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Is it the ECM

07 Camry. 128k. Original owner. Problem began 6mo. ago. Engine seemed starving for fuel. Fuel filter and pump replaced (cause that’s where shade tree guys start). Diognostic tool purchased and this is where it gets interesting. The code was “misfire in #2 cylinder “ 002 I believe. After every item replaced the symptoms went away … for a while. I’m talking ignition packs, plugs (twice) and injectors. The last fix lasted 3 weeks. My wife reported she barely made it home today. Try to accelerate and the car tries to die accompanied by a flashing check engine light. I simply cleared the codes took it for a test drive an it ran like a freaking TOP! And it will for two or three weeks gradually getting worse. What else could it be besides the ECM. I’m at my wits end.

A flashing Check Engine light indicates a major misfire is occurring.

What were the codes you cleared?

Tester

P002 I believe. “Misfire in #2 cylinder “

You apparently had P0302 . . . misfire #2

There’s still quite a bit more diagnosis to be done . . .

hook up a vacuum gauge at idle

compression test dry and wet on all cylinders

injector balance test for all injectors

use a noid lite kit . . . are the injectors being properly pulsed?

check out the wiring to the coil(s) and injector(s) . . . any obvious rat damage?

and so forth

there’s no reason why a bad fuel filter and pump should affect only #2 cylinder . . .

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I did do a compression test, the only one I know how to do, and the cylinders checked out. Why would the problem go away once the codes were cleared?

We need numbers dry and wet, please

151 to 155. How do you do it wet

Again. Why would the problem go away just because the code was cleared if there was a physical problem?

I used to carry a spare computer and when I had a problem I couldn’t find would swap it out. Once I even did it when I was dead on the side of the road. In 500K miles I never had a bad computer. Not saying it doesn’t happen but likely something else. The only other thing I would do is check the pins and connectors for good contact and maybe some dielectric grease, then concentrate on number 2.

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statistically speaking, the engine control module is rarely the problem . . .

assuming you have the 4-cylinder, your compression is fine

142psi is the minimum, so you’re in good shape

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When a misfire is detected the PCM can shut off the fuel injector for that cylinder to protect the catalytic converter, when this occurs shutting off/restarting the engine will enable that injector if no misfire is detected.

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Here’s a few possibilities for a misfire on a specific cylinder

  • problem w/fuel injector or its electronic pulse input. use noid test light or o-scope to verify injector is being pulsed the same as the others, ohm-out electrical connection between ecm and injector, swap injectors between two cylinders to see if problem moves to the other cylinder

  • compression problem. if compression test passes (as in this case), could still be a sticking valve that doesn’t stick during a compression test for some reason. supposedly there’s a known problem called TCS “Toyota Camry syndrome”, has been mentioned on the Car Talk radio show, caused by sticking valves.

  • spark plug problem. swap plugs between two cylinders, similar to swapping injectors.

  • coil problem, test as above.

  • ignition timing problem, possibly caused by faulty crank or cam position sensing. o’scope testing would prove/disprove.

  • this last one wouldn’t normally cause a single cylinder misfire, so less likely, but intermittent misfiring can be caused by a faulty cat. The ceramic insert can break and sometimes the two parts lines up, and sometimes it doesn’t, depending on how it is jiggled. temporarily removing the cat is one way to prove/disprove.

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My 1993 Toyota pickup had similar symptoms several years ago. Tested everything myself and found all sensors and adjustments were in line per the shop manual. Ended up taking it to the dealer as a last resort where they replaced fuel pump, injectors, ignitor, plugs wires, checked compression, valve adjustment, etc., (threw parts at it) but could not find the problem. 6 weeks later I brought it home, unrepaired. The only thing there is no test for is the ECU which according to the shop manual is diagnosed by replacing with a known good unit. I replaced it with one from a wrecking yard and it has run fine since.

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The problem turned out to be a small leak in the head gasket. As the car would sit the coolant system pressure pushed coolant into the #2 cylinder eventually causing a misfire which the ECM reacted to. My mechanic scoped the cylinder to find the leak. I’m a little baffled by the compression check but We added a bottle of Kseal and with three or four days of driving there are no more check engine lights or codes. Thank you all for your input and your willingness to help. Jay.

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