HY7

Hi all. I'm having issues with my engine after installing Megasquirt and I'm unsure if I should continue to drive my car. I would appreciate any help you can provide.

2004 Miata (not MSM) - 82,000 km
Bought used. Previous owner added cruise control
Live in Canada, using 91 Octane gas (highest available). Ambient temperatures about 15 oC (60 oF)
I've done no work to the car apart from taking it to a shop for a prepurchase inspection and regular maintenance. I've had no issues at all (only stalled once due to driver error in the 3 months I've had it).

Today, I took out the old ECU and replaced it with Megasquirt PNP following their provided instructions. I reconnected everything and also installed a MAF delete with a pipe from FM. When I started the car, it sounded different than normal but started fine. Initially, there was an issue where the MSTuner couldn't work with my ECU firmware. I had to update it online and then it worked (it was showing me accurate RPM readings and such). I used a timing light to ensure that the timing was accurate (I very slightly adjusted it but it was pretty close). I did not touch any other settings on TunerStudio. I changed the ignition back to "Use Table" as the instructions indicated.

I noticed that when I was decelerating with the clutch in, the car would get quite low on RPMs and stalled a couple of times. I drove it for about 20 minutes without major issues but I didn't go much past 4k rpms.
I took a break for 2 hours and tried to start it again. It didn't start the first time but then it did after that, although the rpms were extremely low. The whole car shook quite a bit (especially with throttle) and it definitely felt abnormal. Giving it gas didn't help. After 30 seconds or so, it seemed to fix itself and the shaking stopped. However, it continues to stall occasionally at stop signs (decelerating with clutch in). I drove it for 15 minutes, parked it for 15 minutes, and then tried again. The same thing happened again (didn't start initially, whole car shook, shaking improved, stalled at stop signs). The oil level and temp were OK. After parking, I also thought there a weird smell coming from the exhaust. I popped the hood and didn't notice anything weird.

Does anyone know what is causing this and what I can do to fix it?

I have a few ideas but I have no idea if they're reasonable or not:
- Is the Megasquirt expecting wideband O2 sensor input? I have a wideband O2 sensor but I didn't install it yet because I'm not exactly sure where to put it (especially if I want to add a turbo later).
- The Megasquirt documentation mentions 93 octane. I can't get that here for pump gas. I read on a different thread that 91 gas in Canada in similar to 93 gas in the US.
- Was there some step where I had to install the base MSQ file from the thumb drive?
- Did the firmware auto-update mess something up? The Megasquirt documentation stresses that loading firmware should be done with the ignition module/coils disconnected. I thought I was updating the tuning program, not the MSPNP (as it should have been shipped updated already, right?). How would I even get the MSPNP to run without having it connected for power?

Thank you so much for any help you can provide.

Barton

First thing you should do is put the OEM ECU back in. Not sure what your expectations were but you can't just plug it in and expect it to work perfectly on the base map. It's just to get you started.
Start reading how to tune it or take it to someone who will.

rwyatt365

This has been said about a million times already but it bears repeating; Simply plugging in a MS (PNP, or not) and expecting it to do all things correctly sill not work. The base tune that came with your MS is just a starting point. You've got a LONG way to go to get it to control your car well.

From what you're describing, you need to first start with tuning your startup and idle parameters. You'd do yourself a favor by doing a datalog of your startup and warmup so you know what's happening and identify any problems. It also wouldn't hurt to save your current tune and then use the auto-tune feature to see how TunerStudio adjusts the settings away from that base tune.

When/if you do that, attach a copy of your tune and the log of your startup sequence so that we can give you some useful feedback. Remember - just saying "my car does xyz, I need help" does not convey NEARLY enough information to provide assistance.

HY7

Hi, thanks a lot for the advice. I mistakenly thought that the Megasquirt tune was fairly conservative with a stock car so I wouldn't have major issues. The car isn't my daily driver so I'll leave it in and figure out tuning.

I read on here that tuning without a wideband O2 sensor is very difficult. I am planning to eventually add some other upgrades, but it sounds like I have to install it now in order to tune effectively. Is that correct?
The AEM sensor I have has these guidelines: (1) 18 inches (45cm) downstream of the cylinder head's exhaust port or turbocharger (2) Upstream of any catalytic converters or emission control devices. Is there a preferred spot that people put them on stock NB Miatas?

Barton

Yes you will definitely require the wideband. A narrowband will basically just tell you if you are at lambda 1 or richer or leaner. Only really useful if you are trying to achieve lambda 1.
Easiest location is to just install the wideband O2 in place of the OEM narrowband O2 sensor in the exhaust.

HY7

Ok, will do. Thank you very much. My apologies for the newbie misunderstanding.