Does this sound like cracked heads or block

[zzzasy]

Replaced my first engine in '98 OBW last X-mas when I drove to South Carolina not knowing about the HG issue. The car stopped on me and it turned out that I had cracked the block or at least that what I was told when I was stranded. The guy had a used '97 engine that he put in. Car had been driving fine. One day I drove it to work with no problems. When I was leaving work, the car would only sputter and holding it to the floor it would only go around 20 mph.

 

Got home (about a 35 miles trip) looked under the car and the cat was glowing red hot. Order the cheapo cats off the web; put them on and the car had a camshaft sensor code;so I changed the camshaft sensor. Took the car out for test drive, sometimes it accelerates fine, but most of the time it had that hestitate state like it did when the cats where clogged. It will barely pull a hill.

 

I'm dreading it, but I believe I may have blown another engine. I cleared all the codes once I put the cam sensor in but I have the CES again. I will pull this code this evening when I get home. I'm losing coolant; so I know the HG is gone on this engine, but do you think the symptons I mentioned means a cracked head or block.

 

ZZZASY

[1 Lucky Texan]

Replaced my first engine in '98 OBW last X-mas when I drove to South Carolina not knowing about the HG issue. The car stopped on me and it turned out that I had cracked the block or at least that what I was told when I was stranded. The guy had a used '97 engine that he put in. Car had been driving fine. One day I drove it to work with no problems. When I was leaving work, the car would only sputter and holding it to the floor it would only go around 20 mph.

 

Got home (about a 35 miles trip) looked under the car and the cat was glowing red hot. Order the cheapo cats off the web; put them on and the car had a camshaft sensor code;so I changed the camshaft sensor. Took the car out for test drive, sometimes it accelerates fine, but most of the time it had that hestitate state like it did when the cats where clogged. It will barely pull a hill.

 

I'm dreading it, but I believe I may have blown another engine. I cleared all the codes once I put the cam sensor in but I have the CES again. I will pull this code this evening when I get home. I'm losing coolant; so I know the HG is gone on this engine, but do you think the symptons I mentioned means a cracked head or block.

 

ZZZASY

 

Too much fuel reaching the cat. Either some kinda seriously bad missfire issues or bad injectors or something. Doesn't mean you couldn't suffer 2 or more problems at once or that one problem can create another.

[zzzasy]

Noticed on the way home that the car runs good while cold. Once it reaches the operating temp it starts cutting out. Pulled the new codes and it says the camshaft position sensor (which I just replaced) and the bank 1 knock sensor. Do you think I bought a bad sensor or that problem is related to some other underlying cause. Would it be prudent to run out and buy a knock sensor or is that coming from some other underlying cause.

 

thanks in advance

zzzasy

[nipper]

Replaced my first engine in '98 OBW last X-mas when I drove to South Carolina not knowing about the HG issue. The car stopped on me and it turned out that I had cracked the block or at least that what I was told when I was stranded. The guy had a used '97 engine that he put in. Car had been driving fine. One day I drove it to work with no problems. When I was leaving work, the car would only sputter and holding it to the floor it would only go around 20 mph.

 

Got home (about a 35 miles trip) looked under the car and the cat was glowing red hot. Order the cheapo cats off the web; put them on and the car had a camshaft sensor code;so I changed the camshaft sensor. Took the car out for test drive, sometimes it accelerates fine, but most of the time it had that hestitate state like it did when the cats where clogged. It will barely pull a hill.

 

I'm dreading it, but I believe I may have blown another engine. I cleared all the codes once I put the cam sensor in but I have the CES again. I will pull this code this evening when I get home. I'm losing coolant; so I know the HG is gone on this engine, but do you think the symptons I mentioned means a cracked head or block.

 

ZZZASY

 

Your engine is fine. For some reason your running either extra rich or extra lean. Physically inspect the knock sensor, if it looks the slightest bit cracked, replace it, or its not terrible expensive, may just want to change it out.

 

nipper

[ferret]

When it is in the failing condition, shut it off, then unplug the Front Oxygen Sensor. Restart it and see of the problem goes away. (This WILL set a CEL that will have to be reset either with an OBDII tester or disconnecting the battery for a few minutes) This will run the engine in 'Open Loop' mode (no feedback for air/fuel ratio). The car will run on a preset of mixtures programmed into the ECU.

If the problem goes away, replace the front Oxygen sensor. This is a nitch problem that Subaru hasn't released any data on, but some dealers and servicers who have come across it have seen it. When warm, the Oxygen sensor tells the ECU that it's running rich and shuts down the fuel injectors. Hence the hesitation and loss of power.

Also every 'red' cat I have seen is from 'too lean' mixtures, not too rich. This was very common on early 90 Honda engines as the valve seats wore and the engines ran really lean. Saw a lot of damaged cats on early 90 Honda's, even heard of 2 that got soo hot the cars caught on fire.

[nipper]

you right, too lean can melt a cat or set a car on fire... brainfart.

 

Didnt know about the o2 trick, that it would cut things that far back.... ill fie that away in my head for later:lol:

 

 

nipper

[OB99W]

Too much fuel reaching the cat. Either some kinda seriously bad missfire issues or bad injectors or something.

I used to think that was the only cause, too. Back when cats were the "2-way" type (converting only HCs and CO), it was true. Since about '77 or so, cats also need to deal with NOx (nitrogen oxides), and so are now "3-way". Modern cats can get too hot with an excessively lean mixture because that's when NOx is especially prevalent.

 

--OB99W

[1 Lucky Texan]

Interesting on the cats - I was speaking from fairly old knowledge.

 

so, shouldn't my cars be molten right now since there is 0 fuel going through them? That's about as lean as it gets.

 

;^)

 

(any links to an explanation of the chemistry that goes on inside newer type converters?)

 

I love learning new stuff.

[OB99W]

No links offhand, Carl; doing a Google search on terms like "3-way catalytic converter" ought to turn lots up.

 

Your response made me realize that I did a poor job of explaining the lean/NOx aspect of cat operation. Of course, there's more to it. HCs and CO need to be oxidized, but the NOx reaction is one of reduction (okay, all are redox reactions, but I'm not getting into the chem that deeply now ). It may seem strange, but the catalyst for NOx reduction can't work unless it's in a rich enough environment. Therefore, engine controls are designed to cause the mixture to oscillate between the rich and lean states, at a fairly rapid pace; that's where O2 sensors come in. Anything that causes that oscillation to significantly change pace or amplitude makes the emissions go up and the cat unhappy. If the O2 sensor signal gets bad enough, the computer is supposed to default to "limp" mode (somewhat rich condition); that's why pulling the O2 sensor connector helps diagnose its condition.

 

By the way, I didn't mean to suggest that a constant lean condition would cause the cat to overheat. In fact, it shouldn't, since lean running would normally suggest low HCs and CO, and even though the NOx would be up, the catalyst for NOx reduction wouldn't work well in that environment.

 

--OB99

[1 Lucky Texan]

No links offhand, Carl; doing a Google search on terms like "3-way catalytic converter" ought to turn lots up.

 

Your response made me realize that I did a poor job of explaining the lean/NOx aspect of cat operation. Of course, there's more to it. HCs and CO need to be oxidized, but the NOx reaction is one of reduction (okay, all are redox reactions, but I'm not getting into the chem that deeply now ). It may seem strange, but the catalyst for NOx reduction can't work unless it's in a rich enough environment. Therefore, engine controls are designed to cause the mixture to oscillate between the rich and lean states, at a fairly rapid pace; that's where O2 sensors come in. Anything that causes that oscillation to significantly change pace or amplitude makes the emissions go up and the cat unhappy. If the O2 sensor signal gets bad enough, the computer is supposed to default to "limp" mode (somewhat rich condition); that's why pulling the O2 sensor connector helps diagnose its condition.

 

By the way, I didn't mean to suggest that a constant lean condition would cause the cat to overheat. In fact, it shouldn't, since lean running would normally suggest low HCs and CO, and even though the NOx would be up, the catalyst for NOx reduction wouldn't work well in that environment.

 

--OB99

 

Yeah, I'd expect reducing the NOx ,even in the presence of a catalyst, probably requires an elevated temperature or possibly the presence of one of the other compounds from the HC or CO reactions. I will try to locate an explanation I can get my braincell around.

 

thanx

[ferret]

This URL point to a UK Ford site, but the explaination is the same no matter who the manufacturer is:

 

 

http://www.fordscorpio.co.uk/cats.htm

[1 Lucky Texan]

This URL point to a UK Ford site, but the explaination is the same no matter who the manufacturer is:

 

 

http://www.fordscorpio.co.uk/cats.htm

 

Not a bad beginning explanation.

 

also, from that site, check out this!;

http://www.picotech.com/auto/lambda_sensor.html

 

VERY detailed O2 sensor stuff with diagnostic hints, etc. particularly interesting for some of us, how easily the sensors can be damaged by coolant in the exhaust or by an ohmmeter!

[OB99W]

VERY detailed O2 sensor stuff with diagnostic hints, etc. particularly interesting for some of us, how easily the sensors can be damaged by coolant in the exhaust or by an ohmmeter!

Thanks for the links, they reminded me of another problem with an excessively lean mixture that I didn't mention. Not only will NOx go up with a too-lean mix, but HCs can too, due to misfire; that would help explain the "lean mix, but overheating cat" scenario. All of this is why it's often not easy to diagnose A/F problems.

 

I knew about not using an ohmmeter on zirconium-type O2 sensors; I've only used a voltmeter to obtain a rough indication, or a 'scope for the details. However, I've never tried heating an O2 sensor (off the vehicle) with a propane torch as suggested in the linked article, but it seems that should work.

 

--OB99W

[1 Lucky Texan]

Thanks for the links, they reminded me of another problem with an excessively lean mixture that I didn't mention. Not only will NOx go up with a too-lean mix, but HCs can too, due to misfire; that would help explain the "lean mix, but overheating cat" scenario. All of this is why it's often not easy to diagnose A/F problems.

 

I knew about not using an ohmmeter on zirconium-type O2 sensors; I've only used a voltmeter to obtain a rough indication, or a 'scope for the details. However, I've never tried heating an O2 sensor (off the vehicle) with a propane torch as suggested in the linked article, but it seems that should work.

 

--OB99W

S0, how would I know what type lambda sensor my soobs have? Or is one type exceedingly rare....

[OB99W]

S0, how would I know what type lambda sensor my soobs have? Or is one type exceedingly rare....

It's a good thing I share your apparent thirst for knowledge ...

 

A little background; both zirconium- and titanium-based O2 sensors are actually ceramic semiconductors (zirconium dioxide = zirconia, titanium dioxide = titania). However, the zirconia type is (mostly) a voltage-generative type, while the titania resistance-changing. ( I said "mostly" because all semiconductors change resistance and generate voltage to some degree with external influences like heat, pressure, and yes, even O2 .)

 

The zirconia is the common one, and as you questioned, the titania rarer. The normal operation voltage of the zirconia units is a max of 1 volt or so, and some ohmmeters can damage the semiconductor.

 

The titania units actually have voltage applied to them during normal operation, since they aren't self-generative, and as long as it isn't excessive, they aren't damaged by it.

 

I'll admit that I'm not that familiar with the exact applications, so without info I just play it safe and use voltage rather than resistance tests of O2 sensors during diagnosis. Of course, having the manufacturer's procedures and specs would really help!

 

--OB99W

[OB99W]

"Nice" pic: http://forums.nasioc.com/forums/showthread.php?t=907773

[1 Lucky Texan]

"Nice" pic: http://forums.nasioc.com/forums/showthread.php?t=907773

 

I guess that goes back to what ya'll have been sayin' about the NOx, etc. I wonder if it's significant which END of the cat is the hottest? Like the upstream end could indicate a lean condition whlie the downstreeam section might be hot in a rich condition?

 

I dunno.

[OB99W]

I dunno.

Exactly, I "dunno" either. The NASIOC poster mentioned "highflow" cat. If back-pressure is significantly reduced from spec, that can play havoc with things that the engine management systems can only compensate for to a limited degree. Or, there might have been existing problems or other mods made before the cat change. Of course, looking like it does, that cat may not remain "highflow" for long. Sometimes you can't just out-engineer the factory with a seat-of-the-pants approach without having some mishaps along the way. Not everything the factory does is related to emissions; sometimes it's just to keep things below the melting point .