SOURCE: 1998 camry 5sfe engine, surging at idle
Check for air leaks in the vacuum pipes in and around the inlet manifold, they have a habit if going brittle and splitting.
Another possibility is the temp sender , if the ecu thinks the engine is too cold it will compensate causing the engine to " hunt". This can be something as simple as a worn radiator cap seal letting air into the cooling system and tricking the sensor.
Hope this helps, Marshall
Yes, having no thermostat can cause the car to run fast as it will still be set in it's "warm up" mode and will be injecting a richer mixture of fuel/air into the cylinders. There may be an additional cold start injector that just works while the engine is cold. You will probably use more fuel like this. It's not a great idea to run with no thermostat anyway because you get uneven hot and cold spots around the engine which is bad for it. Cheers
Testimonial: "many thanks ben ive renewed themostat and problem solved "
SOURCE: In my 2000 Saturn SL1 I am experiencing very high idle
had same problem 2 years ago change idle air control clean throttle body , erg valve .It only would idle high when i left it out in the cold all night. When i leave in my garage it would not idle high. With help from a Saturn mechanic found intake manifold gasket was blown and giving me all kinds of false codes.Now its been 2 years i having the same problem again seeing this again makes me think i having the same problem again it emission time again
Hello
The
engine and the automatic transmission (transmission control is only
for automatics, engine is still computer controlled no matter the
transmission type) in this vehicle are computer controlled and in
most cases when a fault occurs a fault code is stored in the memory
of the computer control module. There are exception to this, such as
the Mass Airflow Meter and fuel pressure problems. What must be done
is to have all the basic testing done such as a scan of the system
for fault codes as well as a check with a live data scanner tool for
engine functions that are not within range of normal, a trained
technician is required to know what is correct and what isn't, then
based on careful diagnostics done from a factory repair manual the
correct part is replaced or the wiring repaired or the computer
replaced (known as the PCM), which is very rarely the problem. Other
basic checks must be done as well such as mechanical problems with
the engine as well as engine state of tune and mileage on the engine.
The transmission can have mechanical issues as well such as no gear
engagement at all or a failed pump or other pressure related
problems.
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