I just bought an 88 Laredo 4.0 with a separeted harmonic balancer - easy fix for $60 and now I am happily driving it around. It seems to run great aside from a slightly rough idle. The previous owner spent a good sum of money replacing most of the hoses and sensors on the top end (egr, pcv, etc) as well as the brake vacuum booster. The last smog test failed HC(PPM) and CO(%) at 15-25 mph with the following results:
I also ran a compression test which ran from 118 to 135 psi accross all 6 with no two side by side of the same pressure.
The engine idles like it is searching around a bit, sometimes it seems a little low but it has not stalled out. I have looked, tested and listened for vacuum leaks but I can't find any. I have replaced all the remaining rubber hoses.
I am assuming from the smog results that the oxygen sensor and/or catalytic converter are bad but I have not thrown any engine codes yet so it is purely speculation. Timing on this is computer controlled so I cant set that. My concern is that I may have an injector problem which has perpetuated the results. I have also heard that there is an Idle Control Valve which sometimes requires cleaning to return a good idle (this may be related to a 2500 rpm idle I had once after starting it on an average SoCal day, a few revs and the idle dropped to normal and never did that again). I'm new to this setup and I'm hoping that some of you may have ideas into common problems I might be overlooking.
Thanks for your help, I have a feeling I'll be around here for a while!
- Mike
Code:
[COLOR=black]------------------------------------------------------------------------------------------[/COLOR]
[COLOR=black][_____]-[_____]-[%CO2]-[%O ]-[_____HC(PPM)_____]-[______CO(%)______]-[_____NO(PPM)_____][/COLOR]
[COLOR=black][ TEST]-[ RPM ]-[MEAS]-[MEAS]-[MAX] [ GP ] [MEAS]-[MAX] [ GP ] [MEAS]-[MAX] [ GP ] [MEAS][/COLOR]
[COLOR=black]------------------------------------------------------------------------------------------
15mph - 1640 - 12.5 - 0.2 - 124 311 [COLOR=red]172[/COLOR] - 0.75 2.05 [COLOR=red]3.50[/COLOR] - 1020 1807 621
25mph - 1584 - 12.7 - 0.2 - 104 261 [COLOR=red]169 [/COLOR] - 0.95 2.25 [COLOR=red]3.20[/COLOR] - 880 1607 588[/COLOR]
I also ran a compression test which ran from 118 to 135 psi accross all 6 with no two side by side of the same pressure.
The engine idles like it is searching around a bit, sometimes it seems a little low but it has not stalled out. I have looked, tested and listened for vacuum leaks but I can't find any. I have replaced all the remaining rubber hoses.
I am assuming from the smog results that the oxygen sensor and/or catalytic converter are bad but I have not thrown any engine codes yet so it is purely speculation. Timing on this is computer controlled so I cant set that. My concern is that I may have an injector problem which has perpetuated the results. I have also heard that there is an Idle Control Valve which sometimes requires cleaning to return a good idle (this may be related to a 2500 rpm idle I had once after starting it on an average SoCal day, a few revs and the idle dropped to normal and never did that again). I'm new to this setup and I'm hoping that some of you may have ideas into common problems I might be overlooking.
Thanks for your help, I have a feeling I'll be around here for a while!
- Mike