Had a bunch of stuff going on... no the least of which was a huge disaster that happened during a head gasket swap - narrowly averted having to rebuild the engine (but I digress). I'm finally back to being able to really tune this thing.

Long story short, I lowered the compression to 9.8, put on 1.6 rockers, and gasket matched the cylinder heads (something I should have done a long time ago). I'm now retuning since I'm able to run much more agressive spark map without getting any knock counts. The engine seems to be much more responsive to tuning than it was before with better results. I couldn't be happier with the the part throttle, AE, PE, and cold starts.

Now to the one remaining issue...

https://www.thirdgen.org/forums/diy-...ncy-shift.html

I had posted this a while ago, but never quite got it resolved. I was able to minimize it, but it's back somewhat worse.

Here are the issues:

Issue 1.) On a hot (or warm) restart, it starts up great and idles. If I drop it into gear it wants to stall. I have to feather the throttle to keep it alive. If I wait for about a minute then shift, it does quite a bit better, but it's never a smooth transition from park to drive/reverse.

I've left off with the closed loop delay timer zeroed out for hot and warm restarts. Playing with this doesn't seem to make any difference.

Data shows on start up that the commanded AFR is dropping down to ~13.2:1. I've played around with the start up enrichment parameters, but it doesn't seem to help.

Issue 2.) When coming to stop (and the more abrupt the stop, the worse it is), right when the engine hits ~1000 rpm, it gets really rough for a split second and will tend to drop below the commanded idle speed before snapping back and idling just fine.

I've played around with the high MAP/low RPM VE's since the engine crosses them during deceleration, as well as the DFCO rpm thresholds. But this issue persists.

Issue 3.) If I leave the car idling in park/neutral for an extended period of time, then shift into drive/reverse it stalls (or wants to stall before recovering). However, if I shift back into park/neutral then shift into gear within 10 seconds or less, no problem. It's almost as if the engine "gets used" to park/neutral and is then "taken by surprise" when I shift into gear.

I have the target idle speed set at 800 rpm in park and achieve it through 0 steps. Idle speed in gear is 700 rpm. O2 threshold is set at 450 mV.



I've read through the stickies regarding stalling, throttle follower and such, but was wondering if anyone else has experienced these symptoms and was able to solve them.

My engine combo again:

350 ZZ4
AFR 180 heads @ 9.8:1
Comp Cams 262 roller
Miniram intake
7730 ECM

 

"I have the target idle speed set at 800 rpm in park and achieve it through 0 steps. Idle speed in gear is 700 rpm."

that may be a problem right there.
when you shift from Park/Neutral to drive or reverse, the trans is pulling the motor down plus the ECM is dropping the idle speed.
im not sure how much lower you could go with your cam, but i would try lowering the P/N idle to the same as in gear idle is set too and see if it helps any.

on my completely stock motor i add some RPM for idle in gear, IIRC around 25
RPM more in gear.

 

I have it set up such that I have the parameter "Add rpm in park/neutral" set to 100 rpm. So you're saying I should zero this out?

How do you add rpm in gear? Is this on a 7730? I don't have that option visible.

 

yes i have a 7730.

i used to have a bad surging problem both in gear and out and i played with a
number of things to get it to settle down.
i don't know what i was thinging about but i was wrong on the in gear speed
adder. i haven't tuned in quite a while and i was going by memory.
so you are right on the way it works.

i turned my laptop on and this is what im seeing.
this helped my surge sitting at idle both in gear and out.
i set the stall savers to have a taper from 0 degrees at zero RPM to 5 degrees at 200 RPM.

for the surge going into gear this helped me.
i have P/N idle speed adder set to add 25 RPM.
A/C adder is at 37 RPM
dead bands are set to 25 RPM.

it seems like there may have been some other things i did, but im not seeing them in my notes right now.

 

I'll give those a try. Thanks! If you (or anyone else) has more info or other things to try, please let me know!! I really want to slay this beast.

 

Shoot. It didn't work. Still wanting to stall.

I took some more data today...

STarted the car and let it achieve steady state idle for ~40 seconds.

At time interval 46 sec, I shift into drive.

Between 46 and 47 seconds, MAP goes from 45kPa to 70kPa, RPM drops to 225. O2 sensor doesn't appear to show anything abnormal. Within the 2 second window I describe below, the voltage is still bouncing between 850 and 350 mV.

At time interval 47 seconds, all hell breaks loose. RPM, target AFR, spark timing, %TPS, all drop to 0.

At time interval 48 seconds, engine recovers and lurches forward as RPM shoots up to 1050. O2 sensor shoots up to 900 mV, target AFR returns to 14.7, MAP is at 56 kPa.

At time interval 49 seconds, engine starts to settle back down and idle somewhat normally.

Any thoughts?

 

Try testing your stall converter. If your stall converter isn't working it may do that. If you can stand on the brakes, shift into gear and hit the gas, it should hit your rated stall speed before it starts to bog. If it doesn't, your convert may not be unlocking. My truck would stall bad, and the torque converter was shot. Also, your map jumping like that means it thinks going under a big load. Is your IAC also moving?

 

I'm able to stall the converter just fine. So I know it's not that. Also, it doesn't do this when the engine is cold when I first start it up in the morning.

The IAC starts to increase as soon as the ECM detects the engine speed dropping below the target idle RPM. But it's not fast enough to prevent the near-stall.

 

ok, If you feel the stall converter is ok, then what you need to figure out is why map jumps so much, does the map jump that much when it is cold? It sounds like you may want to try forcing open loop and see what happens.

 

Have you disabled the stall saver SA feature? If not I would recommend it. In the Tuning Guide Book sticky is a link to the $8D stall saver thread and how to disable it (chap 5, '7730).

The stall saver cuts the SA back to the base timing. Which on modified engines causes it to stall.

RBob.

 

yeah, if it's not the stall saver. try adding some timing, then maybe a little fuel in that 70kpa low rpm range.




another reason why i went 59 on my n/a car. closed throttle table made my life easier.

 

Yup. Did that a long time ago. I had read through your sticky thread about how the SA actually causes a stall rather than prevents one.

 

I was thinking about my data last night and I'm actually thinking now I may be getting too much fuel. With the delta MAP so huge, I'm thinking I may be getting a shot of AE that's equivalent to a WOT burst, and possibly drowning the engine in fuel.

So, what I've done for the next run is to take the AE Delta MAP PW Multiplier vs %TPS and set it to .5 for 0% TPS. I figure the only time I'm going to see a quick delta MAP at closed throttle would be when I'm changing gears at idle. Now I just need to find the time to run it with this and see what happens.

 

At time interval 47 seconds, all hell breaks loose. RPM, target AFR, spark timing, %TPS, all drop to 0.

This sounds like the ECM has gone through a reset procedure from a lack of DRP. IOW, the engine RPM went so low that the ECM thought it stalled. Which has the ECM doing a partial reset to get ready for a cranking event.

Although, this is a symptom, not a cause.

There is a closed throttle SA table, the values there may need to be tweaked. Personally I usually disable that table. Or change it so that it is only used during 'in idle' conditions.

On modified engines the idle stabilization SA is usually too great. It can help to substantially reduce or eliminate it until the result of the tune is nearly done.

One thing to look at is the IAC steps at warm idle in park/neut, then again when in drive. The park/neut steps should be about 20 - 30. Then with a minimum amount of increased steps when in drive.

Idling at 800 RPM with 0 steps is not a good idea. On MPFI setups it is better to have 20 - 30 steps at idle with the ECM handling it.

If the steps are too high in drive then the engine can stall when coming to a stop. Also, look at the throttle follower steps. They too can help in preventing a stall when coming to a stop.

It is normal for the engine to idle higher when in prk/neut then when in drive. This can be adjusted at L862E. Which is an adder for when in prk/neut.

I don't see an IAC bump in the cal for when the trans is put into drive. If there is one it can be helpful to prevent stalling.

RBob.

 

Thanks for the tips.

Yes, I have already zeroed out the spark advance/retard vs idle speed error tables. They were causing hunting and zeroing them out solved that.

Hmm... you're saying it's actually good to have some steps in park/neutral. I've always been under the impression that 0 is the best. But, hey, I'm open to trying new things. I'll try that too.

Right now I add 100 rpm for park/neutral. Is that too high?

I'll also try adding some throttle follower steps. Maybe that will help the transition back to idle when coming to a stop.

 

The 0 IAC steps at idle is from TBI set ups. Although I prefer 5 - 10 steps for a TBI. The reason is that it allows the fuel to be pulled past the throttle blades. More air goes past the blades then through the IAC. Which pulls the fuel along with it.

For a MPFI set up it is better to have some steps in place. Some intakes distribute IAC air to each runner. So it is better to idle with a handful of steps for better air distribution.

A 100 RPM increase in prk/neut seems excessive. Maybe make it 50 RPM increase and also raise the warm idle RPM to 750. Part of the issue may be that the 700 RPM in drive is on the low side.

RBob.

 

I'll try 750 rpm. Problem is I'm running a factory LT4 torque converter and it's pretty tight. The tendency to want to creep forward requires increasing counter effort on the break pedal.

With my Miniram, there are no IAC passages in the manifold and I'm no longer running my little add-on IAC distribution manifold ever since I conquered my idle misfire. So whether through the main throttle blades or the IAC, the air is getting dumped into the main plenum. The only thing would be is if somehow the IAC is faster-reacting if some initial steps are present than if you're running at zero initially??

 

YES.... YES!!!!

I got it!!!


Turned out it was the freaking charcoal cannister. The one I had was the wrong cannister for a 7730 Camaro.

I was under the hood of a friend's 91 TPI Camaro (thegooseman on this board) and happened to notice his cannister was different than mine. He said he had an extra one on hand and gave it to me. I just put it on and bingo! The stalling is gone! I shift into gear and it just idles... no stalling or even wanting to stall.

Geez, I would have never guessed that the CCP system would have had such an effect on idling characteristics. I would have been screwing around with this thing indefinitely if I hadn't happen to notice the different cannister.

I have zero steps still in park, but I can set the idle at 712 rpm in park and have it at 687 rpm in drive. Perfect!

 

Natural question - what are the differences between the two CCP cans????

Photos please (if possible)

//RF

 

There are both normally open (N.O.) and normally closed (N.C.) solenoids. Most code masks have an option bit to define which one it is. It is easy to check the solenoid, if it passes air with the ignition off then it is N.O., otherwise, no air then N.C.

The '92 Camaro has a N.O. solenoid. Needs to be activated to turn off purging. I have another CCP can/solenoid that is the same exact canister but has a N.C. solenoid on it. Came from a Caprice (IIRC) of about the same year.

ULTM8Z, good to hear you have it figured out. Note that the CCP vent to the TB should be on ported vacuum. And usually runs a small restriction in the port.

RBob.

 

Here's what I was running vs what's on the car now... clearly the correct one is a lot simpler installation.

 

Thanks to everyone for their suggestions though. I really appreciate everyone's time.

Yes, I have the setup now identical to thegooseman's 91 TPI setup. Very convenient to have a factory car to reference.

 

with a canister purge problem i would have expected you to have more problems then what you had.
when my purge valve started sticking open the IAC counts were all over the place as were the BLM and Int. talk about a tuning nightmare. after sitting over night, one day it would start out rich, go lean, then go back rich. the next day it may have been fine in the mourning and rich that evening.
thinking about it i would almost bet some of your other problems were related to the canister. have you taken a log while driving it with the new canister yet?
at any rate im glad you finally got it nailed down

 

Haven't had a chance to drive it yet. Yeah, I'm curious what other parts of the tune will be impacted by this now.

 

Thanks for posting photos of the CCP. Yes, I run late model (it appears identical to yours) in my TBI setup. Donor vehicle was '90 B-Body. During initial conversion effort I used original, non ECM controlled CCP can (circa '75). This explains strange idle that I had at the time - and you have confirmed it. Thanks for posting and congratulations on finding the source of your idle problem.

//RF

 

Ok, so I just drove the car. Not much was different at speeds significantly above idle, though I'm not really shocked about that. Ingestion of fuel vapors at higher engine speeds is probably a much less percentage of total fuel flow than it would be at the lower idle speeds.

BLM seemed to dip a few points at about 1500-2000 rpm (I'm at 122-124 instead of 128 where I was before) but other than that the data showed that the calibration was still ok as-is. Throttle tip in was also seemed to be a little crisper, but that could be a figment of my imagination- it was already pretty crisp to begin with.

Any rate, the ability to shift into gear without feathering the throttle is a nice improvement- especially during parallel parking!!