enigma9o7

Something been going on lately and looking for ideas. 2003 ES300.

From a stop, if I accelerate normally (slowly), no problem. However, if I try to accelerate a bit fast (not flooring it or anything) the car goes for a half a second, then stops, then goes, then stops, then goes, then stops, basically bucking and jerking (until I let off the gas).

No CEL. Seems to happen 100% of time when engine is cold, but not 100% sure that it goes away when hot (it's my wifes car, I don't drive it much, but been driving it mornings lately to drop off kids). Freeway driving is normal, including accelerating.

PFB

Often it's caused by a cracked snorkel hose behind the air filter. When you accelerate the engine tilts in such a way that the crack opens up and lets unmetered air into the engine.

You need to remove these hoses and check them Carefuly by flexing them. If you find a crack, you can fix it TEMPORERALY with electrical tape.

If I'm right, you should not have any symptoms while accelerating in reverse.

Phil

ES300NZ

+1 for ^ what phil wrote, also ..

.. broken engine mount, engine floating away and pulling intake tube off allowing unmetered air in.
.. knock sensors & harness.
.. I got nothing beyond that, .. it's an odd one, sounds like vacuum though.

enigma9o7

Thanks much for reply!

I'll definitely check out any hoses on the back of airbox, and testdrive in reverse... and look at the mounts.... However the explanation doesn't quite make sense to me. The air isn't metered until the MAF which is after the airbox, so even if extra air was getting into the airbox or the hose between airbox and MAF was leaking or even completely missing it should still be able to measure all the air going to the engine, just some of it might not have gone thru the air filter... or am I misunderstanding...

If knock sensor going off, that wouldn't throw a code I'm assuming? Is there a way to easily monitor knock sensor to see if that's causing things... could ecu pull timing for excessive (false) knock...

I already replaced the air filter last week and when putting the airbox lid back on (kinda PITA btw) noticed a missing hose on the front (which was identified as going into a "T" by users of this forum, thanks!), but it's possible it was there when I started and dropped into the engine bay abyss that I couldn't find... anyways put on new T and hose and didn't affect anything so if it was missing before, didn't seem to be the cause of this problem.

PFB

The snrorkel hose(s) that I was referring to is the one after the MAF, not in front of it.

I can't remember if your model has 1 or 2 such snorkel hoses, but check both of them.

Also, knock sensors do throw unique codes.

Phil

Mphidd

I just got my 99 Lexus es300 worked on yesterday for a bad engine mount. They also replaced the stabilizer bar in the car. I haven't had much time to drive it a lot since yesterday, but so far I haven't noticed any jerking when driving.

enigma9o7

Thanks much. It was indeed the hose you described. Running good now.