I thought that...

I would be thinking carbon buildup in a vehicle with so few miles on it.
A good high rpm highway run or a good run in 4 low can sometimes blow
the carbon out or a de-carboning job 'will' clean the carbon out for
sure. They have products your mechanic might be able to use or you can
slowly let the engine ingest a pint of water while you keep the revs up
enough to prevent a stall. One of my older vehicles flunked emissions
and I just paid the guy to do an upper cylinder clean. It then passed.

The water shock will clean the carbon out. I use ATF instead of water
for this just because I was taught that way and know it cleans the
combustion chamber like new. When I worked in garages, they use to do
the ATF cleanout on city driven vehicles to get rid of run on and
pinging under load. I always do this before a head gasket job so I have
everything clean for inspection. It makes a massive cloud of smoke though.

I have been told you can use a vacuum line to suck the water into the
intake for this job. Something like the PCV line would do I believe.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Canadian Off Road Trips Photos: Non members can still view!
Jan/06 http://www.imagestation.com/album/pi...?id=2115147590
(More Off Road album links at bottom of the view page)

kaigoneq@yahoo.com wrote:
> Thanks for the responses.
> Yeh, it seemed like the EGR. So I started checking for replacement EGRs
> for my Jeep.
> Cannot find any at any site.
> I have a service manual and so I looked up EGR.
> Jeep removed the EGR from the wranglers in 1990. So my 1993 does not
> have one.
> It might be regulated by the computer. Maybe the hose is plugged or
> something.
>
> Jim.
>
>
> Outatime wrote:
>> High NO usually indicates a problem with the EGR valve, plugged EGR
>> passages or a leak in the EGR vacuum circuit. I had the same problem
>> with another vehicle last year, and a replacement EGR valve solved the
>> problem.
>>
>> Warning: don't buy an aftermarket EGR valve --they're junk. Go with an
>> OEM part regardless of cost. I learned this lesson the hard way.
>

 

I thought that...

I would be thinking carbon buildup in a vehicle with so few miles on it.
A good high rpm highway run or a good run in 4 low can sometimes blow
the carbon out or a de-carboning job 'will' clean the carbon out for
sure. They have products your mechanic might be able to use or you can
slowly let the engine ingest a pint of water while you keep the revs up
enough to prevent a stall. One of my older vehicles flunked emissions
and I just paid the guy to do an upper cylinder clean. It then passed.

The water shock will clean the carbon out. I use ATF instead of water
for this just because I was taught that way and know it cleans the
combustion chamber like new. When I worked in garages, they use to do
the ATF cleanout on city driven vehicles to get rid of run on and
pinging under load. I always do this before a head gasket job so I have
everything clean for inspection. It makes a massive cloud of smoke though.

I have been told you can use a vacuum line to suck the water into the
intake for this job. Something like the PCV line would do I believe.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Canadian Off Road Trips Photos: Non members can still view!
Jan/06 http://www.imagestation.com/album/pi...?id=2115147590
(More Off Road album links at bottom of the view page)

kaigoneq@yahoo.com wrote:
> Thanks for the responses.
> Yeh, it seemed like the EGR. So I started checking for replacement EGRs
> for my Jeep.
> Cannot find any at any site.
> I have a service manual and so I looked up EGR.
> Jeep removed the EGR from the wranglers in 1990. So my 1993 does not
> have one.
> It might be regulated by the computer. Maybe the hose is plugged or
> something.
>
> Jim.
>
>
> Outatime wrote:
>> High NO usually indicates a problem with the EGR valve, plugged EGR
>> passages or a leak in the EGR vacuum circuit. I had the same problem
>> with another vehicle last year, and a replacement EGR valve solved the
>> problem.
>>
>> Warning: don't buy an aftermarket EGR valve --they're junk. Go with an
>> OEM part regardless of cost. I learned this lesson the hard way.
>

 

I thought that...

I would be thinking carbon buildup in a vehicle with so few miles on it.
A good high rpm highway run or a good run in 4 low can sometimes blow
the carbon out or a de-carboning job 'will' clean the carbon out for
sure. They have products your mechanic might be able to use or you can
slowly let the engine ingest a pint of water while you keep the revs up
enough to prevent a stall. One of my older vehicles flunked emissions
and I just paid the guy to do an upper cylinder clean. It then passed.

The water shock will clean the carbon out. I use ATF instead of water
for this just because I was taught that way and know it cleans the
combustion chamber like new. When I worked in garages, they use to do
the ATF cleanout on city driven vehicles to get rid of run on and
pinging under load. I always do this before a head gasket job so I have
everything clean for inspection. It makes a massive cloud of smoke though.

I have been told you can use a vacuum line to suck the water into the
intake for this job. Something like the PCV line would do I believe.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Canadian Off Road Trips Photos: Non members can still view!
Jan/06 http://www.imagestation.com/album/pi...?id=2115147590
(More Off Road album links at bottom of the view page)

kaigoneq@yahoo.com wrote:
> Thanks for the responses.
> Yeh, it seemed like the EGR. So I started checking for replacement EGRs
> for my Jeep.
> Cannot find any at any site.
> I have a service manual and so I looked up EGR.
> Jeep removed the EGR from the wranglers in 1990. So my 1993 does not
> have one.
> It might be regulated by the computer. Maybe the hose is plugged or
> something.
>
> Jim.
>
>
> Outatime wrote:
>> High NO usually indicates a problem with the EGR valve, plugged EGR
>> passages or a leak in the EGR vacuum circuit. I had the same problem
>> with another vehicle last year, and a replacement EGR valve solved the
>> problem.
>>
>> Warning: don't buy an aftermarket EGR valve --they're junk. Go with an
>> OEM part regardless of cost. I learned this lesson the hard way.
>

 

bllsht wrote:

> Give up on the EGR already. It doesn't have EGR.
> Anything that increases combustion temp can cause high NOx. Carbon
> buildup, wrong spark plugs, slow O2...

I agree; very high combustion chamber temps will be the problem.

If not equipped with an EGR "system", other reasons for high NOx are:

* Incorrect timing (too far advanced)
* Excessive combustion chamber deposits (check with compression guage)
* Lean fuel mixture, which can be caused by many things including O2
sensor problems, intake leak, MAF problem, etc.
* Hot spark plugs which can ignite the fuel mixture prematurely
* Badly functioning cooling system (would have to be VERY badly
overheating to cause this)


I would start with the simple stuff; verify timing and advance
mechanism, do a compression check on all cylinders (water injestion can
often knock out what's in there) and verify the cooling system temp with
a digital thermometer and DVOM to verify fan engagement temps. Change
the spark plugs with known proper type. If that all checks out, it's
time to find out why the fuel mixture is too lean.

 

bllsht wrote:

> Give up on the EGR already. It doesn't have EGR.
> Anything that increases combustion temp can cause high NOx. Carbon
> buildup, wrong spark plugs, slow O2...

I agree; very high combustion chamber temps will be the problem.

If not equipped with an EGR "system", other reasons for high NOx are:

* Incorrect timing (too far advanced)
* Excessive combustion chamber deposits (check with compression guage)
* Lean fuel mixture, which can be caused by many things including O2
sensor problems, intake leak, MAF problem, etc.
* Hot spark plugs which can ignite the fuel mixture prematurely
* Badly functioning cooling system (would have to be VERY badly
overheating to cause this)


I would start with the simple stuff; verify timing and advance
mechanism, do a compression check on all cylinders (water injestion can
often knock out what's in there) and verify the cooling system temp with
a digital thermometer and DVOM to verify fan engagement temps. Change
the spark plugs with known proper type. If that all checks out, it's
time to find out why the fuel mixture is too lean.

 

bllsht wrote:

> Give up on the EGR already. It doesn't have EGR.
> Anything that increases combustion temp can cause high NOx. Carbon
> buildup, wrong spark plugs, slow O2...

I agree; very high combustion chamber temps will be the problem.

If not equipped with an EGR "system", other reasons for high NOx are:

* Incorrect timing (too far advanced)
* Excessive combustion chamber deposits (check with compression guage)
* Lean fuel mixture, which can be caused by many things including O2
sensor problems, intake leak, MAF problem, etc.
* Hot spark plugs which can ignite the fuel mixture prematurely
* Badly functioning cooling system (would have to be VERY badly
overheating to cause this)


I would start with the simple stuff; verify timing and advance
mechanism, do a compression check on all cylinders (water injestion can
often knock out what's in there) and verify the cooling system temp with
a digital thermometer and DVOM to verify fan engagement temps. Change
the spark plugs with known proper type. If that all checks out, it's
time to find out why the fuel mixture is too lean.

 

bllsht wrote:

> Give up on the EGR already. It doesn't have EGR.
> Anything that increases combustion temp can cause high NOx. Carbon
> buildup, wrong spark plugs, slow O2...

I agree; very high combustion chamber temps will be the problem.

If not equipped with an EGR "system", other reasons for high NOx are:

* Incorrect timing (too far advanced)
* Excessive combustion chamber deposits (check with compression guage)
* Lean fuel mixture, which can be caused by many things including O2
sensor problems, intake leak, MAF problem, etc.
* Hot spark plugs which can ignite the fuel mixture prematurely
* Badly functioning cooling system (would have to be VERY badly
overheating to cause this)


I would start with the simple stuff; verify timing and advance
mechanism, do a compression check on all cylinders (water injestion can
often knock out what's in there) and verify the cooling system temp with
a digital thermometer and DVOM to verify fan engagement temps. Change
the spark plugs with known proper type. If that all checks out, it's
time to find out why the fuel mixture is too lean.