89 formula TPI

on my 89 Formula 305 TPI - occasionally, every few weeks, my check engine light will go on. when it happens, it's a few seconds after i start the car after it's been sitting for a week or so. I noticed last time it happened the RPMs dropped a little then the check engine light popped on. after a few drives it will go away. reading the ECM reveals trouble code 32 and 44. The RPMs dropping makes me think it's lean exhaust...


32: Digital EGR Circuit (i just replaced the EGR with a brand new one and cleaned out the manifold for carbon and used a new gasket)

• Faulty EGR valve. (mine is brand new)
• Faulty or loose wiring and/or connections at the EGR solenoid. (it only has one plug...)
• Faulty, loose and/or leaking vacuum hoses to EGR valve. (what else would i check here there is only one hose that plugs in to it?)

44: Lean exhaust

• Faulty or loose wiring and/or connections at the ECM.
• Incorrect fuel pressure.
• Faulty or leaking throttle body gasket.
• Faulty or leaking intake manifold gasket.
• Faulty or loose vacuum hoses.
• Water in fuel.
• Faulty oxygen sensor (this was changed a few years ago, less than 1000 miles on it)

i have two codes stored, but i am afraid to clear the computer and see which one keeps triggering it because the car is running pretty well even with this issue. one last thing to note is the exhaust does smell rich, is this the system overcompensating for the lean exhaust? i also suspect it may be a faulty ECM, but that is just my gut...

thanks guys

vetteoz

iTrader: (13)

Run the diagnostics
Sort the O2 problem out 1st

http://www.chevythunder.com/o2_sensor_code_44.htm

http://www.chevythunder.com/egr_code_32.htm

89 formula TPI

thanks for those diagrams, i'll definitely try it out this weekend though i don't believe it's an O2 issue, as i replaced that when i first got the car. although ti's a few years old, it has less than 1,000 miles on it.

those are very helpful though

89 formula TPI

According to the flow chart, in order to test the o2 sensor, i have to ground the ALDL and then run the motor? didn't know it was safe to start the motor when that is grounded...

also does the flashing light mean it is in open or closed loop...it is not clear from the flow chart

89 formula TPI

was able to get back out today and tested a theory i had, when i first started my car after sitting for a few days, i revved the engine a little to keep the rpms from dipping after I first started the car. as i suspected this prevented the SES light from triggering. i shut it down and came back out 10 min later and started it without revving the engine and the light came on. i am wondering if the lean fuel code is coming on for that split second the rpms dip at start up.

89 formula TPI

okay finally got out there to test it. reset the computer started car and got code 32. reset the computer again and this time unplugged the temperature connector on the EGR and the light did not come on. this means i have a fulty ground or wire per the flow chart.

i reset the computer again and plugged back in the temp connector and expected the code 32 to come back but it didn't. i inspected the green wire and it looks fine, i cannot find where it's ground though because it goes into about 100 wires into the firewall. i don't think the wire is the issue it looks fine. i suspect it is the ECM. what are symptoms of a bad ecm?

http://www.chevythunder.com/egr_code_32.htm