idle problems

[BeerForMePlz]

Im hoping you guys may have some ideas on my problem.Car is a h/c 347 nothing crazy.Swapped heads and added a fast 90 set up.The problem consists of hanging idle around 2k,bucking below 1900 in 1st gear and cold start issues.Obviously you would suspect the tune but my tuner is good and its on and off,sometimes it has none of these problems.So far the IAC was replaced and the fast intake was meticulously sealed so no leaks.Im using the new UMI TB ,starting to suspect that may be the issue.Anyone experienced this before?

[CollinsAuto]

Try putting a return spring on the TB to keep it shut.Check to see that the TB cable has sufficient slack. Seen that a few times with aftermarket TB's

[BeerForMePlz]

Tb is not sticking ,tryed that.Going to swap to a NW TB.If that doesnt work tuner thinks it may be a corrupt file in the tune.Hopefully its one of the two cause this thing is a bitch to drive at low rpm's.

[JS1965]

Did u spray the intake down for leaks...
If u ported it or took it apart it might be that bro....

[CollinsAuto]

Tell your tunner to turn off all of the idle adaptives.

Tb is not sticking ,tryed that.Going to swap to a NW TB.If that doesnt work tuner thinks it may be a corrupt file in the tune.Hopefully its one of the two cause this thing is a bitch to drive at low rpm's.

[BeerForMePlz]

Its not the intake ,it was assembled and sealed extra good after finding a leak.What exactly are idle adaptives?

[CollinsAuto]

If the tunner your using has no idea what the idle adaptives are. Find a new tunner.


Its not the intake ,it was assembled and sealed extra good after finding a leak.What exactly are idle adaptives?

[redhardsupra]

definitely sounds like a TB calibration problem. with a bigger TB the engine is gonna 'eat' more air than what computer thinks is commanding. the effective area table is the biggest single determining factor. then you just need to tune the running airflow/desired airflow tables and you should be real close to normal. this is normal and expected of any bigger TB.

[viper99ta]

How do you recommend changing the effective area table for a 90mm TB? I know RAF but not the effective area

[redhardsupra]

http://forum.efilive.com/showthread.php?t=4816&highlight=effective+area

this thread has some good explanations and a link to a spreadsheet i made to make life easier. if you're using non-circular TB then i'd have to modify it a bit. I've made it work with all kinds of TB's before so it shouldn't be a problem. Let me know how it works out for you.

[viper99ta]

I'm already using your RAF spreadsheets; I didn't realize you had one for effective area, thanks!

[redhardsupra]

I'm already using your RAF spreadsheets; I didn't realize you had one for effective area, thanks!
you actually don't have to use the RAF spreadsheets anymore, these were made before HPT2.x came out, now you can just work of a custom histogram.

[viper99ta]

OK, a little confused. The spreadsheet shows a value for ETC throttle area conversion. How do you apply the single value to the table for IAC steps vs Desired Idle Effective Area?

Or am I an idiot and just need to change the stock value of .0255 in 'ETC Area Scalar' to the new single value and leave the above table alone?

Found this from Chris at HPTuners:


1. The PCM calcs a base idle airflow from the RAF table
2. it then does the adaptive idle correction, throttle cracker or follower correction depending what state the vehicle is in
3. it then converts this airflow (g/sec) to an effective area (sq.mm)

at this point there are two options the PCM has to convert the effective area into something useful to control either the IAC Stepper Motor or the ETC:

4a. For non-ETC vehicles, the PCM uses the IAC Steps vs. Effective area table to work out the number of steps from the effective area. This table has effective area as the axis and steps as the looked up value. The number of steps is used to control the stepper motor.

4b. For ETC vehicles the PCM multiplies the calculated effective area (from step 3) by the ETC scalar which then gives a % as the output. ie. sq.mm x %/sq.mm = %. This % is passed to the ETC code to control the throttle at idle.

[redhardsupra]

dont change the IAC steps, just just 'effective area per 1%' table. use the second tab in the spreadsheet, it's got a bunch of different values with the popular ones highlighted. use that value in the scalar for 'effective area per 1%'. also, if you're dicking with idle, remember to reset the TPS sensor. another good tricks are to use the live spark control (as it ignores all modifiers) and find a spark value that makes it idle nice at the desired RPM. once you find out what it likes, put that in the idle park (or drive if it's a stick) spark table at the cell corresponding to the MAP/RPM tuple you observed the best idle at.

[viper99ta]

Thanks Marcin.

[BeerForMePlz]

The weather was nice today so I drove the car quite a bit.The one thing that is repeatable is that the idle hangs once in neutral until coming to a complete stop.Does that imply anything specific?

[viper99ta]

Usually the RAF is off.

[CollinsAuto]

to much throttle cracker vs road speed airflow.

I am telling you find the idle adaptive enable and shut them off. They will drive you crazy adjusting the RAF.

The weather was nice today so I drove the car quite a bit.The one thing that is repeatable is that the idle hangs once in neutral until coming to a complete stop.Does that imply anything specific?

[BeerForMePlz]

Im going to mess with it tomorrow with the tuner.I will mention the idle adaptives and see whats up.Thanks for all the input .

[BeerForMePlz]

We spent a few hours today tuning and still have hanging idle issues.The odd thing is occasionally it will start acting normal with no changes to the tune,like on and off randomly.We checked for vacuum leaks,the intake has been taken apart and sealed well,tried 2 different TB's and still the same issue.My tuner is good and this is a mild car compared to others he has tuned.Does anyone have any other ideas?This car is possessed !

[redhardsupra]

post logs/tune

[BeerForMePlz]

Ill see if I can get the tuner to post them or maybe he can chime in .I know so little about tuning I cant properly describe what all he tried.But basically its not doing what its told to,changes to the tune do nothing.Also fwiw the car is running hotter than it was previously,not over heating just noticeably warmer.

[CollinsAuto]

Sounds like the idle adaptives and idle spark stabilizer are to some degree overiding you requests.



Ill see if I can get the tuner to post them or maybe he can chime in .I know so little about tuning I cant properly describe what all he tried.But basically its not doing what its told to,changes to the tune do nothing.Also fwiw the car is running hotter than it was previously,not over heating just noticeably warmer.

[BeerForMePlz]

This keeps getting weirder.The car started over heating,pulled the thermostat and it was cracked.Replaced with a 160 and shes good.Some how the hanging idle was gone,at least for almost a week.Then bam started to do it again.All that was done was a thermostat swap and disconnected the battery.If anyone has any ideas here I would really appreciate it.Im just about prepared to set this car on fire!