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Old 10-17-2008, 10:01 PM   #1
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Default Road trip leads to misfires

I am running an MSPNP9093 with 10G loaded. I decided to take a road trip to continue to break in my new engine before I power tune (I had about 1.5k miles on it before I left for the road trip). Half way from San Jose to Portland (CA to OR) I started getting periodic misfires, or what felt like misfires (it would get worse and then go away for a while, especially after I stopped).
I am still in Portland and am trying to figure out what is going on. If anyone has the time to look at the short log I took during a quiet period but with a few events I would appreciate it (my laptop battery died so I got one log and then called it).
The events are at 559, 572, and 910 seconds in the log. I will attach a picture as well if that helps.

Not sure it helps the diagnostic but the car is a 91, 1.6 (Rebello engine), 550 injectors, MSPNP9093 (cap mod, tps mod, mapdaddy sensor) and a bunch of other stuff.
Attached Thumbnails
Road trip leads to misfires-misfire2.png  
Attached Files
File Type: msq megasquirt200810161839.msq (35.2 KB, 91 views)
File Type: zip datalog200810161839.zip (255.7 KB, 40 views)

Last edited by aseer; 10-17-2008 at 10:11 PM.
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Old 10-18-2008, 04:01 AM   #2
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Check your grounds. with the cap mod done you shoudl be ok,

edit: so drunk, will update tomorrow.

Last edited by Savington; 10-18-2008 at 04:29 AM.
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Old 10-18-2008, 04:05 AM   #3
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Check your grounds. with the cap mod done you shoudl be ok,
The grounds look good at the block, I'll pull the MSPNP next. Does the signal profile look like a bad ground (would that cause a dropout like the ones in the log)?

Thanks for looking.
Dave

(Matt suggested I chase down the 5V line on the TPS)
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Old 10-18-2008, 05:24 PM   #4
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I checked the grounds and they look solid to me. I did find a couple of wires disconnected. One is the narrow band o2 connect which always is tied off. The other is a wire whose purpose I do not remember (tracing back into the passenger compartment and then disappearing under the dash). The install was done so long ago that I cannot remember what it is for. I'll attach a picture (the brown wire with blue markings that looks like it is meant to attach to the splice connector(red), towards the left of the picture). I'm am still on the road (now getting a flat tire repaired, this trip is spectacular so far...), if anyone can tell me what that cable is for I would appreciate it (I do not have the tools to tear everything apart out here).

Not sure it is related to the misfires in the original post, that still worries me.
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Old 10-19-2008, 10:21 PM   #5
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quick update. The car has now died twice on the road while driving at highway speeds (I switched back to the MSPNP9093 base code in case it was a HiRes issue but the dropouts continued and twice they caused the car to die).
Not sure if that picture I posted of loose cable is related to the dropouts but if I don't figure this out I am going to be stuck shipping the car back to CA. If anyone has any ideas (what might be causing the dropouts I posted, or what that disconnected cable next to the splice connecter might be) I would really appreciate it.

Dave
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Old 10-19-2008, 11:04 PM   #6
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What's with all the **** tapped of the CAS signals?
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Old 10-19-2008, 11:09 PM   #7
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What's with all the **** tapped of the CAS signals?
The install went in almost 1.5 years ago and all my notes are 600 miles away. There is a ton of stuff on the car, I am trying to get the records pulled remotely. (that disconnected splice connector sitting next to the brown wire worries me but I don't want to plug it in unless I know what it is)


If more or better pictures would help, let me know. I am fucked right now.
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Old 10-19-2008, 11:20 PM   #8
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Does the log/picture look like an ignition kill event? (the car does have an aftermarket alarm)
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Old 10-19-2008, 11:31 PM   #9
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Your Throttle Position log matchs your Duty Cycle. I think that has something to do with it. You're tripping accel enrichments randomly and that's when the spark and fuel cut out.
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Old 10-19-2008, 11:41 PM   #10
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Your Throttle Position log matchs your Duty Cycle. I think that has something to do with it. You're tripping accel enrichments randomly and that's when the spark and fuel cut out.
So if I go from TPS based Accel to MAP based Accel, would that make a difference?
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Old 10-20-2008, 12:14 AM   #11
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Quote:
Originally Posted by Braineack View Post
Your Throttle Position log matchs your Duty Cycle.
?

At all three times noted, I see TPS remaining steady, while RPM, Spark° and injector PW drop sharply and in perfect sync. TPSacc remains at unity:


I don't think it's grounding, as all of the analog inputs (MAT, CLT, TPS, WBO2) remain steady during the event, as does BattV.

This has all the hallmarks of a flaky CAS input signal.


Aseer, that brown wire you point out is obviously not an OEM wire. Thus, we can't tell you where it goes.

It looks to me like that red vampire tap is attached to the white/red wire wire of the CAS? The fact that the CAS wiring has been fornicated is highly suspect given the nature of the problems in the log. That W/R wire is the +12 supply to the CAS- if it has been compromised and is intermittent, then this could be your problem.
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Old 10-20-2008, 12:19 AM   #12
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Agreed, the tap is not OEM. I was hoping it was part of a standard retrofit that someone might recognize, the other possibility is that it is part of the Clifford G5 alarm install, I will be talking to the installer tomorrow. (all my notes on the install are 800 miles away)

It does not sound like the TPS Accel is the issue, too bad as it is an easy fix.

Last edited by aseer; 10-20-2008 at 12:43 AM.
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Old 10-20-2008, 01:00 AM   #13
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Quote:
Originally Posted by aseer View Post
Agreed, the tap is not OEM. I was hoping it was part of a standard retrofit that someone might recognize, the other possibility is that it is part of the Clifford G5 alarm install, I will be talking to the installer tomorrow. (all my notes on the install are 800 miles away)

It does not sound like the TPS Accel is the issue, too bad as it is an easy fix.
The vampire tap goes into the white wire.

Also wiggling it while idling did nothing. (not sure if the signal would be more sensitive when driving).

Last edited by aseer; 10-20-2008 at 02:17 AM.
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Old 10-20-2008, 01:38 PM   #14
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White wire is either the CAS input or one of the coils, and if that vampire tap cut it halfway through, you're going to get misfires. It could be that the wire is damaged and if it is, that would be trouble.
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Old 10-20-2008, 04:11 PM   #15
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White wire is either the CAS input or one of the coils, and if that vampire tap cut it halfway through, you're going to get misfires. It could be that the wire is damaged and if it is, that would be trouble.
Looks like it is a coil input wire. I'll post a picture. You noted that a bad coil wire would not cause the pw to zero out. I can get this fixed but I wonder if something else is going on.
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Old 10-20-2008, 04:19 PM   #16
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Hmmm.

Ok, the white wire is the low side of the "A" coil. The igniter provides a closure to ground on that line to charge the primary.

The conductor does not appear significantly damaged, so I suppose this may be a red herring.


As I said in the PM, I still think your CAS may be marginal, and the relatively privative input circuit on the MS is falling prey to noise that the OEM ECU was filtered against. The fact that you observe this behavior to correlate to underhood temperature contributes to this theory.

Whatever is going on here is a CAS trigger problem. Without seeing scope traces of the actual CMP and CKP lines at the MS it's hard to be more specific, but my gut feeling is that you've either god a lot of noise on those lines or you are having intermittent dropouts at the CAS.
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Old 10-20-2008, 04:27 PM   #17
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Originally Posted by Joe Perez View Post
Hmmm.


As I said in the PM, I still think your CAS may be marginal, and the relatively privative input circuit on the MS is falling prey to noise that the OEM ECU was filtered against. The fact that you observe this behavior to correlate to underhood temperature contributes to this theory.

Whatever is going on here is a CAS trigger problem. Without seeing scope traces of the actual CMP and CKP lines at the MS it's hard to be more specific, but my gut feeling is that you've either god a lot of noise on those lines or you are having intermittent dropouts at the CAS.
The problem definitely occurs after I have been driving a bit, and it does not happen at idle nears as I can tell (I sat there for 20 minutes and nothing happened once I pulled over). It happened again once I get back on the road. I suppose that could be a temp issue (namely something marginal now goes flaky as it heats up)?
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Old 10-20-2008, 04:56 PM   #18
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I am going to look for a place in/near Seattle to swap the CAS, I don't see that I have a choice (this CAS went in not long ago but it was not new).

http://www.miatarepair.net/index.html
Looks like a decent option.
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Old 10-28-2008, 01:57 AM   #19
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Default Made it home, problem not fixed.

By way of a short update. I did find a guy to swap the CAS (Main Page @ miatarepair.net) . He has a barn full of miata parts and a bunch of miata's sitting around in the middle of Maple Valley, WA (literally in the woods). He came in Wed. evening and pulled a CAS off of a 92 and swapped it into mine (he also spliced the frayed ignition coil wire). The car seemed to run fine back to Seattle (late at night, we had a couple of beers afterwards, Coop is a good guy). I took off to Portland that morning and had no issues (3 hours of very light driving).
The next day I decided to try heading back to the Bay Area (CA). About 4 hours into the drive I thought I was home free, then on an incline the dropout hit (car did not die but almost). I pulled over and started logging (and sweating as I was not heading back to Portland or Seattle). I found that the dropouts could be reduced to almost zero by very light driving (light on the throttle and coasting when possible).
With many stops and much tense gripping of the wheel I got home after 13 hours.
I'll attach a sample log (minor drops at 15776, 16356, 16382, 16663), also note the noise profile at idle and on throttle, it seems to get much worse on throttle (I have no idea what level of noise is normal).
Matt suggested it might be the alternator regulator getting noisy and leaking into the MSPNP. If anyone else has other suggestions for things I should look at please feel free to chime in. I do appreciate everyone's advice, all of it helps me (and it was great to have folk checking in while I was stuck 800 miles from home).
For a car that I started as a stress reliever during my divorce, it has now topped anything my ex-wife ever did (though not yet as expensive).

I'll attach a few pictures as well as the log/msq. The one labeled Noise shows how the noise on the PW signal goes way up as I go on throttle while the alt noise stays relatively constant.
Attached Thumbnails
Road trip leads to misfires-noise.png   Road trip leads to misfires-drop4.png   Road trip leads to misfires-endidle.png  
Attached Files
File Type: zip datalog200810241432.zip (344.5 KB, 44 views)
File Type: msq megasquirt200810241431.msq (35.0 KB, 75 views)
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Old 10-28-2008, 02:01 PM   #20
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Disconnect your TPS and switch to MAPdot. Everything seems to correlate with your throttle and that's a simple thing to check. Worth a shot at least. It looks like the higher your TP, the more noise.
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