Narbs

Any time I come across an interesting car problem which I end up solving, I like to share my experiences with the community which will hopefully help someone else out there having similar issues.

Last week I came across a situation where a 2007 Acura TSX with around 90K miles was having severe drivability problems with very poor idle where the car would turn off if I did not press gas pedal, CEL, VSA Module & Emissions messages simultaneously flashing. Idle problems would disappear if I was able to rev past 3000 RPM but poor idle would resume once the RPM dropped to 1000.

First thing i did was to pull the CEL Code which was P2647. Looking it up in the service manual, it mentioned the VTEC pressure switch being high (meaning it was reading high pressure). My first thoughts were that it was most likely an oil issue (too much oil) or a bad pressure switch. However, I could not understand why a bad pressure switch would cause all of these symptoms simultaneously at idle. The service manual stated to test the pressure switch which turned up to be fine so why was the ECU reading high on the pressure switch? Faulty ECU perhaps? a short?

Everything pointed to an electrical problem taking into account the numerous system malfunctions and piss poor idle. However, I decided to pull off the VTEC solenoid assembly to check mechanical malfunctions before diving into the dreaded electrical malfunctions. This is what I found after pulling off the VTEC solenoid assembly:


The burned on oil deposits were horrid! Upon closer inspection, I noticed that the piston valve that controls oil flow to the cams was seized up in the open position! (VTEC ALL THE TIME BRO!) It didn't take long to find out the reason behind this from all the burned on oil depots and sludge. What had happened was that enough deposits were accumulated around the shaft and piston which increased the diameter ever so slightly causing the shaft to bind up, sending constant oil pressure to the VTEC cams all the time. This explained the poor idle below 3000 RPM and fine at higher RPMs.

From the ECU's standpoint, the VTEC Pressure Switch was telling the ECU that "we're in VTEC mode now" but the ECU had not initiated the solenoid. I'm assuming this along with poor idle caused the system to go into safe mode causing the VSA and Emissions messages even though those systems had nothing to do with the problem.

My guess is that either poor quality oil was used or too infrequent oil changes caused these deposits to build up over time. The tolerances in the VTEC assembly are pretty fine.

The best bet would have been to replace the assembly since it's fairly inexpensive ($140) but I decided to clean it to see if I could get the function back. After half a can of parts cleaner and working the shaft with a pair of pliers, I was able to free it pretty nicely. Here's how it looked like after cleaning:


I would imagine a dirty VTEC solenoid assembly could potentially cause an intermittent bind which would have been more difficult to pinpoint so if you are getting a P2647 which comes and goes, I would open up that sucker and give it a good cleaning before changing any parts.

There's also quite a bit of discussion whether or not you should clean the VTEC solenoid. My answer to that is if you've purchased your car used, you have no idea how well maintained the car has been so it would be a good idea to give it a thought especially knowing how easy it is to remove. Just go buy the gasket ($5) because if you install it using the old gasket, there's a 90% chance it will leak.

To sum it up... Here are the symptoms of a seized VTEC solenoid piston valve stuck in the open position.

Symptoms: Very poor idle at low RPM which clears up at high RPM, CEL P2647, VSA System Malfunction Message, Emissions System Malfunction Message, Engine Whine at idle (due to VTEC being engaged at all times)

mrgold35

Sounds like the owner just put gas in the car and ran it a lot on the hwy?

I had a similar situation with my RDX and Acura had to replace my VTEC solenoid (not sure if it was an oil build-up or equipment failure). The RDX had all the same symptoms plus sh-awd in limp mode. Lucky for me the RDX was still under the 7/70,000 powertrain warranty and they gave me a loaner 2012 TL for a few days.

I’ve been using Mobil oil since my second oil change and I stick to the M.I.D. schedule on my TSX (+97,000 miles now). I am thinking the syn oil will help against this type of build-up in the engine.

Simba91102

I disagree the with hypothesis that highway driving might cause this; I think just the opposite would be the case. It would seem to me that a long history of very short trips (not allowing the oil to come up to operating temperature and holding it there for a while) could cause the deposits possibly caused by contaminated oil. It's takes longer for the oil to come to temperature, and that extra time can be considerable in cold weather. Time on the highway allows the oil to get hot and stay that way, burning off any moisture and the chemicals that are the result of the combustion process. The old adage that can accompany "it might be high miles, but they're all highway" actually is a good thing for a variety of reasons, including letting the engine loaf at full operating temperature for long periods of time.

Mskierki

Thanks for the info/pictures/background. It is always good to have some details on these issues. If it has happened once, I am sure that it is going to happen to someone again.

Miamicarfan

This is good to know. Where does the gasket go?

mrgold35

I was thinking more of the overall mileage of +90,000 miles for the 07. Depending if the TSX is an early 07 model (fall 06) or late 07 (fall of 07), the owner would have to put between 12,000 to 15,000 miles per year on the TSX. This is the same range I put on my TSX and RDX and I can easily drive 30-60 miles running around town every day (60% hwy).

It looked like the owner just ran the TSX with mostly hwy driving thinking they can go longer between oil changes. I have a neighbor with a Dodge Ram truck and he thinks he can go +10,000 miles on regular oil between once a year changes, he just tops it off as it get low. I've had my 06 TSX for +6 1/2 years and this is his 3rd pick-up during the same time, go figure?

Narbs

The gasket goes in that funky "8" shaped groove. The gasket also has a built in screen over the bottom inlet opening to prevent large particles from entering the VTEC system.

Narbs

You are absolutely correct. The owner mentioned that he thinks 70% of his miles are highway due to 40 mile highway commute from home to work per day. I was also told that he performed oil changes based on the maint. indicator though he mentioned that sometimes he would go a couple hundred miles over but I'm sure Acura has taken that into consideration.

After thinking over it some more, I think what might have happpened is the lack of VTEC engagement due to long highway driving caused the oil is sit in the inlet chamber and heat up causing it to burn onto the metal. Either that or just crappy oil. I told him to use a synthetic blend from now on which should prevent this.

Narbs

Here's another closeup of the two chambers (bottom is inlet, top is outlet). You can see that the inlet has most of the buildup while the outlet is pretty clean. This supports the theory of lack of VTEC engagement due to long highway drives. I've scraped off some of the crud so you can see the contrast.

Miamicarfan

Where exactly is this Vtec solenoid in the engine bay? Can you take a pic of the engine bay with an arrow pointing to this part?

Simba91102

This is a very interesting thread and the info is greatly appreciated. I do have a problem assuming that any of this was normal though. Now that we have a liitle background on how the car was driven over the last 6 years or so (none of which was included in the original post by the way), it sounds like the owner/driver's driving habits and car care routines were/are as common as dirt. I think that if most (if not all) of the proposed causes for this problem were accurate (with the possible exception of perhaps NEVER changing the oil), the roads would be crawling with VTEC Honda's and Acura's suffering from the same problems that befell this car. I'm wondering if we were to open up this VTEC solenoid in most any car (w/ VTEC) we'd find similar conditions in the making. If you can't tell, I guess I'm skeptical about having touched on what caused this. For one thing, my wife's car is at close to 180K miles (07), and my recently departed 05 was close to 179K. Her car is driven like 95% highway, and I was at probably close to that percentage too. With the exception of both cars using synthetic oil since new, I have to question the possible causal relationship to highway driving (since both cars still drive like new) and these deposits. This is a good discussion and it's a good example of the value of a forum like this.