CTSC bypass valve question

[jwmelvin]

I'm cross posting here out of the hope that someone knowledgeable can help me, since I think the issue relates to the CTSC.

http://www.nsxprime.com/forum/showpost.php?p=1840389

My car has an occasional rich stumbling issue on startup. It seems to be related to a slipping belt and the more I think about it, it must be slipping on the SC and somehow starving the system of air. I would have thought that even without the SC spinning, the bypass valve would let air be drawn through the intake (in reverse of the purpose of that valve). Is that incorrect?

Does it make sense that a slipping belt at idle would cause rich running (10:1 AFR)?

To clean the bypass valve, do you think that I could do so through the intake plenum, by removing only the blower itself and not the full intake assembly? I have the original intake, with a welded top plate. My thought was that I might spray some carb cleaner into the bypass valve.

Anyone know the details of the valve in case I want to replace it?

Do you agree that it is unlikely the belt is slipping on the alternator? And that if I have a new battery and see 14V at idle (even when stumbling), that the alternator seems to be working okay?

 

[jimminh]

No idea on the age of your system, but mine hadn’t been touched since it was installed in ’99. Car ran bad unless on boost, but the guy I bought it from was oblivious to how it should have been, so he just lived with it as both he and the car progressively faded with age.

The main flaw in the original CTSC is the bypass hose, which was just a shaped rubber hose that didn’t react well to the heat of the crankcase vapors, and it was never intended to survive a vacuum. Here’s a couple of pictures of what my hose looked like. Not only was it nearly completely collapsed, but the rubber layers separated and the inner bubbled up nearly plugging the entire path.

The only time the belt is going to slip is at high rpm when it's making boost. If you can get one of those flexible inspection cameras you might be able to get a look under the manifold to see the condition of the hose. Removing the blower assembly from the manifold isn't that difficult, just one or two really difficult to bolts on the front side.

I did a sort of getto fix instead of getting the repair/update kit from Driving Ambition, http://www.drivingambition.us/searchresults.asp?cat=96 which wouldn't fit my ancient wipple without cutting it up, kit is designed to fit the later blowers. I ended up using a copper plumbing 90 degree fitting and couple of short pieces of a fuel filler hose to replace the single long radiator type hose comptech used. Not very pretty but cheap and effective. There are a few threads covering this situation already, and I used them as a guide on how to fix it.

good luck.

 

[jwmelvin]

Yes, thanks for the reply. I did have my bypass hose replaced with the Driving Ambition kit, when I first bought the car. That fixed the hunting idle problem, which I understand to be from a vacuum leak. It took some modifications to get things to fit right on my Whipple.

My take on the belt was pretty much the same as you: that I don't see why it would slip unless high rpm. Tightening it seemed to fix the problem but there may be more than I know going on. If the blower is spinning, then there should be plenty of air going to my engine, which points back at a spark issue. I still welcome any additional thoughts the community may have.

 

[nsxnut]

If the condition is all the time than I could be the bypass hose.

The comptech high boost kit has a fuel pressure regulator in the engine bay.
As these get old the spring get's soft. Is the problem only when the engine is hot?
Try turning on the key and letting the fuel flow through the fuel pressure regulator and back into the tank for a min or two.

This will cool the fpr and may be your issue?

Later,
Don

 

[jwmelvin]

The issue has been only when cold and it occurred both with the Comptech RRFPR and now with a new OEM FPR. Thanks for the thought though.

 

[DDozier]

The issue has been only when cold and it occurred both with the Comptech RRFPR and now with a new OEM FPR. Thanks for the thought though.

Jason reached out to me via email and I am adding a copy of the email here that I sent back to him on my thought with his issue. I am hoping that if this solves his issue the info will help others with similar problems should they stumble on this thread via a search.

Jason, Sounds like you have a fun one on your hands my first thought based on what you described is you may have oil sludge in the vac lines. However P1201-P1206, along with P0300. This is almost always the case, if you get a random misfire you usually get all the singles as well. While we are OBDII these car are just barely OBDII. Honda never made any significant change in the ECU after '97. Production numbers are to low to warrant a redesign of the ECU. It is smart enough to know there is a problem but with out a dead short on a single coil it will report almost any single misfire as all misfires with the random code as well.

What I suspect is a possible problem is the VAC line feeding the FPR may be filled with oil and until the car warms up and operates under vac for a while the FPR line is clogged and causing the FPR to run at about 10 PSI higher then normal. That combined with the fact that the fuel trims are pulling fuel even with fuel pressure in the normal 46-49PSI at idle tells me your map is a little rich but do not change that yet. We need to know what the fuel pressure does from key on till the problem goes away to rule that out. If fuel pressures are higher like 56-60 PSI after startup then you have an issue with the FPR or the vac line that is feeding it.

On start up the ECU is in Open Loop and Warm Up Enrichment, this causes the car to start rich and idle rich (11.5-12.5) as it is less likely to stall while rich than lean and the extra fuel aids in heating up the cats, once the idle drops from cold start high idle and starts to trim the car should quickly hit the 14.7 mark and start to fill in the STFT and LTFT data, the transition is what you want to watch very closely and watch for trends in the STFT and Fuel Pressure. This may not show up right away as a pattern but if it is happening regularly there will be a pattern. I will try and find a startup log of my car so you can see what the data should look like, but I have to dig through about 200 logs at this point and almost all of my logs start after the car is warmed up and ready for dyno pulls or running at the track.

This vac line filling with oil is also an issue with the bypass valve and MAP sensor. So if you can clean those out it is something you should do once or twice a year. The CTSC pulls the vac reference for the MAP, FPR, and Bypass from 1/8" nipples on the bottom of the intake, very hard to get to, and they are the lowest point in the intake. If the intake ingests oil from the PCV and does not burn it oil collects in the bottom of the intake and will fill the vac lines. Disconnect the vac lines at each device and blow air through them to clean them out. If this works but only for a while there may be a large amount of oil pooled in the bottom of the intake and a catch can may need to be added to the PCV system to limit the amount of oil ingested into the engine. New rings that did not seat properly can make this issue worse.

Does the car burn OIL?

Did the car get a break in cycle on non-synthetic oil to seat the rings after they were replaced?

Dave

 

[jwmelvin]

Dave is an invaluable source of energy on Prime for boosted cars. He has focused me on the fuel pressure regulator, which appears to be failing to respond to manifold pressure. I will update when I know more.

 

[jwmelvin]

I will continue my updates in my other thread as it appears the issue is related to the fuel-pressure regulator.