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01 MR2 Spyder - Diagnosing Misfire


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ltclutter
New User

Apr 17, 2016, 5:48 PM

Post #1 of 8 (1472 views)
  post locked   01 MR2 Spyder - Diagnosing Misfire  

Posted in general troubleshooting cause so many components affect it.

2001 Toyota MR2 Spyder, 1.8L 4 cylinder, 150k-ish miles on car, engine swap about a year and a half ago to a 34k mile engine which would have maybe 48k on it now? Not much more than that.

Ok, so I started getting the random misfire and misfire on cylinder 4 code about a week ago. Always on a cold start, worse at idle, lasts til I get to running temperature. My O2 sensor had been intermittently flagging as bad, so I took this as a sign.

I have:
Replaced all three O2 sensors.
Swapped coils
Replaced sparkplugs (gapped and torqued)
Run half a tank of gas treated with fuel injector cleaner
Compression tested the cylinders, which passed with solid readings all between 190 and 200.

Shortly after replacing the sparkplugs, on my test drive, I got two new error codes. "Power voltage down", which I can't seem to find a whole lot of information on, and a driver side rear wheel speed malfunction, which I am currently chalking up to the misfire randomly robbing me of a quarter of my power and then gaining it back in the middle of a turn. That said, figured I'd list it anyhow because I'm not a fantastic greasemonkey by any stretch of the imagination (please use small words for me), so being wrong on that wouldn't surprise me.

I took my car to highway speed earlier today after babying her into running temp. She held at 65 mph with zero problems. I'm at a loss of what's wrong. I feel like fuel is ruled out if I'm not misfiring constantly, I had money on my compression test failing on cold engine, I don't know what else to check.


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Apr 17, 2016, 6:02 PM

Post #2 of 8 (1465 views)
  post locked   Re: 01 MR2 Spyder - Diagnosing Misfire  

Why would you rule out fuel? Have you verified spark during the misfire?

There is no code that tells you an 0/2 sensor is defective, or any other part for that manner..



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



ltclutter
New User

Apr 17, 2016, 7:06 PM

Post #3 of 8 (1451 views)
  post locked   Re: 01 MR2 Spyder - Diagnosing Misfire  

In my admittedly limited experience, every fuel issue I've ever had was aggravated by putting a load on the car. If I rev up, it doesn't cause the misfire to become more frequent, if anything, it does the opposite. Was I wrong in ruling it out?

I tested for spark, but now that I think about it, the engine was warm at the time. I will give her a whirl in the morning to make sure she's had plenty of time to cool down and report back. Is there any better way to test than pulling it and grounding it?


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Apr 18, 2016, 1:57 AM

Post #4 of 8 (1437 views)
  post locked   Re: 01 MR2 Spyder - Diagnosing Misfire  

The best way is to use an adjustable spark tester. It's the only way to know you have sufficient spark. It needs to be able to jump a gap of at least 1/2".






~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



ltclutter
New User

Apr 19, 2016, 9:58 AM

Post #5 of 8 (1419 views)
  post locked   Re: 01 MR2 Spyder - Diagnosing Misfire  

Took a bit since it was raining all day yesterday and no garage or cover, but I tested and I think we have our problem.

It sparks. Perfectly. Nice, strong blue. But, it wasn't sparking often. So I pulled the one next to it and tested it. Sparked a whole lot more often.

I can't test for a bad wire myself cause all my wiring is run inside plastic covers, so I'm gonna swing by a shop or two to get estimates on replacing all the wiring running to the coils. Figure if one is frayed, cut, or whatever the others can't be too far behind. I'll update again when I know for sure baby's fixed. Thanks for the help.


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Apr 19, 2016, 10:01 AM

Post #6 of 8 (1418 views)
  post locked   Re: 01 MR2 Spyder - Diagnosing Misfire  

That could mean the spark is arcing somewhere along it's route so if you have a distributor cap and rotor, be sure to change them also.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



ltclutter
New User

Apr 25, 2016, 12:02 PM

Post #7 of 8 (1382 views)
  post locked   Re: 01 MR2 Spyder - Diagnosing Misfire  

Following up with the resolution.

So, not only was the wiring to the coil adapter cracked, but he found some wire wear all the way up to the ignition. It looks like the guy who had the car before me tried to replace some of the wiring, but instead of actually replacing the wiring, he cut some of it, left the rest, laid all the wiring, and then taped and zip tied everything back into place. There were layers and layers of electrical tape over the wiring.

Was about $415ish for diagnostic, new coil adapter, and two hours of labor. It took him closer to four and a half, but I think he felt bad he didn't have it out by the promise time.

Thanks for the help. If you want anything clarified or pictures or anything let me know.


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Apr 25, 2016, 12:06 PM

Post #8 of 8 (1381 views)
  post locked   Re: 01 MR2 Spyder - Diagnosing Misfire  

Glad to hear you got it resolved.
Closing this now as solved.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.







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