Engine Sputtering and jerking.
 

Hey everyone,

Hope everyone is well.

I had a blast at the tail of the dragon but missed going to the Fontana village since i had to be back in Miami to go back to work. well my car behaved well through the whole endeavor.

Today I drove the car to Kendall (Approximately 44 miles back and forth) and while on the highway in 60 mph i see my A/F gauge went crazy and my car starts to jerk and sputter (The A/F Ratios where anywhere between 12.7 to 22.3 and it would not steady for a bit).

My car has 112462 miles and is an 04 Mazda base with MSP3Pro. where should I start. to fix this and should i stop driving the the car until I fix it?

Any suggestions how i can fix it.

Probably not the best idea to continue driving.

Foremost, need to establish whats going on. Jerk and sputter sounds like classic misfire, along with wavering AFR - but the cause needs investigation. Bad coil? Fouled plug? Losing sync? Too rich? Stuck injector?

Plugs would be my first look. Old plugs are difficult to read - but if you pull them and a pair (1+4, 2+3) are noticeably fouled, I would lay blame on the coils - which NB2's aren't known to be the most resilient.

I had to drive it to work today since it's my last week at my job.

The car drove okay and occasionally gave the sputter and jerk.
I was able to log it on Mega squirt. and you can see the log file on here. hopefully it helps.
I will change the spark plugs on my car today in the afternoon at work. i will also do a compression check.
Tell me what you think.

Thanks in advance.

Don't see any sync loss, so that somewhat eliminates cam/crank sensor failure. AFR erratic mostly lines up with timing errors, so pretty much expected misfire. Most of the troubleshooting is gonna be meatspace though, that's about all I can tell from the logs.

Spark plugs changed
 

So I changed the spark plugs, they didn't look that bad.

https://cimg9.ibsrv.net/gimg/www.mia...b702951e49.jpg
https://cimg2.ibsrv.net/gimg/www.mia...06c0a97f99.jpg

So i drove it and i logged again, it it sputtered allot less. what else can you recommend so i can continue repairs.
The car feels a lot better with the new spark plugs. Now it sputters way less. but tell me what you think on the logs.

Old plugs are difficult to read, new plugs are a little easier since they're less stained. I'd hate to advocate throwing parts at something, but my next guess would be coil packs. Log is showing less misfiring at higher RPM, which kinda follows because mixture is easier to light off at higher piston speed - more timing errors are occuring < 2500-ish rpm.

If new plugs helped, but didn't make the problem go away completely, I would look at coils, coil wiring, injectors, and injector wiring. MS isn't commanding any weird pulse width to your injectors or dwell/advance to your coils, so it's not necessarily tune related. But we knew that since you hadn't made any changes.

Can you post the tune?

Only way you're going to be able to read the plugs is if you key the car off immediately during the misfire and pull the plugs to look. If you keep driving and idle it, it'll clean them up and you'll only be looking at your plugs during idle.

Here is the tune
 

Here i'll place the tune.

I bought new coils and wire sets for my car. when i get them tomorrow I'll place them immediately.
I'll run the log again. and pass it along. I don't really know how to read the logs that well.
I'll keep you guys posted.
If anyone has time can you guys teach me how to check out the logs and how to read them i would like to learn how i can read errors as well.
Thanks in advance.

Ignition coils have been changed
 

I changed the ignition coils and wires. i am still getting the jerk. i will log it tomorrow in case. and send the log.

Thanks for your help guys.

results
 

Good morning everyone,

So I drove my car today on the highway and midway through it started to stumble again.
Ignition coils and wires and sparkplugs have been changed. i will place the log to see if anyone can see anything. i nooticed that my AFRs went crazy but i was holding a position and it should have stayed in 15.2
Thanks in advance.

If you're happy with the tune, that's all that really matters, although there are a number of things I would personally change. I looked at it 24 hours ago, but from what I remember, your air density curve is a little aggressive, pulling too much fuel, and there's some weirdness in the initial value/fuel table around idle going on.

That being said, I'm fairly certain this is a mechanical problem, and anything we see in the log is going to be just a reaction to whatevers failing.

You asked about logs, so I'll explain a little about what I'm looking at. Open the log above, and set the top graph to RPM, MAP, AFR, and TPS. Set the second graph to RPM, SPK: Spark advance, AFR, and PW. The RPM and AFR sort of "focus" me, helping me to look up and down between 2-4 graphs and know I'm looking at the same spot in the log. Once you find what you're looking for, you can switch the repetitive values to something else. TPS, RPM (cam/crank), MAP, and to an extent AFR, are the most important sensors in your MS. SPK and PW are all you really buy the ECU to do, output proper fuel and ignition to make your car run. That's a very basic explanation of course. Once you find where something is happening, and why it's doing it, then you look at more precise values to see what's causing it to happen.

In the log you posted above, if you scroll over to 243.5 seconds (the blue line is your "cursor"), you'll see that RPM, MAP, and TPS remain fairly constant, looks like you're just cruising on the freeway. But at 243.5, your AFRs go from 15s to 10-12, and begin fluctuating rapidly. If you look at PW, nothing really changes, so you're not commanding more fuel. If you look at EGO corr 1, it starts going crazy. This is in response to the dip in AFR, you need to turn off EGO correction for future logs/diag. Then at 260 seconds, shit really hits the fan, that's the misfire you're feeling.

I don't have a great answer as to what's causing this, my biggest suggestion is another log with EGO turned off, but others may chime in with more info.

Hey Curley

If you want to help with the tune, i'll be more than happy to accept a bit of help.
I saw on the log viewer what you saw but when it comes to saying it might be a mechanical problem, what would you suggest, i have changed plugs and coils and wires.
Also how can i turn off the EGO so i can run the log without corrections. On tuner studio.
Thank you in advance

Under fuel settings, afr/ego control, set algorithm to “no correction”, press burn, and it’ll ask you to cycle the key.

I’d try this first to rule out a dying wideband sensor

turning off EGO
 

Okay i'll try that when i get out of work.

Hopefully it's the wideband.

Keeping fingers crossed.

EGO correction off results
 

Hey Curly, so I turned the EGO correction off as stated.
i logged the car, it drove normal like nothing happened.
Can I ask if you can check the log once more to confirm. maybe I am not seeing something you are. maybe it jerk just a little and I didn't notice.
I do allot of freeway driving like you noticed on my way to work.
Tell me what you think or what i should do. would it be something else or is it the Wideband? Would i have to change the whole gauge or just the sensor.
I have an Innovate LC2 Gauge. and some times it stays stuck on 7.4 or it will blink at 7.4 even though i do the calibration.
Thanks in advance.

I think curly nailed it - I don't see timing errors in the last log. And since I love failure stories, I'm going to guess you drove exuberantly at the dragon, and that overheated the wideband, which then failed during cruise and tripped up EGO feedback leading to misfire.

so should i get a new sensor or the whole wideband with gauge?

On the latest log, at 758, your wideband starts going crazy again. If you didn't feel anything, together with the issues you stated above with calibrating it, I would say there's a good chance at the very least the sensor is going bad. It would be a little strange if a bad wideband sensor caused misfires, as it's a feedback sensor, not directly involved in the fueling or ignition calculations. Like I said earlier, those sensors are cam, crank, MAP, TPS, and AIT if you're settings are aggressive enough. But stranger things have happened.

It's always a good idea to check your wideband wiring, ensuring the sensor ground is grounded at the ECU not chassis, chassis ground is secure, power source is secure, and all splices/connections can be tugged on fairly aggressively without ripping apart. But if that all checks out, usually sensors just die. 4.9 sensors are very sensitive to impacts, even knocking them loose and taking them out of the exhaust can cause sensors to fail.

I'll respond to your PM in a minute.

I have the ground connected to the same ground at the ECU, on the engine block. tell me if thats correct or if not i'll have to find any other faults. i'm buying the sensor tonight to see if i can get it changed by the weekend.