incharlest

Need a little advice on what order of things to check first, second, etc... I have a 2000 es300 that I maintain in excellent shape. Recently at lower speeds the car hesitates or stumbles. The car idles fine and in neutral the car revs with no trouble.
When I first noticed a slight hesitation it motivated me to install the fuel filter that had been sitting in my garage for the last 2 months. The car ran excellent for a week or so but the hesitation slowly came back. so I pulled the MAF sensor and cleaned it. I'm not positive that cleaning the MAF fixed it but it did run great for the next 3 or 4 days before the hesitation started again. Cleaned the MAF again today but the car is still hesitating. Throughout this ordeal I never once got a check engine light.
I've checked the vacuum hoses and all seams to be fine but I haven't put a gauge to it. Pulled a couple plugs and they looked normal. I hate to keep driving it with the hope that a code comes up soon.
I have a simple code reader but was thinking of buying one of the $200+ code readers as I believe they can provide some useful data to help diagnose problems like I'm having.
Anyway, if you were in my shoes what would you check first, second, etc...?
Thanks

hzt30

Try cleaning your throttle body. Also, check for correct fuel pressure.

You can buy a code reader that shows data PIDS for less than $100. Scan data will show you a lot of needed information. You can look at fuel trim, check O2 sensors, etc.

DRACO A5OG

The Idle Control Valve, can be a PITA and may not throw a code. do a search on how to clean it and you will be smiling.

incharlest

Thank you for the input. I will try both of these ideas and will let you know how things turn out.

PFB

Make sure to eliminate a partially blocked exhaust/Cat system as a possible cause.

Phil

DRACO A5OG

+1 if you are consuming allot of oil and out the exhaust

incharlest

No luck yet.
Pulled and cleaned throttle body and IAC. No blocked exhaust I believe. Very little oil consumption considering 180,000 miles.
I'd like to add that the stumbling / hesitation does not seem to occur when the engine is cold. However, once the car is at normal operating temp. it begins stumbling.
I'm starting to think it is time to pull all the injectors?
Any other ideas?
Thanks

canucklehe

a bit of a stab.... would a throttle position sensor cause these issues? (my first guess was throttle body, but you say you cleaned that).

what about the coil packs? (not sure how you check or diagnose them, but it wouldn't surpirse me if a malfunctioning coil pack caused the symptoms you describe).

sometimes I splurge for a diagnostic fee, even though it pains me to do it. but sometimes cheaper than guessing and chasing parts that don't need replacing. I just spent $90 to diagnose a shot stator on my quad. As it turns out, i would have replaced stator first, but i didn't mind knowing for sure.

rebornS14

any updates? just wondering because your symptoms sound very simluar to my transmission problems right now.