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Discussion Starter · #1 · (Edited)
my 2001 Taurus starts and run good, but i have a small problem from the time i bought it. at idle engine speed slightly goes up & down, it can be heard like a rhythm up/down. unfortunately my RPM tech is out and cant provide right values. but its like the sound heard from big trucks when in idle, rpm goes up/down. when i stop at signals and on (D) i hear engine sound constant..then slightly it goes down then picks, it happen few times and suddenly a momentary knock then after some times again it gives a knock.

if i make it to (N) then the knock is not there but the engine rhythm is the same & i feel at a particular point when the rpm comes down it make a missing, then picks.

hope i explained correctly, any one has experienced the similar problem? what could be the right cause? what are the areas do i have to check?
 

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Discussion Starter · #3 ·
did you pull any codes??? with the problems you are having they maybe related with some sensor issues.

i don't see any light for fault code, can there be any fault code without check engine light on? you can say the idle speed slows down that could be the reason why it some times misses momentarily, but picks immediately couldn't observe any vacuum leak, where to check then? may be vacuum regulator?
 

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I've been listening to my engine like a hawk for the past few weeks after having been put off by a few awkward sounds. But I've since read that the Duratec is just a loud engine. I've even heard it described as being almost diesel-like in the noises it makes.

Though mine does have a rhythm to it as yours does, along with a rough/jumpy idle. I've already done plugs/wires so I'm thinking the last thing to check is the PCV valve/hose. But beyond that I'm clueless.
 

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a cam shaft postion sensor thats getting ready to go can cause that miss idle issue. also the egr valve or paths might be almost clogged. tecs with high mileage often have that problem. search other threads for the egr issue lots of info on it
 

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a fault code can be in the system but not ready to kick on the cel.. ive pulled codes in the past with no light on
 

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Replace the IAC valve... a clogged one it won't set any codes.
 

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Discussion Starter · #8 ·
Replace the IAC valve... a clogged one it won't set any codes.
what about cleaning it instead? also it has a servo motor, so when its set at a particular place during idle, how can the valve clogging can play since its on a feed back loop?

any one has experience to get it ok by replacing IAC?
 

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Sure you can try. Mine didn't want/liked to be cleaned, it was still getting "stuck". I had to replace it :D
The actual position of the valve is not monitored by a loop, the only feedback monitored is the engine RPM. That makes it a slow reacting loop... PCM sends a bunch of pulses and the valve integrates those with the included spring to position in a certain place.
 

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^+1. Might remove and try cleaning the iac with throttle body or brake cleaner spray, as they are a bit pricey, or replace. If not the iac, check for vacuum leaks, tps, maf (clean with crc maf cleaner spray), iat, ps pressure switch. Might also check for a knock sensor code if so equipped.
 

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Discussion Starter · #12 ·
Thanks to all of your for your replies, i missed to mention on my start that all the observation i made was when AC was running. i got problem with my AC compressor few days before and it is fully death now. . today i had to drive it again without AC to take it to work shop, i found the engine is smooth now on idle, i think the compressor was the one which was giving variable load to the engine causing knocks. before the compressor got damaged it jammed and belt slipping was there.

May be some of you have already experienced this....hope this problem will not occur with a OEM compressor i would replace.

just need some advise on what are the sensors i have to replace on a periodic basis and what are those can be cleaned and put back, i am thinking to do a preventive maintenance.

thanks
 
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