engine codes

[leadvillek5]

okay so my engine is running like #$@! checked codes and #32 = egr and #45 = o2s rich. i have an old school egr with old school heads and intake.i checked the egr and it is not stuck open or closed. the o2s is a heated sensor. the engine runs bad at idle like it is running on 5 of the 8 cylinders. but running down the road it runs great. i pulled the spark plugs one at a time to check the color of the electrode on the plugs. the front two plugs look good lite tan in color. the rear two plugs are the same as the front . but the center plugs are black and sooted up. anyone have any ideas on where i should being with diag on this one. fuel pressure is 11 psi @ idle and goes to 14 psi under load. also exhaust smells rich at idle. i have a variable fuel pressure regulator

lancer

 

[dyeager535]

I'm at a loss at this point as to how exactly the TBI stuff "knows" the EGR is not working right, as it has to have a temp switch or something, somewhere, to know that EGR is not working right.

I think it's been decided that '88-91 TBI setups likely have an EGR solenoid, earlier does not.

I'm going to theorize there must be a temp switch in the EGR circuit (maybe in the valve) that is hooked to the ECM, and when the EGR solenoid opens, the ECM isn't seeing the change in temp it is expecting.

Going to go look at the '91 wiring diagrams and see if I can find out for sure how GM did it.

Do all the vacuum lines for EGR check out as good, and are hooked up correctly?

Here is a link to the '91 wiring diagram showing the EGR solenoid. The link seems to work like this, if not, let me know I'll point to the directory. I don't see on the ECM pinout where an EGR temp switch has an input though, so the EGR code must be thrown another way.

 

[leadvillek5]

yes all vaccum lines are right and yes it does have a switch or soleinod of some kind that is inline between the egr and intake manifold vaccum.

lancer

 

[dyeager535]

Here's something: MAP sensor

I'd be suspect of the MAP sensor. This explains how the system works. (code 32) EGR isn't in operation at idle so I'd bet the rich condition is from another cause. EGR open would cause a lean condition. According to that, cruise is the only time the test is run. Clear the codes (pull ECM fuse) and then see what happens. Rich code SHOULD come back once the thing goes closed loop. EGR code should not. Rich condition code is more than likely on a timer, for 2.8L MAF, (for example) it takes 1 minute after engine start.

Since the EGR test is looking at vacuum translated to voltage, AND you have a rich condition indicated, it stands to reason that the MAP sensor is not working correctly, whether a bad hose to it, or bad sensor itself. The voltage reading is skewed initially, indicating the ECM needs to dump more fuel under unusual circumstances, (idle, rich code) and when EGR is tested, the skewed MAP voltage is influencing that test. I don't think the code 32 chart is your answer though, not with the rich condition at the same time. No link to any code 45 charts for MAP, I bet MAP is listed as possible problem for that too.

Seems logical to me anyway.

 

[leadvillek5]

thanks for the info. i will check the map sensor diag charts on all data