Topic: 22RE Idle issue

[N2Frodn]

What I have:
87 Toyota Extracab 4x4, 22re, 279,000 on it, unknown miles on rebuilt motor (PO claims it was rebuilt). Stock except for Thorley smog legal header, aftermarket exhaust piping, high flow cat and flowmaster muffler.

Truck overall runs very well, plenty of power (for what it is), passes smog without issue.

When sitting, it idles fine at ~850 RPMs.

But, when I come to a stop, idle drops to ~450 rpms, stumbles and stutters. Idle will slowly climb back up to 850, it takes about 10 seconds to do so. It returns quicker if I feather the gas pedal slightly.

The problem is not in the brake vacuum system, if I coast to a stop it does the same thing. Problem also presents itself if I the truck returns to idle when in motion.

Usual tune up items have been addressed (plugs, wires, cap, rotor, fuel filter). All replaced with factory parts.

TPS was found to be bad when addressing a different issue (it was hanging at full throttle position when hot), replaced with factory part, adjusted to spec.

MAF was tested and found to be within specs listed in FSM, temporarily swapped with another known good unit just for the heck of it.

EGR system is clear and functioning

O2 sensor within FSM listed spec

AC Idle up circuit is functional.

Timing is set to factory specs and responds to test jumper.

Throttle body is clean

CEL is functional, no codes.

I am pretty much stumped at this point. Don't really want to keep throwing parts at it (a 3rz swap is in the long term plans for this truck). What am I missing?

Thanks in advance.

[emsvitil]

What happens if you rev it up, then take your foot off the gas (while sitting still)?

Does it return to normal idle speed or drop low?

[2manytoys]

I'm taking a stab in the dark here. What about the dashpot or whatever the linkage is called on the throttle cable side of the throttle body?

I think it is supposed to keep your throttle blade from slamming all the way shut when you let off the gas. It sort of cushions it so you don't get the problem you have.

There shoud be specs for that and your throttle stop.

[emsvitil]

My dashpot broke, and it doesn't have his symptoms..............


There's a fuel cut circuit for deceleration, but you're supposed to be moving; plus it turns the fuel back on at 1600rpm.

[N2Frodn [OP]]

Just went and took the truck for a spin.

At ~75mph on the freeway, 5th gear. Put it in neutral, rpms dropped to below 500.

Accelerated from a light, hard on the gas up to about 4500 rpms in 2nd. Lifted off and it did the same thing. Took about 10 seconds to recover to normal idle.

Tried to replicate the problem with my driveway (not moving). Does not present itself. Even put the transfer case in neutral and ran it through the gears for the heck of it.

The dashpot under the throttle bellcrank has a cracked boot on it. But if I am not mistaken, wouldn't that cause the opposite problem (above normal idle dropping as the stop settles?

[emsvitil]

The dashpot is for pollution control.  The boot is just for dirt/crud exclusion.

The automatic transmission doesn't have it,  so it's really not necessary.

A working dashpot only delays the full closing about 2-3 seconds anyway....


I can only think of 3 things.

The ECU isn't during the injectors back on at 1600 rpm.     

or

The cold start injector is on or leaking.    This causes a rich mixture that takes awhile for the ECU to correct (while correcting, the idle speed goes back up).

An injector is leaking,  loading up the manifold with fuel...

[N2Frodn [OP]]

The cold start injector shuts off after the truck warms up. Unless it is turning back on... Hmmm, come to think of it, I had a broken wire on one of the coolant temp sensors. I would imagine that is what tells the ECU to turn the cold start injector on. Will check my repair to see if it has a short in it and temporarily disconnect the cold start injector to see if that helps.

I have no idea of the condition of the injectors, doubtful that they have ever been serviced. May have to pull them and send them off for a testing/cleaning.
 
Do any other Toyota injectors cross over? I would rather get a set from the junkyard and send them off to get serviced, then swap them out for the ones currently in my truck.  

There are also a couple of vacuum lines that are suspect looking (kinda dry rotted). Where is a good place to find good quality line and how many feet of it do I need? Guess I might as well do all of them.

Dang! There I go spending money on this motor.  Told myself I wasn't gonna dig into this engine, just keep it running and save my $ to pick up a 3rz to swap in.

Thanks for all the help so far.

[emsvitil]

I know you replaced the TPS, but check the idle contact switch on it.........

Does it happen with the AC on?   (do full cold with open windows so it doesn't cycle off)

[N2Frodn [OP]]

The problem does manifest itself with the AC cranked.

Idle contact switch?

Got a couple hours to futz around with my rig again.

Tested and adjusted dashpot to specs listed in FSM (just for the heck of it).

Tested decel fuel cut off per FSM. Cuts off between 1600-1900 as listed in FSM.

Blocked off IAC in TB for testing.

Double checked all vacuum lines for proper routing.

Tested for vacuum leaks (none found)

Found melted O2 sensor wire that could have been shorting against the header. Repaired.

And, the results of all my testing and tinkering.... Problem is still there (Dammit!)

Thinking it is injectors or a wiring harness issue at this point.

Troubleshooting intermittent problems sucks!

Just thankful this rig isn't a daily driver.

ETA: Just drove the damn thing around for a bit. Problem is still there but I did find another issue. Radiator top tank is hot as is upper hose. Lower hose cold, radiator has evidence of a leak. Also heater not working very well. I would imagine a plugged radiator would cause all kinds of funky temp readings at the very least.
Hmmm.

[N2Frodn [OP]]

Replaced radiator, thermostat, hoses, heater control valve.

Flushed cooling system (Was nasty).

Also removed, cleaned and tested coolant temp sensor.

Cooling system is now functional. Heater no longer works (probably plugged with crap).

And........Problem is still there.

Went and found a deserted industrial area last night and did some testing.

I tried full throttle, dragstrip style launches straight to hard braking.
Same launch to coasting
Slow, normal type driving
Lugging the engine, 4th gear at 30mph type driving.

Problem showed up under all these circumstances, about 1 in 5 times, normal the rest of the time.

When I lift off the throttle, the engine pauses briefly at the normal idle setting, then falls below it. It is also accompanied by a slight stumble and a bit of bucking when at light throttle.

Problem does not occur when A/C is on, idle only drops to ~1100rpms.

Also noticed that two injector O rings are fubar and I have several vacuum lines that are cracked. Will do vac line replacement today and start looking for a good source for replacement injectors. I would send mine in, but I would prefer to keep downtime to a minimum. 

[N2Frodn [OP]]

In case anyone was wondering...

Figured out what the problem is.

Lazy EGR valve. Hangs up every once and a while and takes about 10 seconds to fully close once vacuum is pulled from it (letting off the gas).

Temporarily disabled EGR system. Truck runs much smoother and the idle shenanigans are gone.

Fear not any AlGore disciples, I will be replacing the EGR valve and vaccum bits with one off my parts truck very soon. (Gotta keep teh earf from warmin ya know).

[chim]

Just a thought to save you some $$.. I blocked off my egr.. removed all emissions and still passed smog...