exninja

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Quick question

I just finished my LDK swap a few weeks ago. It seems like the idle has a little more vibrations than it used to. It's possible that I just got used to the squishy Kia Rio I was driving for two months, but I think it's more vibey. I noticed on my boost gauge that at idle it'll sit at ~20inHg when it's warm, but before warm it'll blip down to like 25 and when it does that the vibes also calm down. The RPM stays pretty constant. The vibes are nothing severe, but just wondering if maybe there's an issue. Stock mounts.

Also, for curiosity's sake, since the car is drive by wire, does the computer keep the throttle open during idle? I also ask because at idle the OBDII says that throttle position is at like 17%. Other cars I've had had an idle air control valve, but this doesn't.

Thanks

SSlobalt

Mine is -19 psi at idle without AC on and -21 with AC on.

exninja

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Excellent. Thanks

tomj77

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-25? Never seen that before. That's a lot of vacuum.

exninja

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It's a quick blip down. I took a video yesterday. I'll post it soon. I never really paid attention to the magnitude before the swap. I'm wondering if the computer is still learning the new engine. Shouldn't be much of a difference, unless the slightly higher compression is changing the idle ever so slightly and making it vibrate more.

tomj77

iTrader: (2)

Quick blip down is no biggy, mine does it in certain conditions. And ur vibes are probably due to not properly reinstalling tranny mounts. Gotta do it a certain way or it vibrates. Loosen the bolts on the passenger side engine mount 3 turns or so, make sure u tightened the back tranny mount first, then front, leaving the passenger side loose a bit, slowly drive around block so engine settles properly , then tighten them. That should fix that issue. Mine vibrated like crazy when I didn't do it right. But that was also with rotated mounts, I'm assuming same prosses with stock mounts

exninja

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Thanks. I'll try that out.

umrdyldo

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P.S. it's not read in PSI.

-20 in HG at idle.
a little less with AC on -18 or so.

exninja

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I'll assume that wasn't directed at me

Well actually...the unit is positive, and should be read as 20 inches of mercury vacuum.

Had to channel my inner Ted Mosby. My wife hates it when I do it to her, so I've got to do it here instead.

And the numbers are helpful. Thanks.

SSlobalt

I think it was directed at me. My bad.

exninja

iTrader: (1)

No biggie. I'm appreciative of the info.

09CobaltSS1

Yes, unlike drive by cable systems that must utilize a IAC valve to maintain idle air flow/rpm, a drive by wire system opens the tb to control the same function as an IAC valve. However, 17% throttle position at idle with the engine up to temp is awfully high actually. I would likely suspect the DAL's, Optimum Torque and Optimum Spark tables need some messaging. I bet if you watched your spark advance at idle with that scan tool you have, along with your absolute engine load, you would be pretty close to zero (0) and even touching into negative timing advance and around 30% engine load. At full operating temp (and A/C off), these engines are happiest anywhere between 10*-20* advance at idle and 15-20% engine load. This should roughly equate to 4-6% tb position just to give you a rough idea.

exninja

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That is great to know. I'll check it again soon, probably tomorrow. I don't think that I scanned it at 180*, but it warms up pretty quickly in Az. I was hoping to avoid a "tune" with the swap but if the numbers hold then it may be inevitable. I also haven't heard much about good tuners in Az...

exninja

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Just scanned again after full warmup. Throttle position is 17%, load is 26%, spark advance is +5*. With AC on, 19%, 35% and +3* respectively. I never checked these numbers before swapping the engine so I can't compare them to what they were. As such, I haven't touched the ECU. Are these typical of the stock tune? I had understood that the LDK was very similar to LNF and thought that the ECU wouldn't need tweaking, but do these numbers mean I'm mistaken?

09CobaltSS1

The high load and low spark advance at idle is a large part as to why it's idling a bit rough. Nothing is really going to blow up on you or anything, however things do clearly need some tweaking.

As far as the engines being similar, they absolutely are. However, if I'm not mistaken, I do believe that the compression ratio on the LDK is slightly higher than that of the LNF. If this is the case, that, and other contributing factors could possibly be compounding, resulting in some minor adjustments needed. Again, it's likely not really a huge deal. Just something that will need to be dealt with.

exninja

iTrader: (1)

That's what I've been thinking as well. I figured the compression might be doing something. Looks like it's time to keep an eye out for an HP tuners and start some serious studying.

exninja

iTrader: (1)

I always just bump the key to get the car started. Twice now I've done it but the car cranked 2-3x and quit. First time I got a tb shut off mil code. Second time nothing. I'm guessing it's related to the timing/high load thing. Any chance it could be something like a gunked-up throttle body? That was something I regretted not cleaning out while I was transferring parts to the new motor.

umrdyldo

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At 75k miles my Throttle body was acceptably clean. Not near as bad as say an LSJ or L61.

exninja

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Here's how it went this morning:
Tried to start the car, but it cranked then shut off with the p2105 (tb shut-off) code. Grabbed my computer and cleared the code. It said the MIL was off but there was still a pending code (same one). I thought that was odd, so I shut it down and restarted. This time it started but went straight into limp mode with mode codes: p2105 (expected, left over), p2107 (limp mode), and p0606 (PCM mallfunction). Shut it down, then restarted and started up fine, or as fine as it has been running. So I'm not sure if the tables just need to be tweaked so that it starts up better in the morning and idles better, if the PCM really is bad, or it's something else? I'm leaning away from PCM bad because it had zero problems before the LNF engine pooped on me. Thoughts?

Thanks for the info. I'm less worried about that now

exninja

iTrader: (1)

Kind of a bump, but new question: Could this be cured by a crank position sensor relearn? I've been trying to figure out just what it does, and I've gotten mixed results. Some say it helps for idle timing, others just for misfire detection...

exninja

iTrader: (1)

Latest:

The car failing to start is annoying. It happened 2 out of 5 times today. I pulled the TB and cleaned it, along with the MAF. Now I'm experimenting a bit. The engine is off and I'm moving the gas pedal. When I'm not on the pedal, the throttle position is 21.2%. Full pedal is 83.1%. When I leave the pedal alone, after 10 seconds it goes to 34.9%. Thoughts?

Started the engine and the throttle position and engine load are close to the same as earlier. I turned A/C on, and now that it's warm the lights dimmed a little, idle is a bit rougher, boost gauge reads 24inHg vacuum. Throttle position is switching between 16 and 18%, load 30-36%, spark advance 4*. Could this be a TPS issue, as in the sensor thinks it's at 17% when really it's much lower, which is throwing off the spark timing, etc? Or is this just something that needs to be tuned? Also, MAF is ~3.5g/s and MAP is 41kPa. Shut off A/C, MAF reads 3g/s, MAP 36kPa. I'm wondering if this is connected to the car not starting. That's the issue that I'm most worried about.

exninja

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Morning bump

I snagged a used TB on ebay to experiment with or fix this. I'm thinking there's something to the TPS readings with the car off. I'd think those should be 0%-100% instead of 21%-83%. It'd be nice if someone has some known good values but I can't find them anywhere. I'm also not sure if that implies a bad TPS or if there's a recalibration that can be done. Unplugging and idling doesn't work.

umrdyldo

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There sure as heck aren't zero. Give me a moment. I'll look for you.

EDIT: 21-83/84%. Same as you. My reading was using a DashHawk

exninja

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Awesome. Thanks.

BTW, this is with the engine off. Just to be clear.

exninja

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My logic here is that the car probably has a set TPS value for starting, like 10% or something (which may be adjusted depending on learned values). If my TPS is telling it that the "zero" value is 20%, then the computer is trying to close the throttle rather than open it a smidge to start, thus my car fails to start. I'm also hypothesizing that the computer is trying to close it more during idle, which explains the 16% throttle position yet I get 24inHg vac sometimes.