It is time to pass emissions and get new registration, so of course my car has been throwing the P0401. I tried Kevin’s work around (who can pass an opportunity to stick it to the man), but it has prevented the car’s computer from resetting. So I’ve broken out the FSM and am working through the ‘proper’ steps. First up is the EGR Vacuum filter. The FSM says to check and clean. My filter is not that dirty, but it is broken into several parts. Called Kristal but they don’t sell the EGR components separately. Seems silly to spend $50+ for what looks like a buck worth of cotton. Found a thread where people debated making replacements out of simple cotton, but the German scientist in me sided with the people that felt that the high heat and simple cotton was a recipe for a fire. So, anyone found a source or safe way to make EGR filters?
EGR Filter?
- Thread starter cook
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Which filter, the one on the modulator or VSV? It is likely irrelevant, have you tested the parts, what color is the sticker/label on the modulator?
The leading cause of your issue is the diaphragm in the modulator having a hole, not holding pressure. The easy test is to apply pressure to the lower fitting and see if it holds, if not it is junk and the new one comes with a filter.
Unfortunately the fix is often not that easy. Once the diaphragm is breached, exhaust gas flows into the control (clean) side of the system, this tends to make parts stick. The first affected is the VSV on the bottom of the intake. The "correct" way to repair is call Kristal and shell out another $60 and it is a pain to get to/change. I hooked up 12v to it and cycled it while cleaning with carb cleaner, then lubed with silicone dry lube. It now passes all of the tests, but still occasionally sets a P0401 code.
So this is where I said
it, not spending any more time, $$$ on this archaic, useless, likely detrimental, system and went to the resister mod. It works great, has never set code, has passed emissions, but is never "ready". Having one system not ready isn't an issue for emissions, but isn't "right".The next step is to plug off the EGR system, so nothing flows, then hijack/modify the signal from one of the sensors, likely the stock EGR sensor and feed it to the ECU. The goal is to reproduce the correct cold and hot reading, so the ECU will think that the system is working properly, set the ready and not set the code. Then the whole system could be removed and the ECU still be happy.
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Kevin,
The FSM refers to it as the EGR as apposed modulator or VSV. Mine has a blue top, and is the only one that pops open to reveal the ruggedized cotton filter. Recognizing it is probably not the issue, I’m following the FSM, learning a little, and this is the first stop along the way.
As for the fix we put in place, it did not allow for the computer to reset. The FSM is pretty direct on this issue, and I should be able to follow it to the end even with my limited skill set.
Which takes me back to does anyone know of a source for these cotton filters?
The FSM refers to it as the EGR as apposed modulator or VSV. Mine has a blue top, and is the only one that pops open to reveal the ruggedized cotton filter. Recognizing it is probably not the issue, I’m following the FSM, learning a little, and this is the first stop along the way.
As for the fix we put in place, it did not allow for the computer to reset. The FSM is pretty direct on this issue, and I should be able to follow it to the end even with my limited skill set.
Which takes me back to does anyone know of a source for these cotton filters?
Have you thought about taking your old one into a parts store and trying to match it up to a new one? You could just cut down one that is a bit too big. A piece of generic filter material will probably do the job just fine. John
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OK, it's the EGR system, the specific part that you are working on is the EGR Vacuum Modulator. No new parts are available, only sold as a unit, so the only option for individual parts is used. The blue sticker indicates that it is the "updated" part, has been replaced, the original had a green sticker. I cut the one off of my rig apart to view the perforated diaphragm, but didn't save it, so don't have a spare filter.
The FSM is great for saying "test this, if the reading is other than this, replace". This often leads to lots of replaced parts, often without success. Sometimes it is best to study how the whole system works and what could cause the problem and the FSM is poor in explaining the "how".
The modulator is a regulator. The big hose at the bottom brings in exhaust, it uses this to sense engine load. The exhaust pressure pushes on the diaphragm that is connected to a valve that regulates/modulates vacuum pressure to the rest of the system. Under some conditions it vents vacuum to atmosphere, so that tiny bit of air is filtered. In other words the filter has nothing to do with the operation of the system. The only time where I have seen a filter clogged enough to effect the operation was when the diaphragm is perforated allowing exhaust to clog it, then it is irrelevant, the whole thing needs to be replaced.
The short answer is: Just about any filter media will work, a piece of scotch brite, etc. This gets back to the original question, does the lower fitting hold pressure, if not the filter is irrelevant, the unit needs to be replaced and will come with a new filter.
The FSM is great for saying "test this, if the reading is other than this, replace". This often leads to lots of replaced parts, often without success. Sometimes it is best to study how the whole system works and what could cause the problem and the FSM is poor in explaining the "how".
The modulator is a regulator. The big hose at the bottom brings in exhaust, it uses this to sense engine load. The exhaust pressure pushes on the diaphragm that is connected to a valve that regulates/modulates vacuum pressure to the rest of the system. Under some conditions it vents vacuum to atmosphere, so that tiny bit of air is filtered. In other words the filter has nothing to do with the operation of the system. The only time where I have seen a filter clogged enough to effect the operation was when the diaphragm is perforated allowing exhaust to clog it, then it is irrelevant, the whole thing needs to be replaced.
The short answer is: Just about any filter media will work, a piece of scotch brite, etc. This gets back to the original question, does the lower fitting hold pressure, if not the filter is irrelevant, the unit needs to be replaced and will come with a new filter.