5.3 Cam Swap / Stand Alone Idle and Throttle Issues

[ccm399]

Hi all,

I have been searching and trying to find a solution to my issues. Newbie warning of course... Well, new to HP Tuners and LS tuning but not new to EFI or racing. I used Accel DFI "back in the day as they say".

Anyway, I have taken a '02 Sliverado 0411 PCM (truck had a 4.8 in it) and converted the harness into a stand alone harness for my 1995 Camaro drag car. The car is equipped with a Powerglide so I have the transmission set to auto non electronic. The PCM has the HP Tuners 1 Bar SD OS installed on it. I have done a segment swap with a 2002 Silverado 5.3 for things like the cylinder volume, VE map, and most everything I found in the compare file that was highlighted green (other than the emissions stuff). I then used the LS3&LS7 file to get the proper injector data for the LS3 injectors I have installed. I have tried opening up a vacuum cap (small about 3/16 ID) so I could get some bypass air.

The issue is I can't get it to idle for more than 15 seconds prior to it just kind of running out of steam. It just kind of trails off and dies 1000, 800, 600, 400, 200 RPM then stops. I also cannot get it to do anything but instantly die if I touch the throttle (even VERY slowly).

I followed the big cam Idle tutorial on here (from another site). I *think* I got everything right but since I am a custom OS there are some differences between the article and my PCM. I also used Russ k's Idle config to plot the RAF and it is showing in the 20's right now but I assume that's because it is so FAT. The IAC steps are 200-300 sometimes as "low" as 160s. I tried setting the RAF to the numbers in the histogram but it won't even try to run. Starts then stalls right away. I am thinking it's too soon to be messing with the RAF number more than the article mentions.

The engine is PIG fat you can smell it really bad. I have tried pulling extra fuel out where it is currently idling (KPa and RPM). But then it simply won't run. It starts and then dies within a second or two. I also tried setting the PE KPa to a higher number so as not to get into PE at idle but even though the commanded A/F is showing better it still won't run and smells really fat.

I do not yet have a wideband O2 sensor but it's so fat I don't think it would help at this point. Bigger fish to fry as they say...

So some details on the combo:
5.3 stock bore and stroke
862 heads ported and reconfigured to an LS3 "style" combustion chamber. Flow ~ 280/210 at .700
10.75 - 1 ish. I don't have the math in front of me right now
Cam 240/256 113 +4 .629"/.604 Yes lots of cam for a 5.3 but its a strip only car with lots of rear gear...
Ported LS1 intake (for now)
Ported LS1 TB (I edited the IAC effective area to be the same as my 2000 TA). No epoxy in the IAC entrance

"Tune" File and some logs (sorry they are so short)
Camaro5.3BaseTune_Idle_Airflowls3 injectorspreadsheet.hpt
2019114LateDay2.hpl
2019114LateDay3.hpl

Maybe I should start from scratch with a 5.3 tune and add the LS3 injectors and such? I'm sure the tune file is a bit of a hot mess but I am trying to learn.

Thank you in advance for your time in trying to help!
Chris

[ccm399]

Couple more details I should cover so as to not waste anyone's time.

I have checked the grounds and they are solid and all connected
Fuel pressure is steady at 58 PSI (bypassing style fuel system with regulator installed *after* the injectors)
Open long tube headers
The only accessory is an alternator. Water Pump is electric
Engine fires right away it's after that the issues start
TB has the stock size LS1 hole in it no modifications. I thought I would open up a plug to get more air rather than drilling.
I have tried opening the blade some but I get into not being able to zero the TPS even after a rest.

[mikemm212]

I'm no expert by any means but you said you have open long tube headers? I'm assuming your O2s are in your collectors and then hit open air in a few inches. If that's the case you need more exhaust piping or your O2's can not read correctly. Post your tune and log file so someone can give you pointers

[ccm399]

Hi Mike,

I posted the tune and logs in the first post although I didn't test to be sure they could be downloaded. I'll do that now. Anyway, this is 100% open loop no O2 sensors. It's a drag only car it will never be in closed loop. 100% agreed though O2 sensor that close to the end of the pipe would be giving a false reading for sure.

Thank you for the reply!

EDIT: Links for tune and logs seem to work OK.

[ccm399]

Also, in doing more research I *think* I might have a solution. At the very least I have a next step!

I was trying to get the AF down so I was lowering the VE table in the idle regions. Then I lowered it more, then more but it was still too rich. Then I found a post about the transient fuel minimum grams and lowered that. After that the engine would hit then die right away. So more research found an instance similar to mine where after removing a ton of fuel from the VE table with little change in AF he dropped the transient fuel minimum grams then the engine didn't have enough fuel to start. I believe that is where I am. I have since gone back and put the VE table back to stock '02 5.3 and I will edit it as per the Large Cam idle guide and start again.

Wish me luck!

[ccm399]

Well that didn't work. I'll get the latest tune file and scans up asap...

[ccm399]

Latest Tune and Scans
Camaro5.3BaseTune_Idle_Airflowls3 injectorspreadsheetv2.hpt
2019116Ls3v2TuneScan1.hpl
2019116Ls3v2TuneScan2ResetTPS.hpl

No idea why it is commanding the AF it is. Digging into that first. Also, spark seems lower than it should be.

Thanks everyone.

[kthunt]

check your minimum injector ms

[5FDP]

The open loop Eq ratio determines the commanded AFR at start up and in open loop. So in the majority of factory tunes it's rich because they want to heat up the exhaust quickly.

You can reduce that table if you wish so it's not so rich but you still need it to request 1.00 after 130-140 degrees so it's always aiming for stoich.

I don't see an IAT sensor in the logs, so if you aren't running one that will cause you other issues too.

[ccm399]

Hello everyone,

kthunt, good call I should have mentioned I lowered that setting. In the idles cells the minimum is .790ms

5FDP, interesting. I hadn't looked for the IAT reading in the logs. I do have an IAT but it's a FAST sensor. I wonder if the trunk PCM needs to know the IAT isn't part of the MAF? As in a different sensor type. I'll have to check into that. Thank you for the tip on the Open Loop EQ. I have those at 1.10 up to 50* then 1.05 up to 86* then 1.00 from there up. I had read someone said they had to put something less than 1 in there table to get the engine to idle with a big cam.

Thank everyone I really appreciate the help!

[ccm399]

If it wasn't reading the IAT should/would it throw a DCT? Just curious as I have not seen a DCT for IAT issues. Researching now.

[ccm399]

5FDP I think I see what you are saying now. The log file isn't monitoring that sensor not that there isn't data. I have added that to the logs.

[ccm399]

The IAT sensor is reading as it should. Shop was ~57 degrees today and that is what the IAT was reading.

So I am starting to make some progress I think. I used the VCM scanner to command 14.0 AFR. At that point the engine seemed to idle but I think it would still stall if left to run past say 15-20 seconds. Without the VCM scanner commanding the AFR was showing 11.6 commanded. More on that later...

So the graphs show I should be putting 30 Gr/sec in the 68* cell and 28.3 in the 90* cell. I then used Interpolate to smooth the cells above those values and below. I haven't had a chance to load this tune yet so I am not able to give any feedback on it. My gut tells me that's too much air but time will tell.

I then turned my attention back to the VE table. Based on the scanner showing 11.6 AFR commanded (and making sure the PE tables were set to 1.00 in the idle cells). I did some quick math and figured I needed to modify (multiply) the VE table in the idle cells by .79. The scans showed the idle KPa was in the 77-87 range so I highlighted those cells and multiplied them by the .79 I came up with as the difference between stoich and the commanded AFR. I then smoothed the area around the modified cells to be sure there were no large changes in the values in the surrounding cells.

Last I made a "hybrid" tune using the previous RAF numbers (stock +4 as per the idle guide) and the modified VE table. Just to try to get ahead of the curve.

Making progress and learning!

Thanks,
Chris

[ccm399]

Well I am starting to get stumped.... Tried three more tunes tonight and not much changed. The REALLY odd part is the timing in the last scan is all over the place (low) and there were no changes made to anything other than the RAF and VE tables. The last tune was a hybrid of v2 and v4 so it had the the lower RAF numbers of the v2 tune and the lower VE idle cell of the v4 tune. Still won't idle and still won't even let you slowly press the gas pedal.

Back to the drawing board....

[travis mccarthy]

I have the same signs with my car crank it starts for 3sec then shuts off. ls3 with powerglide.

[ccm399]

Hi Travis,

Sorry for the delay. I have stepped away to try to get a fresh perspective. So far I can only get the car to idle for a max of 20 seconds. It still won't take *any* input from the pedal without dying almost instantly. Honestly since this is 100% a bracket car I am REALLY starting to lean toward going to an MSD 6014 and a carb. Not sure it is worth messing with the stock PCM to get it running. I had a tuner look over the tune and he got it to idle better in the same 20 second period but it just won't go past 15-20 seconds no matter what I do.

[5FDP]

Post your most recent tune file.

[ccm399]

Here it is.
20190127.hpt

And the scan from it
2019128Scan1.hpl

Thanks!

[amello7580]

I don't see TPS signal in scanner, can you check your tps signal?

[ccm399]

There should be TPS voltage in there maybe I uploaded the wrong one. Stand by