2000 3.4 weak or slow startup

[Y2K-4runner]

Our recently purchased T4R cranks longer than normal when starting. The issue is much worse when it's been driven and still warm. It does have the the 0171 code that keeps coming back after about 15 minutes of driving each time I reset it. I had AAMCO check it on theirs and they got the same code. He told me it was lean bank 2 and could need a rear oxygen sensor. I cleaned the MAF and that didn't change anything. It almost acts like it isn't getting enough fuel. Our Jeep does this so we just prime the system by turning the key to ON 3 times. That treatment doesn't seem to affect the Toyota. Would a rear oxygen sensor affect startup? I'm thinking is it a fuel issue, possibly a regulator of some type It idles just fine and seems to pull good when accelerating. Anyhelp with trouble shooting is greatly appreciated. Thanks!

 

[kball]

P0171 is not activated by the rear O2. The aamco mechanic is wrong. It's either the front or pre cat O2, the MAF, or a vacuum leak most likely.

The hard starting could have to do with the code or it could be a weak fuel pump.

 

[dorton]

If there is contamination on the MAF sensor's sample wire, it will cause the code, and also will cause the extended starting.

You can use electrical contact cleaner, or brake cleaner to clean said filament. Be careful, as it's fragile. Try it and see if it helps.

 

[Y2K-4runner]

The MAF had some black carbon on the one side and I took care of that with a cue tip and some alcohol when I cleaned it. The contacts looked clean but I will check them again. Where do you check fuel pressure on a T4R? Is there a shrader valve that I can put my guage on?

 

[dorton]

The MAF had some black carbon on the one side and I took care of that with a cue tip and some alcohol when I cleaned it. The contacts looked clean but I will check them again. Where do you check fuel pressure on a T4R? Is there a shrader valve that I can put my guage on?

If it doesn't do it under a l load, fuel pressure is probably fine. I don't recommended using a cue tip for cleaning the sample wire on the MAF sensor.

 

[kball]

It sounds like you cleaned the bulb on the outside of the MAF not the actual sensors inside the tube. Do not touch them with anything including a q tip. Just spray contract or MAF cleaner down the hole and let it dry completely before reassembly.

No schrader valve, you need a special tool with a banjo style fitting to tap into the fuel line.

 

[Y2K-4runner]

I cleaned the wires with MAF cleaner. It is starting normally and the check engine light appears to be staying off. Thanks very much for your help.

 

[Jon]

I had the same thing. I removed and cleaned the entire throttle body. It worked immediately but a day later the problem was back. Ended up replacing the fuel pump to fix it.

 

[koulee]

P0171 doesn't affect the motor on startup. To fix the startup problem, check your starter contacts (these wear out and can be replaced), fuel pump (damaged due to running low on gas all the time or just old), fuel filter (if its clogged), and battery (if its low on charge or old).

For P0171, the causes are what they have stated:

1. Front or precat O2 sensor. Replace with a Denso and reset your ECU.
2. Dirty MAF. Clean BOTH wires with MAF Sensor Cleaner. Anything else and it can be damaged.
3. Vacuum leak. This is a tough one because there are lots of vacuum lines of varying sizes all over the place.