2012 4.6 Long Crank when Engine Warm

[wmcii]

I drive a 2012 4.6 with 105K miles and absolutely love the car. I bought it used with 70K miles and have had it for 3 years.

About a month ago, I came out of the store after being inside for 20-30 minutes and my 2012 4.6 would not turn over. In actuality, I just didn't wait long enough. I tried again and after 5 seconds or so, the car started. I went home and didn't think much of it. The next morning I got in my car, pressed the start button, and it started with no issues. I thought it must have been a 1 off issue.

I came to realize that I would continue to have this issue whenever the car was warm and tried to start it after 10 minutes of being off and before the engine cooled down. I typically didn't have the issue if I started the car within 5-10 minutes of turning it off. Pretty strange. I also had the car stall several times when at a red light. When I had trouble starting the car 2 times in a row, the check engine light would come on and the car would go into limp mode. It subsequently went off after starting 2 times without any issues.

I did find this thread and it got my pointed in the right direction (Need some help 2010 4.6 Long Crank on startup).

My initial thinking was that I had issues with my fuel pump. I purchased a used fuel pump on ebay and replaced mine only to continue to have the problem. At this point, I was back to trying to determine the problem. I recall seeing that someone said they had the crankshaft position sensor replaced and this fixed the problem. I had initially discounted this because it didn't make sense to me. In reality, it was my lack of understanding of what the crankshaft position sensor actually does. When I finally hooked up an OBD-II device, I saw a P0335 - Crankshaft position Sensor "A" circuit. A quick google indicated that the crankshaft position sensor monitors the position and rotational speed of the crankshaft and sends the information to the engine control unit so it can make appropriate adjustments based on operating conditions. Symptoms of a bad crankshaft position sensor are:

1. Issues starting the vehicle
2. Intermittent stalling
3. Check engine light
4. Uneven acceleration
5. Engine misfires or vibrates
6. Rough idle and / or vibrating engine
7. Reduced gas mileage

At this point, I was willing to invest the $65 for the part. Replacing this sensor is actually pretty easy. It sits between the firewall and the engine. With an extension on my ratchet I had it replaced in about 10 minutes. And it worked! I waited several weeks before posting this because I wanted to be sure the issue was truly resolved.

After replacing the sensor, I also noticed that the engine ran smoother on a cold start when the RPMs are a higher (before they drop to ~500).

Hope this helps if you have a similar problem.

 

[AndreP]

I drive a 2012 4.6 with 105K miles and absolutely love the car. I bought it used with 70K miles and have had it for 3 years.

About a month ago, I came out of the store after being inside for 20-30 minutes and my 2012 4.6 would not turn over. In actuality, I just didn't wait long enough. I tried again and after 5 seconds or so, the car started. I went home and didn't think much of it. The next morning I got in my car, pressed the start button, and it started with no issues. I thought it must have been a 1 off issue.

I came to realize that I would continue to have this issue whenever the car was warm and tried to start it after 10 minutes of being off and before the engine cooled down. I typically didn't have the issue if I started the car within 5-10 minutes of turning it off. Pretty strange. I also had the car stall several times when at a red light. When I had trouble starting the car 2 times in a row, the check engine light would come on and the car would go into limp mode. It subsequently went off after starting 2 times without any issues.

I did find this thread and it got my pointed in the right direction (Need some help 2010 4.6 Long Crank on startup).

My initial thinking was that I had issues with my fuel pump. I purchased a used fuel pump on ebay and replaced mine only to continue to have the problem. At this point, I was back to trying to determine the problem. I recall seeing that someone said they had the crankshaft position sensor replaced and this fixed the problem. I had initially discounted this because it didn't make sense to me. In reality, it was my lack of understanding of what the crankshaft position sensor actually does. When I finally hooked up an OBD-II device, I saw a P0335 - Crankshaft position Sensor "A" circuit. A quick google indicated that the crankshaft position sensor monitors the position and rotational speed of the crankshaft and sends the information to the engine control unit so it can make appropriate adjustments based on operating conditions. Symptoms of a bad crankshaft position sensor are:

1. Issues starting the vehicle
2. Intermittent stalling
3. Check engine light
4. Uneven acceleration
5. Engine misfires or vibrates
6. Rough idle and / or vibrating engine
7. Reduced gas mileage

At this point, I was willing to invest the $65 for the part. Replacing this sensor is actually pretty easy. It sits between the firewall and the engine. With an extension on my ratchet I had it replaced in about 10 minutes. And it worked! I waited several weeks before posting this because I wanted to be sure the issue was truly resolved.

After replacing the sensor, I also noticed that the engine ran smoother on a cold start when the RPMs are a higher (before they drop to ~500).

Hope this helps if you have a similar problem.

My 2011 4.6 had very similar issues and read a P0335 code as well. Unfortunately, I didn't see this thread before taking it to the shop and it cost me $450. Oh well, at least it fixed the problem and the car is running good again.