Idle surge, '98 LS1

[BADFNZ]

I'm experiencing a random idle surge on my '98 LS1 Camaro. I last got a tune back in 2005 or so, but since that time, the idle has gotten progressively worse. It's not horrible, just annoying. Every once in a while, while driving, the car will die when coming to a stop with the AC on. I've replaced the O2s which improved the idle a bit, but not enough to completely eliminate the surge. I rarely drive this car, so I've put it on the back burner until now and finally just got tired of dealing with it.

Mods are heads/cam/FAST90/full exhaust/4600 stall. Cam is a 230/234 .600/.600 111 LSA with 110 ICL (nothing too radical).

I'm going to post my tune and a log of the surge. Let me know if anything seems out of the ordinary. Also, this is the first time I've posted a log so I hope it works!

[gn2beatu]

Have you cleaned the MAF lately? If it has been running good for 6 years, and suddenly goes bad, the first place I would NOT look is the tune.

[BADFNZ]

Have you cleaned the MAF lately? If it has been running good for 6 years, and suddenly goes bad, the first place I would NOT look is the tune.

It hasn't just suddenly gotten worse, it's gotten worse over the years. It's never ran 100% perfect, which is why I'm thinking there may be changes to be had in the tune.

[BADFNZ]

Just to add, I've looked through all the idle stickies, but most of them suggest adding "X%" to "X table" and the problem is, since I don't have my stock tune, I don't know if these changes have already been made. This is why I'm hoping someone can look at my tune and see if these changes have been made, or if anything looks out of the ordinary.

[Cantalope Kid]

Download a stock tune from hptuners.com. Login and go to the tune repository. Save a stock file for your year/make/model. Load you existing tune in the Hp Tuners Editor software...then use the compare drop down to load the stock tune...now compare side by side.

Use the following link for idle tuning adjustments: http://www.hptuners.com/forum/showthread.php?t=36318

[Cantalope Kid]

Run the idle air config from post # 2 in link above for folks here to evaluate the results.

[BADFNZ]

Run the idle air config from post # 2 in link above for folks here to evaluate the results.

Results are below.

1-Cold start, idle
2-Idle after ~5 minutes of being on
3-Idle after ~7 minutes of being on
4-Idle, then 2000 rpm, then put in gear

Let me know what you guys see.

[BADFNZ]

Any help? I'm deploying for 30 days next week so I'd like to finish this before I leave.

[Rinkrat456]

From the looks of your "stock" tune, unfortunately, I'd start over with a real factory tune and go from there. I see issues with your VE and MAF tables, spark tables are horrendous and I don't agree with some of the other parameters your previous tuners did for you. Even by your own idle scans it's easy to see what your engine wants and what the tune is giving it are not the same.

[BADFNZ]

From the looks of your "stock" tune, unfortunately, I'd start over with a real factory tune and go from there. I see issues with your VE and MAF tables, spark tables are horrendous and I don't agree with some of the other parameters your previous tuners did for you. Even by your own idle scans it's easy to see what your engine wants and what the tune is giving it are not the same.

Thanks for the response.

What do you see in the idle scans and in my tune that aren't jiving? Any specifics? I'm just starting out here, so I hate to start from scratch. I did look at your big idle tuning thread and made the initial changes, but I haven't loaded them to the PCM yet because I wanted to get some feedback before going forward.

[Rinkrat456]

Thanks for the response.

What do you see in the idle scans and in my tune that aren't jiving? Any specifics? I'm just starting out here, so I hate to start from scratch. I did look at your big idle tuning thread and made the initial changes, but I haven't loaded them to the PCM yet because I wanted to get some feedback before going forward.

That idle thread was assuming you're starting with a stock tune after a cam/heads/intake swap (or any combination of the three). You can use your tune if your VE/MAF table is right, your spark tables are right and you don't have any other issues to chase your tail with. Unfortunately, you do have VE/MAF issues, your tune's spark tables are half the problem and there's room for improvement in the idle speed and base running airflow (that's what I noticed right away in the log).

For now, I'd make a few initial changes and force a speed density open loop platform so you can dial in your VE tables better, followed by the idle tuning. Don't rush right into idle tuning. Get your VE sorted out first by driving your car around and monitoring the scanner.

My suggestions are as follows:

1. Set your idle speed higher and lower in some areas, but most importantly smooth the transitions more. See attachment, sheet 1. In my opinion, your car doesn't need a 950 idle speed when warm, it's not that aggressive.

2. Either use the stock spark tables (all of them) or try the attached spreadsheets for suggestions. See attachment, sheets 2 through 4.

Then go out and dial in your VE table, monitor knock retard and adjust accordingly. Once you have your idle to 4/5000 tuned to all be within +/- 5%, focus more on your idle areas. Idle areas should be within 1-2% error. With the car at operating temperature, use the scanner to verify your IAC count. It should be in the 40-70 range. Scan and log this event. If IAC's are below 40, you either have a vacuum leak or your throttle blade is stuck slightly open. If your IAC counts are above 100-310 at a warm idle, you'll have to open the throttle blade a bit to let more bypass air until IAC counts are within the 40-70 range.

Let the car cool down over night, then early in the morning do a Russ-K idle air config to tune your base running airflow. Use the scanner to disable your fans, and do this from a cold start until you're overheating (210-230*F is a reasonable place to stop). Do this first while in Park. Let the car cool down completely (preferably overnight again or for a minimum of 4-5hrs) and do the Russ-K config again while in Drive, holding on the brakes until almost overheating again. Copy the data from both Russ-K events into your idle airflow tables.

After you've completed everything I just suggested, your car should idle better. It will take you a couple days to accomplish everything. Log as you go, and post revised tunes as you go too.

[BADFNZ]

Thanks a lot for the response.

Unfortunately I'm starting my deployment/TDY tomorrow so I won't be able to tackle this until I get back. I used RussK's idle-airflow config last night and made the changes in the RAF table (only once). The log showed negative STIT throughout. I don't have a wideband so I hate to start messing with my upper RPM and WOT settings. Those were rock solid when I originally got my tune. Are my current tables that bad where if I just messed with the idle from where I am now, that it'd be counter-productive?

[Rinkrat456]

A wideband isn't necessary for part throttle tuning. I use STFT's all the time, last night in fact, on a H/C/I LQ4. I tuned everything up to 4000rpms using the narrow band O2 sensors, dialed in the idle and let the owner bring the car into our local dyno shop to finish the rest. He just wanted it drive-able for now, so that's what I did.

We must have a different understanding of what it means to have "rock solid upper RPM and WOT settings". I can't say what you had before was rock solid. If all you did was focus on idle, however, try to get the STFT's all within 1-2% below 2000rpm's. It's plenty safe to use the STFT's for that area of tuning.

[BADFNZ]

Thanks. By rock solid, I meant it took us a while to get the WOT tuning dialed in to where I wanted it. I hate to mess with it without a wideband, but like you said, up to 4000 shouldn't be a problem.

[Russ K]

BADFNZ, try this tune. 1998's only support 24 bytes when scanning. your at 32.

Flash this tune and do a cold start scan til operating temp in park with the attached idle .cfg file, don't touch the throttle while scanning. Then save the scan file and repeat in gear.

Then post the 2 scan logs.

Russ Kemp

[BADFNZ]

Well, my deployment/TDY got cancelled 12 hours before I was supposed to board the plane (gotta love the military), so I was finally able to load your tune Russ. The attached file is the cold start in Park only. I'll have to do the one in-gear tomorrow. I didn't get any surge but I'm guessing this is mostly due to the higher idle speed. Thanks again for the help so far.

[BADFNZ]

In gear log below.

[BADFNZ]

One thing I noticed was the only 2 histograms that were working were the Desired Airflow. All the others weren't showing any data. I'm assuming this is the 24 vs 32 bit you were talking about, but it doesn't look like it's fixed.

[Russ K]

Looks real close, but you need to open the throttle stop screw 1 turn to get the IAC under 310 when the car is first started. Make sure that the TPS is 0% at idle, if not back off the screw 1/4 turn at a time.

Just have a desired idle airflow histogram, that's all you need.

Russ Kemp

[BADFNZ]

I opened up the TB screw half a turn, but the IACs were too low, so I backed it off 1/4 turn and it seemed to work well. The Desired Airflow numbers were pretty solid from the tune. Everything was idling fine, so i decided to lower the idle rpm across the board by 50 rpm to see if it would still idle. Well, I got a little surge in gear, but it worked it self out and held fine.

So now that it seems the RAF table is good, where do we go from here to get rid of any remaining surge? Should I just bump the idle back up to where it was? Also, I noticed when I go from Drive to Park, the RPMs jump way up and then slowly come down. Any way to fix this?

I'm attaching some logs and my most recent tune.

Log 1-In park after RAF changes
Log 2-In gear after RAF changes
Log 3-Park, gear, park after TB screw changes
Log 4-Gear, park after lowered idle (this is where surge takes place)
Log 5-Park, gear with AC on

Most recent tune is in next post.

Thanks again!