88mjblue Posted April 12, 2015 Share Posted April 12, 2015 I tried looking this up but found more info on this relating to the AW4, where idle rpm can vary depending on if it's in drive/park/neutral. So what is the normal factory idle, at operating temperature/closed loop, stopped, manual transmission, neutral, no accessories/loads, Renix 4.0L? Link to comment Share on other sites More sharing options...
Blue XJ Posted April 13, 2015 Share Posted April 13, 2015 I think mine is right around 750-800 rpm. 4.0 (4.7 stroker) AX15 (used to be AW4) Link to comment Share on other sites More sharing options...
88mjblue Posted April 13, 2015 Author Share Posted April 13, 2015 Does the tachometer's 0-1000 increments go from 0-500, 500-750, 750-1000? It's weird because it's missing the 0-250 like the other 1000s... I'm assuming its scaled properly from 500-1000, but then the 0-500 is compressed for some reason. Link to comment Share on other sites More sharing options...
gogmorgo Posted April 13, 2015 Share Posted April 13, 2015 Yeah, it does something like that. I was never really sure whether it skipped a bit or just started at 250. Link to comment Share on other sites More sharing options...
Blue XJ Posted April 13, 2015 Share Posted April 13, 2015 I think that's how mine goes. I've never really paid attention to it. It shouldn't need to read below 500, since the engine doesn't go that slow. Link to comment Share on other sites More sharing options...
88mjblue Posted April 27, 2015 Author Share Posted April 27, 2015 Here's where my idle is at now: (I'm assuming this is 500rpm, hard to tell with this scale skipping) A little background: In an attempt to correct my hunting idle, I did the following: - completely removed and thoroughly cleaned throttle body - adjusted butterfly stop screw - removed, cleaned, & re-installed IAC (Q: Is there meant to be a gasket - in addition to the o-ring??) - cleaned mating surfaces and installed new throttle body gasket - adjusted TPS according to Cruiser's tip for engine TPS adjustment (0.83 Volts) Interesting part is when I first start it up, it goes to (what I think is normal) 750 rpm idle, and stays there for a while. Then after driving it a bit, it goes down to the ~500 mark. The idle is still hunting around, acting the same as before these adjustments, but just at a lower rpm. Link to comment Share on other sites More sharing options...
buckwheat Posted April 28, 2015 Share Posted April 28, 2015 I'll be watching this closely as my truck has the same issue, and I have tried the same solutions. I wish you luck fixing it. Link to comment Share on other sites More sharing options...
Knucklehead97 Posted April 28, 2015 Share Posted April 28, 2015 Thats exactly where my idle is when warmed up. I've been thinking I have a low idle but I've done everything to try and fix it... Link to comment Share on other sites More sharing options...
88mjblue Posted May 8, 2015 Author Share Posted May 8, 2015 Still having trouble with my idle here... I thought it could have been the IAC valve since I tried cleaning that really well and thought I may have damaged it with all the throttle body cleaner I used. So I purchased a new one and installed it today. No luck, may be even worse now. I have the same problem: idles around 750 rpm, but once it gets up to operating temp, then it drops down to 500 rpm. However, this time I noticed that when I revved it up it almost stalled when it dropped back down, so I shut it off and left it at that. What could that be? Why would a brand new iac make that condition worse? For what it's worth, I bought the Standard Motor Products AC12, I read that was a good quality one. Link to comment Share on other sites More sharing options...
88mjblue Posted May 8, 2015 Author Share Posted May 8, 2015 Also, it's still exhibiting the "hunting idle" syndrome (or HIS) Link to comment Share on other sites More sharing options...
88mjblue Posted May 9, 2015 Author Share Posted May 9, 2015 I read through another thread on here that had a similar problem, and thought it might be the O2 sensor. I replaced the O2 sensor today since the one in there was one from 1990 and I wanted the peace of mind. Anyway, that didn't do anything, still the same. I thought I read that renix 4.0s don't have a warm-up idle, is that true? It seems once the t stat opens up the idle drops to 500, weird... Link to comment Share on other sites More sharing options...
Knucklehead97 Posted May 9, 2015 Share Posted May 9, 2015 I would check the TPS. I have a stalling problem as well. TPS and MAP sensor. And when replacing the TPS (if it comes to that) try and find a MOPAR replacement. They're not bad priced on Ebay if you search hard enough. Have someone get you a part number if you can. The reason I say get a MOPAR one is because I had an Airtex and it lasted a total of 10 minutes. I currently have a Standard Motor Products one and I kinda have a gut feeling it is what my problem is. Just really don't want to buy ANOTHER TPS. Already changed my fuel regulator and O2 sensor twice... Link to comment Share on other sites More sharing options...
cruiser54 Posted May 10, 2015 Share Posted May 10, 2015 All symptoms of a bad O2 sensor. Use NTK. Not Bosch. Link to comment Share on other sites More sharing options...
88mjblue Posted May 10, 2015 Author Share Posted May 10, 2015 I've got a brand new NTK O2 sensor in there. Link to comment Share on other sites More sharing options...
cruiser54 Posted May 10, 2015 Share Posted May 10, 2015 I wonder if it's giving power to the internal heater of the O2 sesnor. Bad relay? One closest to the radiator in that bank of relays on the passenger fender, right behinf the big starter relay with all the wires on it. Link to comment Share on other sites More sharing options...
88mjblue Posted May 12, 2015 Author Share Posted May 12, 2015 Checked the relay, it's good. (clicked 85-86, and 0 ohms 34 to 87) Checked the wiring to the O2 sensor: - could not get 12-14V from the heater (orange wire) - got 5V solid for O2 signal to ECU - 0.01 ohms ground to neg battery (A = orange (heater); B = black (common ground); C = grey (O2 - ECU) <---- This is correct, right? For the heater test, do I need to have the engine running and back-probe? Or can I just have ignition on? Link to comment Share on other sites More sharing options...
HOrnbrod Posted May 12, 2015 Share Posted May 12, 2015 For the HOs, the engine has to be running to measure the O2 sensor 12V heater voltage since the voltage comes from the ASD (Auto Shutdown) relay. I would ASSume the Renix is the same as you don't want the O2 sensor heater coil energized w/o the engine running. But it's Renix, so who's knows - they are not logical. Try disconnecting the O2 connector, start the engine, and check for 12V across the heater supply and return pins, harness side. Also measure the resistance across the same pins while disconnected, engine off, on the sensor side. The O2 heater coil resistance should read ~5 ohms. Link to comment Share on other sites More sharing options...
cruiser54 Posted May 12, 2015 Share Posted May 12, 2015 Checked the relay, it's good. (clicked 85-86, and 0 ohms 34 to 87) Checked the wiring to the O2 sensor: - could not get 12-14V from the heater (orange wire) - got 5V solid for O2 signal to ECU - 0.01 ohms ground to neg battery (A = orange (heater); B = black (common ground); C = grey (O2 - ECU) <---- This is correct, right? For the heater test, do I need to have the engine running and back-probe? Or can I just have ignition on? Have it running to be sure. Link to comment Share on other sites More sharing options...
Megadan Posted May 12, 2015 Share Posted May 12, 2015 My truck still has some idle issues before it's warmed up, which is kind of the exact opposite of yours. Once my engine reaches temp, it holds a strong and solid 600rpm idle. Anything below that, or if I shut it down and it sits for a few minutes, it takes a minute or two to get back to a steady idle. When the idle waivers, it sometimes sounds like it is about to stall out, then it bumps right back up to a good idle. Rather confusing at this point. Link to comment Share on other sites More sharing options...
cruiser54 Posted May 12, 2015 Share Posted May 12, 2015 My truck still has some idle issues before it's warmed up, which is kind of the exact opposite of yours. Once my engine reaches temp, it holds a strong and solid 600rpm idle. Anything below that, or if I shut it down and it sits for a few minutes, it takes a minute or two to get back to a steady idle. When the idle waivers, it sometimes sounds like it is about to stall out, then it bumps right back up to a good idle. Rather confusing at this point. Tested O2 sensor? Original injectors? Link to comment Share on other sites More sharing options...
Megadan Posted May 12, 2015 Share Posted May 12, 2015 New O2, tests perfectly. New injectors.Once it's up to temp, it's rock solid. It's only when it below temp that the idle will stumble a bit, but it has never died. Link to comment Share on other sites More sharing options...
88mjblue Posted May 12, 2015 Author Share Posted May 12, 2015 O2 sensor heater is working, and although I don't have an analog meter, I did see 1-4 volts alternating, so I think O2 sensor + wiring is good. i read it could be related to intake/exhaust gasket, and I did notice this checking it out: Seems like just one bolt is missing, not sure if that's a big deal, but I will get a replacement from the junkyard soon. I also have the 746 injectors and am thinking I will combine jobs by taking fuel rail off, replacing intake/exhaust gasket, re-torqueing with all bolts present, then putting in the new injectors. Link to comment Share on other sites More sharing options...
Megadan Posted May 12, 2015 Share Posted May 12, 2015 that's one of the 3 exhaust studs that you are missing. Would definitely cause an exhaust leak if it's not sealing. Link to comment Share on other sites More sharing options...
cruiser54 Posted May 13, 2015 Share Posted May 13, 2015 Yeah, but no driveability issues. Link to comment Share on other sites More sharing options...
88mjblue Posted May 13, 2015 Author Share Posted May 13, 2015 Hey everybody, thanks for trouble shooting me through this, what do you make of this recent discovery: - I have the engine at operating temp, idling low at 500 rpm - I loosen TPS, adjust it up till idle goes to 750 rpm, tighten T20's back down - idle stays there, I think everything is back to normal, yay! - I drive it around for a bit, rpms go back to 750 like it should at idle - I get back home after a 5-10 minute drive, the idle is back to 500 rpm again..... Maybe I don't fully understand the tps, and that is normal behavior. Anyway, I re-adjusted the tps using 17% of 4.88 = 0.829 V, and I'm back to square one here. Also, I went through the throttle's full motion and watched the tps voltage, smooth throughout the range. Is it safe to rule out the tps, or did this adjustment test prove anything? Link to comment Share on other sites More sharing options...
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