I am still having problems with my 4runner.
It's sputtering again. And by sputter I mean it coughs until it dies. Then it takes a few minutes to finally get started again. And once started it runs really rough for a while and blows tons of black smoke out the exhuast. Once it smooths out it purrs, but lately it is has gotten worse. Now when I step on the gas it seems to choke a little, also when I accelerate it chokes.
I have changed the spark plugs, wires, rotor and cap, fuel filter and the air filter is spic and span. The TPS is clean as a whistle and the air flow meter is functioning properly. I just don't know what else there is.
The last I did was I hand adjusted the TPS and that smoothed the idle right out, and it ran beautiful for about a week (I even got 575km/tank of gas, and before I was lucky if I got 400km). But now it seems the problem is back.
If you can offer any advice please do.
JP

 

try unplugging the cold start injector, it could be sticking open when you initially start it... other that that, the other things that could put that much fuel in it would be if the AFM is malfunctioning, or the main injectors are sticking intermittently

 

idle speed ok? fuel filter clogged? not really sure but start from the basics and work your way up

 

Check for a vacuum leak.

 

Is there an easy way to check for a vacuum leak?

 

tell me how a vacuum leak can cause a extremely rich condition, I'm not seeing it....

 

Ive fiddled around with the TPS on mine when i was diagnosing a lean miss, i had the TPS off of the throttle body turning it by hand, it had no major effects on the running of the engine, the TPS may have something to do with it running poorly, but i doubt that it is the major cause, try unplugging it and run the engine to see if it helps. Now, the AFM is the input that the computer relies on for most if not all fuel delivery, i bet the problem lies there if its not a mechanical problem with an injector, just recently my friends 22re started running poorly, sputtering, it would run lean sometimes, other times it would puke out black smoke, it turned out to be a faulty AFM even though it checked out fine on the bench, I'm not saying to run out and buy one, but just keep this in mind.....

 

I should of asked this up front, but is your truck carbed or EFI? Because what I'm going to say only applies to EFI motors w/02 sensors. Vacuum leaks are one of the most common sources of running rich on EFI motors.

You have a vacuum leak somewhere after the mass-air meter. Your computer is calculating fuel requirements based on the amount of air coming into the motor as told by your mass-air meter, and it knows what to expect the 02 sensor to tell it based on this. The vacuum leak is letting more air into the combustion chambers, but it's after the meter so it's unaccounted for, therefore after the combustion is done the 02 sensor says, "Whoa, wait a minute, that looks lean, add more fuel!". So it adds more fuel, but regardless the 02 sensor is always going to read leaner than what would be expected since the vacuum leak is letting more air in, so it's always going to ask for more fuel.

You can have the same symptoms if you have an exhaust leak up-stream of an 02 sensor (I've had this problem before). Net result is the same: 02 sensor sees the exhaust gas is leaner than expected and says add more fuel.

Hope I explained it ok. I know that it's counter-intuitive, but it's how it works. You'd expect to run lean with more air being let in, but what happens is the 02 sensor is always trying to compensate. Now, if you're carbed then I have no idea and nothing else to add to your thread, hehe.

Easiest way to check for vacuum leaks is to start the motor and spray all the vacuum hoses/connections with something like starter fluid. If the rpms spike when you spray it somewhere then you found the leak. Good luck!

 

I test mine for vacuum leak with propane UNLIT! This may not be all that safe, but spraying liquid fuel isnt much better.

 

You say the air flow meter is working, have you checked with an ohm meter? Also, check the water temp sensor, the one for the computer. The ecu uses the signal for air fuel ratio and there is an air temp sensor in the air flow meter.

 

Puff's rig is an 87, so its EFI.

 

the leak will add more air which will lean out the mixture, the ECM will see this and richen the lean mixture to compensate for the leak, thats the job of the O2 sensor, to correct small fuel mixture problems, it will not go overly rich because the O2 sensor is seeing an actual lean condition from the vacuum leak, if it was a exhaust leak before the O2 then it would be rich because it is getting a false reading

 

Just speaking from experience. I've see it happen both ways before (vacuum leak and exhaust leak).

Most recent was a crack on a header tube on a mustang. It was a very small crack, you could barely see it when the header was removed. It was so small you couldn't even hear an exhaust leak, even while driving, but if you ran the car and stuck your head under the hood on the passenger side you could smell it. This car idled @ 10:1 afr. It smoked like a chimney under throttle and was barely tuneable in the upper rpm's. Replaced the header (and o2 sensor on that side to be safe) and it was back at 14.x:1 at idle and able to be tuned.

Anyways, it's worth looking and checking all your options, if for no other reason than to rule out what it isn't.

 

Cold Start Injector sounds like a good place to start. Unplug it and see.

 

Unplugged the cold start injector and it didn't seem to help. Still puffing black smoke. Also tested the AFM and the TPS with the OHM meter and they both check out. Will check the air hoses for vacuum leaks. Any other suggestions?

 

Check for exhaust leaks, too. Are your O2 sensors good?