1995 Avalon surges or hesitates while cruising at 50mph or more
i have a 1995 avalon that surges while crusing down the highway. This "surging" doesnt occur until the car is fully warmed up (15 min), and becomes more noticable as speeds increase to 60mph. To more accurately describe the surging i would say the car briefly slows or hesitates slightly (1mph or less) every 3-5 seconds for about 1/2 second. It remindes me ALOT of a carbureted car that is running lean.
I will list the things I know and or have checked, hopefully somebody can point me in the right direction or let me know what i am missing.
I have owned the car for about 1 year, it has run perfectly. It has 200,000 miles on it, and it does not burn any oil. No check engine codes, except an o2 sensor heater which has been that way since i bought the car. Has not had any effect on the way the car has run before, so i doubt it is causing my problem now.
The fuel pressure is good, 34-40 psi while driving.
I cleaned the MAS, EGR ckt checks good (engine stumbles when activated). I have monitored the engine data with my scanner and I am not "losing" any imput signals from any of the sensors i have looked at.
The o2 sensors toggle/change state, and the fuel trim numbers are 5% or less. I will mention that i did change bank 1 o2 sensor with another used sensor like 8months ago to try to eliminate the sensor heater ckt CEL, but it did not correct the problem or have any effect on the way the car ran.
I did notice the the o2 readings would sometimes be lean on one bank and rich on the other bank, could this be causing the ecm to "freak out"? IDK, i tried looking at the injector pulse width to see if they were shutting off, but they kept at 6.x miliseconds the whole time.
Dont know what to check next, any input would be GREATLY apreciated!
Why would it only cause a problem once the car is warmed up and only above 50 mph? Snice the pcv valve is connected from the valve cover to the air intake tube wouldnt any problem it may be causing occur whenever the engine is running
My Avalon ran like a top unless it was raining. when it would rain, after some time of driving in it, my porr car woud stumble all over itself. I finally decided to bring it in to my dealer and they looked the whole car over. I thought maybe it was electrical since it was affected by water but turns out the throttle body was just filthy. they said it looked black. After they cleaned the TB, I've never had the problem again.
__________________
"Fools", said I, "You do not know, silence like a cancer grows.
Hear my words that I might teach you. Take my arms that I might reach you"
But my words, like silent raindrops fell, and echoed, in the wells of silence.....
Jason Johnston
Toyota/Scion of Des Moines
(800)342-7045
Why would it only cause a problem once the car is warmed up and only above 50 mph? Snice the pcv valve is connected from the valve cover to the air intake tube wouldnt any problem it may be causing occur whenever the engine is running
thewhitt
it's a $4 part, takes 2 minutes to install and controls the vacuum in the intake, which in turn controls a lot of other things. before troubleshooting ANY condition that might involve vacuum i certainly would assure that a new and properly functioning pcv valve was installed. that will save you lots of trouble and wild goose chases.
when i cleaned the MAF. That was one of the first things I did, it did not change anything. The car runs fine for 15 minutes or so until fully warmed up, and the problem ONLY exhibits itself during steady state cruse conditions...
I believe it has to be something that the ECM is doing, I.E. it is adjusting things based upon inputs from the sensors. Problem is I cant see/figur out what sensor/sensors may be giving me the problem (if any).
How do these cars act if the vairable valve timing control system acts up?
Your 95 shouldnt have VVTi so that wouldn't likely be the issue.
Cool that you cleaned your TB. That's ruled out. PCV is a cheap easy part to replace. Might as well do it anyway. What kind of fuel are you using? maybe you're getting a little bit of pre-ignition every once in a while durring cruising and the knock sensor is kicking your timing back a bit to compensate. You could try a higher octane fuel through a tank and see it that helps the issue?
__________________
"Fools", said I, "You do not know, silence like a cancer grows.
Hear my words that I might teach you. Take my arms that I might reach you"
But my words, like silent raindrops fell, and echoed, in the wells of silence.....
Jason Johnston
Toyota/Scion of Des Moines
(800)342-7045
and when the problem occured i filled up with 93 octane jst to rule out bad gas. I thought i looked at the timing numbers while crusing and that they didnt change, but i will double check. Since the load is light and the throttle position is low and i didnt hear any audible "ping" i dont suspect that. I can check the ignition advance with my scanner, if the knock sensor is enabled i should be able to see a change in the ignition advance numbers...
i will post ronce i have checked, anybody have any other ideas as to what to look at next?
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1999 Toyota Avalon
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