Hey guys I'm new to Toyotas and I just bought a 95 4runner and I'm having issues with it running rich. I've already disconnected the cold start and it got better but its still running rich can I get some ideas on what it could be and how I can diagnose it.

 

Check engine light on?

 

No check engine light

 

Pull codes. When is the last time the o2 sensor was changed? Chances are, that's your problem.

 

What symptoms are you getting from running rich?

 

What engine??

 

Its a 95 4wd sr5 3.0L, there's no issue with the cold start I've already counted that out helped a little not much I'm getting a smell of fuel out of the exaust and poor execelleration I'm not sure when the o2 sensors were replaced I just bought it and haven't been able to drive it too much but when I start it it drips like a sooty water out of the exhaust

 

All I know it has is the 3.0L

 

Poor acceleration poor fuel economy no rough idle

 

Check valves had same prob

 

After many hours and dollars i fixed it and traded a dude for my four walker for a four runner with a 3.4

 

How would I go about doing that?

 

Have you checked for codes? Done anything to diagnose? Find a factory service manual online and buy yourself a cheap multimeter. You will need them both.

 

There are no codes

 

hmm i would check the MAF sensor, spark plugs, oxygen sensor, and vacuum leaks.

 

There are a couple vacuum lines that have screws in them and all the sensors are good.

 

I think the screws in the vac lines indicates a "tinkerer" somewhere in the trucks history. I would find a vacuum diagram and make sure everything is routed correctly and not leaking (this just fixed a rich running bad idle issue on my 2.4 and cost nothing but time).

Poor signal from the 02 sensor can cause mixture issues without triggering a code or CEL. Might inspect the connector and wiring for damage and corrosion which can add resistance, giving a faulty reading to the ECU. There are also ways to test the signal with a multimeter under the hood but i have never done that, you can search for the procedure.

You can test the VAFM with a multimeter to make sure it is operating within specs. This is easy enough to do on the vehicle and there are instructions and vids available online.

Less likely (but possible with a PO tinkerer) is that the VAFM has been adjusted to rich'n the mixture, i would check for signs that the cap has been previously pulled off. Again, this is a longshot possibility.

I have also read that low ignition voltage can can result in not all fuel being burned in the engine. I would check the wiring and connections for corrosion and damage then look up the procedures for testing the coil and other ignition components.

Off the top of my head these are the steps i would start with because they cost nothing, assuming you have access to a multimeter. I am making the assumption that all these steps apply to your generation truck and engine, someone please correct me if i'm wrong.

Good luck!

 

I would also take a quick look at all of the ground wires on the engine block. Make sure they are all there and in good condition, this helps to provide a good ground for the spark plugs to fire at full capacity.

 

I went down to the Toyota dealership today and talked to them and they said the 3vze motor everything runs on vacuum look at all the vacuum lines and that's most likely the problem.

Turns out the person that owned it last ran the vacuum lines on the throttle body wrong

Thanks for the help guys