Need help- 3.4 rough idle and rattle

Hoping for some help or guidance 🙏 Driving to pick up my induction heater to install headers on my 996 and it didn�t go to plan. Drove to my shop today and it drove flawless, shut it off, got back into the car 15 mins later and it stalls after start up. I try again and it starts up but runs with a rough idle and a light rattle when it revs. I pulled it around the parking lot to park it and it seemed like it was low on power though I�m only 60% certain of that. No CEL sounds like a mechanical issue 103,000 miles on car ims done at 70,000 i can�t check deviation at this time im thinking I need to check cam deviation. I dont have a tool for that but I suppose I could buy it. https://youtu.be/BfdRLj3WWgw?si=5sYg7ZxFQ7-ShdNY https://youtube.com/shorts/ug9CpXe7TY4?si=vrO0ehAeBKV7WjT7 Thanks!!!

Oh no! Good luck with troubleshooting! When you say, �sounds like something mechanical�, can you describe the sound more? What it sounds like, location, and when it happens? (All the time, At idle, reving up, sitting still, driving) auto or manual? Is it intermittent? Have you tried starting again cold.

Maybe a failing fuel pump or the internal hose ruptured?

Quotes source post: 19893104

Thanks for the replay Maroon8 Here is a video You Tube (also posted above). You can hear the rattle just start as i rev the engine but i was reluctant to rev harder or longer. Car is manual. clutch in or out didn't seem to matter, but i wasn't paying particular attention to when clutch was depressed. It is constant. I haven't tried a cold start

In car hot start. not touching the gas pedal You Tube

I was able to scan the car and had the following codes. I started engine after having the battery disconnected and it started right up and idled fine. About a minute after starting the rough idle came back. Upon scanning i found the following: P1602 - (108) Power Supply P1319 - (62) Misfire, Emissions related P1313 - (50) Misfire, cylinder 1, emissions related P1314 - (51) Misfire, cylinder 2, emissions related P1315 - (52) Misfire, cylinder 3, emissions related I have more info if anyone has any insight. I cleared the codes and rescanned with the engine running and got P0341 - (112) Camshaft position (CMP) sensor 1 The engine is running rough at idle. I gave it a couple of throttle blips and it sounds like there might be some chain slap (tensioner?) and i did get one off throttle pop so i assume some unburnt fuel which never has happened previously. Unless directed otherwise I plan on pulling the filter to inspect and possible pulling the pan. How do you check cam deviation with Motronic 5.2.2? I can do it with my 986 which is running 7.2 Thanks!!

A decent scanner should tell u but i think the early cars may only read 1 bank. It sounds like ths variocam may be stuck in the advanced position, the pads r too far gone or u skipped a tooth. Non of the tensioners control the chain for deviations. It is possible the long chain skipped or the cam gear slippped too. Get the cam deviations and u should be able to read actually cam timing with the scanner. That reading will jump at about 3k rpm. The cam deviations r a smoothed value and dont move but since u cleared the dme it may take a few starts ro read correctly. May be heading toward pulling the cam covers......?

Quotes source post: 19907026

thanks for the reply de jeeper. Durametric is showing zero 😞 Do you know if it can be read in 99s with motronic 5.2.2?� I�m assuming 0.0 is a null reading.

Im guessing that the 0 reading is because u reset the dme. May need to run it some? See if u can find the actual value to see if it changes when the rpm goes over 3k.

I see 0 too using durametric on my 99 3.4, unfortunately. I believe/suspect durametric cannot read cam deviation on DME 5.2.2.

I was able to read my cam deviation numbers with Durametric on my 99 -DME 5.2.2. This was in 2019 with version 6.5.5.5.

�99�s should show both cam deviations UNLESS your car is RoW or has a RoW flash on the DME.

Hrmmm. A US car without a tune, that I won�t rev to 3k for fear of damaging it. Guess it�s coming apart :/ thanks!

Fact that you said it ran fine for a little bit after disconnecting your battery makes me think electrical, not mechanical. What about swapping out the bank 1 cam sensor? That's your primary fault code and you're not getting a bank 1 cam reading. The other codes are possibly/likely the consequence of the low idle (power supply) and running rich on bank 1 (misfires). You could also swap the bank 1 and bank 2 cam sensors and see if the code follows. The surging off idle is interesting. Could just be the DME trying to compensate for loss of bank 1 position info, I assume that's also causing the misfires. But if you look at the electrical diagram for your car (99, 5.2), the cam sensor in question (hall sensor 1) shares power with the throttle valve potentiometer (throttle position sensor). Possible you have a fault impacting power supply to both, explaining the rough idle as well as the surging (faulty TPS reading increasing enrichment). Just a thought.

Thanks @sublm8 I left the car in storage and am just now looking to get back on it. Sensor isn't too expensive but looks like a nightmare to get to. I"m not entirely clear how to get to the sensor but I understand it's buried near the AOS and starter in a hard to get to location. It's been a while since i've been under the car so I can't entirely remember what it looks like near the transmission. Hopefully it's a loose connector or bad sensor.