CEL triggers only while cruising

[MIHELA]

Did you ever figure out what code you were getting? I had an EGR blockoff and the code would only set ofter cruising for about 15 minutes or so. Also the advice about the heated O2 is spot on. They are a good mod even for stock systems.

 

[Madison Mehlhose]

I completed the heated o2 sensor modification. No change with the issues I’m having.
I’m starting to think fuel delivery...

 

[Madison Mehlhose]

I checked the fuel pressure. 12 psi at the throttle body
I got a new ac delco fuel filter and that seems to have brought some power back but I’m still having the o2 sensor code.
I did notice something new today. The SES light was on for the o2 code, cruzing down the highway I wanted to get around someone so I open it up to wot and the code went away within 5s. So I retriggered the light by cruising for a bit and test to see if wot was the trigger, it was. So for some reason wot “cures” the ses light.

SOS! SEND HELP! Mayday! Please give me some ideas and feedback.

 

[skylark]

I'm betting the problem is in the EGR circuit. It's been so long so I don't recall the details but you have to be within certain conditions in order for the light to set. It only happens when you're cruising and dropping speed or increasing throttle input will make the light go away.

 

[Madison Mehlhose]

It’s got a new egr solenoid and the valve works. The port was cleaned 2 weeks ago when I had the heads apart.

When the code sets it meets code 13 perfectly.

I’d be really interested to see if someone is producing the same voltage as me from the o2 harness side to ground KOEO. About 1.5v

 

[Madison Mehlhose]

I moved the diaphragm on the egr valve and the engine started stumbling. Are they pretty sensitive valves or is this test good enough?

 

[Madison Mehlhose]

Code still setting after cleaning the MAP sensor. The code will clear after idling after a few minutes [noticed while i was sitting at a light for a minute].

Please help, any input is welcome.

Any thought about the temperature sensor? Its less than a year old but my temps have been reading high [I ignored it because i think the cluster is bad]. Maybe if the engine is too hot the code will set??

 

[ram1220]

For what it's worth my 90 Sierra 5.7l would set a CEL only at highway speeds after about 5 minutes. I changed the O2 sensor as well as the EGR valve and I haven't had the problem happen in over 5 years.

 

[Madison Mehlhose]

I think i almost got it solved, i went and got a vacuum hand pump to test the valve, its bad, very slow leak. Makes sense why it took a while to set a light and wasn't throwing a EGR circuit code.
So i bought a new EGR valve and i have it in my hands now but it doesn't seem to be an exact replacement. I look back to RockAuto where i bought it [2141432 is the PN] and it says its an aftermarket ACDelco part, weird. Anyways, it comes with all these orifice washers which correlate to the original part number. So i took the old EGR valve off to check the part number and its not on the chart, of course -_-.

Does anyone know what orifice i need to use for my 1989 5.7 350?

Thanks in advance.

 

[someotherguy]

You haven't given my advice much credit but I will still caution you to avoid the "one size fits many" EGR valve. They rarely do what they're supposed to. There are OEM EGR's that are application specific available for your truck.

Richard