93 Z28 LT1 emissions help
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93 Z28 LT1 emissions help New to the site and looking for some advice, please excuse me if this is covered or discussed in a different thread but I was not able to locate anything. I have a unique situation where any ideas or information would be very helpful
the project is a 1993 Z28 Lt1 auto and the problem is getting the car to pass emissions. The problem is the HC's are at 19000 ( yes almost raw fuel ) at a certain RPM range
what is crazy the car has been tested over ten times and
there is zero consistency in the test results.
so I will list everything that has been done to help take them off the board as possible soultions:
NEW:
• EGR
• Plugs \ wires
• Fuel pressure reg
• Charcol canister / lines
• Purge valve
• All check valves on the smog
• Air pump
• Fuel injectors
I have no information from the previous owner. The previous owner was more the type of turn the key and go. The car has a fast chip sticker on the cal but the shop says it does not appear to have any tune to the ECM
about the only thing I have not tried is locating a factory prom
with all original and testing the car that way. If somebody know where I can locate one Any ideas at this point would really help.....
the project is a 1993 Z28 Lt1 auto and the problem is getting the car to pass emissions. The problem is the HC's are at 19000 ( yes almost raw fuel ) at a certain RPM range
what is crazy the car has been tested over ten times and
there is zero consistency in the test results.
so I will list everything that has been done to help take them off the board as possible soultions:
NEW:
• EGR
• Plugs \ wires
• Fuel pressure reg
• Charcol canister / lines
• Purge valve
• All check valves on the smog
• Air pump
• Fuel injectors
I have no information from the previous owner. The previous owner was more the type of turn the key and go. The car has a fast chip sticker on the cal but the shop says it does not appear to have any tune to the ECM
about the only thing I have not tried is locating a factory prom
with all original and testing the car that way. If somebody know where I can locate one Any ideas at this point would really help.....
Thread Starter
Registered User
Joined: Jul 2017
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[QUOTE=96lt1m6;19676614]New cap and rotor
NEW spark plugs
New wires[/QUOTE
i have not changed the opti spark
was kind of avoiding it but had considered it. I guess I get the water pump and do that as well since you have to take it off to get the the spark
NEW spark plugs
New wires[/QUOTE
i have not changed the opti spark
was kind of avoiding it but had considered it. I guess I get the water pump and do that as well since you have to take it off to get the the spark
TECH Veteran
Joined: Apr 2008
Posts: 4,985
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I think bad CATS are more likely the issue than the Opti. If the car is not misfiring or plugs fouled, I would leave it alone.
Confirm you have no exhaust leaks pre 02's. broken exhaust manifold bolts or leaks pre 02 will make PCM dump fuel
Confirm you have no exhaust leaks pre 02's. broken exhaust manifold bolts or leaks pre 02 will make PCM dump fuel
The coolant temp sensor fails to bottom of scale, being -40 degrees. When the PCM thinks it's cold, it dumps fuel to try to warm up the coolant. This is the sensor in the water pump, not the one in the side of the block.
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That is the crazy thing about this, scanned a couple different times and not a single code.
Have made sure the header gaskets are seated properly and bolts are tight, 93 has the ECM which uses the three sensor's rather than the MAF sending real time intake temperatures and adjusting the fuel to air accordingly.
I did replace the TPS as mine was in very bad condition.
Would the CAT's be giving it inconsistent readings? on some tests it is close and others off the chart. Would Pre O2 leak throw the service engine light ?
any ideas on how to locate which cylinder is not burning ?
All the responses are great information and very much appreciated!!!
Have made sure the header gaskets are seated properly and bolts are tight, 93 has the ECM which uses the three sensor's rather than the MAF sending real time intake temperatures and adjusting the fuel to air accordingly.
I did replace the TPS as mine was in very bad condition.
Would the CAT's be giving it inconsistent readings? on some tests it is close and others off the chart. Would Pre O2 leak throw the service engine light ?
any ideas on how to locate which cylinder is not burning ?
All the responses are great information and very much appreciated!!!
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Brett Foote TECH Veteran
Joined: Apr 2008
Posts: 4,985
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Would the CAT's be giving it inconsistent readings? on some tests it is close and others off the chart. Would Pre O2 leak throw the service engine light ?
any ideas on how to locate which cylinder is not burning ?
All the responses are great information and very much appreciated!!!
use a IR temp gun on each exhaust port and if one is considerably lower temp...that cyl is not firing. You would certainly have a "miss" if that was the case
if you have been running rich for some time...that can clog (read kill) CATS, especially if they are already 20 years old with a bunch of miles on them