dr bob

Bill--

Remember thatthe sniffer is in place --after-- the cats. Trying to diagnose mixture from CO after the cats is borderline futile. However, the other symptoms NOx and HC both point to a lean condition. It looks to be lean causing a lean misfire and the high NOx. The car would be driving pretty poorly.

Mike NJSharkfan, see if you can borrow a known-good MAF from another lister local to you. That will be a quick way to find out if that's the problem.

You can attach a voltmeter to a known good oxy sensor and get an idea of rich/lean conditions.

The good news is that your car will come to life once you get this problem nailed, and your royalty payments to the gas gods will also drop substantially, at least on a per-mile basis.

Bill51sdr

True that Bob. My reference to the CO was replying to other's suggestion that a CO adjustment could be in order, which IMO will not do a thing in this situation. That's what the "CO tubes" are for, if they are even still in place!

My diagnosis was based on the extremely high HC and NOX readings, which may be as I stated be a result of or is resulting in a misfire. I think the MAF or O2 is a good place to start.

John Speake

If he can't adjust up to the spec 0.6% CO, (as I suspect may be the case) then this is a very good indicator that the MAF is bad.

The test pipes are before the cats...

Bill51sdr

Mike Frye

OK,

I found and fixed some vacuum leaks, and was able to adjust the idle down to 750 (although it often hangs around 1000 still). I took it back through inspection and passed for NOx this time , but my HC is still not good.

It's definitely running smoother, although I'm still feeling a little vibration on accellerations that I think might be a miss, but could be something else. She's got gobs of power and runs well, I just don't know.

Several responses said to test the MAF. I'm looking into this next.

Here's the report.


I only have until 11/30 to get this right, so if anyone can help with this I'd really appreciate it.

RngTrtl

This is OT, but how much does an emissions test cost to get done? Do you get to keep coming back until you pass for free, or do you have to keep paying? In Dixie we don't have to have emissions done and I am curious about this process. Thanks

Mike Frye

RngTrtl,

No, the rule up here is that you can get a state inspection as many times as you need to for free, but you have to provide documentation that something was done. Either a reciept from a shop or reciepts for parts if you did it yourself. I just did some adjustments and they gave me a hard time because there were no reciepts, it's a good thing there was a change or they may have been more difficult.

They only give you 45 days from when it was originally due though, so my time to get it done is almost up. If I go past that time, and I get stopped, it's a ticket for 'failure to inspect'. I think there's some kind of waiver process you can go through as well if you continuously can't pass and the car is really old. I don't think that will be necessary for me though, I just have to keep trying.

PS- They love me there(not). There's only one or two people who can drive a stick and one of them is a woman only 5' tall. When they see me coming they call her over to give her a hard time. She can't even see over the wheel when I get out because I keep the seat waaay back.

I just ordered an 02 sensor even though I haven't metered mine. I figure if it's not bad now it soon will be. I'll also pull the MAF and see if I can figure out if it's OK or not.

I just posted the results for those (like me) who are interested in what each type of fix would do to the numbers. I'm also too cheap to order all of the parts and do it at once, and I'd rather figure out what was really wrong.

Lorenfb

Besides checking:

1. temp sensor
2. MAF sensor
3. O2 sensor

One should not assume that the fuel pressure is correct, i.e. the fuel pressure should always be
checked as part of an emissions problem troubleshooting which appears to not
have been mentioned (unless an oversight on my part).

Since both the NOx & CO are O.K. but the HCs are off, the problem may be a weak cylinder;
e.g. fouled spark plug, leaky injector. Do a little more troubleshooting before spending money
on parts, e.g. pull spark plug wires while running to locate a weak cylinder.

Mike Frye

Loren,

That's a new one on me. I'm definitely in the camp of identify-and-fix rather than swap-and-test.

I replaced the plugs after my first inspection (I had no maintenance history on it, so don't know how old they were). I have another set I was planning to put in now that I've got it mostly sorted out. Since I had many vacuum leaks I expect some plugs are fouled.

How do I go about checking fuel pressure?

I haven't done the 'pull one wire at a time while running' because it didn't seem to be idling rough at all, but I'll definitely give that a shot as well.

And thanks for your time. I know this is a relatively old thread, and I appreciate everybody's help.

Lorenfb

"How do I go about checking fuel pressure?"

You need a fuel pressure gauge.

"I haven't done the 'pull one wire at a time while running' because it didn't seem to be idling rough at all"

That's true, but a cylinder may be borderline and not having complete combustion
causing high HCs, i.e. unburned hydrocarbons. Another approach to locating the problem
is to troubleshoot the system open-loop (O2 sensor disconnected) to determine why a high
HC level.

Lizard928

be careful while pulling the plug wires off as you can get a serious jolt if you should be grounded yourself.

I would be replacing the O2 sensor as it is a wear item, if this doesnt fix it then I would be looking at the MAF. I doubt it is a dead cylinder, but a compression and leakdown test would be what I would do to comfirm/disprove that theory.

Mike Frye

Loren,
'You need a fuel pressure gauge.'

OK. I guess that test is going to the end of the list, 'cause I don't have one and wouldn't know where to hook it up if I did.

For the 02 loop test. I still need to get under there, but as Lizard said, it's something I'll need anyway at some point, so I may just replace that one if it gets here in time.

Lizard,
Compression looked good in the cylinders, I posted them here a while ago, didn't do a leakdown test. Also thanks for the warning on the wire check, been there, did that, got the shock.

I'm going with the MAF/O2 ideas for now, since it's really not running rough at all, although on accelleration I do feel a little hesitation sometimes (could be pilot error as well). I'll try to pinpoint it if I can (rpm range, if it always does it the same or is intermittent...)

Thanks again for the ideas.

Lizard928

the fuel pressure guage is easy to hook up, if you look on the passenger side fuel rail you will see a closed nut on the end of it. Remove this (be sure to catch the ball bearing inside) and screw the fuel guage on yourself. Very simple.

A compression test will not always turn up all the problems, it will only turn up MAJOR problems.
I had a 944 friend who had a blown head gasket @ 91k miles. it was blatently obvious that the gasket failed on the #3 cyl, did a compression test and it read within 10 PSI of the other ones. but a leakdown test showed the problem alot more. We ran the tests just for his benifit. But just removing the plugs made it obvious that #3 had let go.

Mike Frye

Lizard,
Thanks for the tips. I'll have to look up some info on fuel guages and where to get one. I've seen some pix where people (I think) keep them on there all the time? I think that would be helpful.

I'll also give the leakdown test a shot, I've seen some posts on how to go about that. I'm hoping that it's something simple. Since I managed to get the NOx better by a lot just by finding some vacuum leaks, I'm hoping it will be something similar like cleaning/adjusting some things that have been neglected.

Thanks again.

tomcat

Hey Mike,

Don't know much about the emissions system but I recently had similar readings in my BMW which turned out to be a disconnected crank ventilation tube. No drivability issues before reconnecting. Maybe check for leaks on the ventilation circuit - but it sounds like you already did.

Also, in the state of Maryland you can get "historical" status which waives emissions. Maybe there's something similar in NJ.

If you need a new cat, you can get one for about $250.