2003 Hyundai SantaFe: Looking for a place to stop.

This Hyundai had just over 200,000 miles and complaints were shaking, noise, smell and low power. I could immediately feel a misfire and since a misfire can cause all the other problems, it was the place to start. The ignition coils were not difficult to access and by killing power to each cylinder one at a time, I found the misfire to be on #3 cylinder. The bank of spark plugs nearest the bumper are cyls 2,4,6. The rear bank near the firewall has cyls 1,3,5 and they are only accessible after removing the upper intake manifold. I pulled a couple of the easier spark plugs from the front to get an idea of the condition of the plugs. They were badly worn. If I removed the upper intake for further checks of the misfire I would at least need to replace all the plugs and plug wires when it went back together.
I wanted to drive the car in case there was something that might not be obvious otherwise, like transmission problems or serious engine noise or even exhaust system blockage. I noticed that the car had the misfire and poor acceleration. Also, the misfire would intermittently start firing normally with a slight boost of power when that happened. That would make it even more likely that spark plugs would fix the misfire.
I came up with the game-plan and got an okay to remove the intake for further checks and replace spark plugs and wires. Ellis pulled the plugs and asked me to take a look. The 2,4,6 plugs were all worn but burning cleanly. The 1,3,5 plugs had all been running in a rich mix with black carbon being the clue.

I remembered there had been O2 related codes stored in the engine computer when I had done a scan. Maybe the sensor for that bank was bad, was my thought. If it needed a sensor on that bank, it would probably be a good time to replace it. When I checked printout though the codes were for the bank 2 sensor. This was bank 1 with the black plugs. 

We decided to just continue as originally planned and ran a cylinder compression test. The rear cylinders all ran quite a bit lower than the front bank but enough compression to hit without a misfire. The new plugs and plug wires were installed and on engine start there was no longer a miss. All cylinders were hitting but that is about all that was gained. The engine still shook very badly at idle in gear even though there was no miss. Acceleration was very poor as if ignition timing was slow. The smell of "rotten eggs" was coming from the converter and there was engine noise. Even though all the clues were there, it took me a bit to realize that the timing belt was probably needing replaced. The rear bank cam timing being out of sync could explain all the remaining problems. Or..... it could just be another step in the journey. Next thing though was to pull the timing cover and check the timing marks. I couldn't get a good camera shot of any of the marks but did manage some snaps with the borescope. Sorry for the poor quality. I can enhance the marks for clarity. The timing marks for the crank gear and front cam gear aligned perfectly. The rear cam was very much out of sync. 

There was also a lot of slack in the timing belt. The tensioner design is such that there shouldn't have been any slack. The problem was the tensioner was original with over 200,000 miles. An underhood sticker indicated the belt had been replaced in 2013. After replacing the tensioner and timing belt this car sounded great and ran very well. Found a place to stop! 

It could still use a bank 2 oxygen sensor. The cam sensor code could be related to the timing problem. But the customer wants to stop here and get through the holidays. 

Thanks for reading!

Kenneth Hayes

G&G Auto Repair