Poor mileage

[98hd]

I finally ran a tank through and calculated it. I'm only getting about 12mpg in my truck. Reg. cab. SB 2wd '90 chev. 2000 ls1 4l60E. Nelson tune (91 oct) put a new MAF, O2 sensors, fuel pump, and corvette regulator/filter in when I did the swap. It's been 1,100 miles since the swap. Fuel pressure is 58psi.

There has been a black liquid spray coming from the exhaust upon startup also. I did notice today that the hose connecting the PVC/valley cover (ls6 setup) to the intake had a small hole under it and I fixed that. Not sure if that will make a change or not.

[RedHeartbeat]

Ouch, are you pulling in cool air or under hood temp air? Are you sure your 02 sensors are working correctly, cycling from about 100 to 900?

[98hd]

Ouch, are you pulling in cool air or under hood temp air? Are you sure your 02 sensors are working correctly, cycling from about 100 to 900?

I haven't gotten to move the air filter yet, it is like in your picture, but attatched to where the MAF is after the 90deg elbow. Not sure how to check the 02 sensors to see what they are doing.

[RedHeartbeat]

You need a scanner to read the o2s. The black stuff may be due to detonation. Are you running 85 or 87 octane with the 91 octane tune? What condition are your knock sensors? A scanner will let you know if you're getting knock. Have you pulled the plugs and looked at them?

[98hd]

You need a scanner to read the o2s. The black stuff may be due to detonation. Are you running 85 or 87 octane with the 91 octane tune? What condition are your knock sensors? A scanner will let you know if you're getting knock. Have you pulled the plugs and looked at them?

I've run 92/93 oct gas since day 1. Don't have a scanner. I haven't pulled any of the plugs yet either, but I will and report back.

[98hd]

Didn't have alot of time so I only checked the # 1 and 2 plugs. Both were light gray on the tip and electrode.

These were also put in at the time of the swap, ngk tr55's

Here is a pic.

[Chevy-Art]

Is your truck a 90 or a 91? Hey Red, what scanner is the best bang for the buck? On the plugs I would stick with the AC Delco. Nice truck, I went to your link on photobucket. Nice job.

[98hd]

Is your truck a 90 or a 91? Hey Red, what scanner is the best bang for the buck? On the plugs I would stick with the AC Delco. Nice truck, I went to your link on photobucket. Nice job.

It's a '91. Thanks for the compliments, I need to update that page with current pics.