V6 with p0352 rough only at idle

[Warmowed]

I have a p0352 code after doing some work on my engine replacing leaking gaskets. There isn't any misfiring and acceleration is normal, but the engine idles too low (~600rpm when normal is 800rpm) and very rough. Is this a vacuum leak (read that a bad vaccum leak could cause a p035x error)? or do I have a bad spark plug? because the engine doesn't have a coil on each cylinder just a central coil pack.

 

[LorenzoGarbanzo]

I'm having the same issues right now on an 07 when I start the engine after it's already somewhat warm. This started after doing a lot of work while I replaced valve cover gaskets a few months back. I've reset the PCM and fixed some broken wiring to the TPS but don't have an answer yet. I'm going to replace the vacuum lines for the EVAP system at the next oil change because they look a bit brittle and see if it helps.

 

[Warmowed]

I found a cheap portable automotive smoke detector on amazon I will try it out to see if it is junk or not but if it works out I can point you towards it. Seems like my only option is to smoke test it, because like you said it seems more like a vacuum leak than anything else. I had replaced 1 vacuum elbow during the repair due to it cracking apart when I removed it from one end of its connection. I think that other things may have tiny cracks that I can't easily see just by looking at it from when they were disturbed during the repair

 

[Warmowed]

I'm having the same issues right now on an 07 when I start the engine after it's already somewhat warm. This started after doing a lot of work while I replaced valve cover gaskets a few months back. I've reset the PCM and fixed some broken wiring to the TPS but don't have an answer yet. I'm going to replace the vacuum lines for the EVAP system at the next oil change because they look a bit brittle and see if it helps.

Well I tried out the smoke gun to check out for vacuum leaks. The thing works a treat but I couldn't find any vacuum leaks >:| so something else is my problem. I can pm you the link if you want to check out the smoke maker (read the instructions for turning it on! needs 6 AA batteries too).
I retightened the intake manifold bolts and that hasn't eliminated the problem. I checked on my OBD reader and I saw in the live data fuelsys1 had a ol_fault check to see if that is your case too. I also checked the spark plugs and wires and everything seems fine. Coil works correctly. I'm a bit stumped frankly

 

[LorenzoGarbanzo]

Well I tried out the smoke gun to check out for vacuum leaks. The thing works a treat but I couldn't find any vacuum leaks >:| so something else is my problem. I can pm you the link if you want to check out the smoke maker (read the instructions for turning it on! needs 6 AA batteries too).
I retightened the intake manifold bolts and that hasn't eliminated the problem. I checked on my OBD reader and I saw in the live data fuelsys1 had a ol_fault check to see if that is your case too. I also checked the spark plugs and wires and everything seems fine. Coil works correctly. I'm a bit stumped frankly

I'd be interested in checking it out. Beats smoking a cigar and exhaling into the vacuum lines.

I didn't see that fault but I did notice a new trend today. I stopped to get gas, hooked up my scanner, and watched the Long term & short term fuel trims. When cranked after warm and sitting for about 5 minutes, it idled rough and presented the p0300 code. Long term for both banks was about 5% which is a fair number. Short term fuel trims for both banks kept climbing until about 35% as it smoothed itself out. I gently revved it and the short term fuel trims went down to between 2-8% and the idle smoothed out. Long term fuel trim was up to about 15% by that point. I drove about 5 minutes until I got home when I checked again and the fuel trims were all around 2-4% which is a pretty normal range, imo.

If I'm interpreting these numbers correctly, I believe the PCM is dumping more fuel into the system to smooth the idle out. I can also smooth the idle out by driving a bit or gently revving the motor. That leads me to believe that something is causing the engine to run lean when started from a warm condition. I've already changed the fuel filter with a new motorcraft unit in the past 5000 miles so I think I can rule that out. Some research has told me it could be winter blend gas causing this but the timing of this started right after doing intake gaskets & PCV valve so I can't assume that yet as there are too many variables. I'm still going to replace those vacuum lines I mentioned in the next week or two when I get around to changing the oil and I'll probably clean the MAF as well.

 

[cancrusher187]

I have a p0352 code after doing some work on my engine replacing leaking gaskets. There isn't any misfiring and acceleration is normal, but the engine idles too low (~600rpm when normal is 800rpm) and very rough. Is this a vacuum leak (read that a bad vaccum leak could cause a p035x error)? or do I have a bad spark plug? because the engine doesn't have a coil on each cylinder just a central coil pack.

Intake manifold lower for the win, Alex.

 

[cancrusher187]

I'd be interested in checking it out. Beats smoking a cigar and exhaling into the vacuum lines.

I didn't see that fault but I did notice a new trend today. I stopped to get gas, hooked up my scanner, and watched the Long term & short term fuel trims. When cranked after warm and sitting for about 5 minutes, it idled rough and presented the p0300 code. Long term for both banks was about 5% which is a fair number. Short term fuel trims for both banks kept climbing until about 35% as it smoothed itself out. I gently revved it and the short term fuel trims went down to between 2-8% and the idle smoothed out. Long term fuel trim was up to about 15% by that point. I drove about 5 minutes until I got home when I checked again and the fuel trims were all around 2-4% which is a pretty normal range, imo.

If I'm interpreting these numbers correctly, I believe the PCM is dumping more fuel into the system to smooth the idle out. I can also smooth the idle out by driving a bit or gently revving the motor. That leads me to believe that something is causing the engine to run lean when started from a warm condition. I've already changed the fuel filter with a new motorcraft unit in the past 5000 miles so I think I can rule that out. Some research has told me it could be winter blend gas causing this but the timing of this started right after doing intake gaskets & PCV valve so I can't assume that yet as there are too many variables. I'm still going to replace those vacuum lines I mentioned in the next week or two when I get around to changing the oil and I'll probably clean the MAF as well.

Seriously, You can check and tourqe the intake bolts all you want but if something shifted putting it on?