2jzge swap into 1990 Supra, High idle

[Bernett]

I finally was able to start my 2jzge engine today and it seemed to run well other than it is idling at 1400 rpms. I have checked all the vacuum lines and they seem to be fine. I checked my throttle connection and there is nothing preventing the throttle plate from fully closing. I read forums and it looks like the IACV is the main culprit with high idle. I disconnected it and it didn't seem to make a difference. I took it off and ohmed it according a a site I read and all the pins Ohmed correctly. I then ran 12v from the B1 and B2 pins to all the S pins and while I heard noise I didn't see any change in the depth of the plunger. I cleaned the plunger and then put it back and ran it and I ended up with the same 1400 rpm idle. I'm thinking I need a new IACV but would like someone's opinion about trying anything else. I installed a JDM 2jzge engine with Dr. Tweak doing the harness. I don't have AC connected and I'm not using the idle up connection for the power steering. The engine sounds good other than the high idle. Any help in deciding to purchase another IACV or try something else would be appreciated. This has been a long process for me and I was relieved to hear the engine fire up today.

Thanks

 

[hvyman]

The iac has 125+ steps. So each step is super small. So you need to ground each pin in sequences with the 2 power pins hooked up to 12v and go around a lot of steps before you will notice w difference.

 

[Bernett]

Thanks. Both times when I removed the IACV the piston was in the same location. It appears to be open quite a bit. Do both power pins need to be powered at once when you ground the other plugs? My check engine light didn't go on when the IACV wasn't connected. Is that a problem? I'm wondering if other sensors aren't functioning correctly if that would affect the IACV. I have a MAP and air temp sensor. When I disconnect the MAP vacuum line the car ran really poorly so I figured it was working. I haven't tried the air temp sensor. My engine temp guage on the dash works. Is that the same sensor that the ECU uses to check engine operating temps? Where did you learn all this?

Paul

 

[Bernett]

I seemed to have solved my high idle issue. It appears to have been the IACV. Thanks to Hvyman and an article in Pro Street I tested my IACV by connecting 12V to the B1 and B2 pins one at a time and then grounded the S1 and S3 pins and the S2 and S4 pins to make the plunger move in and out. It was actually interesting to do it . If you supply 12v to either the B1 or B2 pin and then ground the S1 and the S3 pins one at a time and keep going back and forth the plunger will move out. If you want it to move in then ground the S2 and S4 pins going back and forth. What I found is that I could get my plunger to move out all the time but I had two dead spots when trying to get it to move back in. I took the IACV apart and cleaned it and lightly sanded the contacts with 400 grit paper. It took a couple of times doing this but I eventually was able to eliminate the two dead spots when the plunger was retracting. I had extended the plunger and put it on the engine and when I started it I couldn't get it to idle. I was pretty sure it would take some time for the plunger to get to the correct spot and I was right. I turned off the engine and then started it again and it settled in at around 500rpms. I then set my timing and I was slightly retarded so when I got it right my engine idled at 700rpms. I shut the car down and waited for it to cool and started it again and it idled at 1,000rpms and then moved to 700 as it warmed up. The attached picture shows which pins are the B1, B2, S1, S2, S3, and S4.

Paul

 

[Bernett]

Unfortunately my high idle problem still persists. I'm learning more about the IACV. I manually, meaning with voltage, close the piston on the IACV and then put it back on the engine. It initially idles much lower. The more I close the piston the lower the idle. Then ever time I turn off the engine and then start it again it seems to idle 200 rpms higher and doesn't go back. This keeps occurring until the idle gets to about 1,400rpms. Then when I restart the engine I initially get a surging idle ranging from about 2,200 rpm to 1,400 rpm. In about 10 seconds the surging stops and the idle settles at 1,400rpms. When I take off the IACV the piston is now almost fully retracted. I attribute the surging to the ECU shutting off fuel because it sees the idle too high. I read that in some other forum that when your TPS is in the idle mode the ECU won't let your engine idle above 1,600rpms. It stops it by shutting down fuel. Then when the engine drops below 1,600 rpms the fuel is back and then the surging continues. I guess my engines settles in below the 1,600 rpm level and therefor the surging stops. I also noticed that when I manually adjust my IACV the grounding of S4 and S2 pins only works when I supply 12v to B2. I can't get plunger to react when I ground the S1 and S3 pins unless I supply 12v to the B1 pin. That wasn't happening a day ago. When I supplied 12v to either B1 or B2 I could get the plunger to move grounding any of the S pins. It sort of makes sense because why would there be a B1 and B2 pin that needed 12v if you could actuate the plunger with only one B pin and 12v. I tested my TPS and it appears to be in spec. When it is fully closed it had less the .5 ohms and when opened slightly using the feeler gauges it loses continuity. So I suspect the ECU thinks its in idle when the throttle is fully closed. I'm thinking I need to get a new IACV but the fact that I can manually open and close the plunger which is what is supposed to happen makes me leary of spending the money. I haven't been able to ohm out my coolant sensor. I think that is the last thing I should check. I know I can obtain a smooth low idle when the IACV piston is almost fully closed. If the ECU could keep it in that position when the engine is at full operating temp I would be fine. Does anyone agree that I should just bite the bullet and purchase a new IACV? I think I can ohm my coolant sensor at my ECU connections. I can't get to it easily under the intake manifold. Any other suggestions would be appreciated.

Thanks

 

[Bernett]

I just ohmed my air temp and coolant temp sensors and the both ohmed that same and were in the range that they should be. I'm running out of options other than my IACV is not operating correctly. If anyone agrees please let me know.

Thanks

 

[Bernett]

I really need some help. You can see that I have posted several replies in a row and haven't had a reply. Have a broken a forum code of conduct?

I just got a new IACV and basically nothing changed with my car. The piston on the IACV was more closed so when I initially started the car it's fast idle was at 1,400rpm and it decreased to 900 rpms. Then I shut it off as I have done in the past and the fast idle speed was 1,700 rpms and it decreased to 1,100rpms. I shut off the car again and started it and the fast idle was now at 2,000rpms and it settled at 1,400. This is exactly the same behavior I had with my old IACV. If I manually set the piston more closed the car initially runs with lower idle speeds both fast idle and idle. Then each time I shut off the car and turn on the car the idle speeds increase until I get to 1,400 rpms. I'm running out of options. I have checked the ECU for leaking capacitors. Everything looked good. I have ohmed my air temp and coolant temp sensors and they are good. I've ohmed my TPS and it seems to be fine including having an idle position. I haven't fooled with the TPS or the idle screw on my throttle body because I just don't think they are off. My ECU doesn't throw a check engine light when I pull off an O2 sensor, or the TPS, or the IACV. When I jump the e1 and te1 the check engine light flashes constantly. I don't seem to get a change in idle speed when it is jumped. I have a JDM ECU and engine. I'm not sure how to check the ECU to see if it is causing the problem. Everything else seems to be OK. The engine runs very smoothly and isn't overly rich or lean as far as I can tell. I really would appreciate some guidance on potential next steps. The only thing I have tried is messing with the TPS and the idle screw. Does anyone think I should try that? Any suggestions would be greatly appreciated.

 

[Bernett]

I did more work on my car today. I removed the intake manifold and cleaned it. I inspected it for any potential leaks. I checked all my vacuum lines again and didn't find any leaks. I put it all back together but didn't connect the air intake hose so I could observe the intake manifold. The engine ran as it has and idled at 1,500rpms. I then shut it down and put a piece of duct tape inside of the intake manifold blocking the air passage to the IACV. The car then idled at 500 rpms and very smoothly. I opened the throttle and the idle settled in at 650 rpms. That is what I expect. For some reason my IACV isn't closing. I have tried two IACVs so I know it isn't them. I can't figure out why it won't close. I checked the wiring back to the ECU and it appears to be pinned correctly. I bought my harness from Dr. Tweak and they have been very cooperative as I have called to ask questions. I did see a post somewhere where the person wired lEDs to the wiring of the IACV to watch when the grounds occurred. I'm just not sure I want to go through all of that to see what is going on. I may need to do that at some point. I really would appreciate someone to provide me with a comment or guidance. I really don't want to try another ECU. Dr. Tweak said I would need a JDM ECU because of my MAP sensor.

 

[Flateric]

Have you done a boost leak test and opened you TB during it to see if perhaps you are leaking around your injectors or anywhere else on the intake side of things.

Check the simple things first and work up from there.

Are you trying to run a map setup with a maf ecu somehow? Dr Tweak is a very informed guy on this sorta thing. I doubt he would suggest something like this if it was not required.

 

[Bernett]

I think I have my idle problem solved. I am able to get the engine to idle with the IACV fully closed. I manually closed the valve and the car idles really nicely other than I'm getting bad vibrations at 900 rpms. I then wired in two toggle switched to manually control the IACV valve and it seems to be working. the ECU opens the IACV when the engine shuts off like it should. When I start the car it idles around 1100 rpms. It then drops to 900 on its own as it warms up. I then use my toggle switch to further close the IACV and I can control the idle speed all the way down to 500 if I want it that low. I know that is not how it is supposed to work but my solution is working. I will take some pictures and show what I have done because it may help others solve their idle issues. The vibrations are another story and thread. I think the mounts I bought from driftmotion are too stiff and are transmitting the vibrations to the car.