Troubleshooting help needed here

[mrsboone]

94 3.slow Someone left it parked for 6 years.
Cleaned fuel tank, new fuel pump, new fuel filter.
Hard to start, runs rough. Put in
new plugs, wires, distributor, rotor.
Runs the same. 4 codes coming up:
Coolant Temperature Sensor
Intake Air Temperature
Intake Air Sensor
Throttle Positioning Sensor
We replaced all 3 coolant temperature sensors, replaced MASS airflow sensor and throttle positioning sensor. All same codes still coming up, still runs the same. Thru all of this, doesn't rev beyond 2200 rpms w/out surging-pulsing engine problem.

 

[nicnmike]

94 3.slow Someone left it parked for 6 years.
Cleaned fuel tank, new fuel pump, new fuel filter.
Hard to start, runs rough. Put in
new plugs, wires, distributor, rotor.
Runs the same. 4 codes coming up:
Coolant Temperature Sensor
Intake Air Temperature
Intake Air Sensor
Throttle Positioning Sensor
We replaced all 3 coolant temperature sensors, replaced MASS airflow sensor and throttle positioning sensor. All same codes still coming up, still runs the same. Thru all of this, doesn't rev beyond 2200 rpms w/out surging-pulsing engine problem.

Have you done a compression test? You can also pull the vacuum line from the fuel pressure regulator and see if fuel is leaking out. Is it possible some of the fuel injectors are clogged or not functioning correctly? They're pretty easy and cheap to rebuild. What about errant vacuum leaks from the air intake ducts? Dorman sells replacement duct work. have you replaced the PCV valve? Checked the timing? Is there any smoke coming out of the tail pipe?

 

[mrsboone]

Have you done a compression test? You can also pull the vacuum line from the fuel pressure regulator and see if fuel is leaking out. Is it possible some of the fuel injectors are clogged or not functioning correctly? They're pretty easy and cheap to rebuild. What about errant vacuum leaks from the air intake ducts? Dorman sells replacement duct work. have you replaced the PCV valve? Checked the timing? Is there any smoke coming out of the tail pipe?

Haven't done a compression test, no fuel leaking. Cleaning the fuel injectors out now. Have repaired many vacuum leaks, cleaned PCV valve. Have checked the timing. Has a slight amount of thin smoke coming from tail pipe, smells like gas more than oil. Still has same problems. Disconnect battery, still hard to start, still same codes, still runs bad. Don't dare to take it out on the highway. We take test drives about 1/2 mile from house. Barely makes it back up steep hill that is our road. Will have to get compression tester. Truck came with a rebuilt engine. Top 1/2???

 

[flyinhawaiian01]

Since there's new plug in it now, and you've run it several times, what do they look like? Burnt? Wet? Any deposits? What about radiator cap, any accumulation of sludge? How's the oil cap look? Any large sludge under the cap?

Pressure and leak down test is definitely something you'll want to do, especially if you have sludge in those areas.

And you might as well do top and bottom if the leakdown test is bad.

Also, when you say you replaced the MAF, was it with another used one that was known to work, or is this a Cardone refurb unit? Those things just plain suck, I have one here that literally has metallic silver paint over part of the slider pcb inside, and because they painted the thing, the flapper door sticks at idle, which makes the a/f mixture fluctuate every time you let off the throttle.

 

[TRDparts4u]

94 3.slow Someone left it parked for 6 years.
Cleaned fuel tank, new fuel pump, new fuel filter.
Hard to start, runs rough. Put in
new plugs, wires, distributor, rotor.
Runs the same. 4 codes coming up:
Coolant Temperature Sensor
Intake Air Temperature
Intake Air Sensor
Throttle Positioning Sensor
We replaced all 3 coolant temperature sensors, replaced MASS airflow sensor and throttle positioning sensor. All same codes still coming up, still runs the same. Thru all of this, doesn't rev beyond 2200 rpms w/out surging-pulsing engine problem.

You said it sat for six years. I'm willing to bet that this is not a part issue.
You probably have rodent damage to the wiring harness. Mice and rats love to chew on electrical wires. I would start by checking continuity on those circuits.

 

[mrsboone]

You said it sat for six years. I'm willing to bet that this is not a part issue.
You probably have rodent damage to the wiring harness. Mice and rats love to chew on electrical wires. I would start by checking continuity on those circuits.

There has been lots of rodent damage, we have cleaned and spliced lots of wires back together--adding in extra wires as needed. Fixed all of the broken wires we could find. Don't know how to check the continuity for each item. Found out how to check the individual fuel injectors, will do that today, (but not the wiring harness). Any tips would be appreciated. Hubby is my mechanic. He says he doesn't know how to check (for example) the continuity of the mass airflow sensor, since it doesn't have a fuse to hook to.

 

[flyinhawaiian01]

Find the thread that has downloadable manuals for the closest year of your 4Runner, I know the '87 manual I have, it has a complete section on probing the ecu and what the expected results should be. If you probe something that isn't what the book says it should be, I'd start tracing that circuit.

Also, the manual has a section on testing the MAF, but I'd suggest just using a really sharp X-Acto knife and cutting the black plastic cover's RTV seal, then carefully popping the cover open and cleaning everything inside with isopropyl alcohol and a q-tip. Make sure the door opens and closes very smoothly and doesn't stick at all. If you slowly close the flapper door with your finger and it doesn't shut completely, you'll have lots of A/F ratio problems that will never be resolved.

Also, you can (although I'd wait till its running properly) adjust for leaner/richer fuel mixture by CAREFULLY(!!!!!!!!) moving the gear inside a tooth at a time each way (iirc, counter-clockwise for richer, clockwise for leaner).


Sounds like you have a lot of work on your hands with this one!

 

[mrsboone]

Since there's new plug in it now, and you've run it several times, what do they look like? Burnt? Wet? Any deposits? What about radiator cap, any accumulation of sludge? How's the oil cap look? Any large sludge under the cap?

Pressure and leak down test is definitely something you'll want to do, especially if you have sludge in those areas.

And you might as well do top and bottom if the leakdown test is bad.

Also, when you say you replaced the MAF, was it with another used one that was known to work, or is this a Cardone refurb unit? Those things just plain suck, I have one here that literally has metallic silver paint over part of the slider pcb inside, and because they painted the thing, the flapper door sticks at idle, which makes the a/f mixture fluctuate every time you let off the throttle.

We have dry,black sooty brand new properly gapped plugs. The black soot starts in the intake manifold, in the area of the egr valve or the cold start fuel injector. Going thru all fuel injectors, intake & cleaning all, refurb the fuel injectors.

No large sludge in radiator cap or oil cap. Yes, the MAF was a rebuilt one. Its not sticking.

 

[flyinhawaiian01]

Well, if there's no sludge in the rad cap or oil cap, chances are you don't have a blown head gasket(s), but I'd still do a compression test to make sure. That'll also tell you if there's a bent/stuck/burnt valve, so I'd do this one as soon as possible. I'm sure you already know this, but I'll put it out there anyways, you can rent the tools from most parts stores, rather than buying one just to use on this engine.

If its hard to start, and its not running well, and you have black sooty plugs that are new, I am thinking either stuck valves, or really badly adjusted valves (these require shims for the v6, and it could be someone messed up putting the wrong shims with a specific valve). Could also be a stuck injector or two, so see how it runs after you get your injectors rebuilt.

 

[mrsboone]

Took throttle body off & intake manifold off completely & where exhaust is reintroduced thru a tube in the intake manifold is a buildup of widespread 1/4"-1/2" of crud. Is this normal? My 2003 Tacoma isn't like this (as far as I know).....

 

[Ahlem]

My vote is several clogged injectors.

 

[flyinhawaiian01]

Took throttle body off & intake manifold off completely & where exhaust is reintroduced thru a tube in the intake manifold is a buildup of widespread 1/4"-1/2" of crud. Is this normal? My 2003 Tacoma isn't like this (as far as I know).....

Sounds like EGR tube. You should clean it out as best as you can. That could be part of the problem, but there's something else going on too.

I dunno how the EGR tube looks on the 3VZE, but a few other vehicles I've owned, a .22 bore brush on a drill and some carb cleaner works very well!

 

[mrsboone]

Got a ton of crud removed, cleaned everything up, refurbished the fuel injectors, replaced a mile or so of vacuum lines, put it all back together, now it runs WORSE than before!!! IDK what's going on--maybe the engine calibrated itself to run with all of the crud in there & now the crud's gone???

 

[mrsboone]

Also, still throwing same 4 codes.

Coolant Temperature Sensor
Intake Air Temperature
Intake Air Sensor
Throttle Positioning Sensor

 

[flyinhawaiian01]

Are you able to swap another ecu in there to test it? Could be just a bad ecu, especially if you've repaired all the wiring and replaced those sensors. See if there's water damage at the ecu's connectors. I'd even take the cover off and see if there's any damage to the board. Burnt traces, water stains, corrosion, etc., should be pretty visible.