Greetings.

I Bought a 93 Tahoe and drove it home it did not run very well.

After cleaning plugs and setting the gap the 4.3 would start right up.

Now just off idle the motor will surge lope and miss and the whole rig will rock from side to side ,slowly.
If it was a plug and wire issue I would assume it would also idle poorly.
I have also checked for loose wires and lines.

Question ...

How long is the fuel pump supposed to run when the key is first turned on ?
The fuel pump runs for about twelve seconds and the stops ,I can hear the relay as the pump stops.

I do not have a fuel pressure gauge .
I might drop the tank and take a look ,it could just be a loose hose .

How can I drain the tank ,I know there is at least 5 gallons in there.

 

it only runs for a few seconds...... it sounds like your having fuel spider issues....maybe a fpr?

 

Very first check is the EGR. These motors have issues with getting carboned up, which sticks in the EGR valve, keeping it open.

Pull it, clean it and reinstall it with the screened gasket (available from NAPA). It's sort of a pain to get to - about 9" of extension with a 10mm socket on the right-hand bolt (put a little piece of paper towel in the socket and the bolt will be stuck inside the socket when you get it out - and back in) and a 10mm wrench on the left-hand bolt. It will probably have black carbon fuzz everywhere, especially where the pintle seats, and possibly some chunks as well. Clean it out well, but gently.

Next, pull and clean the IAC valve - that's a Torx bit. The end of it (sort of like a hat) will probably be blacker than black. Clean the end gently as well. Be careful with the O-ring and, when you reinstall, lubricate it with a little engine oil.


If neither of these clears up your issue, then I'd pull the IMTV in the upper plenum. Two T30 bolts pull the plastic cover that says Vortec, then 2 smaller Torx screws on the IMTV. Spray a little WD40 around it and twist it gently until it comes free. If you can see clean spots on either side, you have a leak under the plenum. If it's on the passenger side, it's the fuel pressure regulator, which is a Dorman/Motormite/Help! part available at NAPA and Advance (and comes with the Torx security bit needed for removal and reinstallation). If it's the driver's side, it's the 'nut kit', also known as the fuel pressure and return lines, also available at NAPA.

Reinstall the IMTV with a little engine oil on the O-ring as well.

Then you have the 10 10mm bolts to pull the plenum. You'll need a 10mm deep socket for that. And a new upper intake gasket.

Or you can buy the parts at lindertech online.

 

I have the egr off now . I assume its the egr its on the front of the intake on the bottom.
I found very little carbon build up in the 2 holes on the manifold, the egr was also clean and moved freely.This part has no vacuum only electrical fitting, can it be taken apart?

I looked inside down through the top and found black I cleaned the IMTV it was very black , I did not see where the was fuel washing an area clean.
I will go look again for a clean area.

Can the fuel spider be serviced?
Links?

Can I drive the Tahoe with it surging like this or will it leave me stranded ? Will it damage something?

I do not have a manual yet.

Thank you

 

Yep, you got the EGR. Little carbon build up is good. Did you push the pintle back a little and clean where it seats against the base? No, you can't take it apart (or shouldn't).

The IMTV should normally be black, as should be everything you can see through its hole.

The FPR can be replaced on the spider. The rest of the spider would just need to be replaced, unless you have a broken poppet clip, not holding the poppet down correctly.

Did you pull the IAC valve to see if it was dirty? It's above the throttle body on the left.

 

Yes . I cleaned the IAC.
I am going to reinspect for any signs of fuel washing .

Whats next?
Should I Remove the plenum ?

Where can I get fuel pressure gauge. Autozone, O'reilleys? How much do they cost?

 

I think you can get a fuel pressure gauge at any of those - plus Harbor Freight. I'm not real sure how much...

Have you checked your cap, rotor and wires? Aftermarket parts there don't last very long - AC Delco seems to be the only way to go.

 

I checked the cap, plugs, rotor and made sure the cap was reinstalled correctly and checked the firing order too.

I am going to pull the plenum based on the engine runs good when it's not surging. This would rule out tune up.
There is fuel coming from the exhaust.

 

Took the plenum off no signs of leaks.

The tabs were broke off the poppets and missing. Some one was in there before.
I turned the key on and checked for leaks,none found.
I pushed the little valve at the back of the motor there was fuel. then i pushed it again and there was no pressure at the valve.

I found anti tamper torx also holding the spider and regulator and I dont have this tool.


Now what?

Drop the tank and check pump assembly?

 

Reassembled.

I have figured out that the motor run and revs up slowly with no surging when the motor is cold ,as it warms the surging returns.

I will now dump 2 12 oz. STP super concentrated fuel injector cleaner in the tank. and see?