98 1500 5.7L Random Misfires

[Chevy-SS]

Originally Posted by Beaner81

Then why only 1 cylendar? I would anticipate a true random misfire in that case. I am certainly not ruling this out I am just trying to fully understand every angle before I drop $400 into this truck.

I cannot tell you why, I can only say that I have the exact same truck and I had all the EXACT same symptoms as you. Shortly after the first fuel pump replaced, I had trouble light come on. At the time, I was in Canada, so I took it to a local dealer. I did not think it could possibly be the fuel pump, as that was relatively new.

Anyway, the read the code as something to do with ignition malfunction (similar to what you are getting). They recommended new cap and rotor, so I said "sure, go ahead". They charged me $150 for total bill - to replace cap and rotor, lol! Afterwards, the truck seemed OK, as I was just driving locally. But then as soon as I hit the highway to head back home in Rhode Island, it started sputtering when I would go up a long hill. Arghh! Very frustrating.

I tried TWO aftermarket pumps and BOTH acted this way. Finally, the OEM pump cured it.

So, when you've exhausted all other possibilities, go get yourself a OEM pump and I betcha you'll be good-to-go.................

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[Schrade]

Originally Posted by Chevy-SS

So, when you've exhausted all other possibilities, go get yourself a OEM pump and I betcha you'll be good-to-go.................

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I'll put money on that.

No pump is gonna' fix a #8 misfire. Ever.

I'll put money on that.

Me: Does the rotor's shaft itSELF feel loose in the distributor mounting shaft (housing)?

[Chevy-SS]

Originally Posted by cbec1999

I'll put money on that.

No pump is gonna' fix a #8 misfire. Ever........

OK, the bet is on

I betcha one US dollar.

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[Schrade]

Originally Posted by Chevy-SS

OK, the bet is on

I betcha one US dollar.

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You're on!



Where's OP? HEY!!! Wake up already!!!!!!!

[thomasstudios]

Funny that you all are mentioning all of this. I am having the same exact problem with my 98 Tahoe 5.7. I also put in an aftermarket pump. What was your verdict? Did you change the pump?

[Beaner81]

I have not been having any problems for the last few months. It appears to be fixed for the time being. I did not replace the pump, the only thing I did was run a couple tanks of injector cleaner through the fuel and my buddy hooked up his scan tool and he said he forced pressure through the injectors. I also drilled a couple holes in the exhaust pipe right before the muffler to decrease back pressure. I don't know what the magic cure was but I have been pushing the truck pretty hard lately and haven't had any issues. I am thinking it was a partially plugged injector caused when I replaced the fuel pump (dirt debris), not the fuel pump itself.

[thomasstudios]

What scantool are you using?

[Beaner81]

Originally Posted by thomasstudios

What scantool are you using?

My neighbor is a mechanic and I am using his SOLUS.

[jgattian]

We have a 98 Van with the 5.7L. Random misfires on Cylinder #8 were linked to a bad valve guide. Valve job $1,800 fixed the misfire. Also our pastors wife's 98 Suburban with the 5.7L has the identical issue and same repair done.