Hi all!

This has been an issue for a while but not bad enough to make me drop everything and fix it. Now that spare time is bountiful, finally getting to some Land Rover projects.

Issue: Rough idle with misfires according to Hawkeye Total. When the truck is idling, you can feel the engine slightly bogging and bucking a little bit, you can feel it in your butt when sitting in the seat and hear the engine bog down a little. Also there is a slight ticking from the Driver side of the Engine but I doubt it is related.

It has only caused the check engine light to come on once. This was after I changed then oil and I was letting it run for a while and after I came back the following codes were present: P0300, P0304 (cyl 4) P0303 (cyl 3), P0305 (cyl. 5) I cleared them and during normal operation they don't come backbut they might be helpful in diagnosing.

What I have tried:

• Smoke test: I did a smoke test today and found some very small vacuum leaks. I tightened some clamps and added some Gorilla tape as a short term check to see if the problem went away. It did not.
• MAF: A while ago I bought a new MAF to see if it would change it. Didn't help.
• IACV: Cleaned out IAVC until it was visibly clean and spun easy inside.
• New Battery: the battery died a while back and the new battery didn't help.
• Chevron 91 Gas has only been used since the engine has been rebuilt.
• Engine has 10k miles or so and oil is clean as a whistle. Probably been changed half a dozen times in that time frame.

Some Data From the Hawkeye:
Battery Voltage: 13.77
Engine Speed: 640 RMP
Throttle Angle: 0.00%
MAF Sensor: 25 kg/hr
Air Temp: 27
Injector Time: 4.3 ms
Desired Idle: 660
Idle Air: 107.4 kg/h
Ignition Angle: 12.75
Ign. Dwell Angle: 0
Engine Torque: 7.8
Load Air: 1080 kg/h
Fuel Trim A: 1:1
Fuel Trim B: 1:1
Knock Correction: -1.5
Ses DS Bank A: .820 V
Sens DS Bank B: .851 V
Sens US Bank A: .815 V
Sens US Bank B: .820 V
O2 Heater Res US: 9.81 Ohm
O2 Heater Res DS: 9.81 Ohm
Misfire Summary: 112
Misfire Cyl 1: 11
Misfire Cyl 2: 18
Misfire Cyl 3: 33
Misfire Cyl 4: 28
Misfire Cyl 5: 24
Misfire Cyl 6: 26
Misfire Cyl 7: 31
Misfire Cyl 8: 20
Engine Rough (1-8): going between 0 and 4, mostly between 0 and 2
Purge Adaptation: -32

One thing to note is as soon as I rev it up a little to 1000 rpm, the misfires go to 0 and it feels very smooth.

Could plug wires being crossed be a problem? Could there be a vacuum leak that my smoke test didn't find? Time to replace plugs, wires, o2 sensors?

Well thanks for reading and I am open to all ideas.

Thanks!

 

Probably an exhaust leak = the ticking at the Y pipe. When you replaced the MAF did you reset the adaptive settings with the Hawkeye? It's always a good idea whenever you are messing with the MAF, or O2 sensors to reset the adaptive settings. It will go to a default state, and then learn from that point on. For example say the MAF was indeed bad and not reading properly. The adaptive settings are now stored with data from that MAF. If you just slap in a replacement it will not just re-learn for quite a few drive cycles.

Have you verified the IAC is clean and it rotates smoothly (off the D2 and in your hand)? If it's badly gunked up it could be completely locked up and not allowing the D2 to idle smoothly. Wire wise spray em down with some mild soap/water at the boots. If it cranks up and you hear ticking then the boots are dry/cracked and they're causing misfires.

 

Mine does the same with rough idle and occasional misfire codes. Seems like a vacuum issue but nothing obvious. This post reminds me I should sort things out.

 

Also make sure the 6 upper intake bolts (2 short & 4 Long) are tight. I've seen plenty of upper intake bolts on Bosch engines loose and causing vacuum leaks.

 

Hey Best! Hope all is well.

How can I diagnose / resolve the exhaust leak?

Yes, I reset the adaptive settings a few times hoping that it would fix things. The MAF was replaced at least 1000 miles ago so it should have adapted by now anyway.

Yes, I took apart the IAC and sprayed carb cleaner in there until it was clean and rotated back and forth when I twisted it.

Regarding the wires, Should I spray them at the end with the spark plug or the other side? I have not heard of this trick before.

 

Lightly spray em down near the spark plug. That is the side which the boot breaks down over time due to the heat. Exhaust leak wise it's probably the gasket where the 6 studs/nuts (3 per side) at the exhaust manifold/Y Pipe connection are. Or it could be the exhaust manifold gaskets themselves. I personally look for black soot or run some seafoam thru the intake and then enjoy the show and you'll find your exhaust leak lol.

 

So I came across another thread said that someone got rid of their rough idle by switching from a Magnaflow exhaust back to stock. I honestly hate how loud the truck is with the magna flow anyway.

I ordered the whole stock setup from Lucky8 and will swap that on. I will report back to see if there is any difference. I will report back.

 

Have you tried some injector cleaner fuel additive? I truely doubt an exhaust is going to cause the issues you're describing.

 

Yeah, l'd dump some injector cleaner in and drive it like you stole it. I'd even start fresh by clearing any codes, after making note of active ones.

 

Had this happen.
Take out your purge valve and plug the intake port
sometimes the purge valve sticks open and let’s vapours go into your intake causing havoc on fuel air mixture and really rough idle at times