ka24e sohc...1990 240sx..engine with 2500 miles since remanufacture
I've had some problems with idle. The engine idles great when cold but idles at about 1700 rpm when at normal operating temp. I've read just about all the valve in the engine. I just read a couple of posts the raise questions. The TPS has a switch that makes when the throttle is fully closed (theoretically) There was also the mention of a "soft idle switch" and a "hard idle switch" Someone please explain what they are and what the difference is???
Now I've went through the tps adjustment procedure a number of times. The potentiometer tracks linear from 2 to 10 kohms. I can adjust the voltage anywhere between the .45 and .55 that I want. When I adjust the TPS like this, the switch in the tps never changes because the throttle doesn't close nearly enough. To position the TPS to a point that the switch does change, I have to twist the TPS completely clockwise. Of course, this completely defeats the voltage adjustment. So, if some of you guys have some knowledge as to how this is supposed to work, please let me know. This idle thing is driving me nuts. I know I have adjusted the TPS and IAA per the procedure I found in the FAQ, but something is missing here. It may be the space between my ears.. thanks for any help you can be to me.
Thanks
TPS questions
There is no hard or soft idle, thats nonsense. Upon startup there's a cold idle, in which the idle is pretty high and gradually comes down to normal. The throttle position sensor has two connections, the one directly on the TPS body is the idle switch, the wire harness that runs off it is the throttle position sensor wires.
Adjust the voltage of the TPS and leave it alone. If your idle is high afterwards, then you need to lower you idle. Disconnect the TPS (fully warm engine) and lower the idle using the screw located on the auxillary air control body. Once you lower the idle, shut down, reconnect the TPS and that should be all.
Adjust the voltage of the TPS and leave it alone. If your idle is high afterwards, then you need to lower you idle. Disconnect the TPS (fully warm engine) and lower the idle using the screw located on the auxillary air control body. Once you lower the idle, shut down, reconnect the TPS and that should be all.
That seems to be the problem. I adjust the voltage. I disconnect the harness and adjust the idle using the screw located on the auxillary air control body. When I receonnect the harness the idle goes up to 1700rpm and basically stays there. That is why I asked the question about the switch. If I adjust the TPS to where the switch changes states at throttle closed, I can get the correct idle rpm. Any other iseas?Thanks
Thanks for the info U12. I did a little more looking at it this afternoon. I'm no Nissan mechanic, but I think I figured a couple of things out based on things I've read (faq and forum). I'm almost positive the TPS is fine. I removed it and hooked up two ohmmeters to it. I was linear from 2kohms to 10kohms. The internal switch made just below 2kohm. I was amazed just how close below 2 kohm it made. The switch closing is NOT what is making the car idle fine when the tps is adjusted full clockwise. I thought that was it because of the sudden dropoff in rpm as it is turned clockwise. it seemed to make the drop in rpm when the voltage from the tps dropped below 0.3 volts.
I followed the adjustment procedure perfectly again. And again, it idles at 1700rpm after the engine is warm. One thing I haven't tried yet is to reset the ECU. I have the battery completely disconnected with the park light switch set to on. It'll be disconnected for about 14 hours before I'll have to reconnect it. If any of you folks have any information as to whether this will do the job or not? I know a lot of electronics can hold memory quite a while. They have capacitors designed to hold voltage on the electronics just to keep from loosing memory. Is this true with this ECU? Is 14 hours long enough? If not, I can power it down over the holiday weekend.
I noticed the switch making did change the AAC and IAA when the mail harness is disconnected. That may be irrelivent.
If anyone has any more info..please feel free!!!! Thanks
I followed the adjustment procedure perfectly again. And again, it idles at 1700rpm after the engine is warm. One thing I haven't tried yet is to reset the ECU. I have the battery completely disconnected with the park light switch set to on. It'll be disconnected for about 14 hours before I'll have to reconnect it. If any of you folks have any information as to whether this will do the job or not? I know a lot of electronics can hold memory quite a while. They have capacitors designed to hold voltage on the electronics just to keep from loosing memory. Is this true with this ECU? Is 14 hours long enough? If not, I can power it down over the holiday weekend.
I noticed the switch making did change the AAC and IAA when the mail harness is disconnected. That may be irrelivent.
If anyone has any more info..please feel free!!!! Thanks
On a 90 model 240 the voltage output is not the primary concern. On this model they are looking for the idle position. Warm the car up and put an ohm meter on the center and lower terminals on the small black connector socket on the tps. Then turn the switch until you have continuity at idle and open curcuit just off idle. Be sure to recheck after tightening screws as this may change the setting. Also clean the trottle chamber before this adjustment so you get a good setting.
I have an education in electronics so I understand more about that than the mechanics. I disassembled the tps and cleaned the wiper on the potentiometer and the switch. I measured it with an ohmmeter. It tracked very linear from 2 kohms to 10kohms. Plus, the switch makes very very close just below the 2 kohm region. I originally thought that when I turned the TPS clockwise, it was that making that brought the idle down into an optimal range. I was wrong. The switch made a long way before the idle came down. ( I was watching it with an ohmmeter ) It seemed that when the voltage got below .3 volts before the idle settled below 1000 rpm. I am going to pull it again and make sure the switch is clean.
It might no even make any difference whether the voltage is correct (theoretically) or not.. The car seems to run well with it set that way. I get a little to picky sometimes when things don't go the way I think they should. Thinks for the help Drjohn.
It might no even make any difference whether the voltage is correct (theoretically) or not.. The car seems to run well with it set that way. I get a little to picky sometimes when things don't go the way I think they should. Thinks for the help Drjohn.
when you say it idles fine cold..what do you mean? it has a high idle when cold like its suppose to or it idles at about 700 rpm as its suppose to when warm? If it is high and just does not drop after warm up I would say check to see if the warm up device is shutting down. ie. wax kit under throttle drum or fast idle air valve located near aac valve. couple other basic things you should check too. coolant temp sensor ohm reading, is it right? Timing? also try to get everything close to normal , Tps adjustment ,timing and so forth by your procedures then once the car warms up check your airflow meter voltage should be around 1 to 1.3volts at idle
Yes, the problem seems backward from what it should be. When the engine is cold, the idle is at about 750rpm . As soon as it's warm, it idles at about 1700rpm.
The first thing I'll check id the airflow meter (since that's the simplest)
. Then I'll pull the check the idle valve and the aac. I've been intending to do that anyway.
UPDATE...When I pull the plug from the airflow sensor, the idle drops to around 500rpm. The voltage, when it's idling at 700rpm (per the tach) is 1.54 volts.:help
The first thing I'll check id the airflow meter (since that's the simplest)
. Then I'll pull the check the idle valve and the aac. I've been intending to do that anyway.UPDATE...When I pull the plug from the airflow sensor, the idle drops to around 500rpm. The voltage, when it's idling at 700rpm (per the tach) is 1.54 volts.:help
sounds like your getting a bit too much air through the meter at idle. try pinching off the air lines to the aac valve. the car should die if it is fully warmed up when you pinch that line off. the line is plumed into the intake air tube just in front of the throttle body..make sure you only pinch the hose that goes to the aac valve..if the car continues to run for an extended period of time with only a slight rpm drop. you got a cold start valve stuck open. I suspect it wont die..once you find the prob and fix it you may have to adjust the aac valve base adjustment so it will idle due to it being turned all the way in at this point.
OK, I cranked the aac valve base adjustment all the way in. I set the tps to where it normally is to get a voltage reading of about .40 volts. I started the engine...it went to 1700rpm..I pinched the large tube, that enters the plastic air tube just in front of the throttle body. The rpm's immediately to 500rpm and would stayed there until tomorrow if I had not turned the engine off....
When i have the tps set fully clockwise (which is the only way it will idle at 750rpm now) and pinch the tube. I get the same results..500rpm
Is the "cold start valve" back where the iaa and acc are located?
:help
When i have the tps set fully clockwise (which is the only way it will idle at 750rpm now) and pinch the tube. I get the same results..500rpm
Is the "cold start valve" back where the iaa and acc are located?
:help
This morning I pulled the acc and the iaa off..there is another valve(?) between the throttle valve and the intake manifold. I pulled the connector and it was very corroded. Also, the temp sensor is very corroded. Ive cleaned them both. I've also replaced numerous vacuum hoses. I've not got it back together yet.I'll post that when I'm finished. if anyone has any suggestions..plz post them. I'm checking this thread fairly often,,,,thanks
I drove about 10 miles. Got back home. adjusted the tps to .40 volts, unplugged the tps. adjusted the iaa down to 700 rpm. I plugged the tps back in and varrrrrooom , I got just about 750 rpm, give or take a few....The real test comes tomorrow morning when I go to work... if it still idles down when I get there, I call it fixed.....
Oh I'm sorry for mispelling AAC in the previous note. I can't keep up with all the acronyms. I do enough of that at work.
Oh I'm sorry for mispelling AAC in the previous note. I can't keep up with all the acronyms. I do enough of that at work.
Well, DAMN !!! I took it out for a freeway drive. Pull up to a stop....up to 1700 it goes. Here's a weird thing though. It seems to idle high only when the car is at a dead stop. If you are going down the freeway or a street for that matter, while it's rolling, pull the car out of gear and let it coast. As long as the car is moving, the car idles down to 750. As soon as the car stops...the idle goes up to 1700. I know this sounds strange. It has done this all along, but I didn't think to mention it. When I came home, I coasted into my drive and their was about a 10 second wait before the idle went up.Not sure what caused that long time delay..LOL
Sorry about the four letter acronym at the beginning of the note:icesangel
Sorry about the four letter acronym at the beginning of the note:icesangel
Well. This is tuesday. Everything seems to have leveled out on my car . After I sent the last note, I went back out and ran the idle alignment once more, I did this by following the procedure. Today, THe car runs and idles really well.
I did notice that on the corroded connectors, those sealers that are in most of the connections were not there. I'm sure this was 90% of the problem. I'm going to see if I can some from Nissan. if thy're not 10 busk a piece...I still can't get over that $115.00 radiator overflow tank geez... LOL:ylsuper
I did notice that on the corroded connectors, those sealers that are in most of the connections were not there. I'm sure this was 90% of the problem. I'm going to see if I can some from Nissan. if thy're not 10 busk a piece...I still can't get over that $115.00 radiator overflow tank geez... LOL:ylsuper