Help with Engine Shudder / Failed Emissions Test

[Bullet4x4]

Hi,

I have a 1988 K5 with TBI. Occasionally, my check engine light will come on after driving on the highway for 30-45 minutes. After I drive on the highway, and pull off to a stop at a light, the truck will occasionally shudder and vibrate heavily, unless I give it a little extra gas to boost the idle speed. After I turn off the truck, and turn it back on, the light will go away. After checking the codes, I found that it was displaying Code 32:

"Barometric pressure sensor failure. EGR valve diagnostic switch closed during engine startup or open when EGR flow requested by ECM".

Today, I failed the emissions portion of the state inspection. This truck had passed the last 3 years in a row without any issues. I suspect that these two problems are related. Does code 32 indicate some sort of vacuum leak? Please advise where I should begin trouble shooting this problem.

Thanks!

 

[Bullet4x4]

I followed the instructions in my manual and did some tests of the EGR valve and solenoid.

I found that when manually depressing the EGR valve while the truck was idling, that the rpms would drop and almost kill the engine. So, this part seemed to be working correctly.

The second test involved feeling if the EGR valve's diaphram would move when the truck was revved up to approximately 2,000 rpm. In this case, the diaphram in the EGR valve did not move. Does this indicate a bad solenoid or clogged vacuum line?

I also pulled the EGR solenoid, and was able to hear it click when 9v were applied to the terminals. What is the next step for troubleshooting this problem?

Thanks

 

[Bullet4x4]

I believe I might have a bad EGR valve and Solenoid. Please let me know if I am missing something. here are all of my symptoms after testing with a vacuum gauge:

1. EGR valve will move when diaphram is pushed by hand, this will cause the engine to stall. It doesn't stick in place, however it seems to take a good amount of force to move.

2. At 2,000+ RPM, I cannot detect the EGR valve moving with my finger.

3. The vacuum pressure directly out of the TBI (bypassing solenoid) is 20 in/hg at idle on my gauge. If I connect this directly to the EGR valve, it still will not move at idle or 2,000 RPM. Hoses and fittings are in good condition.

4. Placing the vacuum gauge after the solenoid (in a T fitting or in place of EGR valve), shows a reading of 0 on the vacuum gauge at idle, and will momentarily spike to 20 and then back to 0 when I open the throttle quickly.

5. Solenoid Terminals were measured at 41 ohms

6. Pink solenoid wire receives voltage with ignition on (engine stopped)

7. With solenoid test circuit grounded, test light will come on between terminals. With the scanner test circuit removed, the test light will not come on.

Is it possible that both are defective? I can't get a vacuum past the EGR Solenoid, and it seems that the EGR valve won't move even when vacuum is applied directly to it. Thank you for your help.

 

[4X4HIGH]

I just posted this for another member here recently and this is how you properly test the EGR solenoid and EGR valve on the TBI stuff. This is from AllData.

 

[GalDemSuga]

Bad EGR Valve

Hi,

I have a 1988 K5 with TBI. Occasionally, my check engine light will come on after driving on the highway for 30-45 minutes. After I drive on the highway, and pull off to a stop at a light, the truck will occasionally shudder and vibrate heavily, unless I give it a little extra gas to boost the idle speed. After I turn off the truck, and turn it back on, the light will go away. After checking the codes, I found that it was displaying Code 32:

"Barometric pressure sensor failure. EGR valve diagnostic switch closed during engine startup or open when EGR flow requested by ECM".

Today, I failed the emissions portion of the state inspection. This truck had passed the last 3 years in a row without any issues. I suspect that these two problems are related. Does code 32 indicate some sort of vacuum leak? Please advise where I should begin trouble shooting this problem.

Thanks!

 

[harry169]

I have the exact same problem with my k5. 1990 TBI 350, I dont have any engine shudder though or vibration like its about to die. I belive code 32 only indicates a problem with the EGR system and not particularly the valve or the siloniod. Make sure the breather on the siloniod is not clogged up. And the EGR valve should not take much effort to move with your finger, only when the engine is off. When the engine is running it will have some manifold vacum behind it. If you replace the EGR valve, make sure you use the exact same size washer ring that goes between the valve and the intake manifold. Mine took one of the smaller diameter washers.

 

[harry169]

Im no expert but I think when you push the valve by hand (when the engine is running) it is supposed to make the engine stutter. Because its changing the vacume pressure to the siloniod wich gives a false signal to the ECM. My guess is replace the EGR siloniod. they made a few different kinds during those years because of some trucks with SMOG systems so make sure they match up exactly right.

 

[4X4HIGH]

Im no expert but I think when you push the valve by hand (when the engine is running) it is supposed to make the engine stutter. Because its changing the vacume pressure to the siloniod wich gives a false signal to the ECM. My guess is replace the EGR siloniod. they made a few different kinds during those years because of some trucks with SMOG systems so make sure they match up exactly right.

Actually, pushing up on the diaphram with the engine running creates a large vacuum leak and that's why the RPM's will go down and the engine will want to die, has nothing to do with the solenoid.