Just curious what those who have done a 3l swap are at. I'm running an untuned portmatched setup and I think my idle is a little low at around 600. I know the PCM sets the idle at 750 on the stock motor. Could the increase in displacement (without touching the computer) result in such a change?
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What's your idle speed?
- Thread starter Parp
- Start date
rexxdoggy
Hard-core CEG'er
My idle on my untuned full 3 liter is right about 600.
Klasky24
CEG'er
Untuned ported is at about 700, exactly where it was prior to the swap.
blu_fuz
New Member Classroom vulture
Idle should always be the same no matter what motor you have in your car 750 RPM. Higher than that you have an intake leak or TB adjustment problem, lower than that - not sure.
Redlineracer12
Addicted CEG'er
Lower than that can be from not enough air getting through idle air control valve...
The needle could also be off though, you could verify by datalogging with Xcal.
RFcsvt
Veteran CEG'er
Mine idles right below the 750 mark. It's a full 3L and for now it is not tuned. It did idle pretty bad at first, but it eventually leveled off and now it seems to be ok. I think if you are untuned and for some reason you unhook the battery then your computer might need to relearn the adjustments because of the different engine. Mine actually idled below 500 for a while. Just a thought, if the car was ok before and is now having an issue then this probably isn't the reason.
rexxdoggy
Hard-core CEG'er
I've had the battery unhooked time and time before doing the transmission swap and it still idles around 600-650. And warmer weather makes it bounce around, too. In the colder weather, it would idle much closer to 750.
Even running untuned on a full 3L it would be at 750? That's what I've heard and seen of my idle being so low, it was because I am untuned. I'm curious.
Even running untuned on a full 3L it would be at 750? That's what I've heard and seen of my idle being so low, it was because I am untuned. I'm curious.
blu_fuz
New Member Classroom vulture
The PCM idle is set to 750 RPM. Ported, Full, 2.5, 3L - it doesn't matter as long as it is a stock Contour PCM, it will/should be 750.
The PCM, unless changed, will always control the idle to 750 rpm. Heck my DD and my SVT tend to idle low, 500~600 rpm at times.
Bossdogg
CEG'er
Im at 750 on the dot...
rexxdoggy
Hard-core CEG'er
Hmmm, so my low idle has to do with the IAC maybe?
Edit: Redline mentioned that.
Edit: Redline mentioned that.
blu_fuz
New Member Classroom vulture
Possibly that or the MAF, IAC, or throttle position sensor is getting a false reading. 600 RPM isn't too big of a deal if you don't have any other related issues going on.
rexxdoggy
Hard-core CEG'er
Okay. Well, I replaced the TPS not too long ago, maybe like, November-ish, I'll take a gander at the MAF and IAC. But yeah, the idle doesn't really give any issues from cause or an effect. It does want to dip a few times, but also people told me that's what happens when running untuned. Doesn't stall, just dips sometimes.
blu_fuz
New Member Classroom vulture
My IAC will act up and I will be at 1200 RPM until I tap the gas again and I have had the car stall out from low RPM also. Ported 3L.
rexxdoggy
Hard-core CEG'er
Yeah, if it dips, I'll tap the gas and it'll return to normal (600). It's only stalled once, and it was super hot outside.
BAD SVT
Addicted CEG'er
I personally think its the O.P's guage. The temp needle is erratic as well. It had that low idle b4 the swap. Also, i've never driven a car which it's rpm needle yearns to drop back down to idle so quickly. When i shift, at a blink of an eye, the needle is at 1k already. very odd...
99Mystique ATX
Hard-core CEG'er
Might be worth a check to datalog and verify that your tach is accurate... I've seen a couple that have been off by 100rpm in the past...
CSVT#49
Addicted CEG'er
One other thing to check would be the idle set screw on the throttle body and of course as everyone has mentioned the IAC. If the set screw is allowing the butterfly to completely close when at idle then you may not be allowing anywhere near enough air flow. Fairly easy to adjust and I'm willing to bet it will solve your problem, but again... this all needs to be verified with a data logger to ensure your tach needle isn't just off.
Blackcoog
Hard-core CEG'er
I believe the throttle body should be completely closed at idle. If the set screw was turned to crack the throttle blade open then it should be turned back so the throttle blade completely shuts. The IAC entire purpose is to pull in air to keep it at idle.
Also, if the throttle body was ever polish or modified internally around the throttle blade it could affect the idle. You should never polish/grind/sand the area around the throttle blade unless you want the car to idle really bad.
Also, if the throttle body was ever polish or modified internally around the throttle blade it could affect the idle. You should never polish/grind/sand the area around the throttle blade unless you want the car to idle really bad.