RPM drop when shifting from P to D

[Mike The Canadian]

Just curious on what could cause this..

My idle is set to around 750-800 rpm in my tune..
Ever since getting the heads done when I shift from P to D it drops to about 400-500 and then raises back up.

What could cause this?

I fixed a tonne of vac leaks (anyone who knows my car will laugh) last time I was at home. It was better but still does it.

I almost want the vac leaks back, stiff tranny mount + idle at set speed instead of above = a lot of vibes!!

[Starglow]

That is normal operation....there are two different idle speeds, one for park and one for when in drive gear so nothing is broken that needs to be fixed. Are you expecting the idle to stay @ 700-800 all the time?

[guiguilandry]

THIS IS NORMAL AS STATED, there is more load applied on the engine when you're in drive so it's normal that for a second the rpm drops... it does the same thing when the fans kick in too...

[sleepyalero]

Agreed

[Mike The Canadian]

Thanks..

Idle speed in D is till higher (only a bit lower than P).
I'm just curious because before I did the heads it wouldn't do it at all.

RPMs would stay constant no matter what you did (once warmed up).

If it's a non-issue I'm not worried!

[MMGT1]

Mike... timing requirements bud. I bet with the heads done we need to bump your timing a couple of degrees going from P/N to D. Your idle should be 775 no matter what position your in, and with ac on or off you should still be 775. Your saying your dropping to 400-500 and then working back up to 775 right? That is where your stall saver kicks in and adds timing to prevent the stall, then the IAC is catching up getting you back to 775. Like I said, pretty sure a little bump in timing for the transition will fix it

[sleepyalero]

I know if im in neutral/park and turn on heat or ac the car will bog down to about 500-600 then jump back up. It only goes down for like .2 seconds though.

[MMGT1]

Sorry sleepy, his was tuned and the idle is a little higher than normal to get rid of some of the vibration from the trans mount he's got in there. I had him rock solid from P/N to D and AC on/off. Just need to scan it and make live change to timing to find the sweet spot again

[sleepyalero]

Ahh fair enough.

[WhiteV6]

I doubt its the heads but I don't know what you did to them. Maybe if it was iron vs aluminum, or a different style chamber. 3400 to 3500 doesn't create such a phenomenon. Nor does 3.1 to 3400, which is a big efficiency change itself.

Easier to scan it and see whats going on rather than guess anyway.

[AleroB888]

Originally Posted by MMGT1

Mike... timing requirements bud. I bet with the heads done we need to bump your timing a couple of degrees going from P/N to D. Your idle should be 775 no matter what position your in, and with ac on or off you should still be 775. Your saying your dropping to 400-500 and then working back up to 775 right? That is where your stall saver kicks in and adds timing to prevent the stall, then the IAC is catching up getting you back to 775. Like I said, pretty sure a little bump in timing for the transition will fix it

I never heard of a stall saver, where is that in the PCM? Seems like there are other times when that might be useful for me....

[MMGT1]

B, go online and search "tiny tuner". Use tiny tuner with your bin file from hpt and then you can see all of the tables not available directly from HP Tuners. You make changes using tiny tuner and then use HP to flash it back to yours. If your bin is not supported you can get it unlocked from his tiny tuner page... there is contact info there as well. You can also go onto HP Tuners Forum and search for tiny tuner. You'll find info on it there as well. The guy that wrote it spent a lot of time on the forums there

Mikes issue also rears its ugly head when timing from Idle to Drive has a gap in the tables or the transition is too far out of whack. **Idle timing not available from HP, have to use Tiny Tuner to get those**Also, with Mikes vac leaks gone, the unmetered air is no longer there, so his fueling is going to be messed up a bit now too. He's got a couple things going on there for sure. Like Ben's saying, need it on the scanner to see what's actually out of sorts

[Mike The Canadian]

I'm sure I'll have some sort of vac/exhaust/miscellaneous leak in no time Paul hahaha

We need to smoke test this bastard and solve all leaks when I get back!!

[tw0123]

Only you can get this stuff Mike!! Glad Paul knows his stuff just reading your crazy problems hahaha!!! When are you coming back home bud ?? Need to get you out to a meet again!

[Cliff8928]

Originally Posted by MMGT1

Use tiny tuner with your bin file from hpt and then you can see all of the tables not available directly from HP Tuners.

I wasn't aware of any way to get a BIN file from HPTuners.... I though that was a DHP thing. HPTuners just saves a .hpt file.

[MMGT1]

I just call them bin files man..lol Old school, to most of us they are all bin files it's just that HPT does save them as .hpt. You use tiny tuner to access those tables we don't have and save it as a .hpt file when your done. Use HPT to shoot it back to the ECM. Your ECM needs to be supported by tiny tuner though, if it's not, they will add it.

[MMGT1]

Originally Posted by Mike The Canadian

I'm sure I'll have some sort of vac/exhaust/miscellaneous leak in no time Paul hahaha

We need to smoke test this bastard and solve all leaks when I get back!!

I can supply the bucket of smoke! Hahahhahahaaa...

[Mike The Canadian]

Originally Posted by MMGT1

I can supply the bucket of smoke! Hahahhahahaaa...

Lets do it up! lol!

[Cliff8928]

Originally Posted by MMGT1

I just call them bin files man..lol Old school, to most of us they are all bin files it's just that HPT does save them as .hpt. You use tiny tuner to access those tables we don't have and save it as a .hpt file when your done. Use HPT to shoot it back to the ECM. Your ECM needs to be supported by tiny tuner though, if it's not, they will add it.

But you still can't edit a .hpt file with tiny tuner yet, can you?

Originally Posted by Cliff8928

But you still can't edit a .hpt file with tiny tuner yet, can you?

Not to my knowledge. It'd be nice though.