2013 SHO Owner - Love my car and will never part with it. Car has got 145,000 miles.

[CharlieB]

First time on the forum and would like to thank anyone and everyone for any help they can provide. I'm an aircraft technician and have worked on cars my whole life
Question 1: Is it true that the SHO 3.5L engine does not have a MAF sensor and in its place, it has 2 MAP sensors. And if this is true can someone describe where to find them.
Question 2: My engine RPM has recently started fluctuating by 200 rpm per second only when there is a load on the engine. Nothing at idle and nothing when your foot is off the gas. It's not an indication issue. I can feel and hear the engine cycling up and down.

 

[Texas Marauder]

NO. 1: No MAF. MAP sensors before the throttle body and on top of the intake. 2 and 10 in the picture.



NO 2: Possibly torque converter, though that usually feels like a misfire.

 

[kryptto]

welcome

SHOnatomy

Lets face it, there is 10 pounds of crap in a 5 pound bag under the skin of our cars. Ford crammed as much as they possibly could in there and even seasoned mechanics can have trouble hunting down where something is. With how expensive the world is, its cheaper to work on your own car when you...

shoforum.com

 

[CharlieB]

NO. 1: No MAF. MAP sensors before the throttle body and on top of the intake. 2 and 10 in the picture.

View attachment 92658

NO 2: Possibly torque converter, though that usually feels like a misfire.

Thanks so much TM. I've been researching the affects of the Throttle Positioning Sensor, MAF sensor, or now MAP sensor. They appear to be capable of causing RPM fluctuations but I'm not sold on the idea that they can cause such a repeatable, second by second fluctuation of the same amount, 200 to 300 rpm.

 

[76FoMoCo]

When was the last time it had fresh plugs? O and welcome.

 

[CharlieB]

When was the last time it had fresh plugs? O and welcome.

Really good question. I have new plugs and coils in my garage to be replaced next week. This will be the first change of plugs in 145,000 miles. I've suspected it which is why I bought them but I still tend to doubt that they could cause such a distinct repetative fluctuation. What's your thoughts on that?

 

[luigisho]

My thoughts are, that is really old to not have been changed. Since you have the replacements already, you should take that variable off the table. At that age and mileage many things are capable of producing running errors. Do you have a scan tool? Not a code reader.

 

[CharlieB]

My thoughts are, that is really old to not have been changed. Since you have the replacements already, you should take that variable off the table. At that age and mileage many things are capable of producing running errors. Do you have a scan tool? Not a code reader.

Just a code reader. Would love having a scan tool. Right now I plan to change all the plugs and coils as well as the Throttle Positioning Sensor and see if there are any changes.

 

[BradM]

Do some research on GDI engines and intake build-up. With your miles, this would be very high on my list for maintenance (cleaning). Odd idle fluctuations with no misfire codes could be a result of carbon build-up in the intake.

 

[CharlieB]

Do some research on GDI engines and intake build-up. With your miles, this would be very high on my list for maintenance (cleaning). Odd idle fluctuations with no misfire codes could be a result of carbon build-up in the intake.

I'm sure it would be worthwhile. I had planned on pulling the intake manifold to change the plugs because everything I've read calls for it to be removed. However, when I looked closely at the engine, it looks like I have access to all the plugs except the left rear as viewed standing in front of the engine looking back. There is a device covering that sparkplug but I'm not sure what it is. Is it correct that the manifold doesn't need to be removed to do plugs and coils?

 

[BradM]

No need to remove the intake manifold to change the plugs and coils. The pipe you see over #3 is the charge pipe coming from the rear turbo. You can remove the coil with the pipe still in place.

 

[Texas Marauder]

I'm sure it would be worthwhile. I had planned on pulling the intake manifold to change the plugs because everything I've read calls for it to be removed. However, when I looked closely at the engine, it looks like I have access to all the plugs except the left rear as viewed standing in front of the engine looking back. There is a device covering that sparkplug but I'm not sure what it is. Is it correct that the manifold doesn't need to be removed to do plugs and coils?

I think you may be confusing the 3.5 Ti-VCT (non-turbo) engine with the 3.5 GDTI (turbo) engine. The 3.5 Ti-VCT engine requires removal of the intake manifold to replace spark plugs.

 

[Zpak]

Once you figure out how to pull off the clips on the coils it’s a half hour job.
Speaking of, slide down the red tab first.

 

[kryptto]

Speaking of, slide down the red tab first.

Gently.... I broke one of mine already with 28K.

 

[CharlieB]

No need to remove the intake manifold to change the plugs and coils. The pipe you see over #3 is the charge pipe coming from the rear turbo. You can remove the coil with the pipe still in place.

Very much appreciated. I'll be sure to pass that along in the future if I'm asked the same question. I hope the plugs and coils change has some impact on the RPM fluctuations
They're getting worse. I should be doing them this week and will report back.

 

[76FoMoCo]

Just undo the cross over pipe on the front half, leave the back attached a just mover it over a little bit. Also twist the coils and pry up at the same time. I helps to have the spark plug socket with the rubber insert to hold the plus too.

 

[CharlieB]

Just undo the cross over pipe on the front half, leave the back attached a just mover it over a little bit. Also twist the coils and pry up at the same time. I helps to have the spark plug socket with the rubber insert to hold the plus too.

Thanks again. It's already been so helpful to have joined the forum. In more cases than not, the more minds the better.

 

[Zpak]

Fixes the problem or not, 145k on forced induction plugs, them puppies are blown out. I’ve pulled them with 20K and the gap grew from .028 to at best a loose .029 up to .031.

 

[CharlieB]

Fixes the problem or not, 145k on forced induction plugs, them puppies are blown out. I’ve pulled them with 20K and the gap grew from .028 to at best a loose .029 up to .031.

Just completed replacing the plug and coils before changing anything else. Did not fix the RPM fluctuations. Next I changed the Throttle Positioning Sensor. No affect on the fluctuations. I plan to clean the MAP sensors next. Any ideas would be welcome. Thanks for all your help so far.

 

[CharlieB]

By the way, the plugs gap measured .042" on all 6 plugs, after 146,000 miles with just a small amount of carbon build up on the edges of the plugs. Incredibly consistent wear for so many miles. They were iridium. New plugs went in at .031"