Issues with starting and backfiring

[fe3xclone]

To start off, I'm using an MS-II in a MS-1 version 2.2 board with 2.300 code.

I had the engine starting and running somewhat okay. At least to the point that I felt I was moving forward in my tuning.

I mentioned in another thread that my idle was changing by about 500rpm or so from cold to hot. I had originally set my idle stop on the throttle body so that I had an idle of around 850-900rpm out of gear cold. But once the engine warmed up, this would shoot up to 1200-1300rpm. So then I backed off my idle stop to get back to the 850-900rpm.
Of course since then, the engine is really tough to start and keep running because the cold idle now is way too low.

I was told to start looking at tuning my IAC which I have but I just can't see a difference in the starting at all making different adjustments to my idle steps.

The engine will not idle on its own and I have to keep blipping the throttle to keep it running. It runs extremely rough (even for this camshaft I have) and I get a lot of loud backfires in my mufflers during this time as well.

Once I can get the engine warmed up, everything seems to smooth out quiet a bit and I can acutally move the car around.

Yesterday I tired messing with it again and now I just can not get it to start. The engine will crank over fine, and you'll hear it try to fire but then nothing. If I blip the throttle you can hear it almost try to start but then still nothing.

I'm kind of at a loss as to which direction to go. I've tried inputing different Cranking Pulse Widths with no luck as well as differen IAC values. Should I increase my idle stop back to what I had once before and try that?

Thanks,

[grippo]

Get the car started however you have to and let it warm up really well, then tune it at idle really well and tune it a few 100 rpm above idle, and even below it if you can. When you do this make sure the warmup enrichment is off and the coolant is above the last temperature in your coolant vs temp table (160 degF is the default). Do the tuning by changing VE and looking for max map, max rpm - do not use an ego sensor, it only confuses the issue. Once the car is running and driving decently everywhere then you can bring in the ego sensor. It would probably be a good idea to also make sure spark is good by tuning the idle spark to get max MAP and or rpm. Also, note what step the idle motor is at. Then stop for the day, don't change anything else.

Now before you proceed further you have to verify 2 things, when you restart the car the next day, by whatever you have to do, and let it warm up, everything should be the same as the previous day. If not, stop - do not do any more tuning until you figure out why it isn't repeatable. The second thing, which you should do the second day so you don't disturb anything the first day, is to verify the idle motor is at the same step as yesterday, and then change the last step on the idle step vs temperature table and verify the idle increases and decreases as you change the step. If it doesn't, again stop and try to fix this. Both of these things have to be working reliably or you are wasting your time doing any tuning. If the stepper doesn't work, I would upgrade to 2.9x code because there were several additions to stepper controls that were added since v2.3x.

[fe3xclone]

Thank you for the great step by step write up! That's what I've been looking for.

I'll look into upgrading the code. I know I tried to check the movement of my IAC valve like the megamanual said by removing it and watching its movement but no matter what value I typed into the computer and downloaded to the ECU, it always made the valve extend further, never retract. I don't exactly what model my IAC valve is but according to Edelbrock, its a GM/Delphi valve.

Thanks,

[fe3xclone]

I think part of my issue is that the engine is now flooded. I tried starting the engine today anyway I could and could only get it to try and fire once. Other than that it just cranks and cranks.
I tried doing a datalog but my datalog doesn't have the file in it for some reason.

What could be the reason the engine is flooding out? Just trying to crank it over too long without it firing? I have my cranking pulse widths set pretty lean I thought. According to the Megasquirt req_fuel calculator, I have a 14.6 required fuel. I know it says that you then take 88% and 23% for the values in the warmup wizard but when I've tried those, it always floods the engine. I've had to go down as far as 6.0/1.5 to get the engine to fire. Is this normal or do I have something not set correctly?

[grippo]

Go with the pw that works. If your engine flooded it could easily have messed up the plugs, so you might need to replace them, it sometimes isn't enough to clean and dry them.

As far as the stepper motor, it is tricky to move the steps, because it wants a change in temperature and there are extended idle and cold cranking options that make things hard to test on the bench. The code is designed not to keep the motor constantly moving so you don't wear it out, so there is a wait of at least 4 secs between moves. But it looks like the motor is responding. To verify it moves both ways temporarily set the coolant temp hysteresis to 0 so it will move even if there is only a tenth deg change in clt. Using the right mouse button change one of the gauges to an Idle step gauge and then open the idle tuning table. Change the last step by a few steps, and observe the step gauge. It should respond in 4 secs or so, but give it a bit longer. The gauge should move toward open and close, and the motor should follow. When done, reset the coolant temp hysteresis back to what it was.

[fe3xclone]

Thanks. I ordered new plugs since I had already cleaned these once before.

Something that got me thinking last night was whether or not my injectors are too big? I know the manual says that if they are too big, you'll run into idle and cruise tuning problems due to the pulse widths being too short. According to my last good data log, my PW's at idle are in the 4.0-4.5 range. Could this be a problem?

[Bernard Fife]

fe3xclone,

4.0 milliseconds is fine on either MS-I or MS-II. Below 2.0 can become a problem for MS-I (especially below 1.7, see: http://www.megamanual.com/v22manual/mtune.htm#idlepw), while MS-II has 100x the pulse width control, and is fine even lower (though the injector opening time parameter must be set carefully if the pulse width is low).

If this was mine, I would try the MegaSquirt on a stim to make it is still working as intended, then I would verify that your idle valve actually works, as it doesn't sounds like it was before.

Lance.

[fe3xclone]

I tested my board with the stim last night and everything seemed to be working properly.

I decided to upgrade to the 2.891 code (didn't see where the 2.9 code was?) but after doing so, now my stim doesn't work any longer? When I plug the stim in, all three of the red LED's on the ECU flash real quick and the outside two green LED's on the stim flash but that's it. Almost like it thinks its still in boot loader mode. However I have the boot jumper removed.

I followed the instructions here: http://www.megamanual.com/ms2/code.htm and used the MS Downloader 2.0 for the install by getting directly through the FTP site.

*EDIT* Okay, I just retried loading the code and now it seems to be functioning. Although my stim board only shows one green light, all of the knobs make the gauges move in Megatune. So I assume that means its working now?

And while I have you guys here, I have a quick question regarding the ignition control for MS-II. I need to modify my board to make this functional but wanted to find out if I do this, can I still use a conventional, non-computer controlled distributor to continue to tune just the fuel side of my EFI before swapping in my electronic distributor and moving onto the spark?

Thanks a bunch for your help!