer since the original one is in there now. That is the only sensor that I have not changed other than the IAT. Does anything sound wrong with that plan? thanks again Link to comment Share on other sites More sharing options...
cruiser54 Posted October 23, 2014 Share Posted October 23, 2014 Thanks guys. Yes I'm familiar with Cruisers tips. I still have not found time to eliminate the firewall pin connector (name escapes me), but I did clean it thoroughly. But yes I will double check the grounds again. However earlier today I had a second to look under the hood, and I DO have the sensor :doh: . For some reason I thought I didn't, too much other stuff on my mind lol. But behind that sensor, there is a fitting for a vaccum line. And that is indeed plugged off, I forgot to mention that in the original post. I know I researched it before, but could anyone refresh my memory on what that port is for? I will clean the IAT sensor, throw in the new o2 sensor just for kicks, and I'm going to order a MAP sensor from the dealer since the original one is in there now. That is the only sensor that I have not changed other than the IAT. Does anything sound wrong with that plan? thanks again Tips 1 through 5 to start off with. Post up the results of Tip 5, after doing everything else FIRST. No shortcuts. Link to comment Share on other sites More sharing options...
JeepComanche89 Posted October 26, 2014 Author Share Posted October 26, 2014 Ok, so i did most of steps 1-5 when first putting the truck on the road about a year and a half ago. However I did not replace the braided chassis ground cable (i know i know no shortcuts). And here is some more background information, I have a pacesetter pos header with a y tube. I had the entire exhaust welded, but he said he couldent get to where the y pipe meets the header, because it hugs the block so tight. So he used exhaust clamps, but unfortunately put one on too tight and egged the pipe out. So what I'm getting at is there is a exhaust leak, BEFORE the O2 sensor, but NOT at the head. So here is what I did just today. 1) looked at side of block grounds. Everything good and tight 2) took off braided cable and cleaned cable, and firewall/head surfaces. Although everything looked fine. 3) took off wire loom and found a taped up crimped connection. 6 black wires going to one black wire, all same gauge. Connection seemed ok, slightly oxidized. I cut the connection out, and soldered/heat shrinked the wires. I disconnected the battery before I started any of this, and left it disconnected for probably 45 minuets. When everything was back together, it started right up but was ideling rough, but did not stall. A few hits of the throttle and it seemed to smooth out momentarily. I left it idle for about 5 minutes, then shut it off. Came back 15 min later, started right up and drove away. I could still feel the loss of power when moving, and idle had gotton worse. Drove it about 6 miles to my destination and the idle improved. Took it out again to several stores, could not feel any problems with it after i left the first store. Then on my antidisestablishmentarianism back home (my last tripof the night), I drove it for a consecutive 35-40 minuets, doing everytype of driving i could think of. I accelerated hard, downshifted hard, drove normally on a highway, nice and slow through a neighborhood with lots of stop signs, idling in a drive through line, back to driving it hard, etc. This whole time I could not feel any of the previous symptoms. I'm not sure what to think. While I was out I got the 4 gauge and terminals for the ground upgrade. So I'm going to throw that in tomorrow regardless, and I still have the bosch O2 sensor. Should I put that in too? Any thoughts? Link to comment Share on other sites More sharing options...
cruiser54 Posted October 26, 2014 Share Posted October 26, 2014 I bet you busted the hose from the throttle body to MAP in the process. Link to comment Share on other sites More sharing options...
JeepComanche89 Posted October 26, 2014 Author Share Posted October 26, 2014 I bet you busted the hose from the throttle body to MAP in the process. That hose was previously broken and had 2 "couplings", but it didnt leak. But today i actualy did break it lol. I repaired it with another line i had laying around, and ended up cleaning the throttle body in the process. Where can I buy a new vaccum line? Also when i was working on that, I noticed the grommet in the throttle body has 2 openings. The line to the MAF sensor is on the bottom, but the top opening has no line, there is an open hole. What is meant to go there? Today I also replaced the braided ground cable per your recommendations, and bolted the one end to the heat shield on the manifold. I'm not sure why thats better than the head but that is what you recommended so i did it. I also made a ground from the negative post to the radiator support like you suggested. the second thing I did was check the resistance on the tps. I was getting .8 ohms, which reached 1.1 ohms when the harness was wiggled. I'm not sure if that is significant enough to cause a ground issue. Its still not 100% but better than it was yesterday. What do you suggest I do now? Thanks cruiser for all of your help Link to comment Share on other sites More sharing options...
cruiser54 Posted October 26, 2014 Share Posted October 26, 2014 That hose is no longer available. The rubber deally has vacuum on the lower part and the upper hole is just to hold the "deally" in. The reason I say to add the ground to the heat shield is that it's easy. LOL. I don't like seeing any fluctuation when the harness is wiggled. Are you saying that you have a new O2 sensor but haven't put it in? Link to comment Share on other sites More sharing options...
cruiser54 Posted October 26, 2014 Share Posted October 26, 2014 Think hard about doing #27. Link to comment Share on other sites More sharing options...
kook911 Posted October 26, 2014 Share Posted October 26, 2014 Think hard about doing #27. I have done #27 and don't let it scare you. Pretty straight forward. Disconnect each side and cut one wire from each side at a time. Solider and heat shrink it. Maybe a hour tops. Link to comment Share on other sites More sharing options...
JeepComanche89 Posted October 27, 2014 Author Share Posted October 27, 2014 That hose is no longer available. The rubber deally has vacuum on the lower part and the upper hole is just to hold the "deally" in. The reason I say to add the ground to the heat shield is that it's easy. LOL. I don't like seeing any fluctuation when the harness is wiggled. Are you saying that you have a new O2 sensor but haven't put it in? Ok, I thought so, just wanted to make sure there was no secret place to buy it lol I just feel that the head provides a better ground than through the heat sheild then manifold bolts. But I trust you lol And to recap, I am getting .8 ohms resistance in terminal B of the tps. When I wiggle the harness, It jumps up to 1.1 ohms. Currently I have a bosh O2 sensor installed. I put that in a year and a half ago when I put the truck on the road. I thought the cause of my problems may be the O2 and bought another new bosh sensor but have not installed it yet. Sorry I know its alot of info, but I appreciate everyones help Link to comment Share on other sites More sharing options...
JeepComanche89 Posted October 27, 2014 Author Share Posted October 27, 2014 I have cleaned the connector well about two months ago. I was planning on eliminating it but things keep getting in the way. But I will try to get it done sometime this week. Link to comment Share on other sites More sharing options...
cruiser54 Posted October 27, 2014 Share Posted October 27, 2014 Good plan. Link to comment Share on other sites More sharing options...
JeepComanche89 Posted October 27, 2014 Author Share Posted October 27, 2014 Should I replace the O2, or wait until i do #27? Link to comment Share on other sites More sharing options...
cruiser54 Posted October 27, 2014 Share Posted October 27, 2014 Funny you should ask that!! On my neighbor's 87 XJ, we were reading the factory scan tool and the O2 sensor switched slowly. He was gonna go get one but I said "Let's wait and do the C101 elimination first." After we eliminated the C101, the O2 switched very quickly like it should.... Link to comment Share on other sites More sharing options...
JeepComanche89 Posted October 28, 2014 Author Share Posted October 28, 2014 Funny you should ask that!! On my neighbor's 87 XJ, we were reading the factory scan tool and the O2 sensor switched slowly. He was gonna go get one but I said "Let's wait and do the C101 elimination first." After we eliminated the C101, the O2 switched very quickly like it should.... Haha awesome, I was think about buying a factory scan tool off ebay. So I will hold out on throwing that in for now, and I will do the C101 elimination. Any place to buy a nice grommet for the firewall? Link to comment Share on other sites More sharing options...
JeepComanche89 Posted November 1, 2014 Author Share Posted November 1, 2014 So I went to eliminate to c101, and found another crimped connection that I must have missed the last time. 3 brown wire w/ white tracer I think, into 1 brown. Soldered/headshrinked it, and then rechecked the resistance on the tps. This time I was getting .3 ohms resistance, and NO fluctuation when wiggling all parts of the harness. So i left the c101 as is for now, and checked the adjustment on the TPS. It checked out perfect. Still saw no improvement, so I replaced the O2 out of desperation. Still no change. Its pouring right now so I can't really do anything to it, but as soon as I get a chance I will eliminate the c101. Any other thoughts? Link to comment Share on other sites More sharing options...
cruiser54 Posted November 1, 2014 Share Posted November 1, 2014 That's Tip 6......... Link to comment Share on other sites More sharing options...
cruiser54 Posted November 1, 2014 Share Posted November 1, 2014 I just revised Tip 5 to be more clear: Cruiser’s Renix Sensor Ground Test This sensor ground circuit affects the CTS, TPS, IAT, MAP, ECU and diagnostic connector grounds. It’s very important and not something to overlook in diagnosing your Renix Jeep as it is common for the harnesses to have poor crimps causing poor grounds. If any or all of the sensors do not have a good ground, the signal the ECU receives from these sensors is inaccurate. Set your meter to measure Ohms. Be sure the key is in the OFF position. Using the positive (red) lead of your ohmmeter, probe the B terminal of the flat 3 wire connector of the TPS . The letters are embossed on the connector itself. Touch the black lead of your meter to the negative battery post. Wiggle the wiring harness where it runs parallel to the valve cover and also near the MAP sensor mounted on the firewall. If you have an 87 or 88 with the C101 connector mounted on the firewall above the brake booster, wiggle it, too. You want to see as close to 0 ohms of resistance as possible. And when wiggling the harnesses/connectors the resistance value should stay low. If there is a variance in the values when wiggling the wires, you have a poor crimp/connection in the wiring harness or a poor ground at the engine dipstick tube stud. Refreshing of the dipstick tube connection is covered in Tip #1, and the sensor ground upgrade is covered in Tip #6. On 87 and 88 models, you could have a poor connection at the C101 connector as well. See Tip #2 and Tip # 27. Revised 11/01/2014 Link to comment Share on other sites More sharing options...
JeepComanche89 Posted November 1, 2014 Author Share Posted November 1, 2014 Yes I thought i did step 6 already, but apparently I found the wrong crimp connection. As I posted earlier in the thread, I found 6 black wires going to one black wire and soldered and heat shrinked it. Yesterday I found another crimp connection that I believe was the correct one mentioned in step 5 and also eliminated it. So its safe to say step 6 is complete and successful. Link to comment Share on other sites More sharing options...
cruiser54 Posted November 1, 2014 Share Posted November 1, 2014 Yes I thought i did step 6 already, but apparently I found the wrong crimp connection. As I posted earlier in the thread, I found 6 black wires going to one black wire and soldered and heat shrinked it. Yesterday I found another crimp connection that I believe was the correct one mentioned in step 5 and also eliminated it. So its safe to say step 6 is complete and successful. You done good. Yep. Thanks for the earlier post. It helped me to clarify Tip 5. Link to comment Share on other sites More sharing options...
JeepComanche89 Posted November 1, 2014 Author Share Posted November 1, 2014 Any other ideas of what it could be? I'm still experiencing the same problems Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now