7.4L vortec carb swap

[klittle1417]

I can't seem to find any information on carb swapping my 1999 7.4L K2500 Suburban.

Any insight? How can I control the auto trans? Etc....

Kevin

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[Christian Steffen]

Probably have to get a standalone controller. Why the swap?

 

[klittle1417]

Getting tired of chasing whatever might be causing the thing to run poorly.

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[Christian Steffen]

What are the symptoms? It may be frustrating, but I don't think a carb swap is the answer.

 

[klittle1417]

It's idles rough. It had been idling fine but would break down at about 3-4k rpm and have no power. Then started to idle rough and has a skip.

Only code showing was bank 1 sensor 1 O2 sensor. I replaced as I could see on the scanner app via my phone that it was not working at all.

Fuel pressure is hovering around 48psi. When I open up the throttle it jumps a little then settle back at 46-48 psi.

I've read that the 5.7 can't run on that pressure but the 7.4 can.

Thought I had it running better but then it started skipping and idling poorly again.

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[JScott23]

I would avoid carb swaps. If you want to stay out from under the hood, carbs require lots of tinkering and adjusting. And that doesn't even begin to get into the fuel economy piece. Stick with EFI, run diagnostics and replace what needs replaced.

(my two cents) I ran a Carb in a GMT400 at one point, my mistake, waste of time and money.

 

[Christian Steffen]

JScott is absolutely correct. Aside from a bad idle, are there any other driveability issues?

 

[Tom P]

Check your spark plug wires. Christian and I worked through a very similar issue on my truck and I either replaced or function tested everything fuel, air, and spark related on my truck until I replaced plug wires and made a world of difference in idle and high rpm situations. Mine were cracked and shorting out. P/O had said they were recently replaced but that was obviously a lie.

 

[klittle1417]

Check your spark plug wires. Christian and I worked through a very similar issue on my truck and I either replaced or function tested everything fuel, air, and spark related on my truck until I replaced plug wires and made a world of difference in idle and high rpm situations. Mine were cracked and shorting out. P/O had said they were recently replaced but that was obviously a lie.

Plug wires and plugs are new. Need to check out the distributor cap tonight.

I haven't driven the old girl much yet. It was idling fine but had a stumble or total lack of power at higher RPM. Then it started to idle rough/skip. Then the stumble/lack of power was intermittent at lower RPM as well.

It does have a valve tick but its not extreme.

Is the fuel pressure I mentioned ok?

 

[Christian Steffen]

Plug wires and plugs are new. Need to check out the distributor cap tonight.

I haven't driven the old girl much yet. It was idling fine but had a stumble or total lack of power at higher RPM. Then it started to idle rough/skip. Then the stumble/lack of power was intermittent at lower RPM as well.

It does have a valve tick but its not extreme.

Is the fuel pressure I mentioned ok?

Might want to check your valve adjustment then. Perhaps a lifter is collapsed and needs replacing. What does thr fuel pressure hit when you cycle the key, but don't start it? Does it hold pressure when you cycle it?