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As stated above I've got two fault codes on my 1999 Plymouth Voyager (base) with 2.4 liter 4-cylinder engine. The van runs well but burns an appreciable amount of oil; roughly one quart every 400 miles. I've owned it not quite a year now. During the winter, in cold weather, the "Check Engine" light would sometimes go out and the codes would clear on their own...but it doesn't get cold and stay cold very long in Houston.

I want to fix this problem and I want to fix it right, but I also want to do the work myself (with one exception...if welding a new catalytic converter in is required, I may be compelled to turn to outside assistance). However, I don't just want to change parts and hope. How can I best pin down the cause of this problem and fix it the first time?

I have a good selection of mechanic's hand tools plus the help of a friend with a much more comprehensive set. I'm willing to purchase a good diagnostic scan tool for use now and in the future; I've been driving Chrysler products since the early 1980s and plan to stick with them. My current el cheapo scan tool reads the codes above in order...P0171 and P0420; when I read the codes using the odometer and ignition key trick the codes I get are 3, 7, and 55 (I recently replaced the A/C compressor and had the battery disconnected for that).

Thanks In Advance for any help with this question.
 

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ehbowen - I think if it was me I'd first look at the downstream O2 switching behavior relative to the upstream O2. There's a thorough description of that in the factory service manual, which is usually only about $15 in electronic version on eBay. Make sure your scanner has that ability,

MT
 

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As stated above I've got two fault codes on my 1999 Plymouth Voyager (base) with 2.4 liter 4-cylinder engine. The van runs well but burns an appreciable amount of oil; roughly one quart every 400 miles.....
With that much oil your engine is burning, more likely than not, you need to replace the C.C.

But you should first address your oil burning problem, otherwise your new C.C. will not last much.

New valve seals might fix both issues (oil burning and P0171).

Good luck.
 

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Discussion Starter #4
ehbowen - I think if it was me I'd first look at the downstream O2 switching behavior relative to the upstream O2. There's a thorough description of that in the factory service manual, which is usually only about $15 in electronic version on eBay. Make sure your scanner has that ability,

MT
Well, I've just ordered an Autoenginuity PC scan tool with the Chrysler-specific add-on package; it should have that ability. (If not, I will be very angry...very angry indeed [/Marvinmartian]!) And I already do have the factory service manual in electronic form; it was one of my first purchases after buying the van a year ago. Thanks for the suggestion.
 

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With that much oil your engine is burning, more likely than not, you need to replace the C.C.

But you should first address your oil burning problem, otherwise your new C.C. will not last much.

New valve seals might fix both issues (oil burning and P0171).

Good luck.
Worth trying. It will be my first time doing this job (the 318 poly-head I rebuilt in the Navy hobby shop 36 years ago doesn't count...); do you have any pointers for this job which would be specific for the 2.4 liter engine?

Edit To Add: Piston positioning...Is it a correct assumption that when the #1 cylinder is at TDC, the #4 cylinder will also be at TDC and the #2 & #3 cylinders will be BDC, and vice versa?
 

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Worth trying. It will be my first time doing this job (the 318 poly-head I rebuilt in the Navy hobby shop 36 years ago doesn't count...); do you have any pointers for this job which would be specific for the 2.4 liter engine?

Edit To Add: Piston positioning...Is it a correct assumption that when the #1 cylinder is at TDC, the #4 cylinder will also be at TDC and the #2 & #3 cylinders will be BDC, and vice versa?
I should add that very recently (two months ago) I did successfully replace my timing belt and water pump, so I do have some familiarity with the front of the engine. It was a bear of a job for a home mechanic, but I completed it in two days. Hopefully it will go a bit easier working on the valve seals since I now have some idea of what's involved with the belt and camshaft sprockets.
 

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do you have any pointers for this job which would be specific for the 2.4 liter engine?

No, I haven't worked on that particular engine.

Edit To Add: Piston positioning...Is it a correct assumption that when the #1 cylinder is at TDC, the #4 cylinder will also be at TDC and the #2 & #3 cylinders will be BDC, and vice versa?

I think so, but camshaft would be in different position.
 

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Discussion Starter #8
do you have any pointers for this job which would be specific for the 2.4 liter engine?

No, I haven't worked on that particular engine.

Edit To Add: Piston positioning...Is it a correct assumption that when the #1 cylinder is at TDC, the #4 cylinder will also be at TDC and the #2 & #3 cylinders will be BDC, and vice versa?

I think so, but camshaft would be in different position.
If I'm understanding the cylinder head layout properly, those camshafts are going to have to come out completely to reach the valve seals. So everything is going to have to be re-timed anyhow when it's put back together. I want to be very very sure on the procedure before I start on it.

I might possibly break down and farm this one out; the timing belt (as I said) was a real bear. The mechanic I used to use for my 300 just quoted me a decent price to replace my fuel pump and fuel filter (car runs OK, but the fuel gauge sender is all over the place and after 21 years might as well); he said that his phone is "not exactly ringing off the wall right now." $225 labor, plus parts...not bad when doing it myself would mean acquiring/renting a jack/stand setup with enough lift to drop the fuel tank. Not to mention the very real likelihood that something back there is so crudded up or rusted that it might need to be cut. I'm bringing the van in to him on Monday.
 

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Edit To Add: Piston positioning...Is it a correct assumption that when the #1 cylinder is at TDC, the #4 cylinder will also be at TDC and the #2 & #3 cylinders will be BDC, and vice versa?
Piston-wise, yes.

Throwing cam timing into the mix, at #1 TDC:
#1 is at TDC compression
#2 is at BDC power
#3 is at BDC intake
#4 is at TDC exhaust

This will be true for nearly every 4 cylinder engine.
Firing order will be 1-3-4-2.
 

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Discussion Starter #10
With that much oil your engine is burning, more likely than not, you need to replace the C.C.

But you should first address your oil burning problem, otherwise your new C.C. will not last much.

New valve seals might fix both issues (oil burning and P0171).

Good luck.
Now that I've taken a closer look at it, I think that the engine is leaking more oil than it's burning. I'm not getting any of that characteristic blue oil smoke, either right at startup (hot or cold) or after the engine has warmed and run for a while. I do still definitely have emissions issues; there's a black spot where the vehicle is commonly parked where idling while warming up in winter, but I'm wanting to take a look at other options besides the valve seals.

The new scan tool arrived just the other day; I'm still learning how to use it. It looks as if it should be able to look into all of the emissions sensors, but I'm still learning which tests to run and how to run them.
 

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With your scan tool, monitor PIDs for O2-B1S1 and O2-B1S2. Both waveforms should alternate. B1S2 should be a delayed and lower value but otherwise mimic B1S1. For a valid p0420 code you will see B1S2 start low and quickly increase. This means that the cat is fouled out and not burning off the nasty hydrocarbons and nitrous oxides as it should.

Since you have a p0171 for running lean, you should see your fuel trims in the negatives - meaning the system is adding instead of trimming fuel to try to compensate. PIDs for those will be labeled something like "ST FT" or "Short Term Trim" and "LT FT" or "Long Term Trim". As the names suggest, short term fuel trim monitors what the engine is currently doing while long term is a measurement over time. Ideally you want both of these numbers to be 0. It is considered normal when at a steady RPM (idle or otherwise) the number fluctuates between 2 and -2, though a good running engine should stay in the 1 to -1 range.

What type of scan tool did you get? I'm very familiar with the Snap-On brand scanners and have also used (and absolutely hated) a Matco and Autel scanner.
 

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All right, I took it out for a road test with the scan tool. I did read the section in the service manual regarding the operation of the O2 sensors, but I'm still not entirely sure what I should be looking for. So I'm going to post the raw data and ask for help in interpreting it.

The first attachment is a PDF of the raw data as logged by the Autoenginuity scan tool on a drive to the local auto parts store.

The second attachment is a BMP graph of the data converted to PNG for uploading
Voyager Data Graph 2020-03-27.png
; if there's a way to zoom in on a specific section I haven't found it yet.
 

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The O2S B1S1 Reading (bottom red) is spiking downward instead of alternating back and forth. The behavior before 20 ticks is almost normal other than being slow. But after that you notice how the line evens out and then drops briefly. That looks like a partially clogged cat, which would be the reason for your p0420.

Don't really see anything on that which would hint at the p0171, but you should check around the intake for vacuum leaks.
 

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Discussion Starter #14
Thank you. Do you think it would be worth trying a dose or two of Cataclean? Or do I just need to budget for a new catalytic converter before state inspection comes due in June?

If the latter, what kind of new cat would you recommend? OEM equivalent, generic, muffler shop special...what differences are you likely to run into?
 

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You could try Cataclean. Worst it can do is not work. And you should really try to make sure you don't have and intake leaks or weak fuel pressure before doing that. That lean condition may affect the performance of it.

If it doesn't do it, go with a direct fit cat. Avoid weld-ons because they just don't last.
 

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Don't really see anything on that which would hint at the p0171, but you should check around the intake for vacuum leaks.
Took a good look at my vacuum lines this morning. Many of them are wrapped with electrical tape. Something rotten or falling apart underneath? Likely. Vacuum hose is cheap; I'll replace them all. The PCV valve, too, and I think I'll look for a clamp...where the hose joins the manifold is extremely loose.
 

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Well, the detective work continues. Yesterday I replaced my vacuum hoses and PCV valve. I reset the MIL and drove into work, bringing the scanner along. When I got there I reconnected and checked again. The MIL is still not on, but there is what looks to be a preliminary P0401 EGR code. Have to take a look at that system next.
 

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Almost three weeks now, time for an update. Hope it's the final one. In the past three weeks I've driven a little over 400 miles and the "Check Engine" (actually, "Service Engine Soon") light has not come on. I'm hopeful that the problem has been resolved. No new catalytic converter, no Cataclean, no valve seals, just a few feet of vacuum hose and a new PCV valve. I do plan to remove and attempt to clean that EGR valve when I get a chance, but when I next catch the inspection station open I'm going to cross my fingers and bring the old girl in.
 

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Good job. Always nice when a few bits of hose get you back in top shape.

Be careful not to let any cleaner get in the diaphragm (flying saucer part) on the EGR. You'll need to clean the seat and pintle thoroughly. A half-assed job can leave a rough seating area where gas can still get through, possibly even worse than before cleaning. Try to avoid using hard tools on the area where the pintle and seat seal. I use an old toothbrush and brake cleaner.
 
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