Rough Idle

[stlryda79]

I have a 2001 millenia 2.5L that has a rough idle when the car is cold. When I first crank it uo it idles rough. CEL has been on for a while and I went to get a diagnostic test done. The codes were IAC, Cylinder 3 misfire, and the knock sensor.

I replaced the knock sensor last week(which took all day), then I replaced spark plugs(hoping that was the problem for misfire), and then I took the throttle body off and cleaned the TB (replaced th e gasket) and IAC with CRC throttle body cleaner.

Not sure if I needed to take the IAC fully apart to clean. However, after cleaning and reassembly, the car still idles rough and idels worse when I drive now and I hear a hissing noise coming from the area where the EGR valve is (Which I heard before).

I unplugged the IAC when the car was running and didn't stall, but the RPMs dropped. When I replaced the knock sensor I checked the vacuum lines for leaks and didn't find any.

Any help before I go out and spend all this money on the IAC and any suggestions on the cylinder 3 misfire?

[yel-low]

IAC typically only goes bad when it is removed and seal broken. Did you replace the rubber gasket or just the throttle body gasket?

I would check your injectors with an ohm meter to see if #3 is dead. That one is typically the one and only one that goes bad on the 2.5 for some reason. I have a write-up on here on how to check your injectors. The typical code is a misfire when an injector goes bad.

I would also swap out your plug wires if they have lots of miles on them. They can also be arcing an causing the misfire.

Can you provide the actual codes? The interpretation doesn't really help much. The actual code means much more as a lot of the systems are interrelated. Although the code might literally read out to be a certain component, only the experienced with your motor can pinpoint you on what the culprit really is.

[stlryda79]

Thanks for the input Yel-low!

The 2 codes were 0300 and VRIS Selenoid. I replaced the VRIS Selenoid #1 and also replaced the distributor cap and rotor. However, I still have a rough idle when the has been sitting for awhile and smooths out in a few minutes. I haven't changed the sparkplug wires or the sparkplugs. Can anyone guide me into the next or have anyone of you had a similiar issue like the one I'm having.

Your input is greatly appreciated!
Thanks

[Am4wag]

I too have a VRIS/check engine light (bad wire from ECU to sol.)at the present.But essentially that has nothing to do w/rough idle as far as I can tell-only adds a boost when accelerating,and soon plan on repair.I did have a rough idle,but all the time,and stalled once at a light.Removed the throttle body and IAC,cleaned them out and idles good now.Also when I had the throttle body off,I cleaned out the 2 (crossover?) holes inside the intake manifold-they were completly stopped up and ridged.

[stlryda79]

I have cleaned out the two holes you are talking about and cleaned the throttle body and replaced gasket. I am going to replace the spark plug wires next. It only idles rough when I first crank it up after it's been sitting awhile and smooths out in 1-2 minutes. The CEL flashes for about 30 seconds and goes solid once the engine smooths out. I suspect maybe arching?

[stlryda79]

do you think I should also replace ignition coil?

[stlryda79]

Also experiencing a very small coolant loss

[Am4wag]

I would'nt be throwing a coil at it yet.They generally start acting up after engine warm up.You could have an idle control issue when cold/sitting-beings it runs fine shortly after startup.Coolant loss could be a hose leaking,or even a head gasket (kind of hand in hand w/cold start missing) (?).

[stlryda79]

I replaced the spark wires and put ngk platinum plugs in. The cel was off and the car was starting up without any problems for a week. However, the other day
I smelled some fuel when I was driving and the cel came back on. P0303 misfire cylinder 3. It idles rough on cold start again and smooths out after 2 minutes. I checked the injectors using yel-lows write up and they all are pretty consistent at 15. Pulled the #3 plug back out and no fluids on it.

I'm stomped, any suggestions from anyone?

[yel-low]

Do a compression test. The rings on #3 could have been fried. Also pull the #3 plug and wire. Have someone crank the motor while grounding the plug on the intake. You should get a good spark. If not then you have a bad distributor/cap/rotor.
If you have the 2.5 then you only have a single coil in your distributor.