I've exhausted everything possible to track this down. Different plugs, 165 to 730 setup, new IAC, everything. My car has some intermitant idle issues.

When you come down from driving, pull clutch in it stalls.

If you first start it, gotta give it a little gas to get the idle maintined, then it will idle forever.

Here is a snapshot of about 25 minutes worth of idle in closed loop.

Desired idle: 700
RPM: 675 to 750
MAP: 58 to 60
Coolant Temp: 208 to 210
MAT: 125
INT: 70 to 73
BLM: 108
IAC: 88 to 91
Learned IAC: 56
Base Pw. 1.9 to 2.0
TPS Voltage: .44v


At part throttle all the way up to WOT I get 123, 126, 128 BLM.
Int goes around 123-128 at part/wot conditions under those BLMS's..

this is _NOT_ under boost..

Suggestions, help, etc.. Please.. I'm going OUT of my freaking mind..


-- Joe

 

..After reading a few posts.. Does the ECM calculate for the air pump? i.e, if its removed does the ecm expect the car to run leaner than it actually is?

-- Joe

 

are you familiar with dashpots ??? if so look into how they function.this is one occasion where a vss and throttle follower come in handy. im not trying to tell you how to tune your car but try a large base throttle idle.

 

Hrmm.. I'll look into that..

Does my scan output on idle look.. odd?? I know its a littel rich but.. too rich? I was thinking about reducing the VE at those spots
by about 20%.. Or should I change the injector constant and rescale??

Vss isn't quite working yet. I also changed to 3.73 over the winter, so my speedo is kinda. high.

ANother thing.. I have the N/s swithc crossed cuz the car used to be auto.. Does having it crossed (N or park) cause the ECM to do anything stilly?? should i put a switch in place?

-- Joe

 

well that could be a problem. it doesnt know to open the iaccomming to a stop.

cut them clean off. they could be cuasing trouble.dont touch them to anything. cut them off then tape them seperately and put them out of harms or grounds way.

 

Hrmm. We'll I'll have to at least put them to a switch so I can start the car.. I'll try that this weekend.

I'm gonna also try one more time resetting iac.

if I let off the gas at a slow speed, in 1st it will stall..

Thanks..

-- Joe

 

joe reset the iac. then keep opening the TB blades until the steps back down to about 20 or so. that should fix your idle woes. your idleing on pure iac not a good situation with a map car.

 

A blown motor, 700 RPM desired idle, and 90 IAC at idle.

A blower consumes HP, trying to idle the motor down that low I could see where you'd have problems.

I'd try setting the min idle to where the engine just idled, and see what RPM that was, and add 50-100 and try that as your desired idle RPM.

 

whats your take on a small blower at idle ?? 1-2 HP tops ??

 

What's your take on how much HP the engine is making at idle?. Then compare how taxing that couple HP is.

 

thats a double edged sword. it might take 7 hp to turn the engine over at idle but itl produce more like 10-50hp depending on the tq output at idle.

 

That is way too rich. You are almost at the point of triggering a rich O2 sensor.

What is your battery voltage? Maybe you need to tweak the Battery Voltage compensation table with that along with your VE Table in the RPM/Kpa of your idle. I also agree with Bruce that you should bump up the idle a bit.

 

this might sound dumb but your tps is .44?That is no good,the iac should be a little lower too.maybe??

 

Reset IAC, set idle to 900 now.. 850 at around 220F, which it should never get to.

I had the injector constant to 23, I put it at 24. See how much that effects things. If it screws everything else up, we'll play direct with the VE at idle.

Wish me luck..

Thanks!

-- Joe

 

When you reset the IAC, what idle speed did you use? I find it better to increase the minimum idle speed of the IAC (over stock values) if I raise the minimum Idle Speed in the eprom because of the cam.

Also, does the minimum Idles Speed that you set in the eprom change when you take the car out of neutral? On an auto car, if you put the car in Drive, the minimum idle speed will drop to 800 rpm if you have it set higher. GM probably did this to the auto bin to limit "engine creep" when in gear with an automatic.

I am just curious if the standard bin does the same thing.

 

Had a lot of things to do so I didnt get to do all I wanted, but here is what I _DID_ do.

1) Shorted ALDL A+B together to extend IAC pintle
2) unplugged iac while this happened
3) shut off car, removed short
4) attempted to start car. yeah right.. Had to hold the throttle
open. Used a torx bit to adjust it undle it would stay stable. Stable = about 900RPM

let it warm up, til fans kicked on, off, and on again.. idle maintained around 900RPM..

So I went home..

1) Adjusted injector constant from 23.0 to 24.0
2) changed temp the fans kicked on, cuz it seems to get
a little hotter than I want. now they kick on at 205 instead of 210.
3) Changed my idle to 900RPM until 220F, then 850 (shouldn't
ever get there).

The good news. I start it, idle pulls to 1500 right away, then levels off around 900RPM. No stalls on initial start, unlike before.

Unfortunately, I can't drive it til tomorrow cuz of an un-related valvecover baffle problem. These aftermarket holley (m/t) covers have the pvc and breather right over a rocket, and even with the crappy baffle it still sprays oil out the breather, and sucks in oil in the PVC.

Any more suggestions? Thanks for the responses guys..

-- Joe

 

It might be that iac.If you want to email me I'll share my method for fine iac adjustments.What about .44v,I thought tat was way too low???

 

Not a smooth idle, just so it does idle.
ie it will run without actually stalling. Let the IAC take some of the load.

 

As I recall all the code on the 8D goes by delta TPS for the TPS stuff, so the initial TPS isn't critical. Maybe someone has a hac handy and can read up on that to make sure.

 

You are right Bruce. The ECM will take your lowest voltage (idle) and use that for 0% and then calculate the max voltage and use that for 100%, and I believe even update. All other tests inside the eprom for things such as initiating Power Enrichment will then be based on the calculated percentages.

The actual voltage of the TPS is not critical for SD. As long as the "idle" and "WOT" is within certain volage ranges, the ECM is happy. Trying to get 4.5+ volts @ WOT or precisely .56 volts at idle is not necessary.

 

Yep, it was stable but not entirely smooth. I'm gonna try and road test it today with the scanner, and see what I get for results.

I've been thinking perhaps, it was just soo rich at idle, that, when you came off the throttle, it couldn't get enough air in to compensate and it stalled. Even with DECEL mode, it just fatted out way to much?

Glenn, maybe you can answer this:

On a Manual car (which mine is now, but originally auto) do you need to short together any of the wires that are normally to the shifter?

Now I know the PARK/N wires are just a starter enable, but does anything else have to be crossed for the ECM to know its in gear?
Or does it just not matter with the manual bin?


-- Joe

 

Joe:

I double checked the pin connections in my GM Factory Shop Manual for Vin F and Vin 8 F-bodies. There are only minor differences in the wiring between a Manual and Automatic.

D14 - 4th Gear (Auto only)
D16 - Park/Neutral (Auto only)
F06 - TCC Lock (Auto only)

and

F01 - Upshift Indicator control (Manual only)

It looks like you don't really need D16 (Park/Neutral either) for a manual either. I wish I had access to a manual SD TPI car to confirm. Maybe someone who is familar with the connectors and how to read the "pins" that has a stock 5 speed SD TPI car could double check to confirm the GM Shop Manual.

 

Yeah.. F01 is the shift light.. Interesting. I didn't know if there was any situation where my ECM might be like "why are we doing 90mph in neutral, and WOT??"..

Right now F01 is un-connected, cuz it was TCC lockup when it
was an auto. Eventually I'll put a nice shift light on the dash
and try to use $8D to enable it.

Thanks for the response. Gonna head down the shop in a bit and do some more tinkerin. Which me luck!

-- Joe

 

Just to clear up confusion= You have a org/blk wire that tells the computer the car is in park or neutral (so it sets the idle mode) then you have a pair of wires that are the neutral safety switch (starter enable) I believe they are yellow and purple, they need to be jumped together so the starter will work. (To do it right you need to run those over to the clutch switch) The manual does not use the org/blk wire (don't connect it to anything) you also have Dk. blue and Lt. green they are the back up lights, you need to connect them to the trans if you haven't already done so.

 

OKie.. Starter enable is crossed for now. THe org/blk is unhooked,
and the dark blue/light green is to the backup lights. So . I guess that isn't causing any problems. Thanks!

-- Joe

 

Thanks Don. That org/blk wire is the same wire that is normally connected to D16 on the ECM for an auto car.

I am currently looking at "playing" with the code for an auto car and see if I can make the "Shift Light" work on an auto car - just for something to play with.

 

Cool...From the way mine works it looks like it is affected by load, so it might only work on an auto when manually shifted.

 

Well... That worked!

Tried to make it still, drove around town for a bit.. All is well, idle holds between shifts at around 1300rpm, then after a while of no TPS (stopped at a light) it goes down to 900rpm.

Thanks guys!!!

-- Joe