Rig: 86 Toyota 4Runner 22re 4x4

Engine idles fine about 850rpms when warmed. But while sitting in drive way, and pushing on throttle the engine surges from 2000 down to 1500 repeatedly, when when full throttle. While driving it surges when when first starting from a stop but after moving there is no surging issue and drives normal.

I Have read and followed there adjustment instructions, have also read 4crawlers and lcengineerings on setting tps. I can get it all set within specs but same issue. But still thought the TPS was an issue, ordered new one from 22reperformance. And was also able to set within specs.

my truck has the older round test jumper plug. Jumpered it out. Only getting one flash which shows normal operation. Engine idle drops like I would expect it to. It’s setting at 5 degrees jumpered. And with jumper removed it jumps up to about 13 degrees.

out of frustration I unplugged the tps and surging does the same thing. I jumpered out the test terminal while the tps was unplugged and I was not expecting it to drop the engine speed. But it did and timing was at 5 degrees with jumpered and tps unplugged.

the TPS is having no affect plugged in or not. What am I missing?

thank you for you time and help in advance.

 

I have posted numerous times on how to set the TPS with a timing light. It is vastly better than using a multi meter. If you don't have a timing light they are common in the tool loaner program at the chain parts stores.
If you set a TPS with a multimeter I can almost bet that when you lock it in place it'll be in a different spot each time. Not when you use the timing light method. And if everything else is properly set the TPS set screws will be pretty much centered in the slot, not oriented towards the end. And once you see the timing mark jump, then back off and lock it down down you know you just nailed it. I'm truly surprised that all the sites with tutorials still embrace the FSM method.

May not fix all the symptoms, but once done you know you can remove that from the list of possibilities.

 

Jimkola ,

I wasn’t so concerned with the setting of the TPS. I’m super comfortable with using multimeter and reading them and I was confident in the positioning of the TPS.

The jumper into the test terminals and the engine idle still dropping idle with the TPS disconnected is what was confusing me. The ECU was getting an idle signal that it shouldn’t have been getting with disconnected. And that the surging happing when the throttle was opened. So I was suspecting an ECU issue.

Luckly I have an 87 Toyota pickup that just so happens to have the exact same ECU in it and swapped it out to test. After swapping it ran great with zero issue. So I figured out my issue. Now just need to find a good ECU to replace it.

But I was very interested in the timing light setting of the TPS, so I searched for one of your posts that showed the method you described and decided to try it. And let me tell you what! It is night and day from the multimeter method. There is no guess work on adjacent. The jump and back to 5degrees is easy to find. I’ll be using the timing light method for adjusting the TPS from now on. Thank you for that info.

 

Man, what luck to have a donor ecu. I'm always reluctant to condemn one, as a failure is pretty rare unless water or something similar is involved. I wonder if cleaning the circuit board would do any good to rescue your bad one. I've seen some interesting instructions on cleaning. You can rinse a board with water and then dry. it just has to be distilled so no minerals are present. Thanks for posting you findings.
That timing light method should be a "sticky" so people don't have to search the threads to find it. I've got it saved as a Word doc so i just copy and paste, but it's be better if it was just easier to find.