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I have a 1991 Toyota pickup with a 22RE engine and manual transmission. It recently developed a miss, especially when under load that has been getting worse and worse. I had it diagnosed and was told to replace the distributor. I ended up replacing the distributor,coil,coil wire, and ignitor, none of which helped. The spark plugs, cap, wires and rotor were also replaced recently. Now the dealer is re-diagnosing it and says there is only 1 volt at a number of test points that should have 12 volts so there appears to be a bad wire someplace which could take several hours and dollars to locate. There also appears to be some arcing going on around the tower of the new ignition coil. This arcing was also present around the old coil. The exhaust also smells lean to me. It also runs slightly better when the engine is warm then when first started. Could the ECM cause this? Any thoughts on what would cause this miss or where to start looking would be appreciated. Thanks a bunch.
Answer -
Hello Dan, welcome to my expert page.
My main concern is the arcing on the ignition coil, this indicates that there is very high resistance somewhere in the secondary circuit,but since all of those components were already replaced I'm kind of at a loss. Basic electric theory tells us that current always takes the path of least resistance so instead of the spark going to where it is supposed to ie: one of the spark plugs, it choses to short itself to ground at the coil because the other path has more resistance, the question is why?
Given the information you gave me, I don't see how it could be an electrical problem in the secondary circuit.
Yes, the ecu could be the cause, but remember all it does as far as engine misfire is concerned is turn the injectors off and on but yes it could be the problem but most of the time it's last on the list of possible causes.
Just let me know one thing, does the engine miss at idle or only under load?
Hello Ted,
Thank you for the quick response.
In answer to your question, it seems to miss while under load, however the arcing around the coil is present at an idle.
I also had some more diagnostics done at the dealer yesterday.
They claim that at the BAT and and a couple of other terminals like the +B1 or +B2, or something like that, of the ECU they are only reading 1.5 volts when there should be 12 volts. They suspect a bad wire somewhere in the wiring harness that runs from the fuse block on the right fender well under the hood, along and through the intake to the ECU and other components.
I hope this helps. Any ideas on where to find this needle in a haystack?
They claim at the dealer it could cost up to $1,000 to find the problem, probably more than the truck is worth.
Thanks again for any help or thoughts you might have on this.
AnswerIn that case I agree with the dealer, there should be 12volts to B+ terminals of the ecu, if there are only 1.5 volts there is a problem, the thing I don't understand is that unless the ecu has at least 10.5 volts it will not turn on the injectors and the engine will not run, but your engine runs,I still see a problem with the coil spark jumping, this is not related to the computer and this problem lies in the secondary ignition circuit, maybe you should get another opinion from another dealer or repair shop, you need to fix the problem at the coil first before condemning the ECU or wire harness.
