idle fluctuates under warm start
05-20-2003, 03:50 PM
#1
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Join Date: Jun 2002
Posts: 50
idle fluctuates under warm start
when i start my car warm the idle hunts up & down about 5 cycles before it stabilizes, and on several occasions has even stalled, what causes this erratic idle behavior? It does not do this on cold starts. I tried to search but it says:
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05-22-2003, 09:27 AM
#3
This can be caused by many things (Check out this thread: http://forums.maxima.org/showthread....hreadid=209413 )
There is a great write up in another link, copied here:
Your fuel-injected engine has an Engine Coolant Temperature Sensor. This sensor sends a signal to the Engine Control Module (the computer). When the ECTS sends a "cold engine" signal the ECM responds by instructing the fuel injectors to deliver a rich mixture. The rich mixture helps a cold engine start and run smoothly during the warm up period. This is similar to the operation of a choke on a carburetor engine.
There are other problems, which cause cold starting, and driveability problems, but the ECTS is the first thing to check. This can be done with an ohmmeter.
On the 4th Gen, the ECTS is located in the water outlet tube close to the engine end of the upper radiator hose. There are two sensors in that vicinity. The one nearest the hose is for the dashboard temperature gauge. The ECTS, the one you're interested in, is adjacent to the gauge sending unit. There is a good picture of these sensors in the Haynes Manual an page 3-7.
With the engine cold, disconnect the ECTS and measure its resistance. Reconnect the ECTS, start the engine, and run it until fully warmed up. Stop the engine, and repeat the measurement. The "warm" reading should be much lower that the "cold" reading. These are the specs:
Engine coolant temp = 68F, ECTS resistance = 2.1 to 2.9 kOhms.
Engine coolant temp = 194F, ECTS resistance = 240 -260 Ohms (or .24-.26 kOhms - roughly, a factor of ten in difference)
The ECTS is a relatively inexpensive sensor and something the home mechanic can replace without special tools.
Good luck!
There is a great write up in another link, copied here:
Your fuel-injected engine has an Engine Coolant Temperature Sensor. This sensor sends a signal to the Engine Control Module (the computer). When the ECTS sends a "cold engine" signal the ECM responds by instructing the fuel injectors to deliver a rich mixture. The rich mixture helps a cold engine start and run smoothly during the warm up period. This is similar to the operation of a choke on a carburetor engine.
There are other problems, which cause cold starting, and driveability problems, but the ECTS is the first thing to check. This can be done with an ohmmeter.
On the 4th Gen, the ECTS is located in the water outlet tube close to the engine end of the upper radiator hose. There are two sensors in that vicinity. The one nearest the hose is for the dashboard temperature gauge. The ECTS, the one you're interested in, is adjacent to the gauge sending unit. There is a good picture of these sensors in the Haynes Manual an page 3-7.
With the engine cold, disconnect the ECTS and measure its resistance. Reconnect the ECTS, start the engine, and run it until fully warmed up. Stop the engine, and repeat the measurement. The "warm" reading should be much lower that the "cold" reading. These are the specs:
Engine coolant temp = 68F, ECTS resistance = 2.1 to 2.9 kOhms.
Engine coolant temp = 194F, ECTS resistance = 240 -260 Ohms (or .24-.26 kOhms - roughly, a factor of ten in difference)
The ECTS is a relatively inexpensive sensor and something the home mechanic can replace without special tools.
Good luck!
05-22-2003, 10:22 AM
#4
Member who somehow became The President of The SE-L Club
iTrader: (19)
Join Date: Jun 2001
Posts: 16,033
Clean your throttle body - goto www.motorvate.ca for instructions.
If that doesn't smooth things out, you will need to clean out your IACV. (Idle Air Control Valve). It's located on top of the intake runners, just after the throttle body twards the fire wall. You can dissassemble it and clean it up with intake cleaner.
If that doesn't smooth things out, you will need to clean out your IACV. (Idle Air Control Valve). It's located on top of the intake runners, just after the throttle body twards the fire wall. You can dissassemble it and clean it up with intake cleaner.
05-23-2003, 08:58 AM
#5
IAC VALVE
Originally posted by njmaxseltd
Clean your throttle body - goto www.motorvate.ca for instructions.
If that doesn't smooth things out, you will need to clean out your IACV. (Idle Air Control Valve). It's located on top of the intake runners, just after the throttle body twards the fire wall. You can dissassemble it and clean it up with intake cleaner.
Clean your throttle body - goto www.motorvate.ca for instructions.
If that doesn't smooth things out, you will need to clean out your IACV. (Idle Air Control Valve). It's located on top of the intake runners, just after the throttle body twards the fire wall. You can dissassemble it and clean it up with intake cleaner.
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