Fathom55

I'm having an issue with my new (old) car. When I start it cold, the car won't idle until it warms up. What I have to do is keep my foot on the gas and keep it around 2-3k rpms for about 90 seconds. After that, absolutely no idle issues.

Is this a tuning issue?

I get some belt squeak at startup. Don't think that's the issue.

I would be surprised if this was a vacuum leak, as it goes away when the car warms up.

Any ideas?

Braineack

iTrader: (62)

aftermarket ECU?

Fathom55

Standalone microsquirt

Braineack

iTrader: (62)

tune.

Fathom55

Think that's something TunerStudio's auto tune can handle? Does the car have to be cold to tune the problem out?

18psi

iTrader: (76)

autotune cannot properly and should not be used to tune idle.
tuning idle, enrichments, and trims is something that needs to be done by hadn.

hornetball

iTrader: (4)

Megasquirt has After Start Enrichment ("ASE") that handles a specified time period immediately after starting and Warmup Enrichment that handles the time period between ASE and when the coolant has come up to temperature. Both of these are tuned by hand and need to be done under actual conditions.

The microsquirt probably has something similar.

Fathom55

Yeah, I think MicroS does have an ASE. I'm wondering if it either wasn't setup or if it's just way off.

Confirm something for me:
My understanding of the problem surrounding cold start conditions involves the fact that the injectors don't atomize/vaporize the fuel well when the engine is cold. As such, the fuel doesn't burn properly, and more fuel must be added at startup to compensate. Then, as the engine warms, theoretically the problem correspondingly disappates until you reach "no enrichment" conditions (or 100% of idle tune). Is that about right?

I don't know if the problem is that it's too rich at start or too lean (no AFR gauge, YET). Don't want to just dump more fuel in, as that could exacerbate the problem and do some bad things, wash out oil, taint oil, etc. I don't see any grey smoke at startup though.

I'm fuzzy on the MS's handling of the transition between ASE and WE. Can someone provide a basic overview? I know just enough about this stuff to make me dangerous.

Thanks for all your help. Really experienced group here.

Phillip

18psi

iTrader: (76)

Yup, you've got the right idea: the fuel sticks to the walls and car needs more of it on cold start


**edit: and don't even THINK about touching anything til you have a wbo2 lol

hornetball

iTrader: (4)

Good discussion here starting from post #3:

https://www.miataturbo.net/megasquir...ng-more-62872/

Fathom55

Ok, update. I took a few logs earlier. Each log subsequently adding a bit more ASE and WUE. Obviously you can only adjust this so many times in a short period, because the coolant temp heats up and thus is no longer a "cold start".

The final log was with an ASE and WUE of ~55% and ~155% respectively at ambient temps (60F) and ~35% and ~135% at about 120F.

Here's a better description of the symptoms. If my foot stays away from the gas pedal, on a completely cold start (60F), the engine will fire and immediately die. Almost like a weedwhacker that fires when you've got the choke on and then dies...

I can keep the car running on the first try with the throttle, which is a royal pain in the ***....especially with my tremendous belt squeak that sings to the beat of the throttle position.

I'm attaching 3 logs (try 1,2, and 4...forgot to record 3). Each log has a bit more ASE and WUE. The final log shows my starting the car, me using the throttle to get it idling, and then letting it idle for a while. You can see it idles like crap for ~45 seconds and then smooths out. WUE is on the entire time the log is running. You can see coolant temps don't rise very much because I was just sitting there idling.

Now, before you go bananas, yes I see that AFR is pegged at 7.4. I'm working with the prior owner to figure out what kind of O2 is on the car, if any. (This may be an open loop setup ). My understanding of MS is that it starts the car in open loop anyway, which does not receive an input from the O2 sensor because the O2 sensor is theoretically not heated up or sending a signal. Am I wrong? This leads me to believe that this particular problem lies elsewhere (and I have a WB O2 in a box ready to be put on the car, no worries...I'm not crazy).

Do I need to dump more fuel in? Running RC550s.

Any help is greatly appreciated. My learning curve remains vertical.

Fathom55

Can post the tune file as well, if anyone wants to see it.

sixshooter

iTrader: (12)

Have you done a free air calibration on the wbo2? A car will not run at all with an afr of 7.4 afaik.

Fathom55

I confirmed that the car is running open-loop, which means there's no O2 sensor installed (WB or otherwise). That is soon to change.

Fathom55

Ok, one specific question I have.

You can see in the 3rd file posted above, when the rpms are rising and falling over and over again, so is the MAP (make sense). Why would the MAT be doing that as well? That doesn't make sense to me...

Any ideas?

Fathom55

Bump for a followup.

Prior owner swears the car had absolutely no cold start issues. What could have happened on the trailer ride over here that could cause these symptoms?