All over the place idle

[LR Max]

Setup: MS2 V3.57 Pre-assembled board from DIY Autotune. Running MS Extra (3.4.0, I think, so not the newest but not bad). Hardware is a 1 injector TBI, fuel only setup currently. I do have a wideband 02 sensor. Engine is a 2.25 4 cylinder normally aspirated. Basically a tractor engine, redline is 4500 RPM.

The truck runs great on MS, actually. However it seems like the idle can go all over the place, especially when cold. I'm going with the IAC kit that DIY autotune provides, but wanted to ask here before I do that, to ensure I'm not masking some other problem that I haven't fixed yet.

So when I start the car up cold, it'll idle at 500 rpm. Then as it warms up, sometimes it'll idle at 500, other times it'll idle at 800. Then I get on the highway, cruise for ~30 minutes or so. Then it'll idle at 950 rpm. As the engine temps come down from highway cruising, it'll come back to 800 rpm. I have checked, my TPS does not show any changes, so it isn't a sticky throttle pedal.

Any suggestions on what to look at? As mentioned before, I'm going to install an IAC soon and work my way to closed loop idling to solve this issue, but wanted to see what others have to say in terms of what could really be the issue. I've attached a tune and a data log for your consideration. Please ignore how rich warm up is...still working on that.

Thanks guys!

[LR Max]

Well for reasons, I can't post a data log...wonderful.

Whenever the internet decides to work with me again, I'll get that up.

[rickb794]

Your VE table does not look happy, lots of low numbers and only a 30 point spread from low to high does not provide much granularity.
Perhaps your req Fuel needs to be smaller?
Im kind of surprised it runs like that.
Did auto tune do that?

But then I see 2 squirts / alternating, Im thinking 4 squirts simultaneous might be a better choice? But I've never done one injector.

All of your wetted wall options are not available, I think those should be enabled for TBI

504cc is only good for 73HP I think you might be undersized.

where is your IAT sensor mounted? I like the air filter...

Have you done sensor calibrations under the "Tools" drop down menu? TPS Temps and O2 (afr)

[racingmini_mtl]

But then I see 2 squirts / alternating, Im thinking 4 squirts simultaneous might be a better choice? But I've never done one injector.

With a single injector on a 4-cylinder engine, that's the only way to have a decent fuel distribution. Unless the engine is running almost entirely on the wall wetting fuel.

Jean

[rickb794]

2 squirts or 4?

He does not have any wall wetting turned on....

[racingmini_mtl]

2 squirts or 4?

He does not have any wall wetting turned on....

I meant 4-squirts/sim. You need one squirt per cylinder otherwise you have a lot of the fuel going to one cylinder (too rich) leaving the next one lean. That is less of an issue the higher the duty cycle is and the distance between the injector and the intake valve does have an impact (but that goes back to wall wetting).

Jean

[rickb794]

Thanks for clarifying, that was the only logical setting i could think of.

I wonder if that is affecting the VE table as well, it is very flat from low to high.

LR I would change the squirts an then see what the VE table wants.

You might read up on the wall wetting settings and enable them.

I would also get a fuel pressure adjustment kit and raise the fuel pressure 15-20% to make that injector bigger.
You will need a ~750cc injector to make 110HP (with some headroom).
Im not sure how far you can go with that injector, is a larger injector available?

[LR Max]

Thanks for the feedback.

It is weird because the TBI came off a 2.5 I-4...that is rated to put out ~140HP or so. My engine is 2.25 liters and if I 110HP is on the table...that would be AWESOME. Factory, she was rated at 75HP, but I've tried to do a few things to add some extra HP (higher compression, cam, oversized piston, etc).

Also to ballpark everyone, this is for my 1973 Land Rover Series 3 (aka, a safari car). The engine is not high revving...nor fast revving...nor...anything fast. So that is what I'm used to. Redline is 4500 RPM, but everything sounds like its about to fly apart at 4,000 rpm. I mainly hang out at the 800 to 2000 rpm range and highway cruise at 2900~3200 rpm.

IAT is mounted right after the air filter. So pretty close I'd say. Currently there is about a foot, foot and a half between the IAT and the TBI. So it should be fairly accurate. I'm planning on changing everything and mounting the IAT right at the TBI elbow. All the sensors are stock GM sensors sold by DIY Autotune, so what is in MS should be fine.

I'll give 4 squirts per cycle a shot. I have noticed that my AFR does bounce around some so it does make sense to go this route to smooth out the AFR.

I'll see about a larger injector. That said, I'm not having duty cycle issues. Sometimes I'd be around 50% duty cycle with my current injector.

Attached is an old file, and what autotune would give me (ignore other things in the file, I've changed a lot in the past month). As you can see, it is everywhere with random peaks in the middle of the table. From my research, it needed to be smooth.

Also please ignore the warm up stuff. Still trying to get that leaned out.

I'll research wall wetting. Sounds like my VE table isn't right, so I'll make that a priority before expanding on something else.

Thanks for the info! I was like, "Yeah this thing is running great!!" but it sounds like I'm doing it wrong

[rickb794]

4 squirts

Simultaneous

Do that first and see what happens.

Another possible explanation for the VE table might be that the fuel pressure is manifold referenced.
As the throttle is opened vacuum drops and the fuel pressure is increased.
This would explain the low spread of the numbers across the VE table.