2010 lr4, 158k miles. Gap IID tool shows a misfire for cylinder #7, no other engine/petrol codes. Symptoms are reduced performance. I swapped coil from 7 to 5, cleared code, and no difference. Still misfire. Changed spark plug with new one, no difference. I inspected the harness for any cracks, no damage. The spark plug from 5 and 7 do not smell like fuel.

If I was to get a voltmeter to the injector or coil harness, what should I be reading? Voltage or resistance? And how much?

Other then that, any advice on what to do next?


PCM-Engine Petrol

• P0307-00 (AF) Cylinder 7 misfire detected
• P0316-00 (AF) Misfire detected on start-up (first 1000 revolutions)

UPDATE SOLVED: BAD CONNECTOR. Wiring was ok but the pins or wiring iside the connector itself wasn’t. Also got the wrong type of connector, but it did work for a month. You have to get this one

 

I’d do a compression test first.

it should be injector or compression issue if the plug and coil are good.

Can you view live data with your reader?

 

Yes. What readings would you like to see?

 

First do compression test on all cylinders. If 7 is more than 25/30 pounds lower, def the issue. If it is low you can put a cap full of oil in the spark plug hole and retest. If numbers come up, it’s a cylinder wall/ring issue. If they stay the same it could be a valve or something else which is a good thing.

for live data my thought was to cue up the live data screen, start it up and see if it’s a hard constant misfire on that cylinder.

good luck.

 

compression is all good. Misfire is constant on #7.

Swapped injector with new one today and still misifre. So new injector, new spark plug, swapped coils, and misfire still exists.

 

Is it only at idle or all RPM? If at idle, check PCV diaphragms.
If it is all the time, given that compression is good and you've swapped known good coil & injector, you probably need to check continuity in the coil & injector harnesses back to the ECM to make sure they are actually getting signal from the ECM

 

did you compare numbers with the other cylinders? Also might be good to do a leak down test.

if injector, spark plug, and coil all check out, it has to be cylinder related or a wiring issue.

you could back probe the connectors and compare values with an adjacent cylinder.

 

Got a magnetic tool that lights up if the coil is working. So the coil for number 7 isnt getting power at all. I did replace that ignitor connector for that specific coil so I resoldered, re-heatshrinked, and retaped it up. Still no power. So its either the connector itself or ECM perhaps?

 

solved, updated OP

 

@newdude what is updated OP?