1990 2.9 Ranger Fails Smog Help!
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Freshman User
Joined: Jul 2004
Posts: 32
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From: San Bernardino
1990 2.9 Ranger Fails Smog Help!
Hello all,
I just took my new truck in yesterday to get smogged to complete transfer. It had a CEL when I got it which turned out to be lean mixture. I found that the O2 sensor wiring was messed up and touching the exhaust downpipe grounding it and sending lean signal. I replaced it with an OEM sensor and no more CEL. This was done prior to smog.
It is a 2.9 Automatic with a MAF and no EGR. I took some Catalytic temp readings after truck being warmed up driving up a slight incline hill in 2nd gear at 25MPH like on the Dyno at smog station. The readings do not seem correct, but thought I would share and see what you all think. First test was 486F in front of Cats, 502F in between Cats, and 380 after 2nd Cat. Another test was 677/643/475 and 3rd was 650/671/475. Does that seem right? By the way, I am getting 19MPG average per tank.
Check out the below link. It is a copy of my Smog results. Any and all comments, tricks, etc. would be appreciated. I am going to try again tomorrow.
http://i5.photobucket.com/albums/y17...RangerSmog.jpg
No exhaust leaks
8 Degrees BTDC
Stove pipe flap closed when warm..ok
Thank you all for your help!
I just took my new truck in yesterday to get smogged to complete transfer. It had a CEL when I got it which turned out to be lean mixture. I found that the O2 sensor wiring was messed up and touching the exhaust downpipe grounding it and sending lean signal. I replaced it with an OEM sensor and no more CEL. This was done prior to smog.
It is a 2.9 Automatic with a MAF and no EGR. I took some Catalytic temp readings after truck being warmed up driving up a slight incline hill in 2nd gear at 25MPH like on the Dyno at smog station. The readings do not seem correct, but thought I would share and see what you all think. First test was 486F in front of Cats, 502F in between Cats, and 380 after 2nd Cat. Another test was 677/643/475 and 3rd was 650/671/475. Does that seem right? By the way, I am getting 19MPG average per tank.
Check out the below link. It is a copy of my Smog results. Any and all comments, tricks, etc. would be appreciated. I am going to try again tomorrow.
http://i5.photobucket.com/albums/y17...RangerSmog.jpg
No exhaust leaks
8 Degrees BTDC
Stove pipe flap closed when warm..ok
Thank you all for your help!
Post Fiend
Joined: Jan 2003
Posts: 9,748
Likes: 16
From: Connecticut
If I'm reading the smog test results correctly, it appears you tested high for NOx. That could indeed be caused by a lean condition, which causes an engine to run hotter. High combustion chamber temperatures are what causes NOx.
A lot of people with early-mid '90s Fords without an EGR system run into this problem (EGR lowers chamber temps, reducing NOx).
One trick to lowering NOx (for testing purposes) is to pull the SPOUT connector which will cause the ignition system to default to 10 degrees BTDC throughout the entire range of RPMs. The dialed-back timing helps lower combustion chamber temps. Once the test is complete, just plug the SPOUT connector back in.
Also, a dirty MAF can cause a lean condition. See: https://www.ford-trucks.com/forums/1...d-pinging.html
https://www.ford-trucks.com/forums/1...-cleaning.html
A lot of people with early-mid '90s Fords without an EGR system run into this problem (EGR lowers chamber temps, reducing NOx).
One trick to lowering NOx (for testing purposes) is to pull the SPOUT connector which will cause the ignition system to default to 10 degrees BTDC throughout the entire range of RPMs. The dialed-back timing helps lower combustion chamber temps. Once the test is complete, just plug the SPOUT connector back in.
Also, a dirty MAF can cause a lean condition. See: https://www.ford-trucks.com/forums/1...d-pinging.html
https://www.ford-trucks.com/forums/1...-cleaning.html
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