Dickinson County Comanche Posted April 14, 2022 Share Posted April 14, 2022 Hello all, I’m still trying to deal with this dang high idle. I have done cruiser’s tips 1,3,5, scoured for vaccum leaks (all vacuum lines come back ok, as does the intake with all bolts tightened, and the throttle body, spray with brake clean came back just fine, no fluctuations in the idle.) cleaned the TB and even used a new one just to see if mine was faulty, no difference. If I pull the EGR valve out, it will stumble like normal, and when I release it will idle perfect, but if I touch the gas again, it will idle up. Even if left idling, it will not idle down after time. It also seems to have a slightly rich mixture, I did put the Bosch 710 injectors in which seemed to bump up power but not effect mixture any. If I get on then it will backfire, unless it is cold, it idles perfectly fine cold and will not backfire. I did relocate the coolant temp sensor to the thermostat housing, however I’ve tried different thermostats for coolant temp and it hasn’t changed anything. Good fuel pressure, good grounds, and good sensors. TPS is adjusted within spec, and multiple MAP, IAC, and TPS have been interchanged with no luck. Could it possibly be an O2 sensor? Link to comment Share on other sites More sharing options...
Dickinson County Comanche Posted April 14, 2022 Author Share Posted April 14, 2022 1 minute ago, Dickinson County Comanche said: Hello all, I’m still trying to deal with this dang high idle. I have done cruiser’s tips 1,3,5, scoured for vaccum leaks (all vacuum lines come back ok, as does the intake with all bolts tightened, and the throttle body, spray with brake clean came back just fine, no fluctuations in the idle.) cleaned the TB and even used a new one just to see if mine was faulty, no difference. If I pull the EGR valve out, it will stumble like normal, and when I release it will idle perfect, but if I touch the gas again, it will idle up. Even if left idling, it will not idle down after time. It also seems to have a slightly rich mixture, I did put the Bosch 710 injectors in which seemed to bump up power but not effect mixture any. If I get on then it will backfire, unless it is cold, it idles perfectly fine cold and will not backfire. I did relocate the coolant temp sensor to the thermostat housing, however I’ve tried different thermostats for coolant temp and it hasn’t changed anything. Good fuel pressure, good grounds, and good sensors. TPS is adjusted within spec, and multiple MAP, IAC, and TPS have been interchanged with no luck. Could it possibly be an O2 sensor? I am not running a knock sensor as of now, however I have not noticed any pinging. I’ve heard that if it’s tuned well enough and that you run good gas, it’ll work fine without. I do have one on order though. Link to comment Share on other sites More sharing options...
MiNi Beast Posted April 14, 2022 Share Posted April 14, 2022 O2 be possibly. Should be able to unplug that and notice a difference to say if good or not.. Link to comment Share on other sites More sharing options...
cruiser54 Posted April 14, 2022 Share Posted April 14, 2022 what did you find on Tip 5? Unplug the flat connector at the TPS and see what happens. O2 sensor won't cause high idle. Link to comment Share on other sites More sharing options...
fiatslug87 Posted April 14, 2022 Share Posted April 14, 2022 Recently someone posted that their TB return spring was binding which caused their high idle. I just solved my intermittent high idle by replacing the two main vacuum harnesses (4.0 Renix), although I could not track down a vacuum leak. Link to comment Share on other sites More sharing options...
watchamakalit Posted April 14, 2022 Share Posted April 14, 2022 My cruise control was holding the throttle open slightly on mine. Link to comment Share on other sites More sharing options...
Dickinson County Comanche Posted April 15, 2022 Author Share Posted April 15, 2022 On 4/14/2022 at 7:17 AM, cruiser54 said: what did you find on Tip 5? Unplug the flat connector at the TPS and see what happens. O2 sensor won't cause high idle. It lowered by about 100-50rpm Link to comment Share on other sites More sharing options...
Dickinson County Comanche Posted April 15, 2022 Author Share Posted April 15, 2022 On 4/14/2022 at 10:19 AM, fiatslug87 said: Recently someone posted that their TB return spring was binding which caused their high idle. I just fixed my intermittent high idle by replacing the two main vacuum harnesses (4.0 Renix), although I could not track down a vacuum leak. It’s almost like the IAC Isn’t closing all the way. I’ve tried 3 different ones and they all seem to only close about 2/3 of the way. I’ve tried 2 different TBs and cleaned them both. Link to comment Share on other sites More sharing options...
Dickinson County Comanche Posted April 15, 2022 Author Share Posted April 15, 2022 On 4/14/2022 at 7:17 AM, cruiser54 said: what did you find on Tip 5? Unplug the flat connector at the TPS and see what happens. O2 sensor won't cause high idle. My IAC isn’t closing all the way, what would cause that? TB is adjusted correctly and is closing all the way. Link to comment Share on other sites More sharing options...
Dickinson County Comanche Posted April 15, 2022 Author Share Posted April 15, 2022 1 minute ago, Dickinson County Comanche said: My IAC isn’t closing all the way, what would cause that? TB is adjusted correctly and is closing all the way. Link to comment Share on other sites More sharing options...
Dickinson County Comanche Posted April 15, 2022 Author Share Posted April 15, 2022 23 minutes ago, Dickinson County Comanche said: My IAC isn’t closing all the way, what would cause that? TB is adjusted correctly and is closing all the way. just just tried a new IAC, it opened up but wouldn’t idle back down again. Something is going wrong other than the IAC. What controls the IAC? Link to comment Share on other sites More sharing options...
cruiser54 Posted April 15, 2022 Share Posted April 15, 2022 ECU. Link to comment Share on other sites More sharing options...
Dickinson County Comanche Posted April 19, 2022 Author Share Posted April 19, 2022 Update: changed the O2 sensor and Knock sensor and it helped the idle. It’ll actually idle down now but it takes a little bit. Now the idle speed is correct but it fluctuates up and down now. I have a feeling it’s the IAC. Link to comment Share on other sites More sharing options...
MiNi Beast Posted April 19, 2022 Share Posted April 19, 2022 23 minutes ago, Dickinson County Comanche said: Update: changed the O2 sensor and Knock sensor and it helped the idle. It’ll actually idle down now but it takes a little bit. Now the idle speed is correct but it fluctuates up and down now. I have a feeling it’s the IAC. Cold start up or when warm? What's the rpm range yet in which it fluctuates? Link to comment Share on other sites More sharing options...
Dickinson County Comanche Posted April 19, 2022 Author Share Posted April 19, 2022 54 minutes ago, MiNi Beast said: Cold start up or when warm? What's the rpm range yet in which it fluctuates? Warm. Cold sits and idles steady. It’ll sit at warm at ~1000rpm then bump down to 850-900 momentarily, then go back up. It’s a consistent idle pattern, like the IAC is too slow going in and out. When it idles down like it should, it’ll go from 750 down to like 500 then back up. Link to comment Share on other sites More sharing options...
MiNi Beast Posted April 19, 2022 Share Posted April 19, 2022 I'm wondering about the temp sensor. Now...? do you even have one? Have you tried to clean up the IAC yet? If unplug it does it do anything? Link to comment Share on other sites More sharing options...
Dickinson County Comanche Posted April 19, 2022 Author Share Posted April 19, 2022 23 minutes ago, MiNi Beast said: I'm wondering about the temp sensor. Now...? do you even have one? Have you tried to clean up the IAC yet? If unplug it does it do anything? I’m running a new temp sensor, but it’s in the place where the HO one goes because I couldn’t get the plug out of the block. Every IAC I have has been cleaned, and the spot in the TB where the IAC goes has been cleaned. I haven’t unplugged it to check but based on the previous issues I’ve had I’m going to go out on a limb and say it would probably idle consistent with it unplugged. Link to comment Share on other sites More sharing options...
cruiser54 Posted April 19, 2022 Share Posted April 19, 2022 Temp sensor as in CTS is in the thermostat housing? Link to comment Share on other sites More sharing options...
Dickinson County Comanche Posted April 19, 2022 Author Share Posted April 19, 2022 32 minutes ago, cruiser54 said: Temp sensor as in CTS is in the thermostat housing? Yes. I don’t have a/c so it’s not the trigger for the electric fan. Link to comment Share on other sites More sharing options...
cruiser54 Posted April 19, 2022 Share Posted April 19, 2022 A CTS needs to be down in the block. Link to comment Share on other sites More sharing options...
JMO413 Posted April 19, 2022 Share Posted April 19, 2022 5 hours ago, Dickinson County Comanche said: Update: changed the O2 sensor and Knock sensor and it helped the idle. It’ll actually idle down now but it takes a little bit. Now the idle speed is correct but it fluctuates up and down now. I have a feeling it’s the IAC. How much fluctuation are you talking? Link to comment Share on other sites More sharing options...
Dickinson County Comanche Posted April 20, 2022 Author Share Posted April 20, 2022 1 hour ago, JMO413 said: How much fluctuation are you talking? About 150-250rpm Link to comment Share on other sites More sharing options...
JMO413 Posted April 20, 2022 Share Posted April 20, 2022 http://www.lunghd.com/Tech_Articles/Engine/Basic_Sensors_Diagnostics.htm#:~:text=RENIX vehicles use a SEPARATE,(See bottom of page.) This site has all the values for each of the sensors. I would definitely look at your CTS values. I fought the wandering idle for a long time. Mine still wanders and definitely idles at a higher rpm in the winter. Link to comment Share on other sites More sharing options...
cruiser54 Posted April 20, 2022 Share Posted April 20, 2022 Link to comment Share on other sites More sharing options...
Dickinson County Comanche Posted June 7, 2022 Author Share Posted June 7, 2022 Opening this topic back up. I borrowed a snap-on brick from a neighbor and my ST and LT fuel trims are locked at 128. No change if you rev it or anything. O2 voltage reads way too high and it doesn’t alternate between rich and lean mixtures. Barometric pressure reads 29” even,Man. Vac is 19.9”, and the map is at 9.1” Inj is 4.0 it also refuses to go into closed loop. I just changed the 02 not that long ago so I’m not sure what’s going on. TPS is within adjustment and the Temp sensor reads 206°F. Link to comment Share on other sites More sharing options...
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