1991 Toyota still having idling issues, I've tried a number of things
09-04-2017, 07:28 AM
#1
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Thread Starter
1991 Toyota still having idling issues, I've tried a number of things
help me... I just acquired a 1991 Toyota pickup truck 2.4l 4 cyl 4x4.. for the longest it stayed under a carport for years and was only started and driven around maybe 1 or 2 times every 6 months...well now that it is almost my every day driver things are starting to mess up on me and break..I have change the spark plugs and distributor, knock sensor, and the idle was still inconsistent , I replaced the idle control sensor, then the throttle position sensor (3x because I kept getting bummed sensors) but the idle is still inconsistent.i tested the fuel pump and change the fuel filter and still idle is inconsistent I checked the throttle return spring and it did have some slack so I added an extra spring to close the throttle when the gas pedal isn't being pushed., still same problem.. so I did some research and I've read I could just unplug the throttle position sensor and drive with out it...I did and her idle is steady. The pictures before the higher rpm is with the air on and the lower Rpm is without air after driving it for 5 minutes to a friend's house.. it's not throwing any codes with the sensor unplugged and I smell the exhaust and she's not running rich.. so my question is do you think the wiring harness for the ECU is damaged or the ECU itself is going out...how can I test the wiring and the ECU? She's my babie and I just want her fixed 
Last edited by Cryptile; 09-04-2017 at 08:33 AM.
09-04-2017, 08:33 AM
#2
Registered User
1991 Toyota still having idling issues, I've tried a number of thingsQuote:help me... I just acquired a 1991 Toyota pickup truck 2.4l 4 cyl 4x4.. for the longest it stayed under a carport for years and was only started and driven around maybe 1 or 2 times every 6 months...well now that it is almost my every day driver things are starting to mess up on me and break..I have change the spark plugs and distributor, knock sensor, and the idle was still inconsistent , I replaced the idle control sensor, then the throttle position sensor (3x because I kept getting bummed sensors) but the idle is still inconsistent.i tested the fuel pump and change the fuel filter and still idle is inconsistent I checked the throttle return spring and it did have some slack so I added an extra spring to close the throttle when the gas pedal isn't being pushed., still same problem.. so I did some research and I've read I could just unplug the throttle position sensor and drive with out it...I did and her idle is in the range is 750rpm without air and about 850 rpm while the engine is cold.. she runs about 1000k without air and 1100k with air... I'm not throwing any codes with the sensor unplugged and I smell the exhaust and she's not running rich.. so my question is do you think the wiring harness for the ECU is damaged or the ECU itself is going out...how can I test the wiring and the ECU? She's my babie and I just want her fixed
Unplugging sensors is not going to fix your babie. No CEL light, odd, but possibly stored code.
Most of the time a TPS unplugged will cause some of the signals to be mute, just a few problems your likely to have: a rich condition most of the time, adding extra fuel when accelerating.
And their are more.
Remember the Toyota engineers didn't put a TPS on to unplug, it's there for a reason.
The 22RE motor is controlled by a computer it's not mechanical.
As for 3 defective TPS's, I find that questionable unless they are not Denso's.
Unplugging sensors is not going to fix your babie. No CEL light, odd, but possibly stored code.
Most of the time a TPS unplugged will cause some of the signals to be mute, just a few problems your likely to have: a rich condition most of the time, adding extra fuel when accelerating.
And their are more.
Remember the Toyota engineers didn't put a TPS on to unplug, it's there for a reason.
The 22RE motor is controlled by a computer it's not mechanical.
As for 3 defective TPS's, I find that questionable unless they are not Denso's.
Last edited by ksti; 09-04-2017 at 08:35 AM.
09-04-2017, 08:39 AM
#3
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Thread Starter
The sensors were from AutoZone and I tested both before plugging them in and I got no readings from the meter.. I got a sensor from O'reily's and I got proper readings from it. I know unplugging the sensors isn't going to fix my problem, I'm trying to find out what the problem is.. I don't know how to test the ECU to see if that is the issue
09-04-2017, 01:24 PM
#4
Registered User
The tps harness needs to be tested in a case like yours. Look at a copy of the fsm for your truck's year and find the tps terminals at the ecu and test each one to it's corresponding end to the sensor. Then test the ecu terminals for correct voltage reading if the harness checks out ok.
The engine can only run in open-loop mode with tps unplugged, which isn't optimal because it's always running rich.
When you fit each new sensor, did you use a multimeter, feeler gauge and the fsm procedure to make sure it fell within spec?
The engine can only run in open-loop mode with tps unplugged, which isn't optimal because it's always running rich.
When you fit each new sensor, did you use a multimeter, feeler gauge and the fsm procedure to make sure it fell within spec?
09-04-2017, 02:53 PM
#5
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Thread Starter
I did use a multimeter, feeler etc on the sensors... everything was in spec...it's like once I got her set she was idling properly but then I would turned her off and start her a few hours later and she would forget and start idling way to high(1500)or way to low(400)... I'll test the wiring harness then the ECU. I'll look it up thx.
09-04-2017, 02:57 PM
#6
Registered User
Do you still have the dashpot adjusted so that the tiny spring under rubber bellows gets compressed as the throttle plate closes? If so, they have a tendency to stick once they get old and can really screw with idle settings. Just remove the hose with the dangling valve at the end and see if the idle stabilizes.
09-05-2017, 03:11 PM
#7
Registered User
Thread Starter
The dashpot on this model does not have a hose on the bottom of it.. I just tested the wiring harness and the ECU and everything checks out according to spec..the idle still jumps once it's warm.
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09-05-2017, 07:45 PM
#8
Get your valves adjusted. I went thru the whole erratic idle/stalling when hot episode that seems common with these models. Couldn't pass CA smog because of it. The fix ended up being valve adjustment. Also check the timing chain.
09-06-2017, 12:11 PM
#9
Registered User
Also check the Vf voltages to see if the ECU thinks it is in range.
You should NOT need an extra strong return spring, unless there are issues with the dash pot.
Idle Adjustment Screw O ring may be dry rotted
Sometimes the throttle butterfly shaft bushings are worn - but that is not the first think I would look for
I would clean out the throttle body
Vac leak in the intake hose where it attaches to the throttle body is also a culprit - mine cracked apart recently
You should NOT need an extra strong return spring, unless there are issues with the dash pot.
Idle Adjustment Screw O ring may be dry rotted
Sometimes the throttle butterfly shaft bushings are worn - but that is not the first think I would look for
I would clean out the throttle body
Vac leak in the intake hose where it attaches to the throttle body is also a culprit - mine cracked apart recently
09-07-2017, 11:35 AM
#10
Registered User
Have you actually adjusted the TPS? These TPS's can't just be bolted on. They have to be properly set. There's a switch inside it that tells the computer its completely closed. If the switch contacts aren't closed the computer will try to high idle. I had a similar problem on my 3.0. It would high idle but if i snapped the throttle closed (press the pedal and slip my foot off the side) it would come down to a normal idle. Cleaned my throttle body and it was good to go. Also, you say the high idle is only with the air on? Does the A/C actually work in your truck. Its supposed to open a valve that allows more air in (essentialy a metered vacuum leak) to compensate for the extra load on the engine
