Hi, Im a newbee on here. Im Mike.

As usual, ive joined cus ive got a problem.!!Hope someone can help or has some ideas.
My Z71 vortec 5.3 is a 99 model. Has always run fine and started great. We disconnected the rear o2 sensor, in the exhaust, behind the cat,so we couldfit a new stainless exhaust. We removed the old exhaust. Then, had to move the truck, and started the engine to move it. It ran fine and we moved it 30 yards. The next day we started and moved it back in the work shop. The engine then stopped. Umm, says I. I wonder why that happened. Spent loads of time and about a week trying to start it. The new exhaust was fitted and the o2 sensor re fitted. Im sure its not broken or faulty, tho it could be.
Its been back firing out the exhaust and intake. Seems like an ignition / timing problem. ! Yesterday it started. Wheeeee. !! Ran for a few minutes and seemed to drop down on to 6 cylinders and revved a bit weak. Turned it off. Struggled to start it again. Ran on 6 ish, again. Didnt drive it. Just let engine run a bit. Didnt seem right, tho the exhaust sounded nice. !!!
Today nothing again. OBD reader and the Superchip 2815 both say no fault codes. There are new plugs in it and they are wet with fuel. Pump is charging with ignition turned on.

Im struggling.; Any ideas. ???

With thanks. Mike.

 

Mike, did you make any other changes? It's certainly running rich. I don't think it's the O2 sensor. Any possibility some plug wires are loose (got bumped)?

 

+1 how about wires on wrong cylinders?

 

I'm thinking plug wires too.I changed my cap rotor and plugs an wires all at the same time.I got the #2 and #4 plug wires switched and it sounds like it did the same thing as yours is doing,spitting and sputtering,no power ect.If you removed the plug wires,check the firing order,if it's right it can still be wrong.Generally the #1 plug wire will be on the distributor at the connector that is closest to pointing at the driver side headlight.If the firing order is right try moving all the plug wires 1 to the right,if it cranks and wont start or sounds worse,go back 2 spots and see if that helps.

 

Thanks guys,
I was thinking spark or distributor cap.
It ran fine before the exhaust was removed. I ran it without the exhaust and 02 sensor in, and it then stopped. Just wanted to clarify that part.
I put a new set of plugs in it after this issue to try and help, and gapped them to 60 thou. It did start again but under duress and struggled. Was on 8 at one point. Its definately not the leads on wrong as ive checked and as I said, it did run on 8 for a minute or two. Now it just turns over and stumbles every now and again, but wont start.
Is that a distributor cap and rotor or a coil pack type thing. Its round like a distributor but has 4 leads out of each side. !!!??? Strange. Cant find how to get it off. Was thinking the cap, if thats what it is, could be cracked or burnt inside.
Just one thing. I earlier said it was a 5.3. I think this is a 5.7
My 02 Tahoe was a 5.3 Vortec, but that was a different engine.

 

Is it a coil pack type ignition?I'm "old school" I deal with older engines.Distributors and points are my thing.Is the spark plug gap .060 for that year engine?I know my 95 305 is .035 plug gap. Could the computer still be freaking out about the O2 sensor being unplugged? Maybe unhooking the battery for 15 min or so then hook up and try again. These new-fangled engines and their computers,I tell ya. Computers are for a desk,not for an engine.

Does it look like this thing on the left?

That's a distributor cap and rotor kit,or so www.autozone.com says,for a 99 Chevy 1500 2wd with a 5.7.
If it's like every other dizzy cap I've seen there will be 2 bolt/screws holding the cap on.If you look at it from the top,you should see them at the bottom edge,they will be on opposite sides of the cap. The one in the pic looks like you can see one screw hole on the bottom left,a loop looking thing sticking outthat the bolt/screw runs thru.

 

Yep. Thats the one. Very difficult to see and remove. Cant see the fittings but will have another go in the morning.
My feelings exactly about computers.
Gapped at 60 cause the book says so. Yes the earlier ones were 35. I think 60 is way to big, but thats what it says. !!!
Tried the battery thing. Ive bought and fitted a new battery as well.

The 02 sensor is the only thing that was touched, tho it unplugged and came out easy with no damage so im thinking it isn't that. Also it's the rear sensor and there are two others nearer the heads so im sure the one i removed only messures burnt fuel after the cat and they dont work for the first 5 mins until the cats warms up. ??? !!!
There are no fault codes so it cant be anything to major. Would the ECU failing thro a code?
Coils usually stop when they get hot so I don't think its that as it wont even start.

God, this is driving me mad. lol.

Mike.

 

and what sucks is it's probably something simple too.It usually is.At least when it's me.I seem to think about everything but the basics.I suppose it could be the ECU.Go thru and check all the wiring plugs that are even close to anything that was touched.Just to be safe if you haven't already.Check fuses too.You never know.[:@] Check the condition of the wiring also.Look for broken,bare and chaffed wires.Gonna drive me bat **** crazy thinkin about it.

 

Go over the distributor and ALL wires connected to it.Plug wire connections and electrical connections too.Check the coil wires too.Make sure they are tight and in good condition.Check for vac leaks.use soapy water or a piece of vac line up to your ear then move the other end up and down vac lines and connections and listen for a hiss if you can get it to run a minute or have someone crank on it.
[:@][:@][:@]@your truck lol

 

Ok. Got the cap off and cleaned it out. Fur off contacts. Cleaned the rota. Put it back together and tried again. Took a few goes but I got it going again. Ran a bit ruff and still back firing out exhausts. Took it for a blast up the road and it felt ok. Quite a lot of power, but when you slow down it still feels ****. Definately not right. Then its real hard to start again.
Got cap rota and leads on order and will fit them tommorrow or sometime soon.
Thought it might be the ignition module as well. That might cause it to back fire while running, tho I dont know if that would thro a fault code up. ?
Getting closer.
Thanks. Mike.