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2.3L ('02-'11) Intake Manifold Vacuum Leak and high idle

Bill

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After months of dealing with vacuum leak symptoms I finally found a vacuum leak on the intake manifold. The leak is located on toward the front of intake runner #1.

A description of the symptoms for anyone who finds this through a search: High idle between shifts. The idle returns to baseline (800 rpm) at a full stop. The symptoms are more severe with the air conditioner on. Idle is higher between shifts and remains high for a longer period of time, but eventually goes down rapidly to about 500 rpm, then recovers to 800 rpm. Sometimes the idle will wander between 1500 rpm and fall to 500 rpm before settling down. Drivability when I'm not in stop and go traffic is fine, but I noticed lack of power going up hills. No codes. All the sensors indicated variables within normal range. However, long term fuel trim was slightly high at 11% most of the time, sometimes going as high as 15%.

The first picture is a view of the are where the vacuum leak is occurring. I sparyed soapy water on it and put a few pounds of pressure in the intake to locate the leak. You can see a bubble behind the shiny area on the manifold. Since I can't see or access this leak without removing the intake I went searching for a picture of it and that the second image is. It appears there is a plug to cover a hole for injection molding (or something else) and it is leaking. Has anyone come across this and knows of a repair that doesn't require a new intake? I'm thinking about trying to pop the plug out and sealing it with a hard gasket sealant and maybe coating the top of the whole area with epoxy after the gasket sealant sets. I'm kind of concerned about the ability of epoxy to adhere to whatever plastic composite the manifold is made of.

Any ideas?

Also, I'm thinking about replacing the injectors simply due to high mileage, and they have become really noisy at times. This is really preventative maintenance because I'll have access to the injectors. Does anyone know the lifespan of the injectors on this engine?
 

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fastpakr

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I'll have to dig up his name, but there's a guy that does great work at rebuilding and balancing injectors for far less than new OEM injectors.

Edit - found it faster than I expected:
Screenshot_20220808-073505.png
 

pjtoledo

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that hole is where the pivot shaft is for the early design intake runner flappers, 2001/2002 ( 3 ? )
if it's leaking I would try course sanding and JB weld YMMV


the injectors in my 367,500 mile 2005 were still working OK when I pulled the engine this spring.
 

Bill

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that hole is where the pivot shaft is for the early design intake runner flappers, 2001/2002 ( 3 ? )
if it's leaking I would try course sanding and JB weld YMMV


the injectors in my 367,500 mile 2005 were still working OK when I pulled the engine this spring.
I came across a few videos about this after I posted. I still have the plug in there so I'm thinking about popping it out from the inside and sealing it with Form-a-Gasket #1 and figuring out someway to permanently secure the plug through some other method.

I think I have an injector that is making a machine gun type noise. It happens right around 3,000 rpm in a very narrom throttle opening. If I back off the throttle or floor it the noise goes away, and the rpm range in which it occurs increases around 2,000 feet in elevation, so I'm guesssing it has something to do with air/fuel and the injectors are the only thing I can think of that could be making the noise.
 

Bill

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I'll have to dig up his name, but there's a guy that does great work at rebuilding and balancing injectors for far less than new OEM injectors.

Edit - found it faster than I expected:
That's in Kentucky. The turnaround time would be too long. I need to do this in a day or two and new injectors are just over $30 on Rockauto.
 

fastpakr

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For OEM or off brand?


It'll be more than a day or two for sure. I think they were back to me in less than a week though.
 

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To many horror stories about cheap aftermarket injectors.
 

Bill

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It'll be more than a day or two for sure. I think they were back to me in less than a week though.
This is my only vehicle, so I need it running.

The Motorcraft injectors are $34 each. Bosch are $32, and SMP are $27. The Motorcraft and Bosch injectors are the same product. The SMP injectors might be the same as well.
 

Bill

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To many horror stories about cheap aftermarket injectors.
I avoid cheap aftermarket products and look for the brands that make products for the auto manufacturers. Of course, that excludes the "economy" lines all the major manufacturers carry so they can sell something to the type of people who shop based on price alone.
 

Bill

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So, an update on this:

The round plug on the intake manifold where the leak appeared to be coming from didn't go all the way through the intake runner. The inside of the runner is cast/molded as if there is a plug on the other side. I sure looked as if the bubbles were coming out of the soapy water from it though. It was very likely that it was the intake gasket that was leaking. When I inspected the gaskets it appears (but it's really hard to tell) that there was a bit of dust on the portion of the gasket that should form a seal against the intake ports on the cylinder head in the same area where I saw the bubbles when attempting to locate the vacuum leak. I also noticed this on the gasket for Cyl 3. The gaskets for the other two cylinders were flat and clean where they contacted the cylinder ports. The spark plug for cyl 4 was white from running a bit lean. I replaced the spark plugs because even though Autolite claims the XP series spark plugs are "lifetime," they aren't. They had 70,000 miles on them, so I just replaced them as part of general maintenance. Before doing all this I had several issues. One was the engine felt like one cylinder was bouncing that was worse when the A/C was on. Now the engine runs smooth when the A/C is off and there is a slight vibration with it on, which is likely normal.

I also replaced the injectors. When I bought the truck the noise from the injectors was loud enough that I was a bit concerned until I figured out what the noise was. The noise must have increased over the years and I just became accustomed to it. I can still hear the new injectors, but they are so much quieter. The Bosch injectors had all the same numbers on them as the original injectors with the exception of a code that probably has something to do with the manufacturing date.

Now the frustrating part. I've had a problem with the idle speed somewhat maintaining the engine speed I was at between shifts. If the engine was at 3,000 rpm before shifting it would maintain that speed or only drop down maybe 500 rpm between shifts. I would do this as I coasted to a stop and when I finally stopped the PCM would take the data from the speed sensor and tell the IAC that I was at a full stop and there is absolutely no reason for the idle to be anything other than 800-850 rpm when at full operating temperature. All this is worse if I have the A/C on. The high idle between shifts is higher, and sometimes increase. When I come to a stop it might take 15 seconds before the idle starts to drop and when it does it usually drops to 500 rpm before recovering and going to 800-850. It stalled a few times. It's also gone from 500 rpm to 1500, then up and down a few times before settling at around 800 rpm. There has been two times that it has gone up at a stop. In one case I came to a stop in a parking lot to check messages on my phone. The idle dropped to 500 rpm, then went to around 800, then up to around 1200, and continued to step up to 3000, at which point I turned off the A/C and it went back to 800 rpm.


When using the scan tool LTFT is 14-19% at idle and drops down to anywhere between 6-10% when opening the throttle. At freeway cruising speeds LTFT is between 7-13%. It's behaving as if I have a vacuum leak. I've smoke tested it, squirt is with soapy water, and tried both propane and starter fluid around any potential place I could access where there would be a leak and I can't find one. I've plugged the ports for the vacuum reservoir, purge valve, brake booster, and PCV as well as replaced the intake and valve cover gaskets, which were needed.

I'm at a loss. Here's the data I have from the scanner. Maybe someone can think of something I'm overlooking.

TPS is at 16.09% with the throttle closed and appears to be tracking smoothly.

Idle is about 810 to 850 rpm at full operating temperature when the truck is stationary.

MAP readings with engine off, key on match barometric pressure. At idle the MAP sensor indicates around 3.5-4.0 psi (24-28 kPa) and increases to around 34 kPa with the A/C on.

MAF is in the 2.3 to 2.8 range at 800-850 rpm.

OS1 running between about .9 volts to around .8 volts, but indicates a leaner mixture when the idle drops to 500 rpm after stopping.
OS2 is fairly steady at around .66 volts with an occasional small fluctuation.

I don't know what else to look at. The IAC really appears to be doing what it's told do to. I suppose there's a possibility that it's operating out of range. There's always the possibility that the valve in the EGR isn't seating properly, but I'm at a loss at how to go about checking the EGR without going through the work of tilting the engine back to gain access to it, and if I end up going through that much work I'm just going to replace it.
 

CavVet2

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I have the same symptoms you describe in the op. Just changed the IAC valve a couple days ago because it was stuck closed and the part had the date 7/23/1998 on it telling me it was probably an original part in my 98 std cab stepside with 2.5l 5 speed. The problem remains…
 

Bill

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I have the same symptoms you describe in the op. Just changed the IAC valve a couple days ago because it was stuck closed and the part had the date 7/23/1998 on it telling me it was probably an original part in my 98 std cab stepside with 2.5l 5 speed. The problem remains…
I've come across many posts with this same issue. Once in a while someone replaces something that resolves the issue. Usually the TPS. There's a lot of people who have replaced almost everything out of frustration without resolution.
 

CavVet2

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I've come across many posts with this same issue. Once in a while someone replaces something that resolves the issue. Usually the TPS. There's a lot of people who have replaced almost everything out of frustration without resolution.
I’m going to first check all the vacuum lines. I already replaced the big one going from the valve cover to the throttle body area. The rubber was so bad on it if you touched it you got black all over your hands. It was full of cracks going all the way through it.
 

Bill

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I’m going to first check all the vacuum lines. I already replaced the big one going from the valve cover to the throttle body area. The rubber was so bad on it if you touched it you got black all over your hands. It was full of cracks going all the way through it.
It would probably be a good idea to replace them, but if you want to make troubleshooting fast you can put a rubber cap on the intake ports to eliminate those lines as a possibility. If you have a vacuum pump you can also check the lines individually for vacuum leaks.

 

CavVet2

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It would probably be a good idea to replace them, but if you want to make troubleshooting fast you can put a rubber cap on the intake ports to eliminate those lines as a possibility. If you have a vacuum pump you can also check the lines individually for vacuum leaks.

I have replaced 2 large lines that were rotten and it seemed okay for a day or so then started it again. Funny thing is when I try to repeat the high idle problem with the engine running in neutral and sitting still it doesn’t do it. It only seems to happen when driving it. I can cap off lines but don’t presently have a vacuum pump.
 

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