'99 SR5 hesitation & misfire; dealer can't locate problem

[bsackamano]

Hello all. My '99 SR5 has about 99,000 miles and has been running like crap for months now. It hesitates very noticeably between 2000 and 4000 RPM. I've also logged the MPG since I bought the truck new. I got 20mpg the first 4 years until I moved to IL and it dropped instantly to 18mpg (due to the 10% ethanol mix I assume). It was right there for the next 2 years, but over the last year has steadily dropped to 15mpg.

It is during this last year that it has not been running well. It started with fuel lean CELs so I replaced the fuel filter and tried several bottles of Techron with no luck. I finally took it to the dealer and they said the air mass flow sensor was bad and replaced it. It ran the same, but the CEL went out for a couple/few months. Now it's back on with several cylinder misfire CELs, random cylinder and cylinders 2, 5, and 6. So I replaced the plugs and wires and tried more Techron but no change. I took it back to the dealer and this time they've had it for a week and can't find the problem! They swapped the plugs, wires, coils, O2 sensors, ECM, tested the fuel pressure, compression, and probably more that I'm forgetting and said everything is normal, but they agree that it is running poorly.

I should also mention I change the oil every 5K with Mobil-1 and the timing belt was changed at about 75K. Does anyone have any ideas? There has to be something they are overlooking.

Thanks for any advice, Jason.

 

[mikes4runner]

Vacum test maybe you have a cracked hose somewhere?

Who did the timming belt?



Mike

 

[bsackamano]

The same dealer changed the timing belt about 2 years ago. And I'll ask them about the vacuum test. Thanks.

 

[bsackamano]

I picked up the truck today to take it for a second opinion. By process of elimination, the first dealer recommends replacing the injectors on the 3 cylinders that are misfiring. All injectors have the same resistance and all seem to be firing properly, but because everything else looks normal, this is the diagnosis. But before I spend $900 to replace the three or $1500 for all six, I want someone else to take a look.

Has anyone had or heard of an injector failure on a 4Runner or other vehicle? I've thought all along that was the problem, but that they were severely clogged, not mechanically or electrically faulty. It just doesn't seem right, especially for three of them to die. Thanks for any input, Jason.