98 Avalon Hesitates/misses on acceleration

[mb_]

I have a '98 Avalon (82K) that's hesitating when the gas is barely applied. It's most noticable from 0-15mph or so, and doesn't start occuring until the engine is warm. If I get on the gas moderately to hard, it's fine. But that first bit of travel in the pedal is where you cruise at or slowly start off, like in a parking lot.

So far I've replaced the air filter, fuel filter, and spark plugs. None of these had any effect. After doing some reading here, I'm wondering if I should try cleaning the throttle body or mass air flow sensor.

Thanks in advance for any suggestions.

[tfeld]

mb,

I would do the things you're thinking of at first--they're easy and should be considered part of your preventive maintainence. The fact that it only happens when the engine is warm makes me think your EGR system is dirty and may require some work. But start with your TB and MAF cleaning; if that doesn't do the trick, then I'd look elsewhere (when doing the TB cleaning, be sure to clean the EGR port on the intake manifold).

Since you didn't say you had any CEL showing, I'll assume you don't. If you're familiar with the EGR system, first check the modulator filter for carbon; if present, clean it off and rotate the filter unit, then replace when you can (it's cheap). There is also a series of tests that can be done on the EGR system (comprised of EGR valve, modulator, and VSV) to let you know where the culprit is hiding. You'll need to check into these if you still have problems.

[mikemetcalf]

I had the same problem with my 99 avalon and had to get the egr valve replaced. That fixed it.

[mb_]

Follow up: I finally got this thing diagnosed, and it was the EGR valve and EGR Vacuum valve.

So my next question is, would it harm the vehicle to just disconnect the EGR? It runs perfectly with it disconnected.

[pinkflydxx]

When your car is exhibiting this problem are you seeing any "bouncing" of the tach/RPM? My car has similar problems when it gets hot, but when it tries to idle, the idle is very rough, as well as when slightly accerating. However, when you accelerate "hard" or get up to higher speeds, seems to run just fine. Please advise. Thanks.

[mb_]

No, nothing on the tach. It idles fine, and runs fine with moderate to heavy acceleration. It's just the light pressure on the pedal where it does this.

[speedysportcar]

Thank you for putting this in the web site. I had the same problem on my 97 Avalon. Switched out the EGR and problem solved.The part cost $230 but it was easy to replace 30min. with basic tools. once again thanks

[ILAvalon]

Originally Posted by speedysportcar

Thank you for putting this in the web site. I had the same problem on my 97 Avalon. Switched out the EGR and problem solved.The part cost $230 but it was easy to replace 30min. with basic tools. once again thanks

I have a '99 Avalon with 84k mi. It also had hesitation problems, at slow speed after warm up, but only with summer time temps. My mechanic suggested that I 'vent' the tank. So, I drove around for 2 days with the gas cap slightly loose. [Burbed the Baby!] It did the trick; no more hesitation. Did not have to mess with the egr system. Thought this was worth the post.

[whopperdad]

.Try cleaning your throttle body at your air intake. with a spay cleaner should help tremendously.