Track car intermittently runs like crap
 

Gents,

I'm doing two back-to-back events at VIR. The weather is glorious. Unfortunately, about 2.5 days into my four day soiree, my car started running like crap.. Again. This has happened before. After several hard sessions, she'll start having high idle AFRs and running almost like she's out of balance. Today, I heard what I thought was a misfire on track. The session was nearly over so I came in. She wasn't idling smoothly. I checked plugs, plug wires, electrical connections, etc., then went out with my students. The next time I took her out, she did a beastly 25 minutes without issue. She ran beautifully. When my next session came, it was back to the high idle AFRs and the rough running on track. Weird AFRs at boost.

Help. I have another beautiful day at VIR tomorrow.

Thanks,

That's a lot of views for no replies. I suspect I'll have some cats deducted.

Thought I'd provide an update.

The car ran great at the track the next day. No issues for three hard 25 minute sessions and two shorter times out giving rides. I packed up and headed home, stopped for gas and coffee. She was purring like a kitten. I'm doing about 60 mph at 3200 rpm or so with AFRs in the high 13s low 14s, when suddenly there's a stumble like 200 pounds had been added to my trailer and the AFR shot up into the 17s. I pushed in the clutch and fanned the throttle a bit. AFRs swung wildly up and down, then she just started running perfect again. That happened one more time.

My route home takes me on back roads through some small towns. I'm outside of Ivor VA doing about 55 and it does it again, but won't come back. I shut her down and parked on the side of a country two-lane with my flashers on waiting to get hit by a sleepy truck driver. I waited a few minutes and tried cranking her over. She started. AFRs in the low 14s, but I could not get any substantial rpms going. I limped into Ivor doing about 15 mph and it just started running again. I eventually made it home.

Seems like my less-than-two-year-old DW300 shit the bed, but I'd appreciate some feedback. I'm running the Flow Force 625 injectors.

When was the fuel filter last changed? It could be getting clogged.

I was going to post the same, but held off to think about it more. If the fuel filter where clogged, then it wouldn't be so intermittent, right? Neither would clogged injectors, it'd just be bad all the time. Almost sounds like wiring/pump related, but then again, last time I had this happen to me I replacedthe pump, filter and fuel lines and never had problems since. Filter would be the cheapest and easiest to try.

You might also try to log it from the MS3, just to see if some basic sensor is getting flaky and feeding the MS bad data.

I would not suspect the fuel injectors. It's not likely that they'll all go bad at the same time and then "recover." The other comments regarding fuel supply are more likely.

I had an IAT sensor go bad (actually was the solder joints on the board) and it told megasquirt air temp was 300° so it pulled 20% fuel and ran lean as hell. Wasn't intermittent though.

The '99's can have Cam sensors that can fail intermittenly, depending on heat. They are also prone to having coil packs start to fail with heat. You can try a data log next time it running poorly and check for sync losses from the Cam sensor dropping out. I know more than a few people who carry a spare Cam sensor at the track. The '99 fuel pumps have been known to fail as well. Good luck!

Gents,

The car sat for about 20 hours. I came home from work today and kicked her over. She started normally and ran smooth as silk. WTF?

I doubt it's a cam sensor, when they fail it's not just a reduction in power, the engine actively shuts off when the MS3 loses sync and maybe restarts a half second later. It's violent, and the MS3 will light the CEL after it's gotten more than 2 sync errors.

Intermittent coil failure could make sense, the unburned gas is ignored by the O2 sensor so it sees all the oxygen that wasn't used and interprets that as being lean. Since the NB is waste spark, losing one coil takes out two cylinders so you lose significant power. It also dumps a ton of fuel into the cat (if present) which will destroy it in fairly short order if you keep driving it in that condition.

Losing the fuel pump or regulator intermittently could do it too -- need a fuel pressure sensor to be sure. Those are pretty easy to add to the MS3 and data log.

--Ian

Coil packs?

Coil packs heat up and fail intermittently. When there is a misfire it registers a lean AFR.

My 99 will start acting up after a few autox sessions, it will develop a hiccup around 5k rpm at full throttle, then if continued to drive the hiccups will become worse and worse, the car would start to stutter at any throttle position above feathering it. if i stop the car, let it cool down fully, its good as new and no problems again.

Already replaced cam sensor, My guess is coil packs on its way out and under full load overheat and cut out intermittently.

Doing LSx coils soon due to this.

Is there a proven coil pack replacement?

New oem coil pack, quality aftermarket coil pack, or switch to GM LSx coils or Toyota COP's.

I am going the LSx coils route right now, costs about $200 with new acdelco d585 coils from amazon, sadfab mounting bracket, and ebay pigtails.
Still need to order custom magnecor wires as well.

I'd like to narrow this down a bit.

I've personally been running Fab 9 Tuning's COP conversion on my NB for the past 25-30K miles. No issues in this time, and I've been DD'ing the car for nearly the past 2 years. I however don't have a boosted car, nor is it tracked, so take this with a grain of salt.

Fab9Tuning Plug & Play Coil-On-Plug Conversion Kit - Fab9Tuning

Fab9 would be at the bottom of my list of ones to goto. Since you have a MS3 going to LS coils is the best option. There are a few different brackets on the market now to make use of them.

I interpreted "quality aftermarket coil pack" as an OEM-style pack NOT from Mazda. I have installed a set of OEM replacements, but would like to have another set on hand in my spare parts box to take to the track, just in case.

Their are not any quality aftermarket ones. You either run OEM from Mazda, or upgraded to a better different type of coils.

The D585 coils are really very easy and painless. I just did it. I also way overthought it.

I've spent an hour searching D585 and Miata, and I don't see it easy or painless. Is there a kit you can point me to?

How much of a "kit" do you want?

The hardest part is the bracket, there are a few out there. Here's one: http://sadfab.com/coilmounts.html

After that you need to wire them up. There's a GM harness you can buy that adapts from a 6-pin (weather pack, I think) to the 4 coil connectors. Then you buy the loose matching weather pack and pins and adapt it to your ECU. You also need some custom plug wires.

Coils can be had from junkyards, RockAuto, or GM.

Alternately, FM sells a kit (https://www.flyinmiata.com/big-spark-kit.html) that uses LS2/LS3 coils instead of the truck ones. It's got all the things you need in one box, including brand new GM coils. The cost on those is what produces the eye-watering price, you can also get it without coils for a whole lot less money if you want to supply your own used/cheap ones. The LS2 coils aren't quite as strong as the truck ones (they're plenty for 20+ psi on a Miata motor, though), but they're physically a lot smaller and the FM mounting location is nice.

--Ian

I will literally put it in order for you because I want you to do this.

Assuming you already have a mega squirt. If not you want this

1. MSLabs Megasquirt MS3 Basic

2. http://sadfab.com/coilmounts.html Mount and wires.

3. GM GEN III 5.3 6.0 LQ4 LQ9 LSX D585 IGNITION COILS W/BRACKETS AND WIRE HARNESS | eBay You can sell the extra coils and get a chunk of money back or keep them as spares. These also come with the pre color coded wiring harness that makes sequential a breeze. I choose to leave it wasted for now.

4. https://www.amazon.com/gp/product/B0140E0NPI/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1 This is optional. You cut off your stock coil connectors. Cut the end of this harness extender and soldier it in then plug it into the gm harness above. You can skip this by cutting your factory harness and cutting the end of the gm harness off and wiring it together.

4. Change your dwell settings in MS. This will take a little googling. I know what I have mine set at but I am not confident in the settings enough to advise using them. Basically dwell is 4ish.

5. This is the wiring diagram I used with my 1994 using a MS Labs MS3. My Tach works and I don't know why so I am going to assume Rev did some magic inside.

6. Here is a pic of how I temped in my wiring while waiting for optional Harness extender. You can probably leave it like this and be fine.






https://cimg8.ibsrv.net/gimg/www.mia...f993993efd.jpg
https://cimg9.ibsrv.net/gimg/www.mia...0ee312eb70.jpg

Holy crap.

Guys, I think his car is stock and on the stock ecu.

In that case you should just go with it stock replacement coil for simplicity's sake.

My sig block is still there, as far as I can tell...

Sig doesn't show up on the mobile app, which is what I'm using today.

So I took her out with the replacement coils and she did the same thing. I had the deck carpet out and the tray cover off above the fuel pump. Every so often the fuel pump sounded like it was coming apart. I don't have my readers and apologize if there are multiple misspellings.

I lost another cat. Jeez. You are the guys that play Warcraft as the big-jugged warrior princess with the tail and the magic sword....

I replaced the DW200 with a Walbro 190 HP. The sound is very different. The last days of the DW200 was a high pitched buzz, whereas the Walbro has a more purposeful groan. She started right up with the new pump and seemed to run normally, but I did not take her for a ride yet. The seat was out to get to the pump, and I plan to replace the fuel filter today before taking her out.

Honestly, with an MS3 and (I assume) larger injectors, why are you running either a DW200 or Walbro? KISS.

I have no idea what you're trying to tell me.

You don't need an auxiliary fuel pump. The OEM fuel pump works just fine. Remove failure points.

The DW200 came as part of the Rotrex kit. I replaced the OEM pump with it, which required wiring in a different pigtail. Now, I fully believe that pump is bad, so I'm replacing it with a Walbro 190, that uses the same pigtail. There is no "auxiliary" pump.

Dammit. Dammit. Dammit. I got the new fuel filter in last evening. So new fuel pump and filter, and new coils. I got to the end of my street and she started doing the exact same stumble, no power, really high AFR behavior.

I swear the fuel pump sounded terrible and I was confident that was the issue. Now what? I hate replacing parts without knowing they're bad.

Thanks,

A data log might show something. Better than the shotgun approach.

I got two logs. One is very small, so here are both. I had to .zip the larger file.

Whatever it is that's going on, on three occasions the car has just died. All the idiot lights on the dash lit up. Once it happened parking in the paddock, once at a stop light, and once while driving coming to a stop. In all cases the clutch was pushed in, so the momentum of the car wasn't keeping it running. That last case, I let the clutch out while I was still rolling and jump started it.

Any help would be greatly appreciated.

Gents,

I could really use an assist here. I've got no idea what to do next but check connections before I start replacing parts willy nilly.

Is there anything in the logs I provided, or do I need to take her out again?

I had the alternator rebuilt early this year. If the alternator is doing something weird, could that cause the stumbling and the engine to die? Could a bad coil pack cause the engine to die?

When I perform the "Fuel Line Safety Procedure" per the shop manual, and pull the connector under the dash above the gas pedal which disconnects the fuel pump so the car starts but drains the fuel line, the car does not start.

Thanks,

I swapped in a complete stock fuel pump assembly and no change. Here's a log. The drive was short. The car died once while I was turning around.

Thanks,

I reinstalled the fuel pump assembly with the Walbro. I removed the fuel pigtail at Pulsation Damper No. 1 and mounted a pressure gauge. It read a steady 63.5 pounds regardless of rpm or when it started running like crap, but I didn't actually take her out. I would have had to remove the hood. She ran long enough to warm up and have the fan come on. When it was running rough, the AFRs would bounce up and down, but the fuel pressure remained steady..

Something strange happened in the third log:

http://www.codrus.com/misc/poormxdad.mid.png

The RPMs decay away, the duty cycle goes down but the PW goes up. Huh? That doesn't make any sense to me. Then it cruises at 248 RPM for a while -- IIRC, from what Reverant says, "250 rpm" is what it shows for an engine that's having certain kinds of sync error problems. OTOH, the AFR stays pretty constant at 12-ish, which suggests there isn't something really crazy happening with the fuel.

Unfortunately, things like battery voltage, TPS, and VSS aren't in the log, so it's hard to say exactly why it's happening. Do you have a voltmeter gauge in the car? If not, I highly recommend hooking one, they're $30 from Summit and very useful for diagnosing weird alternator/battery problems.

--Ian

Ian,

Thanks. I had a spare alternator rebuilt by a reputable local company to try to give me some more amps. It's the alternator that's in there now. I've been tempted to swap in the other alternator, just to see what happens. It's free, but an aspain.

Any point in taking her out without the hood to monitor the fuel pressure?

Are you using laptop logging or SD card logging? I'm assuming SD card because of the limited fields, right? If so, and if you can easily reproduce the problem, then personally I'd say go log it with the laptop hooked up because that will capture a lot more fields than the SD card logging does. At the very least, that should give you battery voltage when these things happen.

Fuel pressure info is also interesting, if you can easily monitor the mechanical gauge while driving then sure. I hooked up an electronic fuel pressure sender in mine so that I could monitor it in the megasquirt logs along with everything else.

I think you're better off gathering more data than randomly throwing parts at the problem.

--Ian

I have an extension cable from the MS3 Basic that puts the SD card at the bottom of the dash above my right leg. I did not know the SD card collects less data.

I'm concerned the problem is getting worse in that there is more crappy running than normal now. I'd hate to take her out and have something fail completely and need a tow home.

In TunerStudio, under "Data Logging" and "SD Card Datalogging" you can configure what goes into the SD card logs. Different versions of the software allow different amounts of data.

As for a tow, there's no way to confirm a fix without actually driving it. Do you have AAA? If not, I'd recommend adding that, keeping your test drives within 5-6 miles of your house, and making sure you bring your cell phone and AAA card with you on test drives.

--Ian

I have USAA with towing. Funny, I called yesterday to confirm towing on all my vehicles...

I got up this morning to a slight smell of fuel in the garage. The Harbor Freight gauge was leaking at the gauge threads. I decided to remove and repair it (or throw it away) rather than driving with it installed. So, I listened to some audience recorded Grateful Dead and swapped out the alternator for a known good one. It ran well long enough that I thought she was fixed. Then, she sh!t the bed just like before. It also seemed to be running hot. It was in the 50s here today, but she was showing 190+ around town with the 180 degree thermostat. It just seemed hot, but it could be my imagination.

To recap, in the last couple of days I've swapped out the alternator, and replaced the fuel pump, fuel filter, spark plug wires and coil packs with new items. The crank position sensor is OEM Mazda and only has a couple of hundred miles on it. The battery is only a few months old. When it runs correctly, she's a beast. The intermittent nature of the problem has me completely boggled.

Did you get a good data log and/or composite log of the failure today?

--ian

I added (or thought I did) BattV to the data logging, but I don't see it. What would you like to see in the log file?

I did get these. 06 is sitting idling in front of the house. She sounded labored.

I will attempt to get an actual composite log today. There are a couple of other diagnostic logs. Should I get something else, too?

Thanks,

Any perceived problems during the recording of these logs? All I can see is that your tune is not all that great. Your AFRs are all over. And start logging with a laptop, so you get more helpful data.

When the engine is running properly, she runs fantastically. The bouncing AFRs are a symptom of the problem. When whatever is happening happens, she runs rough, makes no power, and the AFRs get lean, even at idle.

Can you please post:

a) a laptop log, these SD card ones are missing too much information
b) happening when the car randomly dies
c) ideally with a pointer to the location in the log where it happens.

--Ian

Roger. WILCO. Probably will have to wait till Friday.

Gents,

Please take a look at these composite logs. The one from 14:50:06 should have an instance where the car died. The other one is afterwards, in case I did not get the logging correct. The last time I had to take a composite log, all I had to do was hit Start and Stop and find the file. The new software has a different implementation and I'm not sure I got it right. Let me know if these are useful. I do have a handful of additional composite logs.

When she died, she was running at a lower rpm than would be normal for the amount of gas pedal I was putting in. She sounded like Daa, Daa, Daa, Daa, Daa... like an old lawn mower trying to run after sitting for the winter, almost as if she was out of balance. I knew she was going to die when I let off the gas.

Thanks,

Gents,

I played around a bit. I know less than I did before.

Soooooooooo, I have four coils--two sets. I took out my timing light and hooked up the inductor to each of the plug wires. When the engine was running crappy, Plug 3 had the most erratic flashing of the timing light, so I swapped in one of the other coils on the driver's side. No real change, so I swapped the other coil in there for the driver's side. No real change. Then, I swapped sides with the coils that were in there. #1 had a more erratic flash, but the engine didn't sound any different, and #3 STILL had an erratic flash. Maybe it's a meaningless diagnostic. I'd like to hear from the experts.

I got a few more logs, this time from the laptop rather than the card. Check out the one from 14:22:36. WTF? 16:41:48 was on a short drive. The rest, one is a composite log, are at idle in the driveway.

Thanks,

Just some additional info.

The catalytic converter sh!t the bed a couple of events ago. I'm running with a gutted cat for right now.

I replaced the bottom end with one from a Japanese Domestic Market importer. I swapped in my rebuilt head, and did a timing belt/water pump job. Then drove to VIR. She's a beast when compared to the 143,000 mile bottom end that was in there.

Given that she ran so well, I want to assume I did the swap and timing belt properly. Is there anything under the cam cover that could have come loose that would cause her to intermittently run badly?

Thanks,

I am more inclined to think you had a bad ground or bad wiring and fixed it on accident by "touching it" when you swapped all this other stuff around.

Here's another log.

Since I had the timing light out, I checked base timing. It was a little off and I tweaked it back to 10 degrees.

I checked all the grounds that I know of, and also got under the dash and pulled and reset the connectors for the MegaSquirt, as well as checking my power shunts in the fuse box.

Towards the end of this log, she started to run rough. I checked the plugs firing again with the timing light. #3 showed dropouts often when compared to the other cylinders. Flash, flash, flash, flash, blank, flash, blank, blank, flash, etc., etc. There was no noticeable pattern. As I mentioned in a previous post, #3 did that even though I changed out individual coils. The plugs are brand new. Is there anything to that?

Thanks,

Back from Thanksgiving trip, I can look at logs now. :)

The composite logs form 11/25 and 11/26 don't show anything. There's a sync loss at the beginning of the 11/25 log, but that appears to just be from startup (it has to sync when you first crank it). The two composite logs from 11/25 are only 24 and 17 seconds long though -- did you really intend to only log that long, or is there something wrong with the logging setup? The composite log from 11/26 is 2 minutes long, but shows no loss of sync.

The two laptop logs from 11/26 don't show much of anything either -- no sync loss happening and AFAICT no stalling. The 14:22 log is 5 minutes long, and at 250 seconds in there's an odd glitch where VSS jumps from 0 to 3.4 stays there for a second, then goes back to zero. Did you roll it backwards down the driveway briefly or something? Nothing jumps out at me on the 16:41 log, but it's only 78 seconds long.

The 11/27 log shows VSS moving around quite a lot. Do you have it calibrated properly? TPS is zero -- was the car moving during the log or parked? If stopped was it idling up on jackstands with the wheels in the air, or on the ground with the parking brake on? The VSS is on the output shaft of the transmission, which means it's physically locked to the differential, so if both rear wheels are not moving, there's no way it can generate any kind of legit signal. If so, then I think there's a strong chance that you have ground issues.

The 11/27 log also shows a lot of spikes in the AFR, up to 18:1, starting around 18 seconds into the log, which is also when the RPM starts getting a lot more ragged. It goes from a nice stable 2.1ms of pulsewidth to something that's moving around a lot but averaging about 2.3 to 2.4. What's your injector deadtime? Assuming it's around a millisecond, that means it's seeing 20-30% more fuel on average, and yet the average AFR value hasn't changed. I'd say that either the car misfiring (and thus blowing unburned air & fuel into the exhaust, which fools the wideband sensor into thinking it's lean because it only looks at oxygen content, not fuel content) or the wideband is measuring incorrectly for other reasons (bad ground, bad sensor, something like that).

--Ian

How old are your plug wires?