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2008 Toyota Camry = After warmup, dipping rpm at idle, 44% LT Fuel Trim 20% ST, Wont start once shut off


Topic starter

2008 Toyota Camry LE 120,000m

Check engine light on

44% Long Term Fuel Trim

20% Short Term Fuel Trim


The car will start and drive fine for short trips to grocery store, drop the kid off at school, etc. 

Long Trips once warmed up  the RPM will drop at idle and the car shakes, if its allowed to stall or the car is turned off it will not start.  After letting it set for 30-45 min it usually starts. 

Troubleshooting thusfar:

Did the cigar smoke test for vacuum leaks = no leaks

Replaced the Mass Airflow Sensor = nothing changed

Used the  cleaner you spray in the throttle body whole holding RMP steady at 2k = nothing nothing changed

Replaced all 4 Spark plugs = nothing changed

ran some gumout Fuel injector cleaner through 2 tanks = nothing changed


Thinking of trying the following:

Cleaning the IAC  Idle Air Control

Replacing Fuel injectors

Cleaning throttle body


3 Answers

Your car thinks its running lean and is adding alot fuel (based on the fuel trim info). Your symptoms sounds like what happens when a car is running rich (or has leaky injectors), hard start when hot, runs poorly. 

Based on that I think somewhere you have a bad sensor reporting incorrect data to the computer. Something like the cars temperature sensor, or a bad 02 sensor. As Doc said, scan it for codes to get a better idea whats wrong. Ill add this, since the fuel trim doesn't suggest the injectors are leaking I don't think theyre bad/ dirty. 

I remember (…) possibly a bad o2

Bingo. most likely it’s this.

your engine computer uses O2 sensors to tune the air-fuel mixture, bad data may cause it to think it’s running incorrectly and mess up the fuel trims.

Replace with OEM / Denso branded units (both are actually made by Denso)

Ok i was afraid of that they are pretty pricy as its not the classic O2 sensors its the newer ones because I've checked the voltage with the scanner and they didnt seem right for the regular sensors. I will for sure get the codes and get them on here so we have accurate info.

The voltage should go up and down, it’s detecting the unburned oxygen (O2) in the exhaust - so there’s more of it flowing right after a combustion.
Other things may be also causing your car to run incorrectly - but this is a good start, as it is a likely cause.


How about some codes?

Im at work now but I can provide some later Last I remember was a lean code, and possibly a bad o2 Ill for sure get them on here when i get home.