Greetings All, I recently bought a D2 and brought it to Maine. It has minimal rust, so I figured an undercoat was a good idea, the salt up here is crazy. Undercoating seems pretty common up here and I went to the local mechanic. Not doubting the job they did, however, when I got the truck back it was running noticeably rough. I'm not 100% sure on the brand name but I think it was "No Drip" from Canandian Oil or something.

Symptoms: check engine light flashing intermittently, lots of vibration at a variety of speeds but most noticeable when accelerating from 30 to 50 mph and at idle. When I let off the gas to coast it runs smooth.

I took it back to the mechanic. Probably important to mention that my check engine light was ON before the undercoat, but NOT flashing, and the engine was NOT running rough. They were basically like "no clue, must be a coincidence". They ran the codes and it came back with multiple cylinder misfires. We talked through possibilities but in the end they told me they're not sure what is the cause and could be many things, and asked me to try some self-diagnosis, such as fuel injector cleaner additive. They also suggested it could be the O2 sensor, mass airflow sensor, maybe a bad catalytic converter. I'm not convinced that the undercoat isn't the cause.

One other note - a lot of different extended family members have been driving the car recently, so another suggestion is that someone filled up with a lower octane gas. Or that I filled up at a station that had a water leak in their fuel storage, which apparently is relatively common here with lower use Premium octanes.

What do you think?

I'm new to owning a Land Rover, so please excuse my ignorance. Very curious everyone's thoughts, thank you in advance!

 

Almost always ignition related. Start with this https://landroverforums.com/forum/di...sfires-126863/

 

Invest in your own scanner, you'll be glad you did, then tell us the code numbers and meanings and tackle the codes. Clear the codes after writing them down, then see which come up first. Follow Extinct's advice and check the ignition system first. Sometimes the generic random mis-fire code P0300 comes up even if only one cylinder is missing. I think the flashing CEL means the misfires are bad enough to potentially damage the catalytic converters (CATs). Get the best scanner you can afford.

 

Thank you both.

@Extinct thanks for the write up - looks like a great way to approach the problem, I'll give it a shot.

I'm thinking that the sensors, O2 and MAF, or valves might be the most susceptible to damage by some misplaced undercoating. Depending on where they're placed. I'll have a look at that first perhaps.

@JohnZo great call. I did get an iCarsoft one...not sure it's a great one. Here's what I got:

0300 - multiple misfires
0301 - misfire cylinder 1
0302 - misfire cylinder 2
0307 - misfire cylinder 7
0455 - evap emission system (large leak)
1300 - random misfire

Makes sense to clear and then monitor which appears first.

It'll take me a bit to get to all of this but I'll report back. Thanks again.