Hi All,

Some background: I have a 92 ES300 which is intermittently missing on cylinder #4. The injector for #4 intermittently gets held open, dumping in enough gas to not burn properly, sending raw gas down the exhaust, causing rough idle, poor mileage, etc.

In doing the diagnostics, I go through all the ECU injector terminals and they all read good voltages, except #40 (injector 4), which will read well for a while, but will then fluctuate going down to 1.5, back up to 7, then back down, once in a while getting back up over 11. This really seems to mirror the behavior of the intermittent misfire.

OK, so the question....

Is this characteristics of ECU problems others here have had, or is there resistance, breaks or other issues building up somewhere else in the harness that I should look for. All the continuity tests seem to come out fine, I just hate to get a new computer when there might be a wiring problem elsewhere.

Thanks in advance,

Ceeb

 

At this point, before focusing on the ECU as being the problem, I would lean towards the Injector as being the problem.

If I were you, I would swap injectors, say 2 and 4, than see if the problem follows the injector or not.

Phil

 

Yes, thanks. I did start at the injectors, pulling them and cleaning them, swapping one for the other, etc.

I should have mentioned going through the ignition and injectors before troubleshooting the injector circuits.

Thanks!!