Car went from being very clean to failing emissons in the last 20K miles.
Two years ago, had the dealer replace the oxygen sensor, put new plugs, air filter, pcv valve and this brought it into passing. This made it pass, but it was no where near as clean as the previous test cycle. The catalytic converter was replaced 25K miles ago at the dealer with oem new stuff. All the emissions stuff is connected.
Car has 200k miles. Doesn't burn much oil, but does leak some oil down the valve stems.
I don't think there are any vacuum leaks.
Car doesn't idle quite as nicely as it used to.
What is the most likely suspect causing emissions failure on this car?
Do some of you make this up to get a rise from us or has it occurred to you all that valves are for gasoline intake and exhaust removal and unless you have (nope) a diesel they don't DEAL with oil much? Have you got a nasty case of blow-by? When was the last time you checked your rings? Did your mechanic even look?
The engine is old and with mobile one oil, it puffs on start up only occasionally. It depends on how long it's been parked, weather its on a hill and that sort of thing. It's done this for ten years and is no different lately.
Yes, it is normal for this engine with this milage. It's no different now than when it passed emissions with flying colors.
I could use some help here > OIL LEAKS DOWN THE VALVES? Is it normal to bleed from the mouth?
I don't think it's normal or you wouldn't ask? We have scads of FI 4.3 Blazer 4X4's in the area and they get beaten up far worse than yours. Don't accept that it's the status quo. If you've got oil leaking into your valves, it still sounds to me like your rings are worn out. ESPECIALLY at 200K. Sarcastic, sure, but I'm only flabbergasted bcuz this seems like common sense to me--it has to be looked after even more after 100-120K. Not to mention it's seventeen years old. I have a 1986 2.5 four and don't I know that (I have only 114K).
Perhaps you could inlcude the test results with this posting so everyone can see then specific question such as HC is out of limit at idle or at certain rpm. It is diff to offer suggestion.
A 4.3 V6 is effectively a 350 small block missing two middle cylinders. Small blocks are notorious for puffing a bit on startup after sitting; it's not a catastrophic situation, and, assuming the smoking desists after a few moments, is not an indication of piston ring/bore wear. Rather, it typically indicates worn valve guides/seals. Worn rings would cause oil smoke emissions continuously and to a more severe degree with the hammer down. Posting the ppm and % numbers from the emissions fail report would indeed be helpful.
As for Mr. D> I don't think it's normal or you wouldn't ask? We have scads of FI 4.3
Not much on the common sence then are you MR. Dinius. Lets see, oil leaking onto the valves. Sure, it does happen. Now Rings worn out. Yep, that will happen too. BUT, the rings worn out CAUSING the oil to leak onto the valves? Well, lets just say it COULD cause a little bit of that IF the rings were worn out enough to be letting enough back pressure into the crank case to push oil through the valve guides and seals, AND the pvc valve is completely stopped up AND ALL of the gaskets sealed pressure 100%. So basically, that is NOT the problem.
So basically, the little bit of smoke at startup is more that likely caused by worn valve seals, assuming that there is only a small amount of smoke that goes away really fast.
December 1998 the car had 205,000 miles on it and tested out at:
HC 0.26GPM state limit 2.00 GPM CO 2.2GPM state limit 30.0 GPM
Comfortably clean compared with limits.
In 2000 The car failed emission for both numbers I think, meaning it exceeded
2.0GPM for HC, 30GPM for CO. At that time, the car had around 214,000 miles.
At that time, I had a new O2 sensor installed, PCV Valve, plugs, oil, air filter.. that sort of thing. The catalyst was replaced around 199,000 miles and should be adequate. The exhaust system is in new condition and the car garage kept. The EGR valve seemed to operate in 2000 when a vacuum was applied but I know nothing about the condition of the ports leading through the EGR pathway.
These repairs brought the car within state limits in 2000, but still very high for the car compared with the previous emissions testing. I think HC was over
1.3 GPM.. As it was driven on the treadmill in 2000, the graph of HC was all over the place from clean to fairly high.
The car now has around 226,000 miles on it. I don't know for sure what is failing but my guess is both HC and CO are out. The paperwork is with my nephew who has the car now. He went to get inspection and emissions. Emissions fails. I don't have the numbers back from him yet. I don't know if they even gave them. It failed.
I know that a little seepage down the valve guides that causes a puff occasionally at start up is not causing the emissions failure. The car has done this for all the time I've owned it, including during the fabulous results in 1998. It's no worse now than ten years ago. I've used Mobile One in this engine since 160,000 miles when I bought it. It's been serviced with adequate oil change intervals using Mobile One. I'm confident there won't be any significant mechanical engine wear in the last 20K miles compared to when I got it at 160K miles.
I doubt very much that the rings are suddenly shot in 20K miles, blow by became outrageous and other assertions that a well meaning newsgroup member posted here.
The plugs looked great in 2000, even with 50,000 miles on them. Even the original one that had never been changed ( hard to reach) before was not aweful.
More likely, something has happened suddenly in the way of vacuum leak, carbon in the EGR path or dirty injectors. The car has seen limited use these recent years because I am in poor health. Perhaps fuel sitting has effected injector function.
I was hoping someone here has experienced and fixed the same rapid deterioration in emissions performance and could point us in the right direction. My nephew can't afford to drop this by Mr. Goodwrench for all new parts. I'll try to get his readings if he has them and post them later.
The car runs good, doesn't smoke and sure has hell doesn't need a ring job.
It would appear that Mr. Dinius' sole purpose as a new entrant into these NewsGroups is to see how many posts he can make in the shortest period of time. EARTH TO MR. DINIUS - We want quality of posts, not quantity of posts in these NewsGroups!!! If you have nothing to say, please remain silent!!!
I'd suspect the valve guides/seals. Sad part is, minor oil consumption can kill the cat over a two year period. (ask me how I know). However, it would help to know the actual readings - what failed, HC, CO, or Nox?
If we go ahead and assume (dangerous, I know) that the car failed on HC, CO or both, as before, we know that the most likely culprit is a fuel control problem. EGR is probably not an issue, as this would likely either be causing low power complaints (stuck open) or a NOx failure (stuck closed). If I further assume (I'm not getting into deeper trouble, am I?) that this is a TBI car, we're dealing with a speed density system. A vacuum leak in theory should only increase the idle speed--the system should meter additional fuel to compensate (ever had a Saturn come in because it was idling at 3000 rpm, only to find the culprit was a disconnected PCV hose?).
High CO typically indicates over-rich mixtures, high HC should be accompanied by high oxygen content as indication of a misfire (if the fuel ain't burnin' at all, neither is the oxygen). Misfires can lead to a vicious circle; the unburnt oxygen from the miss is read by the O2 sensor as a lean condition; we then go richer, foul the plugs worse, and may continue misfiring and going richer until the cat goes Chernobyl. This should, of course, be noticeable to the driver ('trailer-hitching' sensation) before things get this bad.
Excessive HC can also be traced to carbon buildup in the chambers--carbon acts like a sponge; it soaks up fuel, preventing it from burning, then when the exhaust valve opens, it releases the HC into the exh stream. The carbon forms, of course, from rich mixtures, so something else would be going on in this case. Of course this isn't set in stone, as tailpipe readings can be distorted by the converter (by its function or lack thereof). High HC and CO reading could also be caused by testing the car while it is cold.
If I was faced with making this diagnosis, I would first do all the obvious stuff, such as checking the air filter, looking for broken/damaged/disconnected wiring, and read the plugs. Check for an exhaust leak at the manifold; if the exhaust scavenging pulses are pulling outside (fresh, oxygen-bearing) air into the exhaust upstream of the O2 sensor, the sensor will misinterpret the ambient oxygen as a lean condition and increase pulsewidth to richen up the motor. I would watch the O2 sensor's output with a scope or graphing multimeter as well (assuming you can get access to one). If you can do this, artificially altering the mixture by indtroducing propane into the TB or inducing a vacuum leak should get a response from the sensor. The ECM should immediately correct, returning the sensor to its appropriate "drunk on a bridge" waveform, of course, but a short, immediate anomaly should be observed from the O2 sensor.
The converter is also a distinct possibility, especially if another failure has caused an over-rich condition; excessive raw fuel in the exhuast cooks cats. Apart from the rotten egg smell (sulfur dioxide) that may accompany a failed converter, I'm always hesitant to blame a (pricey) converter unless I have the luxury of using OBD II's downstream sensor as a comparison (no such animal on an '84).
Now that I have babbled on after making assumptions, let's hear some other opinions...
I'm not going to venture a guess about mechanical or electrical problems but I will tell you this. I had the same problem on three different (high mileage) vehicles and it cost me $2 to fix. I just flushed the engine with Gunk 5 Minute Motor Flush, changed the oil and filter and then drove on the interstate for about 30 miles (voila' - problem solved). It works for me but will it work for you? Only one way to find out.
One guess is that the intake manifold gasket might not be sealing, allowing oil to enter intake runners. This is at best a guess. Chevys are known for intake manifold gasket failure, usually accompanied by coolant leakage.
Thanks for your detailed answers. You seem to understand the issues better than those here saying the engine is shot and similar comments. I have some more data, including the recent emissions report now and I'm not sure how this would effect your conclusions and advice. If you have anything to add, I'm keenly interested.
Concerning the other post about an oil motor flush I think its a bad idea to disturb any grunge that might have collected inside the valve covers where it could get loose and block an oil passageway in this high milage engine. I think it might be a good idea to change the oil before retesting though, and maybe go up to 10W- synthetic in place of 5W- to reduce seepage past the valve guide. BTW, the seepage and puff at start up is a very occasional thing which and happens when the car is parked on certain slopes and restarted 30 minutes later. There is no smoke on wide open throttle or any other time.
I believe all the vacuum lines are connected okay. We've not looked for manifold leaks, intake or exhaust. The air pump is connected. All the emissions stuff is intact. I never saw any reason to detach these devices.
The test in December 1998 at 205,000 miles showed
HC 0.26 GPM state limit 2.00 GPM CO 0.26 GPM state limit 2.2 GPM NOx .5 GPM state limit 3.0 GPM
I think that is a pretty good showing for a car with this milage. I'd buy another if they still made them.
I think the car got a new catalytic converter around 190,000 something miles. I had the converter replaced then becuase it was plugged. I believe it was the original converter too. The result was the car had no power at wide open throttle. I guess that is what you mean by "trailor hitching" effect. The car then felt like it was towing a tractor trailor behind it. It plugged rather quickly and dramatically too. From 160,000 miles to 190,000 miles the car passed with the original converter.
From the 160,000 miles point until 200,000 or so, the car would ping at light engine loading and cold weather after an hour of freeway driving. It would bring the check engine light on after an hour of highway driving. I think the computer code reported EGR issues on the primitive computer as read using the "paperclip" method. I'm not sure, because the error message for codes was different on each web site I looked at for this information. I don't have the shop book. I don't recall the codes read out on the dash lamp now. Might have been 32, and 43 but my memory fades. They either were MAP sensor or EGR depending on the web site. There are no codes in the computer now.
In 2002 the car failed emissions. I had a new O2 sensor put on, new plugs, air filter, pcv valve and new plugs. The old plugs looked great too. There was no significant oil, carbon or deposits on them and no cracked insulators. I had change them previously at 160,000 miles. One plug seemed to be original to the car. It seems most cars have one of these plugs that are too difficult to reach. My friend had smaller tools and got it wapped. I did the work at 160K and my 1/2 inch socket set that could not reach the one plug.. and the others look pretty good so I had reached a point of diminishing returns I thought. That original plug really looked good for the age too. In fact, they all looked better than any
15,000 miles old plug on my old 350 cubic inch 68 Firebird. There is a (temperature?) switch on the EGR valve, and it's wiring was loose, so I had this swapped out too when things failed in 2002.
Anyway, in 2002 the car passed marginally at about 60% of the state limits, which compared with the '98 readings tells me there was still a problem. I still need to get those readings, the paperwork is somewhere. But pass is pass and I drive very infrequently, so it didn't interest me much The car no longer pinged or brought the check engine lamp on after an hour's driving.
The new test is run now 15mph and 25 mph. The readings are as follows:
15 MPH HC 105 (pass) state limit 108
25MPH HC 137 (fail) state limit 106
15 MPH CO 0.06 (pass) state limit 0.61
25 MPH CO 0.12 (pass) state limit 0.12
15 MPH NOx 1389 (fail) state limit 823
15 MPH NOx 1457 (fail) state limit 750
My nephew didn't know to drive the car on the highway a bit before driving to the test station, so he jumped into the car and drove right over. The catalyst was probably not up to working temperature when he got there. D'oh! It probably wouldn't have made the NOx pass anyway though. I think the HC would have been sneeked through had the car been warmed up instead of being driven less than ten minutes in traffic.
My friend who has the same engine in his GMC Jimmey says that he rebuilt the throttle body with a GM kit and his passed afterwards. He also said that the EGR passages become blocked with carbon with these high miles. He had 140,000 miles.
I've read around the net that high NOx means the mixture is burning too hot and that failure of the EGR circuit can cause this... along with catalytic converter and some other issues. The HC is a bit high too and I think that means it's running rich. I think that 15 and 25 mph are fast enough to try to open the EGR path. So perhaps that is the issue.
My friend with the GMC is planning to visit to clean and reassemble the injector TBI assembly. I'm open to more suggestions before he comes next week. We really need this to pass on the next go w/o spending lots of dough. If it needs a new converter, we'll buy one. On my truck, I've replaced the cat and it made very little difference though. The engine has to be working right first.
Thank Mark and others who contributed thoughtful ideas!
I repeat : "EARTH TO MR. DINIUS - We want quality of posts, not quantity of posts in this NewsGroup!!! If you have nothing to say, please remain silent!!! You've said a great deal of nothing in the gm NG, so don't start the same nonsense here. A quick check on Google under the name "Steven Dinius" reveals that you wander around from NG to NG irritating everyone with your asinine comments. This is evidenced by the attached Google Link which shows 118 posts under this name alone and gawd knows how many other trolling aliases you have! A quick view of several of your posts says it all! A quick warning to regulars to the Group, don't waste a lot of time reading Steve's posts because they are basically all the same. They lack substance, say nothing, and only serve to irritate members.
The only ass is U. I don't care one way or the other if you fart around looking for my posts Does that make you proud?
Steven Mark Dinius
416 NE 3rd St Ontario, OR 97914
DOB: 06-26-66 Nampa, ID
you're in Canada
I repeat U are still an ass
former tags: snipped-for-privacy@cyberhighway.net, snipped-for-privacy@fmtc.com, snipped-for-privacy@fmtc.com NO suspensions for any reasons--changed ISP and dropped accts when money was low.
I ain't no damned troll. I am bipolar. Diabetic. Hypertension. Cholesterol. Arthritis. Sick of idiots hastily calling me an idiot. F--- you. Look in the mirror while you chew on your toast. You ain't Jesus either. Bark without thinking. You got a block setting. Use it. I am not anonymous nor did I create a false tag that would bounce back with . And maybe not too happy about my relationship falling apart. Sorry if it gets in the way.
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