Slight Rough Idle and TBI help

[jedi_jackson]

New to the page and bought my father in laws 1994 K1500 4x4, 5 speed, with the 4.3. It has a little bit of a rough idle but not bad. Swapped out the plugs which were in pretty rough shape and replaced them with AC Delco Double Platinums. Still runs a but rough. Tried cleaning the throttle body with some spray cleaner which didn't really help and I noticed the spray pattern from the injectors. Took a video but not sure if this is normal or not. Kinda makes a clicking noise like a valve tapping. Any help would be appreciated.

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[SUBURBAN5]

New to the page and bought my father in laws 1994 K1500 4x4, 5 speed, with the 4.3. It has a little bit of a rough idle but not bad. Swapped out the plugs which were in pretty rough shape and replaced them with AC Delco Double Platinums. Still runs a but rough. Tried cleaning the throttle body with some spray cleaner which didn't really help and I noticed the spray pattern from the injectors. Took a video but not sure if this is normal or not. Kinda makes a clicking noise like a valve tapping. Any help would be appreciated.

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I'm not a TBI guy but to me that doesnt look normal. It's been a long time but I had a friend that had a 4.3tbi and I believe both of his sprayed constant

 

[PlayingWithTBI]

They are supposed to spray in a synchronous pattern. 1 injector pulses for 1 cylinder intake, the other sprays for the next cylinder intake, and so on back and forth. The intake manifold is designed to feed in that firing order too. The naked eye rally can't see this though. I agree it doesn't look right, it s/b smoother. The ECM/PCM fires the injectors (by grounding them) when it gets the pulses from the ICM. 1st thing I'd do is check all the wiring and connectors in the dizzy and going to the computer.

 

[Schurkey]

Verify fuel pressure
Connect a scan tool, look at the data stream.
Cranking compression test
Perhaps a cylinder-balance test
Verify TBI base gasket, clean idle air passage and throttle body/throttle plates with aerosol carb cleaner
Assure all vacuum hoses are snug and connected where they should be
Verify that EGR is not leaking exhaust gas into the intake at idle

 

[jedi_jackson]

Ok...I don't have a scan tool for anything pre odb 2. So far I have been able to check a couple things. First is I pulled the vacuum lines on the TBI and the one on the driver's side I circled in the picture didn't really have vacuum. The other 2 do but I also checked the EGR valve and it's not moving with any throttle. I can take my hand and move it and it changes the idle. Pulled the vacuum line that goes from what I believe is the solenoid for the EGR to the EGR valve and I couldn't feel any vacuum. Could the solenoid be bad?

 

[tsr2185]

Ok...I don't have a scan tool for anything pre odb 2. So far I have been able to check a couple things. First is I pulled the vacuum lines on the TBI and the one on the driver's side I circled in the picture didn't really have vacuum. The other 2 do but I also checked the EGR valve and it's not moving with any throttle. I can take my hand and move it and it changes the idle. Pulled the vacuum line that goes from what I believe is the solenoid for the EGR to the EGR valve and I couldn't feel any vacuum. Could the solenoid be bad?

I actually just checked my a port today that I have capped off. Which goes to the evap canister. I didnt have a vacuum at all there.

 

[thinger2]

Solenoid might be bad but if the egr is sticking you wont develop enough vacuum to move it.
It is really common for the egr valve to get internally carboned up.
Get yourself a "might vac" about 40 bucks and well worth the money.
Dont bother with the ones from the loaner tool program at the parts stores. They are always broken and full of brake fluid.
Pull the vacuum line off of the egr valve, hook up the mighty vac. See if you can get it to hold about 14 inches of vacuum
If it wont pull a vacuum at all or it bleeds down
Either the egr is stuck or the diaphram is bad.
If that happens, stick your fingers in and push the egr shut and try to pull a vacuum.
You will often find that just moving the diapragm under vacuum and releasing it several times may get it to break through the crud ring inside and make it function again.
The idea is to see if that diaphram is still good.
You can, if you are very carefull about it, clean the inside of the egr valve.
And I would try. Aftermarket egr valves are a shitshow of garbage.
I am at 235k on the factory egr.
It is just one of the normal maintenance tasks on the schedule.

 

[jedi_jackson]

Ok, I'll check that...I was able to check to see if I have vacuum on the EGR side of the solenoid and there is no vacuum. I do have vacuum going into the solenoid from the TBI.

 

[Schurkey]

There's going to be no vacuum to the EGR nipple on the throttle body at idle. It's "ported" or "timed" vacuum--there's only vacuum when the throttle blades have opened a bit. Probably the same for the canister purge hose nipple, too.

There's no vacuum through the EGR solenoid until the ECM commands the solenoid to open.

If you apply external vacuum to the EGR valve, it should open. My '88 has a negative-backpressure EGR valve, which I think is common on the TBI engines. They'll open with external vacuum even if the engine is shut off.

My EGR wasn't opening because the vacuum hose supplying vacuum to the EGR solenoid also branches-off to the AIR pump solenoid, and that part of the vacuum hose had a hole in it. I spliced the hard plastic vacuum tubing with a section of rubber vacuum hose, which gave me vacuum to the EGR solenoid. Then the EGR didn't open because the diaphragm leaked. Replaced the EGR valve; I think it's good now.

I've seen the vacuum passages in carburetors plugged with debris. No reason that couldn't happen to a TBI unit. It's rare, though.

You're gonna need to come up with a scan tool if you're going to be working on computer-controlled vehicles. Dicking with engine diagnosis without one is two steps away from madness.

 

[jedi_jackson]

There's going to be no vacuum to the EGR nipple on the throttle body at idle. It's "ported" or "timed" vacuum--there's only vacuum when the throttle blades have opened a bit. Probably the same for the canister purge hose nipple, too.

There's no vacuum through the EGR solenoid until the ECM commands the solenoid to open.

If you apply external vacuum to the EGR valve, it should open. My '88 has a negative-backpressure EGR valve, which I think is common on the TBI engines. They'll open with external vacuum even if the engine is shut off.

My EGR wasn't opening because the vacuum hose supplying vacuum to the EGR solenoid also branches-off to the AIR pump solenoid, and that part of the vacuum hose had a hole in it. I spliced the hard plastic vacuum tubing with a section of rubber vacuum hose, which gave me vacuum to the EGR solenoid. Then the EGR didn't open because the diaphragm leaked. Replaced the EGR valve; I think it's good now.

I've seen the vacuum passages in carburetors plugged with debris. No reason that couldn't happen to a TBI unit. It's rare, though.

You're gonna need to come up with a scan tool if you're going to be working on computer-controlled vehicles. Dicking with engine diagnosis without one is two steps away from madness.

Do you recommend a scan tool for pre odb 2? I have a few different odb2 scanners but I know they do me no good for this truck being a 94.

https://www.autozone.com/test-scan-and-specialty-tools/code-reader/p/innova-gm-obd1-code-rea

This is the only thing I can find but it only reads codes.