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2009 V6 that has started hesitating/surging under acceleration above 2500rpm.
I replaced the fuel filter couple of weeks ago, I thought at the time it had improved but if it had it hasn't now.
Pulled a spark plug, looked ok. Cleaned the AFM, no difference.
Doesn't throw any codes.
I learnt about fuel trims over the last couple of days and logged a drive today.
Long term fuel trim seems quite stable at around the 8%, both banks.
Short term fuel trim under acceleration starts off between 3% and 5% but once the motor reaches around the 2400rpm all of a sudden the short term fuel trim goes -12% on both banks.
Now as this is around when it starts hesitating/surging I'm assuming that this is related.
My question to the knowledgeable forum what do you think would be causing this? Where would you start looking given this information?
Many thanks.

I have the same issue. 2006 4.0L V6. I've only owned mine for about a year and it's done it as long as I've had it. Mine doesn't seem to drop RPM, but you definitely feel a pause or surging in the rate of acceleration. I haven't checked fuel trims so might have a look on the weekend if I get a chance.

I've come to the conclusion that it is the fuel pump getting a little weak. I bypassed the fuel pump resistor and running 12v to the pump all the time. No more hesitation and both the fuel trims sit pretty close to 0%. I intend to replace the fuel pump at the next service.

Thanks for posting your findings! I didn't get a chance to test mine over the weekend. That level of diagnosis sounds a bit beyond my capabilities, but I might ask my mechanic to change out the fuel pump on my next service as well. Can I just ask, if bypassing the resistor solves the issue, is there any danger to just removing the resistor (or leaving the bypass in place)?

Bypassing the resistor has solved the issue and there is no problem with leaving the bypass in place but it doesn't solve the fact that the fuel pump hasn't gotten a little weak.
Toyota run the resistor at low engine loads to try and extend the life of the fuel pump, it also quietens the fuel pump. I can hear mine running from outside the vehicle easily now.
How long the fuel pump will last running at full power all the time I don't know.

hotmetal1000 wrote:Bypassing the resistor has solved the issue and there is no problem with leaving the bypass in place but it doesn't solve the fact that the fuel pump hasn't gotten a little weak.
Toyota run the resistor at low engine loads to try and extend the life of the fuel pump, it also quietens the fuel pump. I can hear mine running from outside the vehicle easily now.
How long the fuel pump will last running at full power all the time I don't know.

It's a short term solution. By taking out that resistor you're increasing the current draw the pump motor is using and so eventually the increased current will burn the pump motor out. If you're gonna do this for an extended period then maybe think about carrying a spare fuel pump so you can swap it out fairly easily when it does go? The other thing you might wanna clarify is whether you're talking about the Tank transfer pump or the engine injection pump. If it's the tank transfer pump then it should not have any effect on engine performance, if however it's the injection pump, then maybe you should talk to a Fuel Injection Specialist, maybe there is some other issues wrong that you're "short-cutting" by taking the resistor out of circuit. The Pump itself should not fail like this at such a relatively young age. It should go strong for at least 300000Km and in most cases still be good at 500000Km.
My 2 Cents!

Rob_Wood wrote:

hotmetal1000 wrote:Bypassing the resistor has solved the issue and there is no problem with leaving the bypass in place but it doesn't solve the fact that the fuel pump hasn't gotten a little weak.
Toyota run the resistor at low engine loads to try and extend the life of the fuel pump, it also quietens the fuel pump. I can hear mine running from outside the vehicle easily now.
How long the fuel pump will last running at full power all the time I don't know.

It's a short term solution. By taking out that resistor you're increasing the current draw the pump motor is using and so eventually the increased current will burn the pump motor out. If you're gonna do this for an extended period then maybe think about carrying a spare fuel pump so you can swap it out fairly easily when it does go? The other thing you might wanna clarify is whether you're talking about the Tank transfer pump or the engine injection pump. If it's the tank transfer pump then it should not have any effect on engine performance, if however it's the injection pump, then maybe you should talk to a Fuel Injection Specialist, maybe there is some other issues wrong that you're "short-cutting" by taking the resistor out of circuit. The Pump itself should not fail like this at such a relatively young age. It should go strong for at least 300000Km and in most cases still be good at 500000Km.
My 2 Cents!

V6 Petrol, there is only the one fuel pump located in the tank.

Replaced the fuel pump, put the resistor back in line and all seems happy. No hesitation and fuel trims are normal.
My fuel consumption improved when I bypassed the resistor. It will be interesting to see if it stays lower now as well now that the hesitation is gone.

How many kM?

100 000km showing on the clock. 55 000km I have done. The vehicle was crashed before I bought it so no idea if it was the original fuel tank/pump.
Having searched on google I did see on another forum where people have had these pumps fail at 100 000km though.

My 2011 has 160,000km on it now on the original pump. Has been supercharged since 100,000km.