I just installed a hotcam kit and got the car running. It starts fine and runs in the stoich/rich area and then after it idles down the air/fuel guage goes down past the last lean bar. I am using an Autometer phantom AFR gauge tapped into one of the O2 sensors. I tried bumping up the air/fuel ratio in the programing but to no avail. Somthing that may be linked is that I am showing less vacume now at idle than I do under constant load (12mmHg at idle, 14-16mmHg under constant load). Could this be a vacume leak somewhere that is causing me to run lean??? Also what are people running for idle speeds with this cam? Right now I am at 900 and when it goes lean, the idle drops further and it struggles to stay running. Any help is appreciated.

 

Something else I noticed tonight. When I turn the key on the AFR gauge starts at the half way point, then slowly goes into the red and finally past the lean area of the gauge. Has anyone had anything similar after reinstalling their engine?

 

When you start the engine with the O2 sensors cold, they will read 450mV.... typically the mid-point of the Stoichiometric range. As the engine warms up, and with the AIR pump running, the output of the O2 sensors will drop to 00X mV's. That would certanily put your A/F gauge at the bottom of "lean". The PCM should then see that the O2 sensors have heated up, and switch to closed loop. At that point, the O2 sensor output should start to cycle rapidly from 0XX - 9XX mV's, turning the somewhat useless A/F gauge into a psychedelic light show. Does it ever work this way on a cold start through warmup?

Are you sure you have the valves adjusted correctly? If the valves are staying open, you'll get some really strange O2 and vacuum readings.

Any particular reason you are measuring vacuum in metric units (mm Hg)? Are you sure you aren't reading a gauge that's calibrated in "inches Hg"? The numbers you posted don't make any sense unless that's the case.

 

I double checked the valves tonight, everything seems like it is where it should be in the valvetrain. My mistake with the vac units, it was inHg. I always used to have the AF gauge bounce throughout the range when the stock cam was in it, now it just stays past lean even after a few 5-7 minutes of idle. Could there be something else that is keeping it in open loop?

 

Are you sure you should be using the same O2 as the PCM? I thought putting the wiring in parallel would cause the type of problem you are having. Try disconnecting the gage from the O2 and see if it goes into CL.

 

Are you sure the AIR pump is turning off after about 2 or 3 minutes? Is the SES light on at all? If its showing "lean" and not going to closed loop, it could be a sensor or wiring problem. But that should set a code. Is it possible something damaged the wiring to the guage while you were doing the cam install?

The PCM and the A/F gauge are reading the voltage across the sensor..... shouldn't matter that you have two devices reading the same sensor. That's the standard way to install the A/F gauges. And as he indicated, the gauge worked normally before the HC install. Something has happened after the install.

 

I replaced the wiring to the A/F gauge, and that solved the problem. I checked the resistance on the wire I took out and it was reading ~250 ohms. I would have to guess it got pinched or something along the way of the install.

Thanks for the help all!!