Hello all, I'm looking for a little help on an EGR issue I'm having. I have an 89 F150 with a 5.8 , C6 , 4x4. I keep getting a code 34(low voltage to EGR) I have reset the computer by removing the battery and running again. I'm getting the code with the Key On Engine Off. The engine light comes on only after driving for 10 mins or warmed up ect..The light goes out after a restart and then come on again after a while. Again this seems to point to a closed loop EGR problem.

I have removed the EGR sensor and the little needle moves freely. I read from 300ohms to 3K ohms approx across the contacts.. I've sprayed and burnished the contacts to the sensor. I have also hooked up a small hand pump to the EGR valve and will hold 20"Hg. I'm reading 20"Hg at the manifold and If I plug into the black line on the vacuum res. (coffee can) I'm getting 18"Hg at idle.

Where do I go from here? I cannot find a step by step trouble shooting guide to know what is the issue. Most of the info is directed to a dead link. If someone can fill me in on some of the info I would be grateful. What resistance should the sensor have and to which contact? How does the EGR valve itself work? What should the vacuum be at the EGR at idle? Maybe there's a leak in the Vacuum system?

The engine overall runs well. I have done a tune up but not wires. My last comment is when warmed up the idle "feels" weak and maybe missing when in gear. Definitely not idling great. The timing is right on the mark. And it definitely seems to correlate with the EGR function. Multiple on/offs and it still CEL's after about 10-15 mins. My last comment is this, the exhaust is clear but feels very hot. I'm not sure it that's normal or not. It could have just been my cold hands but I could not hold my hand over the pipe for mare than a few seconds. (I have a full stock exhaust)

thanks for any help.

 

Code 34/KOEO: EVP circuit above the closed limit of 0.67 volts.

Typical cause:

1. EGR valve not fully seated due to carbon build up on the pintle seat.
2. Faulty EVP sensor.

You measured the resistance of the EVP, but did you measure the output voltage? That code indicates it is above 0.67 VDC with the engine at idle/closed EGR valve.

 

Well, I thought I had it. I pulled the sensor and lubed the EGR valve. I also replaces the "green" plastic line from it's source to the valve. When Idling without the CEL on I'm seeing 5 volts to one f the wires and nothing to the others. I had the truck idling for about 15 mins. I was not seeing the Check Engine Light, unfortunately on the way to work it kicked on. I'm going to try and catch it at lunch with the light on. does anyone know what I' supposed to be reading on the wires coming out the the EGR sensor? Could the EGR valve just be a bit sticky?? not alway's fully releasing??

thanks

 

Fuel Injection Technical Library » EGR Valve Position sensor (EVP)

 

OK that's getting me somewhere. I was playing around with it yesterday. And I was getting 0.60v at idle. I'm thinking it's right at the edge and isn't taking much to go over. When I use my hand pump the EGR valve is a bit "notchy" sounding. I wonder if it's hanging up. Can these valves be cleaned??

 

Yes they can be cleaned. If the build up is really bad you may need to use a large drill bit. I have used a small driver and brake cleaner on several occasions with good success.

 

Well, I think that's was it. I was not able to get the EGR valve off completely. But I pulled it away from the manifold sprayed the poop out of it with carb cleaner inside and out. And worked it with my vacuum pump. I'll admit I did not think it would work. No code on the way to work..

Now the idle is still a bit rough at idle, kinda lumpy. I'm not sure where to go from here. I did not change out the wires yet but I'm not seeing any crossfiring. I'm wondering if a injector is sticking or clogged. I'm going to put another can of seafoam in it. My only other thought is the PO put a cam in it. I mean it's a short bed 4x4 with a 5.8, C6 and 4.11 gears on 31's. He used it to tow a car trailer.

thanks for the help rla2005

bob

 

Anytime, we are here to help each other!

 

I need to take that back, it just popped up again. Im certain it's the EGR valve. I'm done for now on it. I'll start spraying that coupling nut . It was on there tight.

 

Heat is your best friend

 

Thought of that but the A/C hose is right there.. I'm going to mess with my IAC valve , I think that's causing my lumpy idle and play with the EGR once I have some time.

bob