1993 4runner #3 Cylinder Miss Fire
07-18-2023, 07:26 AM
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1993 4runner #3 Cylinder Miss Fire
Hey Everyone,
I have a 93 4runner 3VZE that I have been having some trouble with Cylinder #3. Below is a list of everything I have done. It also is running rich which I think the engine is compensating for the bad cylinder.
Replaced Cap & Rotor along with plugs and wires.
Tested all injectors and the one on #3 was bad but after being replaced nothing changed. Also went back in and swapped the new injector to another cylinder that I knew was performing correctly.
Compression was checked and that is reading correctly.
When I tested to see if the issue was fixed after the tests I would rev the RPM's and removed the plug wire and it has no effect on the engine.
I also swapped out the Ignitor and that did not fix the issue.
Plan on testing the injector wire with a noid light next.
I am wondering if the ECU could be the issue or the rocker is stuck. Any insight on this would be much appreciated
I have a 93 4runner 3VZE that I have been having some trouble with Cylinder #3. Below is a list of everything I have done. It also is running rich which I think the engine is compensating for the bad cylinder.
Replaced Cap & Rotor along with plugs and wires.
Tested all injectors and the one on #3 was bad but after being replaced nothing changed. Also went back in and swapped the new injector to another cylinder that I knew was performing correctly.
Compression was checked and that is reading correctly.
When I tested to see if the issue was fixed after the tests I would rev the RPM's and removed the plug wire and it has no effect on the engine.
I also swapped out the Ignitor and that did not fix the issue.
Plan on testing the injector wire with a noid light next.
I am wondering if the ECU could be the issue or the rocker is stuck. Any insight on this would be much appreciated
07-24-2023, 03:28 PM
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It's unlikely the ECU is bad though the noid light will either verify the injector is or isn't getting the signal. Could also be a damaged wire if its not.
Have you verified the plug is sparking? Which rocker are you talking about? This engine is DOHC, so no rockers or push rods. Bad cam lobe or a receded valve perhaps, but compression test should show an issue.
You say compression is good. 10% of 100psi and 10% of 60psi could be the difference between running or not. What were your numbers?
Lastly, did this happen before or after you replaced parts?
Have you verified the plug is sparking? Which rocker are you talking about? This engine is DOHC, so no rockers or push rods. Bad cam lobe or a receded valve perhaps, but compression test should show an issue.
You say compression is good. 10% of 100psi and 10% of 60psi could be the difference between running or not. What were your numbers?
Lastly, did this happen before or after you replaced parts?
07-25-2023, 06:24 AM
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"Single" Overhead cam (but a single cam for each bank). DOHC is for 4 valves/cylinder.
If you have an (ignition) miss, the unburned fuel will make it appear to be running rich. The O2 sensor can pick up the un-used O2 and then go even richer. So first, check for ignition miss. Put the inductive pickup of your timing light on each plug wire. If the timing light flashes the plug fired.
If you have an injector stuck closed (or not getting signal), again you'll have too much O2 in the exhaust. A noid light could help. (FWIW, remember that all injectors open at the same time. Also, the ECU opens the injector by grounding one side, so the injector has battery voltage to ground on both terminals until the ECU calls for it to open.)
If you have an (ignition) miss, the unburned fuel will make it appear to be running rich. The O2 sensor can pick up the un-used O2 and then go even richer. So first, check for ignition miss. Put the inductive pickup of your timing light on each plug wire. If the timing light flashes the plug fired.
If you have an injector stuck closed (or not getting signal), again you'll have too much O2 in the exhaust. A noid light could help. (FWIW, remember that all injectors open at the same time. Also, the ECU opens the injector by grounding one side, so the injector has battery voltage to ground on both terminals until the ECU calls for it to open.)
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