90 Ford Escort 1.9 EFI - KOEO and KOER Codes

Dang, ain't nothing simple? Never would have thought of fuel pressure, just assumed that the EGO sensor went bad. Not sure how fuel pressure factors in, however.

Thanks, Matt

Thanks for the info. No money spent on parts yet, still following leads to determine the exact problem, as you suggested. Picked up a fuel pressure tester, instead. As much as fixing the problem, I also like to tinker, which one reason why I'm still driving a '90. Gives me something to mess with about every six months.

Ran another test, getting KOER 45. Checked the thermactor valve and getting suction on the outlet (going towards the air box). I think that's the outlet, because I thought the air is pulsed to the air box using pressure from the exhaust.

No code 16 this time.

I checked the fuel pressure, reading at 32 psi. The manual says it should be 39 psi, so definately low. It was time to replace the fuel filter, so I tried that, but no help. Still 32 psi.

The manual says that the next step is to check for leaking fuel lines, malfunctioning fuel pump, and leaking injectors. With a 1990 EFI Escort, can anyone suggest anything else worth checking? Is there a fuel pump filter as well, near the vicinity of the pump? Also, I have one of those whiny fuel pumps, original from the factory, if that helps.

Thanks, Matt

Whoops, I read that thermactor thing wrong, looks like the exhaust pulls air into the air box.

You need to check the pressure regulator. The two most likely failed parts are the regulator and pump.

Just to clarify, with the engine running the fuel pressure is actually hovering at about 34 psi. Shutting the engine off causes the fuel pressure guage to climb up to about 40 psi. Not familiar with testing fuel pressure, and looking for some thoughts on interpreting these readings. Maybe the fuel presure is OK?

Thanks, Matt

The regulator on this car is vacuum actuated, so there should be a pressure drop between 2 and 10 psi from the factory spec? At least that's what the pressure tester literature says.

When I turn the ignition off the regulator does go up to about 40 psi. Increasing the idle speed also drops the pressure from about 34 to

Having the pressure regulator go would be a real bummer! I can't even see the thing underneath the intake manifold.

Thanks, Matt

You really need the manual, and not a generic literature from a test package. For example Tempo/Topaz the fuel pressure engine running is a minimum of 45 psi. Most information given from testers, do not go into detail for each vehicle you can test with it.

I'm going to check it again tomorrow and see how it goes with unplugging the vacuum to the fuel pressure regulator. If It goes up to 40 without vacuum, and running at about 34 with vacuum, maybe time to move on to replacing the EGO sensor.

Thanks for the help, Matt

I have the chilton and haynes manuals, but no details in either book on pressure drop at idle, just specs fuel pressure at 39 psi (wish it said ~35 at idle, would've saved me some head scratching). Having poured through the manual looking for bits, I picked up the tester literature on a whim, which is where I was tipped off about the pressure drop (was a general comment regarding EFI engines). Some google searching helped put together how the pressure regulator works with the manifold pressure to manipulate the fuel pressure at different engine speeds.

Thanks, Matt

Another symptom with this car, the idle has been running high for a few weeks now, about 1500 RPMs when sitting at a light, etc., with no pressure on the gas pedal. I took a look at what I think is the throttle air bypass valve, what's on top of the fuel charging assembly, air intake, etc., it has a wiring harness connected to what looks like a solenoid. I thought maybe the high idle could be due to too much air getting into the intake. When I unplugged the solenoid from the wiring harness, the idle went back to normal (~1050 RPMs). After about a minute the engine started choking, I think, with the idle going down to about 500 RPMs, must be suffocating without any air I thought. Plugged it back in and it went back to 1500 RPMs.

Could a bad throttle air bypass valve, if malfunctioning, cause both a high idle and an EGO "always lean" condition if allowing too much air into the engine? Could this explain the lean condition the EEC is reporting, if too much oxygen was in the exhaust gasses, while also raising the idle? Maybe the bypass valve is having an effect on the EEC to cause a higher idle?

Thanks, Matt