OK... my check engine light's been going on and off since I finished putting my motor in after rebuild. I put in an LT1 cam, headers/y pipe, open element filter, and different fan switch/thermostat. I got it scanned by a friend tonight, and here's what codes came up-

23- manifold air temperature- this one should go away, I ran the car for a while without the temp sensor when i switched to open element
13- oxygen sensor- When I put in the headers, I drove it for a while before welding in the O2 sensor fitting. This one should go away, too
42- electronic spark timing monitor error- I advanced my timing to 7*, I'm guessing this one was triggered when I had to disconnect the brown wire to set the timing, so it should also go away
33- MAP too high (low vacuum) for 5 seconds when throttle opening was under 4%.... don't know about this one
32- EGR failure- I guess my EGR is bad...?
43- electronic spark control failure- again maybe when I had the brown wire disconnected to do the timing?

Anyway... the light comes on when I'm on the highway for a while, then it's off when I park and come back to the car. Any help with these codes and how they relate to this problem would really be appreciated!

 

unhook the battery for a minute to clear the ecm, then see if the codes return

 

Ok here'
heres some suggestions to check your EGR.

Locate the EGR on the passenger side of your rig.
Take your fingers (maybe with gloves it gets hot). Reach underneath the egr, put your fingers up inside one of the holes in the egr, and press upward (inward), your car should start to idle rough and stumble, because your allowing too much exhaust into the intake.

If it does not idle rough, or stumble when you pull in on the EGR, it is likely that your passages may be plugged with carbon. Not allowing exhaust into the intake, this will cause detonation highe,r combustion temps,possibly a timing retard, taking away a bit of power, and increasing operating/combustion temps.

If it does stumble when you pull up on the EGR you can move on to checking it's function. Have somone press on the acclerator while you have your hand on the egr, if you feel it move up when the RPMS increase you know the valve is working.

If the EGR does not move when you hit the RPMS go up, check the vacuum hose attached to it, at idle you should feel no vacuum as you increase the rpms vacuum should appear and vacuum should intensify as the rmps go up, if you have vacuum to the EGR at part throttle, and the EGR diaphram doesn't move its most likely plugged with carbon and needs to be replaced or cleaned.

If you have no vaccum to the egr at part throttle, then check the solenoid, next in line. Check all the electrical connections. Check the opposite side of the solenoid, to make sure you have constant vacuum to it. If theres no vacuum going to the solenoid you found your problem, replace the hoses.

If you have vacuum going to the solenoid, but no vacuum when hitting the acellerator on the EGR side, you know somethings wrong with the solenoid itself.

33-vaccum to low I belive this is possibly caused from a bad egr system, if the EGR is stuck open it basically is a HUGE vacuum leak.
32- Check everything related to the EGR


I hope this helps you out, attached apitcutre so you can check out if its connected right, and see what I am talking about

 

Wow... thanks a lot bro. This will definitely help. I've gotten rid of all the codes except the EGR one, so this should help me pin it down. Thanks again!

 

Anytime, I hope that helped ya out, and please let us know what you found so we can add it to our mental notes

 

OK i bought MTchevy1's car and i dont think it was tuned. Do you think with the LT-1 cam it would bring the power out if i tuned it?