'93 chevy with 350 surges under load. spark plug pictures

[hrc200x]

Have a '93 chevy 1/2 ton 4x4, 350 motor, auto tranny. 90k original miles, but has had headgaskets done within the last 10k miles, also at that time was new rotor, cap, wires, plugs. It recently started surging/hesitating under load. All 8 cylinders were at 150 psi (cold motor) give or take 10 psi. Timing is right on 0 degrees with the wire unplugged. Here is a picture of the spark plugs. Cylinders they came from are what the numbers are. The passenger side plus appear wet because they were in during compression testing the driver side so have fuel on them. I see there is a recent post about surging and the EGR...

[scotts62]

If you cap the EGR does it go away?

[hrc200x]

Cap the vaccum line to the EGR? Will try that tommorow.

[scotts62]

I have a '93 and it runs like crap with the EGR plugged in and know its not right to but i have it plugged off and it runs just fine. Engine light comes on on long drive down hwy but mine is just a work truck so its not that big of a concern for me. You may want to figure it out if you care about fuel mileage.

[hrc200x]

Plugged the vac line to the egr and still same issue. Went probably 6 miles round trip, check engine light never came on. Any other suggestions? Do those plugs look good to you?

Its just under medium load when it hesitates. Throttle to the floor it seems fine, accelerating slow seems fine.

[hrc200x]

The EGR is stamped with a N. So I did the tests to it. It held vaccume with engine off, started the engine and the needle moved. With engine running pushed on the valve with finger and engine started running rough. Hooked vaccume to the TBI side of the EGR solinoid and it wouldn't let any vaccume through. From what I've read everything tests good.

[ChevyTech]

Test the fuel pressure with the engine running.

[hrc200x]

Anyone got a link to a fuel pressure tester that will work?

On another note I've had a fuel filter I've been putting off installing for many months as the lines look very rusty and I'm afraid will open a can of worms. Seeing as heat is the only way to get rusty stuff loose I'm going to use a torch and have a garden hose within arms reach. Good thing gas these days isn't as flamable as it used to be.

Also, where is that spring located that seems to break in many pieces? I think its part of the regulator.

[scotts62]

Originally Posted by hrc200x

Anyone got a link to a fuel pressure tester that will work?

On another note I've had a fuel filter I've been putting off installing for many months as the lines look very rusty and I'm afraid will open a can of worms. Seeing as heat is the only way to get rusty stuff loose I'm going to use a torch and have a garden hose within arms reach. Good thing gas these days isn't as flamable as it used to be.

Also, where is that spring located that seems to break in many pieces? I think its part of the regulator.

Well my common sense is telling me that that is not a very good idea... By the time the bang happens you will not have to worry about the hose..

Just try and use some penetrating oil like PB blaster or something, i bet it will help because they put the filters on there for a reason.

[powerdriver 1958]

hrc200x , NEVER USE HEAT OR OPEN FLAME ON FUEL LINES

Make no mistake , Gasoline is just as dangerous as it has always been .

[truckdude239]

please for the love of everything holly dont not heat your fuel lines, use pb blaster on it go out and shot them with pb blaster every couple hour and it should coome right loose

[ChevyTech]

Originally Posted by hrc200x

Anyone got a link to a fuel pressure tester that will work?

On another note I've had a fuel filter I've been putting off installing for many months as the lines look very rusty and I'm afraid will open a can of worms. Seeing as heat is the only way to get rusty stuff loose I'm going to use a torch and have a garden hose within arms reach. Good thing gas these days isn't as flamable as it used to be.

Link from the sticky at the top on forum index:
At post #5 I talk about fuel pressure testing.
http://67-72chevytrucks.com/vboard/s...d.php?t=375132

Note:
I would never use a torch on a fuel line.
Use some penetrating oil.

[ChevyTech]

Originally Posted by hrc200x

Also, where is that spring located that seems to break in many pieces? I think its part of the regulator.

Yes it is the fuel pressure regulator spring that can break.

Photo on a broken spring at post # 17 in this thread:
http://67-72chevytrucks.com/vboard/s...d.php?t=347247
Fuel pressure test also covered.
The thread goes on to cover many topics that can cause a surge including EGR.



Illustration links or photos that show the fuel pressure regulator spring in the TBI unit:
http://chevythunder.com/gm_throttle_...ction_pg_1.htm
http://www.snflupigus.com/Partspics/image054.jpg
http://www.cfm-tech.com/InstallationPhotos.htm

[k5hart]

Hey that my old spring! Ahh the memories. Seriously...read the above thread. Chevy Tech went into a lot of detail working through my problem. I had the wrong replacement EGR at one point and it ran horrible. Do you know if it's been replaced recently?

I would also replace the fuel filter before getting too deep. DO NOT use a flame anywhere around the fuel system. Use the PB Blaster or other means to get it loose.

I would also double check vacuum lines and throttle body gasket for vacuum leaks.

Good luck and please don't use the torch!

[hrc200x]

I used a torch to get the lift pump loose on my '92 6.5 diesel. Lift pump on that model looks exactly like and mounts like a fuel filter on a '93 gas engine. Just heated the nuts and it came loose. I do realize that diesel isn't as flamable as gas. I would think as long as the gas stayed in the fuel line and never was exposed to the direct flame it would be fine. Gas isn't as flamable as a liquid as it is a vapor. Its going to need heat or a new fuel line all the way from the tank.

You southern guys haven't experienced "rust", WD, PB, JB, Kroil, has no effect on these types of fittings. The rust is so bad on these it looks like it has probably rusted down to the next smaller size wrench. Wouldn't surprise me if the nut is rusted its self to the line, so the line will just twist without heat.

For instance if us northern folk want to remove the nuts off u bolts on a vehicle from the early 90s or older that have never been removed before, its a 99% guarantee the torches are comming out. Even then if the nut breaks loose it will be a loosen, tighten, loosen, tighten type process as the nut cleans the threads out on its way off.

[hrc200x]

One more thing, if it was fuel pressure wouldn't it be worse at higher RPM?

[speedygonzales]

You need to see what the pressure is during the problem. It may not be coming up like it should at higher rpms.

Could also be a restriction. Like bad injector, clogged filter or dirty pickup sock.

[powerdriver 1958]

Originally Posted by hrc200x

I used a to get the lift pump loose on my '92 6.5 diesel. Lift pump on that model looks exactly like and mounts like a fuel filter on a '93 gas engine. Just heated the nuts and it came loose. I do realize that diesel isn't as flamable as gas. I would think as long as the gas stayed in the fuel line and never was exposed to the direct flame it would be fine. Gas isn't as flamable as a liquid as it is a vapor. Its going to need heat or a new fuel line all the way from the tank.

You southern guys haven't experienced "rust", WD, PB, JB, Kroil, has no effect on these types of fittings. The rust is so bad on these it looks like it has probably rusted down to the next smaller size wrench. Wouldn't surprise me if the nut is rusted its self to the line, so the line will just twist without heat.

For instance if us northern folk want to remove the nuts off u bolts on a vehicle from the early 90s or older that have never been removed before, its a 99% guarantee the torches are comming out. Even then if the nut breaks loose it will be a loosen, tighten, loosen, tighten type process as the nut cleans the threads out on its way off.

Do yourself a favor and ask someone like a neighbor or a mechanic if they would use a torch to heat a gas line . This is a bad idea .

From what I read you have made up your mind to do this so you need a spotter to run for help ,just make sure they are at a safe distance when you start this ...... Please rethink this idea

[scotts62]

[ETsC10]

NO!
DO NOT cut with a torch!!

I don't care what your previous experiences were...
if they were similar to this, you were VERY lucky!

[hrc200x]

Not going to cut it, just put some quick heat to the nut to help it expand.

[scotts62]

I think you like getting people riled up about it verses just doing it. Everyone is telling you that its not a good idea so there should at least be something there telling you that? Im kinda curious to see what fixes your problem not about putting heat to something flamable.... makes no sense to me.... but anyways get that bad boy off and lets see what fixes the problem.