Misfire Mystery

[bdrlgion]

'97 6cyl T4R, 250k mi. Love "Big Red" and this one's giving me a case of the Mondays.

I started smelling raw gas about a week ago. Not constantly and not super strong, but a whiff here and there. Then three days ago the shudder started - fluctuating RPMs, rough especially at idle. Then two days ago the CEL came on - code P0302/misfire cyl 2.

So far, this seemed identical to my experience w/ a faulty injector (diff cyl, though) a year back. Swapping that injector was relatively easy, and solved the problem, as it was on the passenger side with good clearance.

Pulled spark plug, electrode looks fine, but motor oil on the plug. Doesn't smell like gas, though I don't have a great nose.

Swapped coil pack to see if issue followed the coil, no dice. Cleared codes, restarted engine, same code popped (P0302/misfire cyl 2).

What's this sound like so far? Valve cover gasket? Injector? Something else? Where would you go from here?

 

[spartacus]

'97 6cyl T4R, 250k mi. Love "Big Red" and this one's giving me a case of the Mondays.

I started smelling raw gas about a week ago. Not constantly and not super strong, but a whiff here and there. Then three days ago the shudder started - fluctuating RPMs, rough especially at idle. Then two days ago the CEL came on - code P0302/misfire cyl 2.

So far, this seemed identical to my experience w/ a faulty injector (diff cyl, though) a year back. Swapping that injector was relatively easy, and solved the problem, as it was on the passenger side with good clearance.

Pulled spark plug, electrode looks fine, but motor oil on the plug. Doesn't smell like gas, though I don't have a great nose.

Swapped coil pack to see if issue followed the coil, no dice. Cleared codes, restarted engine, same code popped (P0302/misfire cyl 2).

What's this sound like so far? Valve cover gasket? Injector? Something else? Where would you go from here?

Swap out the spark plugs with dual electrode ngk or denso see if it help.
Denso K16TR11, NGK BKR5EKB-11, toyota part 90919-01192

 

[Bad Luck]

'97 6cyl T4R, 250k mi. Love "Big Red" and this one's giving me a case of the Mondays.

I started smelling raw gas about a week ago. Not constantly and not super strong, but a whiff here and there. Then three days ago the shudder started - fluctuating RPMs, rough especially at idle. Then two days ago the CEL came on - code P0302/misfire cyl 2.

So far, this seemed identical to my experience w/ a faulty injector (diff cyl, though) a year back. Swapping that injector was relatively easy, and solved the problem, as it was on the passenger side with good clearance.

Pulled spark plug, electrode looks fine, but motor oil on the plug. Doesn't smell like gas, though I don't have a great nose.

Swapped coil pack to see if issue followed the coil, no dice. Cleared codes, restarted engine, same code popped (P0302/misfire cyl 2).

What's this sound like so far? Valve cover gasket? Injector? Something else? Where would you go from here?

OEM recommended spark plug is dual electrode, but that shouldn't have any effect on spark in your case. I would start with plugs and wires since they are relatively cheap and spark plug replacement interval is 30k miles.

Valve cover gasket isn't going to cause a misfire in one cylinder. If there was oil in the spark plug tube then you'll need to replace the spark plug tube seal(s) in the valve cover if you wanted to fix that.

 

[Toaster134]

I'd begin with starting it and let it idle, then walk around smelling for gas. Any signs of leakage at fuel rails, fuel pressure regulator, the hard lines? Fuel pump acting as it should? Try running through some of the fuel system diagnostics in the Field Service Manual and see if anything is acting out of sorts.

 

[bdrlgion]

I wish I had more time to troubleshoot myself, but didn't, and needed the truck operable asap. Took it to the shop, gave them the run-down, and a new set of wires later - back in business! One of the spark plug wires wasn't operating, and that took care of it.

 

[ke263565]

I'm having a minor idle issue. New plugs/wires/coils. I just get this occasional dip in RPM. I think my injectors might be just old. Did you have any issues with that?

 

[spartacus]

I'm having a minor idle issue. New plugs/wires/coils. I just get this occasional dip in RPM. I think my injectors might be just old. Did you have any issues with that?

Testing and cleaning the maf might help also the throttle body.