2.7L Misfire in Cylinder #4

Hi guys, I’m struggling to solve a misfire in cylinder #4 on my 2002 Tacoma with 2.7L 3RZ engine. Could use some help.

Background:

4x4 with 220,000 miles. Has had CEL for a while with EVAP related codes P0441, P0446. Have been living with that for several months, no noticeable impact to performance. Then it started running noticeably rougher at idle for 1-2 weeks. At this time also started getting P1133 – which is A/F Sensor Circuit Response Malfunction (Bank 1 Sensor 1).

Then all of sudden while driving on the highway engine started to misfire bad and CEL started flashing. Drove 1 mile to next exit, pulled over and checked codes. Registered a misfire in cyl 1, 3, 4. Limped it home (15 mins away) and started to troubleshoot.

Troubleshooting:

Cleared codes and let engine idle. Constant hard miss, CEL flashing. Checked for new codes. Only misfire in cyl 4. Repeated this test several times – it was always only just cyl 4. Started to wonder if problem is isolated to cyl 4 and driving with unbalanced engine could have triggered the misfires in other cylinders as in initial codes.

Checked compression in all 4 cylinders.
#1 – 175psi | #2 – 150psi | #3 – 175 PSI | #4 – 180psi

Seemed like valves were good.

Moved on to ignition and swapped coil packs and spark plugs from cyl 4 to cyl 1. Cleared codes and repeat. Still only misfire in #4.

Next Fuel injectors. Removed the injectors and cleaned/tested each with pressurized carb cleaner and a 12v battery. The #4 injector worked, but seemed to spray more of a stream than a mist. After several cycles of carb cleaner it looked more like a mist. The other 3 all seemed to mist everytime.

Re-installed injectors but swapped #2 and #4. Cleared codes and tested. NOW getting misfire in cyl 2 AND cyl 4. Strange. My theory at this point was something was still wrong in cyl 4, and that problem cooked the #4 injector which was now failing in cyl2. Either way decided I should replace injectors. Got 4 brand new Denso injectors from FiveO motorsports (good price at $57 each). Replaced injectors and Fuel filter.

After this the engine still ran very rough, but did not throw CEL even after idling for 15 mins. Then took it for a short test drive. Hard to tell if getting a constant hard misfire. Seem to alternate between rough and really rough (though never smooth). After about ½ mile CEL started flashing again. Checked codes and still getting misfire in cyl 4. Also had a new code P0171 System too Lean (Fuel trim). HOWEVER, realized when putting it back together I forgot to clamp down the airbox lid, so it was slightly loose. Not sure if that could have been related. I will clear codes and repeat that test next.

But I’m starting to think this is a fuel pressure problem. Perhaps the fuel pump is failing? The new injectors and fuel filter could have made a slight improvement, which is why it took 15+ mins to throw the code instead of immediately.

Any tips on how to test fuel pressure on the 3RZ? There is no shrader valve.

I was thinking of purchasing this gauge that bolts directly onto the fuel rail Fuel Pressure Gauge Kit 2RZ/3RZ (lceperformance.com), but looking for simpler solution if possible.

I’m also wondering if bad gas could be a factor. There’s a quarter tank in there. Maybe I should siphon it out and put some fresh fuel in.

Looking for any other suggestions you might have. I need to get my truck back on the road to drag my dirtbike around!

Thanks

 

I noticed reading your post that you didn't list changing your spark plug wires. I just fixed a misfire code on my 5VZ engine by replacing the spark a plug wire with a spare. I've since installed all new wires and plugs. you might want to look at changing your wires.

 

2002 should be coil on plug

 

Yes, sorry I should have clarified that. This is distributorless with coils on plugs. Thanks for the suggestion though.

 

My bad, I was just throwing out ideas. I've never worked on a 4 cyl, so I thought they might be similar.

 

Hi guys, I have an update

I rented a fuel pressure gauge and plumbed it inline as shown in the picture. I'm only getting 5psi when the motor is running. On my jeep the same gauge reads about 50psi. I read the 2.7L should be 31-37psi when running.

So I was thinking Fuel Pressure Regulator or Fuel pump is causing low pressure. I just replaced the FPR since that was easy. No change.

Before I go for the fuel pump, I want to make sure I am getting an accurate reading with the gauge. I realized the fuel flows into the back of the fuel rail and then out the FPR, and I plumbed the gauge in AFTER the FPR. Could it be normal to have such low pressure on the exit side of the FPR??

I realized the aftermarket gauge that LCE sells installs under the FPR so would not have this problem.
https://www.lceperformance.com/Fuel-Pressure-Gauge-Kit-2RZ-3RZ-p/2019121.htm


Hoping someone has experience with this... before I open the can of worms related to the fuel pump... Thanks!

 

You need to be on the supply line to check fuel pressure, it looks like you are on the return line. You will see little to no pressure on the return line, I seriously doubt the engine would even run on 5 psi of fuel pressure.

 

Thread couple years ago mech made the checker by gutting and old pressure reg so pump full pressure gets thru to that guage...
I saved my old reg just to do that....one day.

 

Do you have coolant in the plug well? This happened to me on my F150 due to a cracked intake manifold (could also be bad manifold gasket). Caused misfires.

 

OK I had a feeling that was the case, thank you for confirming. I'm going to get the LCE pressure gauge then to be sure before moving on.

 

interesting idea. I wonder if it would even build enough pressure without the FPR?

 

When you say in the plug well, like around the top of the plug when it is installed? If so no, its dry.

 

Yeah that's what I meant, if no, then great.

 

ok got it, thanks for the suggestion

 

Unless I'm missing something I'm not sure what good that would do other than tell you the max pressure the pump can supply, it's not gona tell you if it can pump enough volume to run the engine and it's not really good for the pump to block off the return line.

 

If nothing else works, I'd suggest new spark plugs and coil/boots. I know you said you swapped them in two cylinders and still got a misfire in #4. Could have misdiagnosed which had the misfire after swapping if you didn't clear codes before checking again? Maybe? I ran into this (also in my F150 later). Had a bad boot. Definitely not the most experienced one on her to give suggestions but I have nothing else to do at the moment and this be my 2 cents.

 

Thanks, the plugs are relatively new, 10k or so and they are the expensive iridium? ones. I def cleared the codes in between tests, and actually I swapped the plugs around too. Thanks for ideas tho.

I ordered the LCE pressure gauge, should be in early next week and I'll post an update.

At this point I hope it confirms low pressure and I will pursue the fuel pump. If pressure is good I'll be stumped!

Thanks

 

Have you ever changed the fuel filter in this vehicle ???

 

Yep I replaced it with the fuel injectors, used oem. After replacement of both the engine runs noticeably better, but still not good. alternates between rough and really rough, gets worse with load.

 

Any update?