Need Help Diagnosing Misfire :( (1 Viewer)

[GTV]

Just finished the timing belt job on my '07. I also replaced the alternator with a 180a from DC Power and replaced the spark plugs with new Denso Iridium long life from Rock Auto. Coils are Denso and were replaced by @2001LC about 96k miles ago.

Engine fired up easily and I bled the air out of the cooling system. I could hear something was a bit off though, it's running rough. Check engine light is flashing. I run the codes and see I have a misfire on cylinder number 3.

I swap the coil to a spare used coil, no change.
I swap the spark plug to one that just came out of the engine, put the original coil back on, no change.
I swap the coil again to the used coil (used coil and used plug), no change.

Used coil/plug makes no difference.

I swap the new plugs between #1 & #3, coils in original locations, no change.
I swap the coils between #1 & #3, no change.

I'm at a loss. What should my next course of action be?

 

[MongooseGA]

This is probably over my head but is there any chance the timing being off would cause a misfire? Seems odd that with different plugs and coils on the same cylinder that it persists. How is the wire going to that cylinder? Pinched, broken, or shorting on anything?

Unrelated, do all 06/07s have black intake manifolds?

 

[GTV]

This is probably over my head but is there any chance the timing being off would cause a misfire? Seems odd that with different plugs and coils on the same cylinder that it persists. How is the wire going to that cylinder? Pinched, broken, or shorting on anything?

Unrelated, do all 06/07s have black intake manifolds?

If the timing was off it would be off on every cylinder on that bank.
Wires to the coil look and feel ok.

Yes. VVTi also comes with a variable length composite intake manifold.

 

[leveeguy]

Was the battery disconnected/reconnected for all the plug and coil swapping?

 

[GTV]

Was the battery disconnected/reconnected for all the plug and coil swapping?

Yes. Battery was purchased last month, I had it disconnected since Monday while I was working on it.

 

[nissanh]

After you installed an old plug and coil, did you clear the DTC? if not, try that. I had a faulty coil and got a used coil and the code was still there. then I cleared the codes and all is good.

 

[2001LC]

First step with any DTC. Clean codes, see if comes back.

98-100 times, issue after a service. Is related to service.

I can think of 3 possibilities, since not #3 plug or coil.

• #3 Fuel injector (FI) gone bad. Discount FI, see if RPM drops, as it should. No change in RPM, 80% changes FI bad.
• Short in or to ECM. Test circuit to/from coil and FI.
• Valve damage, when crankshaft turn, while T-belt off. Borescope inspection and compression test #3.

BTW. Unrelated, but need inspecting/done:

S.A.I. Filter Modification, in VVT engines. To prevent its failure! Alert Alert!

We've a $2.00 part in the S.A.I. (secondary air injection) system of the VVT engine, that is taking-out ~$7,000.00 $15,000 $25,000 (inflation) in parts. WOW! I've a very easy and cheap WORK AROUND. You are going to love this ;) This thread is dedicated to the 4.7L 2UZ-fe VVT engine, in the...

forum.ih8mud.com

 

[GTV]

After you installed an old plug and coil, did you clear the DTC? if not, try that. I had a faulty coil and got a used coil and the code was still there. then I cleared the codes and all is good.

I did clear the codes, but not after every test that I did. I will test and confirm again. It still felt rough though, I would assume if I fixed it it would smooth out but the code would remain.

First step with any DTC. Clean codes, see if comes back.

98-100 times, issue after a service. Is related to service.

I can think of 3 possibilities, since not #3 plug or coil.

• #3 Fuel injector (FI) gone bad. Discount FI, see if RPM drops, as it should. No change in RPM, 80% changes FI bad.
• Short in or to ECM. Test circuit to/from coil and FI.
• Valve damage, when crankshaft turn, while T-belt off. Borescope inspection and compression test #3.

BTW. Unrelated, but need inspecting/done:

S.A.I. Filter Modification, in VVT engines. To prevent its failure! Alert Alert!

We've a $2.00 part in the S.A.I. (secondary air injection) system of the VVT engine, that is taking-out ~$7,000.00 $15,000 $25,000 (inflation) in parts. WOW! I've a very easy and cheap WORK AROUND. You are going to love this ;) This thread is dedicated to the 4.7L 2UZ-fe VVT engine, in the...

forum.ih8mud.com

I don't understand what you mean by "Discount FI, see if RPM drops, as it should."
I was thinking I could swap injectors between 1-3 and see what happens, but if there's an easier way I'm all ears.

Not sure how to test circuit to/from coil and FI

Valve damage has crossed my mind. I've built HP engines in the past so I know what valve interference feels like. Unless the interference was incredibly slight and just barely enough to tweak a valve. Anything is possible of course but it's hard for me to imagine that is what happened.

 

[nissanh]

did you spun the engine by hand before firing up? felt any resistance?

 

[2001LC]

D

I did clear the codes, but not after every test that I did. I will test and confirm again.



I don't understand what you mean by "Discount FI, see if RPM drops, as it should."

Pull wire housing block, off #3 FI. Since #3, it easy to pull off while engine running. If injector work as it should. RPM will drop when power (wire) removed. If on the other hand. Fuel injector not working as it should. Disconnecting wire housing block from it. Will have no effect (RPM remain the same).

I was thinking I could swap injectors between 1-3 and see what happens, but if there's an easier way I'm all ears.

Requires, removing fuel rail. PITA just for a test.

Not sure how to test circuit to/from coil and FI

You'll find in diagnostic section of FSM.

Valve damage has crossed my mind. I've built HP engines in the past so I know what valve interference feels like. Unless the interference was incredibly slight and just barely enough to tweak a valve. Anything is possible of course but it's hard for me to imagine that is what happened.

When I have a misfire DTC, and confirmed not a bad spark plug or coil. Checked fuel injector.
I'll check for spark. While plug out. I check compression and borescope cylinder.

 

[GTV]

did you spun the engine by hand before firing up? felt any resistance?

Yes I did, everything felt normal.

D

Pull wire housing block, off #3 FI. Since #3, it easy to pull off while engine running. If injector work as it should. RPM will drop when power (wire) removed. If on the other hand. Fuel injector not working as it should. Disconnecting wire housing block from it. Will have no effect (RPM remain the same).

Requires, removing fuel rail. PITA just for a test.

You'll find in diagnostic section of FSM.

When I have a misfire DTC, and confirmed not a bad spark plug or coil. Checked fuel injector.
I'll check for spark. While plug out. I check compression and borescope cylinder.

View attachment 3866375

Disconnecting the injector is a great place to start. Then I'll check spark as well. Hopefully tomorrow but maybe not, I've gotta step away from this thing for a moment.
Thanks again Paul, your guidance is very much appreciated.

 

[baltistyle]

Do you have a noid light you can hook up to check the injector harness? And do you have an electrical tester to test the wires from ecu as 2001 suggested?

 

[2001LC]

I'll add. It is possible a wire or sensor issue with cam or crank sensor. But that's a 1 in 100 shot, and pure speculation on my part. Since you should see all cylinders with issue, or crank no start. Not just #3 DTC. But engine run time and number of starts matters, in when and which DTC trip. We need 3 occurrences, under certain conditions for most DTC. Which is defined in diagnostics section of FSM, under the DTC found.

 

[2001LC]

Any progress?

 

[GTV]

Nope, I’ve had company all week until this morning and I’m very hungover today Tomorrow looks promising though.

 

[TahoeZ]

I had the same issue after my last timing belt replacement. Swapping plugs and coils with a different cylinder had no effect. Ended up being the injector. Figured it was just a coincidence. This makes me think it was somehow related but I can’t figure out how. Follow up when you figure it out.

 

[2001LC]

"coincidence" do happen!

 

[GTV]

Any progress?

I disconnected the #3 injector while running and it made no difference. Still need to do a spark test.

 

[FxFormat]

Can you swap injectors with another cylinder and see if it’ll jump the misfire to another location? Next gotta do a compression test and see what it is.

I disconnected the #3 injector while running and it made no difference. Still need to do a spark test.

 

[GTV]

Can you swap injectors with another cylinder and see if it’ll jump the misfire to another location? Next gotta do a compression test and see what it is.

I was thinking I could swap injectors between 1-3 and see what happens, but if there's an easier way I'm all ears.

Requires, removing fuel rail. PITA just for a test.

Gonna test for spark first. If it's sparking then the injector is definitely the culprit.