bad idle while engine is cold!
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bad idle while engine is cold!
Hi I have a 2000 f150 5.4L and recently when i engine is cold it start to idle very poorly like between 300 and 500 rmp. If i give it a little gas is stays at a good idle. My check engine was on but i replaced my catalytic converters and o2 sensors no the check engine light went off. I just would like to know what it could possibly be before i start just replacing more stuff?
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That is what I was thinking I took it off and it was pretty dirty so I cleaned it pretty good. So I will know tomorrow morning when I take it out it is suppose to be 25 degrees out. I will let you know if it works if not I was thinking maybe the MAF sensor or maybe a bad vacuum hose.
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well i changed my IAC and it still did not fix the problem. It is not as bad as it was but it still wants to die when it is cold. Also my check engine light popped up again so i am bringing it in tomorrow to see what else it could be. If you have any suggestions please feel free to let me know what you think.
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You should reboot the computer because it is still thinks the issue is still there.
The cold start sequence is not a simple function.
Here is how it goes.
Key to Run looks at the head temperture to tell the computer what to set up for fuel, ignition timing and opens the IAC full and runs the fuel pump a couple second then stops.
At cranking, the fuel pump turns on and finishes the fuel rail priming pressure.
At start when quite cold, the idle should go high, then slowly come down to about 650.
Along with all this is the battery recharge load on the motor.
After about 45 seconds to a minute +/- the Ox sensors heat up to at least 600 degrees and take over control of the fuel.
So you see the sequence is not simple.
Try the reboot then see if there are other issues.
Good luck.
The cold start sequence is not a simple function.
Here is how it goes.
Key to Run looks at the head temperture to tell the computer what to set up for fuel, ignition timing and opens the IAC full and runs the fuel pump a couple second then stops.
At cranking, the fuel pump turns on and finishes the fuel rail priming pressure.
At start when quite cold, the idle should go high, then slowly come down to about 650.
Along with all this is the battery recharge load on the motor.
After about 45 seconds to a minute +/- the Ox sensors heat up to at least 600 degrees and take over control of the fuel.
So you see the sequence is not simple.
Try the reboot then see if there are other issues.
Good luck.
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After installing my IAC i had my computer reset so the check engine went off. But it still idles poorly and the CE light came back on so i am going to get the code read in the morning but this is just really pissing me off. I was told it might be a bad vacuum hose but i would have no clue where to start looking and how to tell if it does have a hole or anything.
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Did you check you pcv valve, its on the pass side valve cover in the middle, it could be sticking , then follow the hose around to the back of the throttle body underneath the IAC and look at the elbow they tend to crack, when its idling rough pull the hose off the pvc and put our thumb on it does the engine smooth out?
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well i forgot to mention i already replace the pvc valve and hose but this morning i brought it in to read the new codes that popped up and it reads that both my banks are running lean? And i have already replaced my both my o2 sensors and catalytic converters so i am stumped. Also i cleaned out my maf sensor, all electrical connections and my TB. so if you have any suggestions please let me know.
Lead Driver
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You need a reality check at this point.
.
If you replaced the cats and OX sensors on a 'luck' attempt, unless you knew you needed them, you spent a lot of money and labor for nothing.
.
....The low idle you have is due to not enough air bypassed around the throttle body, as evidenced by the low idle.
.....If the IAC connector were to be removes from a fault free motor, the idle would also go low "as a normal result" because it allows the IAC to fully close with no control from the PCM..
.....The low idle and lean codes usually do not go togather because one is not enough air and the other 'lean codes' is to much air.
.....Your being difficult to help the way you are going about it.
Start over again.
.....What are the codes , not your discription of them?
.....What is the present state of drivabilty? Is the idle still low?
.....Then we will work on the causes if you want..
.
If you replaced the cats and OX sensors on a 'luck' attempt, unless you knew you needed them, you spent a lot of money and labor for nothing.
.
....The low idle you have is due to not enough air bypassed around the throttle body, as evidenced by the low idle.
.....If the IAC connector were to be removes from a fault free motor, the idle would also go low "as a normal result" because it allows the IAC to fully close with no control from the PCM..
.....The low idle and lean codes usually do not go togather because one is not enough air and the other 'lean codes' is to much air.
.....Your being difficult to help the way you are going about it.
Start over again.
.....What are the codes , not your discription of them?
.....What is the present state of drivabilty? Is the idle still low?
.....Then we will work on the causes if you want..
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PO171 and PO174 Bank 1 and 2 running too lean
When i stopped at a stop light in the morning when the engine is cold the rpms drop to under 500 and the engine sounds like it is going to die. Once i accelerate it is fine, also once the engine hits optimal running temp it idles just fine.
When i stopped at a stop light in the morning when the engine is cold the rpms drop to under 500 and the engine sounds like it is going to die. Once i accelerate it is fine, also once the engine hits optimal running temp it idles just fine.
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Well i think i fixed the problem. I went to o'reillys and bought some electrical cleaner and cleaned my MAF sensor and any connector i could find. I let my truck sit out for about 5 hours in 30 degrees and it idle great so i will check again tomorrow morning and check again.
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well the idle is back. I was told by a mechanic that it is my EGR that is clogged. Which could be true due to on of my hoses that connect to the large metal tube that attaches to the EGR was broken and was sucking in anything it could. I replaced the hose but is the mechanic right.
