91 Geo Metro Check engine light Code 51

[Baniya]

I have a 1991 Geo metro 3 cyl. 5 psd with 198K miles and an engine rebuild at 115K miles. The check engine light had previously been intermittently coming on for multiple days and then turning off for some days – It’s usually on more time then off. In the 6 last months it been remaining on almost permanently sometime the light would be off when I first start the car but then it would go back on; most time its on even when I start the car. The last time I got it smogged, 4 months ago, I changed the spark plugs only (not the wires) and it cleared the check engine light for about 1-2 weeks and then went back on permanently (even when first starting the car). I’m now selling my car and I need to clear the check engine light so it can be smogged for the buyer. I got the diagnosis code by the number of flashes of the check engine light. I got CODE 51 – “Exhaust Gas Recirculation (EGR) system circuit.” The probable cause (as listed by Haynes) – “Check for a faulty connector or circuit. Also a high resistance in the Solenoid Coil. “I’m not sure what this means. Is there a particular connector or circuit I should be inspecting? What is the solenoid coil? My car runs fine I have a only lost about 2-3 mpg, and I don’t feel any loss in power or any unusual drivability issues so I want to rule out the catalytic converter, but I have not tested the upstream or downstream exhaust pressure, and don’t have the tools to do so. I do get some exhaust or some hydrocarbon odor in the car at initial start or while the car is warming up. I don’t believe it’s the O2 sensor because there is a different code for that (Code 13). Please help if you have any ideas. I going to get a new PCV valve and try to clean out the EGR valve today.

[Woodie83]

That's the most common thing these engines do, the EGR system is clogged up with soot. A proper cleaning will require removing the intake and exhaust manifolds.

[carpenter_jai]

I had an egr code in the late spring (the last one). I cleaned out the EGR really well and the code went away. It only took two weeks for the code to come back though. I went to the wreckers and got myself a "younger" EGR and the code has not been back since.

Jai