Hi,

My car (99 accord ex 4 cyl) seems to run better the first few minutes but as it gets to normal op temperature, the power and acceleration seem to go down. I was wondering if the 02 sensor is bad and messing things up when the car goes into closed loop( when it reaches normal temperature).

Would it be a good idea to just disconnect the o2 sensor and see if the car runs the same even if it warms up, so that I can conclude that the o2 sensor may be the culprit? I know that the CEL will come on but any other issues?

Thanks

es

 

Disconnecting o2 sensor -> car isn't running.

 

Why??

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by eswaroop &raquo;</TD></TR><TR><TD CLASS="quote">Why??</TD></TR></TABLE>

Because your 2 o2 sensors (obd2) the ECU take the air/fuel mixture from both among other readings and adjusts your car accordingly. If you get a CEL you will almost automatically run very very rich to try and prevent detonation (like a safeguard your ECU does). If you get a CEL why don't you just pull the damn code and fix what is wrong?

 

you can always pull out your o2 sensors and check them... if you do a search on Oxygen Sensor.. someone posted a picture with the symptoms of o2's damaged to normal... that should help...

 

I AM NOT getting any CEL that is the whole problem!!!!!

But the car is running just shitty.

 

Sometimes o2 sensors will just get nasty but not bad enough to throw a CEL and when they do throw a CEL your car will run like complete ****. I would say run some BG44K through your fuel system and if it still runs like *** I would either replace the o2 sensor or check the fuel filter, spark plugs, wires etc etc

 

The reason your car runs better(in a very small margin) in the morning when you first fire it up is because the rich mixture before the normal opertion temp.

without going into close loop, your gas mileage probably gonna suck really bad.
UNless you drive WOT and Full brake all the time

 

I replaced my spark plugs, though the old ones seem just sooty not worn out. Dont know what but something is making the car retard the timing too much..

 

then go get the damn thing tuned up we do drive accords... theyre gonna be pretty slow. you werent driving something really quick recently to make your car seem wimpy were you?

 

Well I have not driven too many cars, but my accord used to drive great until the "tune up". What tune up are you talking about? I had the valves adjusted, just put in new spark plugs, the oil is pretty much new, mobil 1..

dont know anything else to tune up..

 

Badly need help figuring out what is wrong.

Here is what I know till date.

No CEL codes

The ignition timing advance is 10 degrees during idle ( must be between 11 and 13 according to the honda diagnostics unit).

The spark plugs are blackened (sooty, so rich mixture)

The o2 sensor is shifting between .1 and .89 volts, but quickly enough or not - I dont know..

The car revs smoothly, too smoothly than it ever did earlier in fact (maybe sign of retarded timing)

I think the exhaust is heating up a lot more than usual (again sign of retarded timing?)

Drives okay for around first 15 minutes, then acceleration and response declines drastically as I drive longer, mileage also suffers.

What could be wrong??

thanks,

es

 

You seem to know a lot without knowing how to fix it.
Do you know any good garages and/or mechanics that you really trust?
While you can replace a lot of parts and maybe eventually find the one that is causing the problem, a really experienced mechanic can isolate and find the problem very quickly and fix it.
I can tell you that your O2 sensor does control both your air/fuel mixture, and it can alter your ignition timing as well. If it is bad, or really fouled, it could very well be giving you a bad mixture as well as affecting your ignition timing in a negative way. So you may as well replace it. They are supposed to be changed every 60,000 miles or so.(Even though I have 201,000 miles on mine. Oh well, it works just fine.) And you may as well go with an OEM from a dealer, one from a parts store is almost just as expensive.

 

Have you changed your spark plug WIRES?
Take out your O2 sensor, let it soak in carb cleaner overnight, reinstall.
What about the EGR system? Have you checked it? Is it clogged?

 

<FONT COLOR="royalblue">Removing will hinder your daily driving performance, but not 1/4.</FONT>

 

Well, I think I have a possible answer to what happened...

The valve adjustment which the dealer did was badly done, all the valves were tighter by .003" or so when I checked them. I think I might have burnt valves due to the tight adjustment. Even after I set the valves back to factory specs, the problem will persist as the valves are already burnt and will not seat properly in their seats.. this will damage the valves further as I keep driving.. as the exhaust gases act like a blow torch on the incorrectly closed valves... Damn the dealer, they are disclaiming that they are at fault and also saying that I should not have corrected the valves.

I really dont know a mechanic I can trust anymore. The acura dealership I went to is supposed to have the best mechanic put on the job, and he did a valve job in which all the valves were tighter by .003 inches ! And I want to minimize this effort of changing each sensor and hence the research.

Do you think it is safe to dip the o2 sensor in a carbon cleaning solution overnight? They are supposed to be really sensitive to such things..

 

And I have not tried changing the spark plug wires, Maybe I should do that? Is there a way to check if they are faulty?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by eswaroop &raquo;</TD></TR><TR><TD CLASS="quote">And I have not tried changing the spark plug wires, Maybe I should do that? Is there a way to check if they are faulty?</TD></TR></TABLE>

get a voltage meter and run a resistance test

 

Any opinions about the possibility of burnt valves which I mentioned before?

 

Hi,

I had a leak down test done today and the results are 8 % on two of the cylinders and 12% on the other two. They say that the rings have seized up due to carbon and that is what is causing the leak.

What do I do now?

Thanks

Es

 

... time for an engine rebuild...

but a leakdown like that could also point to burnt valves... as you said, they may not be seating properly.

so it's maybe time to rebuild the head...

either option is expensive and shitty.

 

What about trying a couple of bottles of techron concentrate and see if the rings loosen up? That is hoping that the valves are not burnt.. I noticed a strong fuel smell in the engine oil and was wondering if it is related to the leaking rings?

 

Hi,

In addition to all the problems mentioned above, I noticed something strange with the exhaust gases on my car, when I ask someone to stamp on the gas and the rpm goes up, and I feel the exhaust stream using my hand, the exhaust gases volume(flow) reduces and becomes hotter, at really high rpms, I almost cannot feel the exhaust flow, only the heat.. What is happening???

Thanks,

es

I have already run two bottles of techron and

 

Hm, check your catalytic converter and check for oil leaks around the head. Also check your distributor.

 

But how can the flow through the cat reduce at higher rpms? It at least should stay the same isnt it?? And there are no oil leaks around the head..