normally when the TPS fails or the IDLE points are out of adjustment the check engine light will come on and a code will be set in the computer. Have you checked for codes? the best thing to do is pull the valve cover and check the cam timing to crankshaft. The guides on both sides are known to break. This will cause it to jump time especially if it has high miles.
Well, that's an Ah Hah, and an Aw Man, at the same time. The Ah Hah because I replaced the head gasket last summer and broke one of those guides. The Aw Man because it would be so much easier to replace the TPS!
And maybe I will. I had not seen an engine light so hadn't checked codes, but I did just now. I got 4-1, 4-2, 5-1. According to my Haynes manual, 4-1 is an open or short in the TPS. 4-2 has to do with the speed sensor circuit, which is something I'm not familiar with. 5-1 is either A/C - which this truck doesn't have - or TPS again. Does this warrant replacing the TPS? or is there another way to test it?
Can you tel; me about the speed sensor circuit? Is that a switch or a valve that I can look at and check?
The code 51 is related to the IDLE points or signal input to the ECU. The 41 has to do with the VTA input to the input which tells the computer the Voltage of the Throttle Angle. There are 2 speed sensors. One is in the trans and one in the back of the speedo head the computer did not see an input at a given time. I would be more concerned about the TPS codes first. Make sure the IDLE contacts are set correctly and the VTA input is fluctuating voltage as the throttle is opened and closed.
"Make sure the IDLE contacts are set correctly and the VTA input is fluctuating voltage as the throttle is opened and closed."
I know I look smart, but can you tell me how to go about doing this? Thanks!
The IDL pin second from the bottom should have 0 volts with the throttle completely closed. As soon as you crack the throttle open the voltage should go to 12 v. The VTA 3rd from the bottom should fluctuate and change according to throttle opening. VCC top wire should be constant. Back probe the wires with the connect plugged in and the key on. Click the link below and save for the resistance tests if you have an Ohmmeter.
The IDL points are not adjusted correctly when the throttle is completely closed the voltage should drop to zero this is why you're getting the code 51. The other TPS code could be an intermittent problem in the VTA reading to the computer. As far as your Corolla goes I will read through what the other expert has posted but generally is considered bad etiquette to overstep someone else's question and answer process. I will send him a note to reply to you further so that he could finish up with you if that is helpful. Let me know.
okay - I understand the etiquette, just wondered if he was on an extended vacation or something, since I asked the question 4 days ago and it doesn't look like he has been online since.
Is there a way to adjust the IDL points?
Click the link below and save for more information on the TPS adjustment procedure. I will send the other expert a message noting that you're trying to get in touch with him you may try responding to his last post and reply to him also.
That other post has been manually closed you will need to contact a moderator or try and open it from your end to get further input from that expert. Let me know when you have the information above.
Sorry for the delay. I had some down time.
I took the throttle body off and cleaned it and am trying to do the tests you sent but I'm a little confused about what I should be doing. I don't get the appropriate readings indicated and I'm not sure if I can adjust or how. The TPS was initially turned as far clockwise at it will go. There was clearance between the throttle stop screw and throttle lever when the valve was closed. I adjusted the screws so that there is no longer clearance. I always have continuity between E2 and IDL and always have continuity between E2 and VTA. I can't turn the sensor any further clockwise.
The throttle stop screw should never need to be adjusted. With the throttle plate completely closed adjust the throttle stop screw that has the 6 mm locking nut until the brass throttle plate just cracks loose from the throttle bore. At this point lock the nut on the threaded screw so that your base throttle plate stop is secured. Then put your OHM meter between the bottom two terminals IDL and E1. If you loosen the two Philips screws and you installed the throttle position sensor correctly in other words so the little tabs are pushing against the spring-loaded sensor mechanism when you open the throttle plate. You should be able to loosen the two screws and slowly rotate the sensor until you have infinity or no continuity between these two terminals. This needs to take place at the specified .033 inch between the stop screw and stop lever So that when you remove the feeler gauge and go against the stop screw you should then have continuity between these two terminals. Tighten the two screws on the sensor and recheck that you have continuity then as soon as you crack the throttle open (ie at .033 clearance) you have infinity or an open circuit in the contact points.
I always have continuity between those E2 and IDL, whether the throttle is completely closed or completely open.
I guess it wasn't the throttle stop screw that I adjusted - it was a similar screw on the lever that goes to the thing that looks like a dash pot.
Make sure that you get the dash pot adjusted correctly and the base screw if you messed with that. Remove the throttle position sensor and make sure that the tabs are installed in the right position so that the sensor is opening. It may not be installed correctly you install it then rotat it so that you feel the spring tension on the metal tabs of the throttle body.
I did double check the tps - even tried it the other way but it was obviously wrong (spun completely), so I have the tabs lined up correctly on the TPS.
How do I know whether or not the dash pot is adjusted correctly?
It is designed to allow the throttle to come back slowly when the throttle is completely closed or released it should not be holding a throttle open. It sounds like the TPS is bad if you cannot get it to go to infinity or open on the two contact points at any position.
I don't have the part number for the 86 to 89 without the particular VIN number my information does not go back that far. You can easily call a local parts store and they should be able to look that information up for you as far as the year range that will fit.
I put in a new throttle position sensor, adjusted according to the instructions you sent, and reset the timing. I'm still getting the codes 41 and 42, the engine lopes at idle and has no power moving. Any ideas? Thanks
The code 42 for the speed sensor should not be a focus at this point that will not keep the engine from running the code 41 is still the computer not seeing the voltage of the throttle angle. Using a volt meter back probe wire and double check the top terminal which is VCC (G/Y) or voltage constant what is this voltage with the key in the on position with the connector plugged in? The second terminal down is the VTA or voltage throttle angle (Y) wire what is this voltage with a throttle closed and then monitor as you slowly open the throttle does the voltage change in correlation with the throttle opening?
I did the adjustments again and it's running better. I have to leave town for a week - My daughter will be driving it if it's running okay while I'm gone. I will check it again next weekend when I'm back and see what it's reading. Thanks for all your help.
Let me know how it goes.