Stumbles A Little But No Stall

[luminaapv3]

I have a 93 Chevy Suburban 5.7 Liter K1500 4WD. I bought the truck cheap and now I'm paying for it Anyways When I first start it up everything is great, after driving for about 5 min it stumbles when you press the gas pedal with a even pressure. Does this in any gear. If i push the pedal quicker it seems to stumble breifly then runs "Better", but I can still feel it running like crap. If I hold the pedal in the "stumble" possition (just giving it a little gas) the truck will start to buck and I feel like I'm in a boat going over some small waves!!!!

Also if I unpug the egr valve vacumm line going from the solenoid to the valve it seems to get a lot better and no more boat waves!

Naturally I assumed that was my problem and changed the egr valve, no help! I changed the egr solenoid, no help!

Someone told me it could be the tps, changed that, guess what, NO help!

To make a long story short people have told me to change a lot of things and like an idiot I did and a couple hounded bucks later I still have a nice boat that like to ride waves~~~~

Below I will list everything that has been done to this truck and maybe somebody on here can tell me to change the thing that is acutually causing my headache .

Replaced:

egr

egr soleniod

plugs and wires

right side manifold gaskets

tps

air filter

oil & filter

gas filter

regrounded every visible ground I could find (down to the metal)

oxygen sensor (in exhaust manifold, one wire type)

ran seafoam through the pcv vaccumm line

pcv valve

pcv valve vacumm line

pcv valve grommet

thermostat

fuel pump relay

MAP sensor

checked all vacuum lines they seem good

ran a bottle of fuel system cleaner through it all (in gas tank)

 

I think I got everything, not sure, I'll repost if I missed something.

anyways I had to do a lot of un jimmy riggin with this truck, the last owner was a complete idiot to put it nicely!

Also this truck will not pass emmissions, had a lot of unburned fuel. Can't remember the name of the failure, I'll repost with more info, it's late, my hip hurts and the truck is in a parking lot behind my house , Don't worry I carry my own violin.

Anyways I'm gonna get a can of starter fluid and poke that around the tbi to see if I can find a vacuum leak (read that earlier in a post).

PLEASE HELP, they are gonna cancel my registration if I don't get this big hunk of metal running properly!

thanx in advance.

Mark

Here are some things I forgot:

I also noticed that the ground wire from the battery is grounded to the engine, should it be grounded to the chassis?

Can I clean the IAC? with what? how to tell if it's no good?

I also had the alternator checked at autozone, that came back OK

Truck doesn't have a tach

Previous owner said they had the trans rebuilt about 3500 miles ago, got papers to show it, although the crapy tech they used forgot to hook up the ground wires, which I did manage to do.

i also replaced the ground wires from the engine to the chassis, but had to do so towards the front of the engine.

prev owner also said he had the fuel pump replaced too, hopefully not by the same guy that did the transmission!

There also seems to be an aftermarket auto start/door opener (no alarm) installed, I don't believe its factory after looking at the hack job under the steering column.

Well hopefully that is all I forgot,

thanx,

Mark

[BigJayDogg3]

I know the answer. It is an easy fix! All you have to do is get the truck . go ahead you can do it. . .

[luminaapv3]

I know the answer. It is an easy fix! All you have to do is get the truck . go ahead you can do it. . .

 

 

O-great, a wise ass like me If you can help check my post I added a couple of thing I forgot, like I said I would, d**n alzeimer's dese, what was I talking about again, o-well I'll have to repost when I remember, until then I'll just keep

[svaiskau]

Sounds simple, but check the transmission fluid.

 

I had a Jeep that had a similar problem and it had a continual leak in a bushing in the transmission... the cheap, simple fix was to keep an eye on it and add fluid every couple months.

 

Hope its that easy.

[luminaapv3]

last time i checked it was ok, but i'll check it again anyways.

Anybody else have this problem?

[bobcat5544]

Pull of the distributor cap look at the under side of the cap and the rotor. Most likely it is jumping spark common problem. If every thing looks good look at the inside of the distributor make sure there is no rust build up.

 

For about $15 I would just replace it even if it appears to be ok.

[Draenor]

Does this happen when the truck is not in gear? +1 Matt, I would also check the ignition advanced or for vacuum leaks.

[luminaapv3]

Pull of the distributor cap look at the under side of the cap and the rotor. Most likely it is jumping spark common problem. If every thing looks good look at the inside of the distributor make sure there is no rust build up.

 

For about $15 I would just replace it even if it appears to be ok.

 

 

I changed the cap and rotor when I did the plugs and wires. when doing this I noticed a lot of rust so I wire brushed as much as I could. I also noticed some rust down where the distributor goes into the engine, is that normal?

[luminaapv3]

Does this happen when the truck is not in gear? +1 Matt, I would also check the ignition advanced or for vacuum leaks.

 

 

This happens in any gear, even neutral . I got under the hood today and pulled the IAC, cleaned it, put a new gasket on and put it back on, then I sprayed around the bottom of the TBI unit with carb cleaner, couldn't find any leaks anywhere. Tested all hoses and they seem fine.

Took off the air cleaner to check out the fuel injectors, when I rev it so it bucks i can hear a loud sucking (air) noise, is that normal? Couldn't really tell if the injectors are ok, Not really sure how to tell, anybody know what I should be looking for .

This truck is really starting to get on my nerves and my time is running out to get it inspected (10-11-o7 is the deadline) .

I really appreciate the help, if you have any other suggestions I'm all ears.

thanx,

Mark

[bobcat5544]

Rust will thorw off the ignition control module signal. Which can cause the truck to run ruff.

[luminaapv3]

Ok guys read somewhere on this forum that the neg battery cable could cause some issues so while I was at my favorite store that I should buy stock in "Walmart" I picked one up and just finished installing it, of course that didn't help one bit, BUT I started messing with the egr again and found something mighty interesting that i missed before .

I checked to see if i had vacuum in the line from the solenoid to the egr valve before and there was none at idle like it should be, but tonight i unpluged the line, put my finger on it and slowly reved the engine and wouldntcha know it, just as it hit somewhere around 1000 to 1500 rpms (I don't have a tach) the line gave a quick suck!!!! and then stopped as I reved it higher. It only lasted for a few seconds, but I'm guessing in those few seconds and when I hold it around that rpm it is opening up the egr valve and letting in exhaust to be reburned, hence the stumble!

Now the crappy part is I have no idea why it is doing this so that still leaves me .

Any help would be highly appreciated, cause now i'm totally stumped until i come up with some other bright ideas.

[luminaapv3]

I thank you all for looking at my problem and scratching your heads along with me .

So to help everyone out I figured I'de take a minute to recap this whole thing. So here it is all nice and neat.

 

My truck:

93 Chevy Suburban 5.7 Liter K1500 4WD automatic

 

Replaced the following with New parts:

EGR valve

EGR soleniod

Spark plugs and wires

Right side manifold gaskets (they were shot and causing a lot of noise)

TPS (throttle position sensor)

Air filter

Oil & filter

Fuel filter

Oxygen sensor (in exhaust manifold, one wire type)

PCV valve

PCV valve vacumm line

PCV valve grommet

Thermostat

Fuel pump relay (located on the firewall)

MAP sensor

Distibutor cap and rotor (wire brushed as much rust from these parts as i could)

Negative battery cable

Replaced the ground wire from the engine to the chassis, but had to do so towards the front of the engine.

Replaced the ground wire from the engine to the fire wall

Replaced the ground wire from the gas line to the chassis (at the rear of the truck, yes there is one back there!)

 

Cleaned, checked or repaired:

IAC sensor (pulled, cleaned, new gasket, put back on)

Regrounded every visible ground I could find (down to the metal)

Ran seafoam through the pcv vaccumm line

Checked all vacuum lines,they seem good

Ran a bottle of fuel system cleaner called "Guaranteed to Pass" (in gas tank)

Alternator was checked at autozone, that came back OK

Fuel pump replaced too according to prev owner.

Checked the fuses, all look good (haven't light tested them yet, kids broke it

Cleaned all electrical connections for all the things I listed here.

 

Other things about my truck:

Aftermarket auto start/door opener (no alarm) installed (not factory)

Trans was rebuilt about 3500 miles ago according to prev owner, got papers to show it, although the crapy tech they used forgot to hook up the ground wires, which I did manage to do.

The electric mirrors don't work (don't know why)

Wires near the right side exhaust were laying on the exhaust, didn't see any exposed wires though, looks like mostly the outer plastic was melted, but not positive, can't get to it really good.

The PCV valve is also clicking away once it warms up, don't know why, there is a very strong suction coming from this line, don't know if that is normal.

 

My last post was with this statement here:

I checked to see if i had vacuum in the line from the egr solenoid to the egr valve before and there was none at idle like it should be, but tonight i unpluged the line, put my finger on it, CAREFULLY streched over the engine and slowly reved the engine and wouldntcha know it, just as it hit somewhere around 1000 to 1500 rpms (I don't have a tach) the line filled with vacuum (sucking)!!!! and then stopped as I reved it higher. It only lasted for a few seconds, but I'm guessing in those few seconds and when I hold it around that rpm it is opening up the egr valve and letting in exhaust to be reburned, hence the stumble!

 

Now the crappy part is I have no idea why it is doing this so that still leaves me .

Any help would be highly appreciated, cause now i'm totally stumped until i come up with some other bright ideas.

Hopefully this helps everyone, hopefully somebody can figure it out, cause I'm about to find a nice hill to accidently roll it down

thankx, Mark

[Black Bart]

I'm going to watch this one with interest , I have a 94 5.7 Silverado with the same problem.

I cant remember how long it has been dooing this 4 to 6 years , the only thing I havent done

is a hydrocarbons test. All the things I have done are listed below.

 

Plugs - changed

Wires - changed

Egr - changed

FPR - changed

Fuel Filter - changed

Intake Manifold Gasket - changed

Oxygen Sensor - swaped with known good one

Checked Fuel Ps - 11 psi

Distributor- changed

Checked computer with laptop both idling and on 15 mile run, no troubles recorded

No Trouble Codes throwen

Truck has 33K miles.

Also did compression check 165psi on all cylinders.

[luminaapv3]

Well once again I was messing with "Big Blue" as my kids call it and I did manage to find an air leak (I'm almost positive) right next to the egr valve. Sprayed a water and soap solution in that area cause i noticed some oil there before and it returned after i had cleaned it up a couple of days ago. The solution didn't really do much until I reved the engine, then it looked like it was boiling, then when i let it idle again i swear it all got sucked into the engine thru the intake manifold bolt! I also noticed it bubbling either from the rocker arm covers or the intake manifold, can't really tell the two are to close together.

I did a quick read on the repair process and it doesn't look to bad, tedious yes, time consuming yes, but not difficult.

I don't know if this is causing all my problems, but i do know it's not helping and needs to be fixed.

Has anyone else on here perfomed this repair? Was it easy? Rough idea of how long it took you?

I noticed in the reply above that you replaced the gasket also, did you discover a leak? and where was the leak located, near the egr? Any info will be helpful.

[MAGNUM]

I have a 92 that did the same thing and It ended up being the upper distributor bushing was wore out and magnet hit the pickup assembly and cracked the magnet. Like yours, mine ran good until it warmed up. hope that helps.