Mechanics

HESITATION

1999 Toyota Camry

Engine Performance problem
1999 Toyota Camry 6 cyl Front Wheel Drive Automatic 202000 miles

Last 2 years, engine hesitates most noteably when cold at 66 km/hr, but also at other times and speeds. It is extremely hard to duplicate on command for the technician. I thought it was the transmission and had it rebuild for $3600. It did not cure the problem. Two dealers could not properly diagnose or cure the problem. Over $800 already spent on this. There had been no engine codes until last week. Engine lite on for just one or two days and dissappeard. It produced code " P0446. Identification: EVAP system - vent control malfunction. Possible problem area: same as P0441. Identification: EVAP control sytem - incorrect purge flow. Possible problem area:
- open or short in VSV circuit for EVAP
- VSV for EVAP
- Open or short in vapor pressure sensor circuit
- Vapor pressure sensor malfunction
- Open or short in VSV circuit for vapor pressure sensor
- malfunction in VSV for vapor pressure circuit
- vacuum hose blocked, damaged, or disconnected
- charcoal canister malfunction.
The activation of the engine lite did not coincided with any other symptoms. Original symptoms remain the same. Dealer said aftermarket fuel filler cap could be problem. I had it for 1 year, well after symtoms started. Still makes hissing sound when opened for fill-up.
What is your guess of the cause?
Avatar
Nselbstaedt
September 7, 2008.



Possible Causes of Engine Hesitation or Stumble: Dirty fuel injectors (cleaning the injectors often fixes this).
Bad MAP (manifold absolute pressure) sensor
Bad TPS (throttle position) sensor
Bad or dirty MAF (mass airflow) sensor
Low fuel pressure (leaky fuel pressure regulator or weak fuel pump)
Vacuum leaks (intake manifold, vacuum hoses, throttle body, EGR valve)
Bad gasoline (fuel contaminated with water or too much alcohol)

Sometimes, what feels like a hesitation is actually ignition misfire rather than lean misfire. The causes of ignition misfire may include: Dirty or worn spark plugs
Bad plug wires
Weak ignition coil
Wet plug wires

Rasmataz
Sep 7, 2008.