Hey all,

I've installed a new cam, nothing extreme -everything else is still stock. The ECM keeps giving me MAP volts high trouble codes, what's the best way to fix this ?? I'm using TunerCat's to edit the bin. I'm running a 350 TBI with ecm 16146299. What's the best and/or easiest way to get it to run smooth ??

Thanx

 

Raise the MAP high diagnostic check point to a higher KPA. My L82 cammed 305 TBI was tossing this code back when I was running the 299. To rid myself of the dreaded code, I changed the value at LD4B5 to greater than 70 KPA. My engine would only set the MAP high code with the A/C on and the transmission in Drive.

;---------------------------------------------
; error 33 param's
; Hi MAP
;---------------------------------------------
LD4B4 FCB 10 ; 45 TPS, limit
LD4B5 FCB 156 ; 67.9 Kpa, MAP limit
LD4B6 FCB 50 ; 5 sec, Time limit
;---------------------------------------------

Also make sure that your IAC has a minimal amount of opening when the engine is hot and in park/neutral. I typically set my engines up to idle with 0-5 IAC counts when fully warmed up, no A/C, park/neutral, and no heavy electrical loads. The engine seemed to idle smoothest with minimal IAC opening. In drive at 700 RPM, I made 12 in/hg of vacuum (12 IAC counts), A/C on brought this down to 8-9 in/hg (20 IAC counts) and set the high MAP code.

 

Thanx for the info - what programmer did you use for your adjustments ?? I'm using TunerCat at the moment & can't find where or if I can make those changes.

 

Before I used Tuner Pro I used Tuner Cat. When I asked Cat to add another parameter they were always cooperative.

 

I built a $10 voltage regulator to increased the voltage on my cammed 305. My new cam pulled 15" of vac instead of the stock 20". The voltage was low and caused a code and lockup problems.http://http://autospeed.drive.com.au...popularArticle
http://http://www.go.jeep-xj.info/HowtoMAPsensor.htm

ENJOY!!!

 

We are tuning by reprograming the chip. So there really isn't any reason to "fool" the ecm by altering any of the sensor's signals. What we do is just recalibrate the VE tables to match up with what the engine needs now.

The problem with doing it the way you are is that when you change a cam the engine vaccume does NOT change equally across the RPM range. You'll have less vaccume for a given load at idle and more vaccume per given load at high rpm's....or you wouldn't move any more air and make more power.

 

That's for the feedback guys !! I definately prefer to fix the issue via PROM editing. Do any of you know how to apply Fast355's edits ?? I'm using TunerCat at the moment, but I guessed by the specific locations he was referring to changing the .ecu file via TunerPro. I had a look at TunerPro, but I haven't used it before - any guidance would be much appreciated !!

Cheers,
Robert

 

Old post, but...

Do you know if this is the same for a 1227747?
Do you know the address for me MAP error limit?

I'm working on a big cammed 383 and can't get the idle quite right. The IAC doesn't seem to be doing what I'm telling it to.
I can't get the steps to go below 40, no matter what I do with the throttle blades (trying to get down to 0-5). I have a high MAP error SES light coming on once in a while (probably due to cam) and I'm wondering if it's causing some sort of limp idle mode??
The other thing I've noticed is that the TPS voltage is around .71 volts. I need to check the %TPS for idle threshhold tonight.

Any input woould be appreciated.
Thanks,
Mike

 

I think I found part of my answer in the HAC.

; Still wondering if this code can prevent the ECM from controlling the idle properly...

 

One solution to idle with a large cam is to idle open loop. The NB 02 sensor and MAP sensor is part of that problem. Removings its CL control at idle will help. I lock OL idle as well as lock SA at idle(17d). Another idea is to confirm you are idleing "synch" and not asynch. Large injectors at higher fuel pressure caused the idle fueling for me to flip asynch back to synch as pulsewidth was not small enough and rpms rose and fell. Granted your idle may be a bit rich as a result but in my case that was no issue as ext was clean. I think the code is just informing you of sensor failure when in fact there is none.

 

Thanks for the response. What do you actually change in the bin lock OL idle? Just change the O/L enable & disable RPM's?
Then just tune The O/L AFR table with the Wideband?

If I get a Closed Loop Flag while at idle, could I still be in Open Loop idle?

 

If you flag CL you are in CL.

My definition file for EBL-ECU supports much more than my prior ECU's 8746 $61 and 7747 $42. But when I used TunerCat they would add options if I requested it. I recall 7747 only one could disallow CL by coolant temp high(220F). That would at least show you if idle condition improves as a test. My file allows a bit to be checked to enable OL idle as well as OL under a certain MPH(20). The latter seemed to reduce bucking(manual trans

QUOTE]Just change the O/L enable & disable RPM's?
[/QUOTE]
I did not know that existed. I presume you can run OL then under a set RPM? Like 1200? That would help. then go to there OL cell you idle in an enrichen a tad and see how that helps. I found for me my car like less SA at idle.

 

Thank you.
I will have to test that next time I'm working on it. (It's my buddy's motor.)

Right now, I'm chasing the theory that the Throttle blades are open too far and The TPS is knocking it out of idle. I can't get the IAC steps to go below 40 (maybe throttle follower?), no matter which way I move the blades. Opening them more just raises the RPMs. TPS is @ .71 volts. So, I'm going to try raising the %TPS for idle threshold.

In the meantime, I told him to clean the IAC passages and put on a new IAC.

 

40 steps is not a sin but 5-20 would be better. Is your idle RPM as commanded in your drive + park/neutral tables? Yes cleaning IAC is a good idea. keep the solvent out of stepper motor by holding pindle down.

I presume your TPS is not adjustible. If so it is a bit high. I think .52 is close.

 

Yes, I could live with 40 if it stayed running, but since it NEVER goes below 40, it has me scratching my head. TPS is not adjustable. As you said, I expected between .5 and .55 volts for the TPS.
According to this thread, it should auto calibrate though-
https://www.thirdgen.org/forums/diy-...-equation.html

Commanded idle is hit & miss. Keep in mind, this is an offroad rock crawler. We don't have the Pk/ Dr wire hooked up. I've done 2 other trucks this way without issue. Just disabled the code 24 flag.

Anyway, Engine warm-
Commanded closed loop idle is 1000 RPM. It doesn't like to be much lower. Engine guy says it should be a little higher, but at 1200 RPM it BANGS into gear with the stock converter.
Stall saver on at 925
Stall saver off at 950
All timing from 0 RPM up to & including 1000 RPM is @25*

Start it up in park. Races initially to 1400 RPM range and drops down to 1000 RPM range. It will maintain 1000 RPM for as long as you leave it sit there. Might dip a little up or down, but tracks back to 1000. Nice and smooth. A little raspy sounding, but not struggling to run by any means. Stall saver doesn't seem very dramatic like other TBI's I've done. No big rush of air and RPM recovery.
Anyway, Put it in gear, stand on the brakes, it stays running for about 20 seconds, then just slows down and dies. Stall saver doesn't seem to do jack squat. If you give it a nudge of gas, it'll stay running. Or, if you drive away, it runs fantastic. IAC seems to follow the throttle since steps go up as you hit the gas. However, as soon as you slow down to a stop, it'll run for about 30-45 seconds before quitting again.
If you drive around in gear, then stop and bump it into neutral, the engine RACES to 1600+ RPM and doesn't want to come down unless you shut it off and restart. Then all is good again.

It's got me puzzled.
If I can get the IAC counts lower, I think it might react better to IAC moves.
Just hard to discern mechanical problems from Chip problems right now.

Ronny,
Thanks for your input. You have no idea how many of your posts I've read and re-read over the years.

 

I believe it does self calibrate and uses .70 for 0% but not sure how far away from .52 it will self calibrate.

What is fuel pressure just before it dies?

[QUOTEHowever, as soon as you slow down to a stop, it'll run for about 30-45 seconds before quitting again][/QUOTE] I wonder if IAC is closing at that point starving it for air?

Can you drop your IAC steps by 50% and see if it will idle solely on throttle stop screw allowing air at idle without regard to IAC?

. Maybe IAC is then opened over 40 steps. I did have my IAC wired incorrectly at one point. Result is it worked in reverse of what it should.

 

I had a chance to play with this some more this weekend, with some success.

I moved the %TPS for idle threshold up and raised the high MAP error limit value. The truck will now start and idle fine. It will also stay running if you drop it in gear and hold the brakes. No more quitting as you come to a stop either. However, I'm not 100% there yet....

1st off, I still can't get the IAC steps to drop below 40 no matter what I change in the bin or move with the throttle blade adjustment. Also, if you drop it in gear and hold the brakes, you can see the IAC steps climb to keep it running. That seems normal. When you put it back in Park, the IAC won't drop back down. It hangs between 105 and 145 steps (engine racing) and will not move at all unless you shut it off and restart. I'm really stumped. I've tried playing with a lot of the IAC parameters, but I can't seem to make any difference.

We put on a new IAC (and tried another used one), and cleaned the IAC passages. We did find a vacuum leak on the intake, which seemed to help when we tightened it down. The owner is going to change the intake gasket, but I wouldn't see an intake leak causing the IAC to hang.

Any ideas?

 

Try this. There is a routine that will remove IAC from controling idle. I believe you jumper the ALDL pins(cant recall which) maybe A-B and that will cycle the IAC and I believe it will close it to zero steps. That routine is used to reset idle speed I recall. With it closed you should be able to determine if there is a vac leak holding idle high. If that routine does not work then I would plug the IAC opening from top of TBI passage way and see if idle drops. I ran my car for a season with no IAC as it was defective and would not close. I plugged the passageway.

Are you using correct IAC for your application? Pindles shapes vary.

Also did you or anyone else replace the harness to IAC? Mine acted much like you describe as I did not have it wired correctly.

 

did you change the coolant temp v. IAC steps table at all?

 

I didn't mess with the Coolant Vs. IAC steps table. I did try adding more kickdown steps, but it didn't help. I was unaware of the different IAC shapes. I will have to look into that. The harness is a painless harness and was in the truck prior to this new motor. It hasn't been molested.

I will try the ALDL IAC routine next time I'm around the truck.
I may try a new bin to start from. Maybe a manual 350 bin and swap in the VE and SA tables from this bin.
I'm also thinking about trying to just swap throttle bodies to see if the probelm persists.

Thanks for your help.

 

i had the same problem until i lowered the coolant temp v. IAC steps table values.

 

Very interresting. How far did you lower the values? Did you change the kickdown adder steps at all?

 

TTT. Anyone else messed with the coolant temp v. IAC steps? If so, what did you do?

 

It will affect idle RPM. cold start very cold start 190dF start.
It also controls idle speed by a forced vac leak. I idle 0 steps so yes I did so by reducing IAC steps at 160-210dF and using my TSS to set idle RPM.

 

Good to know! Thanks!