View Full Version : Rom Tune question

05-20-2009, 04:02 PM
Recently my car has started to bog off the line. This happened once up at the dragon a few weeks ago, and then just this past week twice leaving the line for starts at an autox.

What is up? Is this something that is related to the AFM? I am wanting consistent running here, but I am to the point that perhaps that is just not possible on any stock 2nd gen equipment regardless of any tuning or modification.

Components are new, O2 is new, knock is your own with new shielded wiring. Injectors have been cleaned by WitchHunters, etc. I can not attribute this to any specific part so much as engine management. All the sensors in the coolant kneck are new, etc. It is all fresh.

I feel that this is an issue with the AFM between the transition point from vac to boost. For the most part the car is smooth on 15psi. Anything lower than 14 and I start to notice some timing being pulled cause its just too rich. Once I'm at 15psi at WOT then things smooth out considerable. That, I'm happy with so obviously the maps by ATS a great!

Only, there is still this consistency issue.

Any idea before I go wasting money or considering other EMS?

05-21-2009, 12:50 AM
I noticed today that my AFM has the trade marks of skipping a few teeth..

As we all have known, the AFM is a horrible little piece in our EFI system!!

The following are not my pictures, but they are what mine looks like on the ring gear of my AFM. I will have my own picture to follow though I just sealed it back up without taking one.

I will reference information as well so that Pattersom on MR2OC gets the credit he deserves for the use of the material.

My AFM's ring gear had the skip teeth marks.. much like these:





I find it interesting that this was noticed and picked up by Scott at ATS.
Then Aaron at ATS made the following comment, "I am starting to wonder if AFM springs can actully get weaker over time and make the AFM easier to open and therefore cause richer A/F's? I've been inside a few AFM's lately and have seen scratch marks on the toothed wheel that looked like the spring had actually slipped too." LINK (http://www.mr2oc.com/showpost.php?p=3529604&postcount=10)

Could this be an issue? The thread on the MR2OC did not go very far, suprisingly.

Slack on the AFM could create all kinds of hesitation issues.

Moving this ring gear back into its original spot would make sense to me. It would be logical to assume initial response and on/off throttle transition would be better if the spring were tighter, it would react quicker.

Would that not be true?

05-21-2009, 01:51 AM
For future ref




05-21-2009, 01:40 PM
Mark you beginning point on your AFM and start adjusting. You can always put it back. Do you have a WBO2 sensor/gauge?


05-21-2009, 02:14 PM
Mark you beginning point on your AFM and start adjusting. You can always put it back. Do you have a WBO2 sensor/gauge?


I'm working on getting a WB as we speak; mine looks to have skipped 3 teeth.

05-27-2009, 02:17 AM
WB is coming, bung is on, still gotta pick up the unit from a buddy. Going to be using an LC1 datalogged on the laptop.

In the meantime, this is my specific AFM:


Looking a bit closer, we can see there are marks that my AFM has skipped two teeth out!


I have never opened and messed with the AFM. I am suprised to see this mark. It would be a counter clockwise movement to readjust back. It would make me believe there is possibly some sloop in the tension of the spring, however much a tooth or two teeth is exactly.

I did turn on the car to see how it moved, it was amazingly linear. I'm very surprised to be honest how exact as I blipped the throttle.

05-31-2009, 09:28 PM
Currently, this car is pulling like a freight train. Very consistent, this is more how the rom tune initially felt. ECU was not reset. Then reset as well, continued same running, good. I will have more accurate information in the future with the WB. and accurate information of what I changed. Currently seeing 15-16psi. I'm waiting for another stumble.

06-10-2009, 02:41 AM
I have taken quite a bit of time with my car to try and locate the issue.

I believe it was primarily an intake / throttle body leak.

I have adjusted the AFM but results have shown nothing negative. I do feel overall response is quicker though! I note this, cause its VERY true! Could also be due to a the vac leak, very easily.

The car is running 12.6 on mild heavy throttle and 10.8 on very initial readings into a full on pull (aborted, only used for initial measurement).

ATS, this car is pulling like a crazy! I haven't put race gas in my rom tune.. but holly crap it feels like I have! I will have some full pulls here soon the more confidence I get in doing it. 15psi is what I'm running right now.

06-10-2009, 02:34 PM
Had to reset the ECU yesterday as I drained the battery working on the car over the past two weeks.

Upon reset the ECU always seems very hesitant until it has a bit of driving on it. I'll be keeping an eye on this because the car had no issues prior to cutting the power, the car was free to pull strong!

I logged a short full throttle pull in 2nd gear on the way into work. Overall the AF's look steady! I'll try to get the graph posted here in a bit.

06-10-2009, 03:07 PM
2nd gear, quick burst, 3K-6K rpm's.

The spike at the end is me letting off to change into 3rd gear, though still got out of gear.

(entering the run at 1.5 seconds)

I'll hopefully have some more shortly as I feel the ECU returns to its happy nature after the reset. I'll try to get a full 3rd gear pull up to at least 7200, my redline is set at 7400 (though typically over 6500 isn't used much by my driving style).

06-10-2009, 06:30 PM
Well, drove the car too work, so figured lunch time was as good a time as any to get some on-ramp pulls.

I went ahead and took it up to 7K RPM this time. Though again, the car just feels like someone put a cork in it since the ECU was last reset.

This run starts 2nd gear -> 4th

3rd up to 7K -> 4th on up to about 7K at cutoff.

ATS - Any idea on this inconsistency? Sometimes it feels completely alive, all of it is there, then others its like someone put a cork in it. I'll try resetting the ECU once more, but if anything I look to be good on fuel at 15psi if not a bit rich.

06-10-2009, 06:51 PM
So, in conclusion -

1. Had checked over the car for a vac leak, even after what I thought could possibly be one, no change.

2. Had check over the AFM and reset it to possibly the stock spring position, no change.

The car felt great for nearly 3 weeks, then the ECU was reset and we are back to being inconsistent.

The only thing I can figure is something in the ECU is either just having a happy day, or not.

06-10-2009, 07:55 PM
I still think this is whats happening:

"The only way out of knock mode is to drive it around some (gently)and wait for the knock/time average to come back down.

You are correct. The ECU does forget its knock count after a full power down of the BATT pin (not just turning off the ignition). When it wakes up again after all power has been removed, it starts on the low octane maps and switches to high octane only after a short interval of time without knock events."

Since the power was pulled on the battery this time, the ECU has a fresh reset. I'm going to be pulling the plug again tonight, let the car sit for a bit and then plug the positive on the battery on once more.

Once thats done, I'm going to do a true ECU reset by pulling the EFI fuse. Then we'll start this process all over.

06-10-2009, 08:24 PM
Remember at the Dragon Clay I told you your car didnt feel like it should. I think youre onto something, but I think youre chasing the same crap all Gen2 owners are dealing with. My gen2 EFI crap ran awesome when it ran good. It was just inconsistent as hell. I replaced everything in mine too, even tried a different AFM, even checked to make sure mine hadnt slipped, etc. Nothing helped. Some days it was fast as hell. Some days it felt kinda meh. I dont think they can romtune that behavior out of it.

I dunno man. I hope you get it sorted, your research is definately good to read over and use for troubleshooting for others. I just know I got tired of it and moved to the Gen3 ECU.

Which of course has its own set of problems too. Lesser of 2 evils it is.

06-10-2009, 08:54 PM
Ya, no doubt I'm onto the issue, I had a week there that this thing was just flying! Obvious additional 25-30hp, all after an ECU reset.

We'll see, I'm just going to continue doing what I have been. There is definitely a 'sweet spot' and I've just gotta figure out what it is exactly that puts the ECU into a happy mode (or more specifically the high octane maps). The obvious answer would seem to be knock count.

I was thinking about it and last time I reset the ECU I did start the car and idle it while getting the WB all setup. So if there is an interval of time required for the ECU to go into the high octane maps, perhaps I surpassed that interval of time and all was good.

This last time I reset the ECU, I initially went out to try getting some info to datalog so it wasn't a gentle initial drive.

I can only assume that due to the different initial loads put on the engine that the ECU has reacted differently in both situations.

We'll see.. if I could keep the car in this happy mode, man its night and day and I would be VERY content with the GenII setup and rom tune. Hopefully I'll have more answers shortly, and perhaps it will help someone else.

06-10-2009, 11:11 PM
Notes for changes:

Removed positive battery terminal

Removed EFI fuse

Removed 3rd plug (consists of our BATT and +B1 +B terminals)

So I have removed all sources of power all the way to the ECU

Sat for about 25-30 minutes, hooked back up positive battery.

Reinstalled the EFI fuse

Plugged back in 3rd plug

Car sits, should be all reset including hard memory for any possible knock counts.

I'm gunna sit on it for a bit, just in that state.

06-11-2009, 03:38 AM
Thanks for the PM on the OC to remind me. Just sitting turned off won't do anything. Letting it idle might work, but you need to go out and drive it gentle...basically you need to fool it into thinking you aren't about to beat on it.

If you really want, I could reprogram you a chip with a milder limp mode, but that's removing a safety feature.


06-11-2009, 03:39 AM
You can do that?!!

06-11-2009, 01:48 PM
Thanks for the PM on the OC to remind me. Just sitting turned off won't do anything. Letting it idle might work, but you need to go out and drive it gentle...basically you need to fool it into thinking you aren't about to beat on it.

If you really want, I could reprogram you a chip with a milder limp mode, but that's removing a safety feature.


Ok, so your thinking its probably the same thing? This is the difference between the low and high octane mapping? Specifically the ignition timing difference?

I would rather not remove a safety feature. I also realize leaving it off won't do anything, but its not my DD so it doesn't have to move right away. I will let it idle and do some gentle driving.

I'll let you know if the car goes back into the high octane dynamic timing. Its a very noticable difference. Thanks for the reply Aaron!!

06-12-2009, 12:37 AM
Ok, the last reset has now made the car much worse.

06-12-2009, 01:54 AM
Did another reset, gentle riding again, pedal is lighter. Mildy getting into it the car feels like it wants to go again, not held back. A small burst felt good, still not perfect, but much better! This is crazy..

06-12-2009, 03:41 AM
I'm getting some race gas tomorrow.. blah...

I bet it all smooths out then when I do.. anyone up for bets? lol

06-12-2009, 02:07 PM
Took the Celica to work, still a bit of dynamic timing being pulled.

I flipped over to the race gas map for the first time, the timing went away. Obviously though this is just on mild driving, as I only have pump gas in the tank.

I then went back to the pump gas map and the timing seems to be better yet again. I did a quick burst, feels good and strong but I still don't feel like it was just ready to rip as it did last week.

I'll be going to get some 100 octane in the tank during lunch as its just up the street from work. I have 1/4 tank of 93 right now, so roughly 4 gallons, mixed with 5 gallons of 100 should put it up to 97 octane. I'll then see how the pump gas map runs, and attempted to try the race gas map for the first time.

I am at least happy that since this reset the car isn't bucking around or breaking up. The ECU seems to have a VERY hard time being happy upon initial start up.

06-12-2009, 05:38 PM
Race gas FTW!!

My results are from a 95.7 octane mix (estimate, 4 gallons 93 and 2.5 gallons 100). I purchased less 100 than I intended, the price has just skyrocketed!


Dynamic timing response seemed very limited on the pump gas map. Felt very happy, though we are currently having a 90 degree day so I didn't push it.
Dynamic timing response was virtually unnoticable on the race gas map. I love the race gas map! Again though just did a short burst as its a hot day here in FL.

The car is back to feeling like its about to burn the tires off! Even in a 90+ degree day. This is 15psi seeing rock solid 10.5:1 AFR's.


Good gas pays!

Perhaps just the last 6 gallons of 93 I got was bad gas.

06-14-2009, 05:18 PM
Update - car is pulling like mad on pump gas tune!

My base timing has slipped! The distributor had rotated some, so placed it back at 10 degrees. It was around 0!! :eek:

The car did do just a bit of dynamic timing retard. I'm surprised by it, as there is still some race gas mix in the tank. I would think that it should be just as happy as can be, but the car definitely feels like it just wants to pick up and go. The response was during light throttle.

The stumble I felt was like the one I encountered at the auto-x. AF's automatically go to 9.5, so its a knock response.

I'll give it some time, reset the ECU and do another gentle drive and see if I can't get this last bit of stumble out of the car. Idle AFR's are 14.6-14.7, its hitting perfect.

I can't attribute the stumble from knock response to the rom tune, nor anything else in the car at the moment. Heavy throttle the car is just lighting the wheels on fire as it did about a week ago. During pulls AFR's are still very good and very consistent.

I'm please to say that I don't believe the GenII EFI setup is at error or the ECU is malfunctioning to produce the inconsistency.


06-17-2009, 04:36 PM
Drove the car yesterday.. perfection.

No timing being pulled, very peppy! My buddy with his swap was definitely impressed by the rom tune, he noted he could really feel the difference between it and the JDM ECU.

Still on the pump gas tune. Things are looking good! 15psi AFR's are still in the 10's. I think it will be time eventually to squeeze out those last few pounds of boost. 17psi should definitely be possible.

Thanks ATS for a great rom tune!!!!! This car definitely makes me pleased with how its running.

06-24-2009, 02:59 AM
Car is still running like a champ. Couple of changes, retarded exhaust gear to 5 degrees and 1/8th turn boost controller.

Lets see and compare, I see about a 10.3 average afr. Run was great, smooth though 2nd gear went by so fast I hit the rev limiter at 7400. First for me, its fighting for traction once again. Car is just flying.


06-24-2009, 03:02 AM
1/8th turn and exhaust cam adjustment had me go from a 9.5 afr run vs a 10.3 now.

Should be a 1/8th more turn left of boost left in the car to be safe. That should be at 11.0 by those numbers. That would be a nice safe margin. Would be interested to know the exact results of the exhaust cam retard. Basically though, I need my exhaust done!

06-27-2009, 05:02 PM
3rd gear pull. I was about 95% in at first and as soon as I was comfortable with the AFR's I planted it 100% throttle at about 3.5 seconds into the run. This was 4-7K under full load. Car is moving! AFR's were at the highest 11.57 and then 11.27 under full load in the upper RPM's. Good, and safe. The lowest was 11.02. Very happy with this tune.

Made my final boost adjustment, there was just a bit more than 1/8th turn left in it to get the numbers above. Was from 16-16.5psi on my gauges.

I also moved the exhaust cam from 4-> 5 degrees retarded. This has resulted in the feeling that over 6K the car isn't dropping off as much. I'm very satisfied with this current setup. Though, the car does sound like a bike now while at idle. The small adjustment just make it run that much more choppy, but as soon as you touch the gas it is all there. Its just the lobe at idle.

No stumbles, great operation.

07-06-2009, 04:55 AM
I JUST noticed this thread.
So what exactly was the issue again, your timing belt jumped or your distributor was set incorrectly?

07-06-2009, 01:46 PM
I JUST noticed this thread.
So what exactly was the issue again, your timing belt jumped or your distributor was set incorrectly?

Main problem was distributor rotated and retarded the engine.

07-06-2009, 11:56 PM
i see.
so now with the timing set correctly, the car still pulls well on just plan pump gas, or is there any race gas in there?

i find it odd that your a/f ratio is so rich. when i tried out your rom tune, my a/f ratio was in the mid 11s on that same ecu. i guess its because you are on a ct27 with the exhaust cam mod, and are able to hit a higher fuel cell forcing the injectors 100% open.

Any plans to put the car on a dynojet and see what it does?

07-07-2009, 12:46 AM
The car was completely not running right though when you had the ECU.

A/F's seem to be right on par though for the mods, ATS says its 17psi on pump gas, 20 maybe on race gas. So its right in that ballpark.

After the distributor issue, I've been on the pump gas ever since I tried prior to put some race gas in to no major different result. That's basically when I knew something had changed and to step back and do the basics. So far, I actually don't know what the race map does still. Though I can imagine!

I'd like to get on a dyno.. only just a few small things and I plan to. Hardest part is still someone I trust with it on there. Soon I hope, we'll see what it is making exactly.

07-07-2009, 01:18 AM
Go to a shop that lets you do your own run. Thats really the best thing to do.
The race gas map probably just adds a bunch more timing. You could probably run that with alcohol injection.

joe's gt
07-07-2009, 01:59 AM
Have you tried playing with the intake cam at all?

07-07-2009, 02:25 AM
Nope, intake cam is 1 degree off (retarded) ATDC from my stock cam lobe. It is on a stock cam gear, I didn't see the need for the intake cam to be adjustable on this setup. Its a known fact that even the GenIII intake cam is retarded 2.5 degrees from the stock GenII intake cam. So this was more than acceptable. I did this on purpose. Sometimes I believe simpler is better.

The main reason for the intake cam is the longer duration, so the engine doesn't have to fight to breath in as much. That was my objective. Tuning the top end of the power curve is done with the exhaust cam.

07-20-2009, 10:40 PM
Hi there, I was just wondering if your GT28RS kit comes with 550's? Also since I'm running a GT4RCwith a slightly different ECU and AFM, will there be issues with a ROM tune? Thanks.

07-20-2009, 10:45 PM
Hi there, I was just wondering if your GT28RS kit comes with 550's? Also since I'm running a GT4RCwith a slightly different ECU and AFM, will there be issues with a ROM tune? Thanks.

I would check the ATS website - http://atsracing.net/

Or start another thread exactly to ask, though don't hold your breath as they are on the MR2OC quite a bit more. Best bet is to check the site and try to call Aaron.

Then start another thread to document and talk about your work :D

07-21-2009, 04:42 AM
thanks for the heads up man, I'm new to this site, but not to to alltracs or the alltrac net scene, it'll just take me awhile to find out how this board works. thanks again for the heads up.