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MORE: Engine idle questions
Car Idle Question and Answer - This category contains featured questions
as examples. They relate to most vehicles.
Question: 2003 Pontiac Grand AM mileage: 29,000. After filling the tank
recently the engine speed became erratic: it would race while driving (tach at 1800
forcing me to keep my foot on the brake in a 25 mph zone); when braking for a turn
it would vary wildly between a couple hundred and 1500 rpm; if breaking quickly
rpm would fall to under 400, would sputter and stall unless I would two-foot.
It continued to do this intermittently, sometimes stalling while cornering.
I took it to the dealer for its 60,000 mile scheduled maintenance; they found no
problem except a possibly partially clogged fuel injector. I used some OTC
fuel injector cleaning stuff to no avail. Took it to a very good independent
mechanic. He spent three days checking sensors, motors, valves, computer,
draining and replacing the fuel. Everything independently checked out A-OK.
He's mystified. What do I do now?Answer: Your car is equipped with
a electronic throttle control. So there is no adjustment. The idle speed is determined
from the ECM. You need to scan your car for trouble codes. A oxygen sensor or Mass
Air Flow has probably shorted and needs replacing.
Question: 2002 Toyota Camry mileage: 70,000. The car
has a rough idle when in "drive" (auto trans, A/C off). In Neutral, it is barely
noticeable. While driving, it is fine. Only when I come to a stop does
it shake. It had a major tune-up (cap, rotor, wires, plugs, filters, timing,
etc.), injectors were cleaned - no difference. The dealer is at a loss and
so am I! HELP!
Answer: Your car is equipped with a electronic throttle control. So there
is no adjustment. The idle speed is determined from the ECM. You need to scan your
car for trouble codes. A oxygen sensor or Mass Air Flow has probably shorted and
needs replacing.
Question: 1990 Chevrolet Corsica mileage: 177,000. Recently had to
replace both throttle position sensor and air idle control valve. The car
never seemed to reset its idle. 2 weeks later am having same problems as before.
What could be causing the TPS and/or AIC to fault? I realize a bad TPS will
destroy the AIC's. I am assuming that is what is happening. Air, electric,
and fuel systems are all showing to be code free.Answer: Replacing the
oxygen sensor should fix your problem.
Question: 1999 Chevy Impala mileage: 127,000. I have taken
my car to three different mechanics to have this problem solved and have yet to
get it lined out. It has extreme hesitation on the throttle, and when the
car slows from normal driving speed to a stop it dies. The idle does run rough
whereas before this problem occurred it purred like a kitten. I've replaced
the computer, map sensor, throttle position sensor, starter relay, and according
to the Chevy Dealer they are not getting any new readouts of problems. I'm
running out of options on this problem. I'm hoping you may have an idea of
what to do.
Answer: Check the EGR valve to make sure it is closed at idle. Inspect
the engine for vacuum leaks and check the exhaust system and catalytic converter
to see that they are not plugged.
Question: 1988 Ford F-150 4 WD mileage: 114,000. My truck problem
is ROUGH IDLE, POOR GAS MILAGE, HESITATION, after a short drive (10 miles) or so,
if I shut the engine off and restart, the motor is hard to start and about 1 mile
down the road the check engine light comes on. I took my truck to several
mechanics and have replaced the THROTTLE POSITION SENSOR, 02 SENSOR, WATER TEMP
SENSOR, They got me an Emissions sticker but the problem still remains. I
recently used the truck's self-diagnostic tester and the following results (codes)
were obtained. KOEA: 31-EVP circuits below minimal voltage. KOEA: 32-EVP
voltage below closed limit. KOEA: 33-EGR valve not opening. KOEA: 41-O2
sensor not switching. RUN CODE: 21-No idea what this one means! RUN
CODE: 44-Secondary air inoperative. RUN CODE: 33-EGR valve not opening.
I'm just an idiot trying to follow a Haynes manual, and not sure where to go from
here, and need some advice! Please Help- the cost of gas is killing me!
Thanks for the help!
Answer: Reset the computer, then turn the key on to see if any immediate
codes are present, if so then repair as primary codes warrant. If nothing comes
up start engine and recheck system. what we are testing for in this problem is to
only repair the most prevalent coeds as it can create the other secondary codes.
Then check the fuel injector resistance to be sure one is not shorted. Check
fuel pump pressure and fuel pressure regulator.
Question: 1994 Isuzu Pickup 4x4 mileage: 46,000. It is in great
shape. Recently when slowing down for a stop, push clutch in and idle speed picks
up and then goes down 3 times before becoming stable. Sometimes goes from
800 rpm to 1500 rpm. Have replaced plugs, filters, wires, O�, and scanned
computer with no error codes. Cleaned throttle body. Checked for vacuum
leaks. Posted this on a newsgroup and at least 4 other people have had the
same problem. Suspect a sensor, but not sure how to tell.
Answer: Check the EGR valve to see that it is closed at idle. Check
for a vacuum leak in the power brake booster. Check for a plugged catalytic
converter. Check for leaking fuel injectors.
Question: 1999 Honda Civic mileage: 60,000. Recently the idle
has become very sporadic. As soon as you start the car the idle will jump
from 700 rpms to about 3500 rpms it will hold and then go back down it does this
over and over, it will do this whether the car is hot or cold. What is causing
this? Please help!
Answer: Your car is equipped with a electronic throttle control. So there
is no adjustment. The idle speed is determined from the ECM. You need to scan your
car for trouble codes. A oxygen sensor or Mass Air Flow has probably shorted and
needs replacing.
Question: 1999 Chevrolet Lumina mileage: 106,500. Vehicle runs fine
down the highway, but after exiting and idling, it "misses" and at times smells
rich. Replaced TPC and gas filter. Some improvement. While
engine was running rough performed an adjustment to the EGR (i.e. tapped it slightly
with a wrench) and problem cleared up. Vehicle ran fine for 2 weeks
and now the same is happening. Again, tapped on EGR and problem seems to be
corrected. Should EGR be replaced or can it be cleaned/repaired? Also,
could the oxygen senor be part of the problem?
Answer: It is probably time to replace the EGR valve.
If a major tune-up has not been done recently, this could be the cause of your problem.
Replace the spark plugs, plug wires, fuel and air filters, etc. Also,
replace the oxygen sensor. In addition, service the fuel injection system.
Clean the carbon deposits from the throttle bore and idle passages.
Question: 2003 Ford Explorer mileage: 42,000. My car misses and
idles very roughly. The idle will drop down suddenly from about 900 rpm to
400-600 rpm then pops back up again. It has had degrees of this symptom
for a few thousand miles, possibly dating back to when the battery failed and had
to be replaced. A dealer tune-up and a couple bottles of gas treatment
have not made things any better.
Answer: Your car is equipped with a electronic throttle control. So there
is no adjustment. The idle speed is determined from the ECM. You need to scan your
car for trouble codes. A oxygen sensor or Mass Air Flow has probably shorted and
needs replacing.
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