Problems with 1994 Toyota Corolla.

[Mark]

I have a 1994 Toyota Corolla SE, 1.8L engine with an AT with OD and 231K miles on the clock. Runs very well, doesn’t use or leak oil, good on gas, and the transmission is solid. However, about 7 months ago the check engine light came on, accompanied by an occasional, random misfire. The error code given, code 12, refers to “engine revolution signal missing.” The warning light been on ever since, despite my attempts to clear it, and the miss, while very uncommon, is still there, too.

Worth noting is when these problems first occurred. I was behind a farm tractor on US 35, moving at 15-20 MPH, for some 6 or 7 minutes. When an opportunity to pass arose, I took it. I floored the accelerator, dropping the transmission into first gear, and away I went. This is when the check engine light first appeared, and the occasional misfires began to occur within a minute of two thereafter. These misfires have been very rare of late. In my trip to Eric’s last week, a round trip of over 100 miles, I did not detect a single misfire.

So what’s the problem(s)? Intake manifold gasket? Ignition coil? Two heads are thicker than one, so I appreciate any and all comments.

Topic

[Joeseph Mama]

since you have a distributor system, I doubt you have a crank sensor, but you will have something similar; possibly a hall effect sensor in the distributor. The ECU can detect cyl #1 TDC when an obvious ‘space’ in the reluctor is detected.

I’d pull the distributor cap and attempt to identify the magnetic pick up. Begin simple electrical diagnosis: look for corrosion or burnt points.

[Its me]

The sensor is in the distributor…

As for the misfire problem, can possibly need new plugs and wires or distributor cap and rotor…

Also, Toyota coils of this era and age are known for cracking and causing issues… The large orange opaque item in the photo is a coil… note the crack at the bottom of it… Yours should be similar to this..

[Mark]

Hey, Eric: You may recall, during your meet-up this summer, that I asked you about a problem I was having with my ’94 Corolla. It was throwing code 12 and missed occasionally at idle. I decided to do a tune-up on it, as it was surely in need of one. Anyway, I pulled the distributor cap and rotor button, noticing that the distributor was leaking oil, and that there were copper wire fragments inside the distributor cap. Sort of a no-brainer. The distributor was bad, so I replaced it today. Reset the computer, and the check engine light is gone–YEA! Problem solved. I’d be remiss if I didn’t acknowledge that Scott Kilmer suggested that as the problem, saying “replace it before it fails, cause it will!” Keep up the good work, Eric. I look forward to seeing you again next summer.

[Author]

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