1986 4runner, Automatic, 22re
My Problem:
the truck sputters and jerks and loses power at random when the engine is under load: accelerating from a stop, driving up a hill, trying to maintain highway speed. This problem is intermittent. Some days it drives totally fine, other days it's barely driveable. I have a trouble code 11: "closed throttle position (CTP) switch OFF during diagnosis"
Recent Maintenance, within the past two weeks:
New fuel filter, new engine air filter, thoroughly cleaned all the injectors, new injector seals top and bottom, new TPS, all new gaskets at the bottom of the intake plenum and at the throttle body, replaced every vacuum line (except the pcv hose which is still in the mail)

I gave up and took it to the toyota dealer. Their diagnosis is that I need an entirely new throttle body, which seems very strange to me because there are no electrical connections on it. The mechanic says that my TPS can't be adjusted because even with the adjustment maxed out it won't show the spec resistance, so it must be something wrong with the throttle body. I have observed this when I installed it and attempted to adjust it myself. I have read that the CTP lives inside the throttle body on some cars but inside the TPS on others. I kind of feel like they ignored my explanation of the specific problems and are just chasing after the trouble code.

So at last here are my questions. Could an out of adjustment TPS be causing such serious driving issues? Could a trouble code 11 be the fault of the throttle body and could that be a cause of my engine sputtering? To me this problem seems very much like a fuel system or ignition issue, I'm having a hard time seeing how replacing my throttle body would make my car stop sputtering

thanks.

 

Yes to all. If anyone has messed with any screws on the throttle body or if the dashpot is keeping the throttle from returning all the way that could happen. What is your idle and timing?

 

I think Toyota only put the dashpot on manuals? I have an automatic. It idles just fine and I don't sense a timing issue, as the problems I'm having are very inconsistent. It doesn't seem to correlate with shifting gears either, mainly it's at its worst when I'm demanding more power from the engine

 

The first thing that comes to mind with the explanation "can't set tps to spec" in my mind is someone fiddled with an adjustment screw that they shouldn't have...

There is a screw that rests against the throttle stop, the same one you put the feeler gauge in when setting the tps adjustment, this sets the throttle plate resting angle it should never be moved except in very rare cases (ex. Ok rare enough I don't have an example!). It may have been adjusted by someone attempting to set the idle speed which is a completely different screw and method of idle speed adjustment. You will find the specified throttle plate opening angle in a FSM.

How ever before I even looked that throttle plate spec up I would run a quick test of the "New" tps to check its capable of meeting the specified resistance when not mounted to the throttle body, it maybe faulty.

Also visually inspect it's the correct orientation/model year, as these did change, the incorrect part will have the blades 90° (roughly) to the mounting holes. It is not unheard of for the wrong part to end up in the wrong package.

Why was this "maintenance" performed exactly, throttle body gasket in particular is a life time item and not "maintenance"..

Was the "intermittent" issue a by product of the recent work (was it there before) or was it the reason for the work?

When you had the throttle body off what was done to it? Was it inspected for wear to the throttle plates carrier shaft (rod the plate attaches to) or the surface it rides on (typical symptom for this being an issue is an erratic idle due to it not returning to same spot when the throttle is released after being opened).

Q&A...

Can a TPS cause intermittent drivability issues?

Yes. If the signal it sends is erratic, or the proper signal is not reaching the ECU as sensed. The ECU falls back to a fail safe mode and bases air fuel mixture off of engine load (VE) as read by the VAFM (air meter) and RPM signal.

In what way might a damaged/faulty, or maladjustment of the throttle body prevent TPS adjustment?

If the shaft doesn't rotate freely such that it reliably returns to the "closed" position (note it's not fully closed, from memory its someone like a 1mm gap or 1°). You get erratic signals from the tps.

A second scenario is the sensor end of the throttle body has been damaged. Either the blades bent or a loosening of the blades to the shaft.

In what way can the TPS make my engine sputter?

It is a primary sensor for the air fuel mixture, more precisely it tells the ECU you want to accelerate the engine RPM. If the ECU doesn't receive the IDL (idle) signal while the throttle plate is closed its going to add fuel and try to bring the RPM up however the throttle plate is closed so the air fuel ratio goes rich and you might end up with more fuel than be fully combusted.

I wouldn't so much describe this effect as sputtering, it's a burble or pop in the exhaust (aka after fire, you'll find this symptom in the FSM with the diagnostics flow chart)..


As mentioned above the the throttle position sensor is a primary control sensor of the fuel system.
Perhaps you meant something along the line of fuel pressure or fuel flow, both critical to and sub systems of the fuel system..

You can test both of these, no need to guess. Fuel has a factory spec, something in the ball park of 38psi off hand. Returned fuel flow.doesn't have a factory spec but the community has come up 500cc/ml per minute from real world tests.

I think you underestimate the role of the tps. But are likely on track with "fuel or spark" being a primary source of your issues. Test and inspect both, but don't forget the subsystems of the fuel pump, fuel regulator, oxygen sensor, ignition wiring from ECU to ignition module and so on..

 

Does it sound like "marbles in a tin can", I don't think I get that analogy but I'm going to use it anyway.. There is a distinct sound where you go from a loaded engine to predetonation that I've not found a text description for that I really agree with yet.. In person it's very distinct and my brain screams, stop trying to kill that engine!

If the ECU detects "ping" it will retard timing which reduces available power.

A simple layman test for this is to switch to the highest octane fuel available at your gas pump, if you are not already using it. The effect this produces is a delay in when the ping occurs, notable by the exhaust note/sound and when the power drops off (higher rpm before it occurs)

 

Thanks for the detailed reply
I will do this when I get the car back from the shop

All of the work described was my attempt to address this issue. Its so hard to know if I had any affect on it because of how random the behavior is. I had the throttle body separated from the intake plenum in order to more easily remove the plenum without having to disconnect the coolant lines going into the TB. This was all done to get access to the fuel injectors.

What I am experiencing is distinctive sputtering. Driving at highway speeds I would even describe it as bucking. but again, not in relation to shifting gears. Once I have stalled completely and had to restart the engine.

 

Ok well start with this injector work. If you weren't smelling or seeing fuel you may have been told and misinterpreted "injector leaks are a possible cause of a sputtering engine". The leak that would cause a sputter is a leak inside the injector such that fuel is getting around the internal sealing surface (aka pintle/valve).

Next up is your description sputtering is certainly the wrong word to use here, which was evident by the elaborated description of bucking and stalling. Be overly descriptive, more is always better..

Stuttering, bucking, stalling, engine cutting out..

These would be symptoms of the ignition or injectors not firing.

A common intermitten problem is where the injector wires are spliced together at the factory in the engine harness. This is located roughly between the upper and lower intake. You'll find that the old protective sheath has been allowing water or even air which then condensates on the splices and corrodes the splice and wire. Lots of good threads on this repair.

A second common issue is the ignitor signal wires becoming brittle due to age or burnt due to lack of heat shields, bad placement of wires/tools/hands while doing other maintenance. These become apparent with a visual check or bend test.

I'm thinking the first is your issue. A simple test is to manipulate the wire bundle with the engine running or not running and an ohm meter attached at the ECU (back probed connector, Google it), a failed result is the engine cuts out or the ohm reading changes (spikes high)...

I'm way past bed time and going to pass you off.to the night shift =D

 

I had a 93 22re that had symptoms of a bad TPS. I unplugged the TPS and started it up. Smoothed right out but had horrible fuel milage and lacked power. Replaced the TPS and it solved the problem.

 

so I did this today, and the TPS does read the correct resistance when removed from the throttle body. Then I unplugged the TPS and drove the truck around the block, no improvement whatsoever. Still really bad stuttering, right now I can pretty much only idle or coast without the truck stuttering, whether the TPS is plugged in or not has no effect

 

And now you've worked through several steps and answered the question..

Nothing wrong with that tps, and its probably not the root issue. Solving this code is this first step it costs you nothing but time, solving codes is alway the first diagnostic step.

Put it on and set the idle position. If you can't set this tell us in detail what is and isn't set to spec, what is giving you trouble. Refer to the above information about the part differences, the "don't adjust me" screw, and throttle body/plate inspection.

Then we can walk through the rrest..

 

You heading in the right direction. You will get this figured out.

 

I just remembered this post and wanted to share my update in case it can help anyone else in the future. Turns out the magnetic pickup coil that lives inside the distributor had a broken/loose wire. Every time the connection would randomly jiggle loose from normal engine vibration the circuit would be broken. This pickup is responsible for telling the ECU the position of the engine so it can time the sparks correctly, so having that connection broken would kill the entire ignition system. Since the wire was not totally severed and only loose, this manifested itself with the symptoms I described: engine sputtering, random loss of power that doesn't seem to coincide with anything, violent bucking when driving at highway speeds.

Bought a new part for $45 rather than fudging around with a soldering iron. swapping the part took 5 minutes. That was months ago, and I've put over 2,000 miles on the car since then with no issue. Thanks to everyone who offered tips or suggestions!

 

Is it an OEM TPS sensor, or a 19,95 Ebay special?

Work on and off sounds like a short in the wiring at first?

Edit: I guess I'm late to the party! Cool you got it figured out. Great tip and thanks for the feedback.