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truck running like crap. and missing

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xsmokey11499x

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ok so the past few days My truck has been running like crap. Missing. etc.

when I start the truck, you can hear the missing at idle.

so I replaced the spark plugs. and the miss is still there.

and now when I go WOT. In park or driving. it will get to maybe.. 3.5 to 4k rpms. then it sounds like It's hitting a rev limiter. Which it has never done before.
when I am driving and it does that, I have to let off or else it just keeps doing the rev limiter type sound.

so.. whats next.. a set of plug wires?
 
Quick and dirty.

While its still dark, open the hood, crank it with no lights on and count how many blue sparks you see from the plug wires to parts of the engine.

Any number above 0 is not good...........

Also, you can get a spray bottle of water and spritz them down while its running and listen for a worse miss or look for sparks.
 
Fordum said:
Quick and dirty.

While its still dark, open the hood, crank it with no lights on and count how many blue sparks you see from the plug wires to parts of the engine.

Any number above 0 is not good...........

Also, you can get a spray bottle of water and spritz them down while its running and listen for a worse miss or look for sparks.
Click to expand...

yeah I didn't see any sparks flying anywhere.
It just seems like the problem got worse after I put the new plugs in.
They are gapped at .35
 
Two possibilities. One, something got damaged in changing the plugs.

Lots of time old plug wires just don't like to be removed and put back on.
Boots can tear without your seeing them, or the connectors on the ends of the wires can lose connection.

Plus, sometimes if you did not lube the boots slightly with silicone or something similar, they might not slide down all the way on the plugs and cause the connection to come unplugged after a while by pushing up.

Or, wrong plugs. You can get away with hotter or colder plugs, they just will cause gas mileage problems or burn up too fast.

But, a classic problem I have seen many many times is switching to Platinum, split-fire, or other aftermarket plugs.
The split-fires just cause problems, and the Platinum ones will very often cause misfires on systems that were not designed for them.

When they first came out, it got so bad on a CServe forum, when someone would write in saying they just put in new plugs and had misfires, we would write back and tell them to get rid of the Platinum plugs.

Whereupon most times they would write back wanting to know how we knew he had put in Platinums?
 
well the plugs I picked up were Bosch Copper Super+.

nothing fancy. Just a regular plug

but what would cause it to cut out. at a high rpm sounding like its hitting a rev limiter. which ... well it doesnt have
 
Like British Slave said, we need more info on the truck.
Is it a K5?
If so, I would definitely suggest replacing the wires, cap and rotor. There to cheap not to. Like Fordum said, If you put old wires back on, you may have made a crack in the insulation worse by moving and tugging on them.
I'd spritz the coil at night also. Make sure you don't see it arc when wet. Look for little white burns on the outside of it also.
While you're in there, switch to ACDelco or NGK plugs. Non-platinum. I my self have seen many misfire issues caused by Bosch plugs. I hate that Autozone and all those other parts stores really push those out.
 
X2 on the platinum plugs..they dont seem to work well in most chevy V8's.in my experience...seen many trucks run WORSE after a tune up with the new plugs ,especially Bosch platinums......................................................But your symtoms sound like you may have a cam lobe that went flat,that will either not let the exhaust out if its an exhaust lobe,or not allow enough fuel/air mixture IN that cylinder,and either can cause skipping,high speed misfires and backfires..........................................................................................I have seen more than one newer GM truck with a junk distributor too,some are made of crap plastic,and they have no bushing for the shaft,and wear egg shaped,and cause all kinds of weird running troubles..............................you may want to check the EGR system and ensure the valve isn't sticking open too...(your check engine light should have come on if theres trouble in that area though)..
 
When you have a high speed limit like you are describing, there are a ton of possibilities.
But, the two most common, and usually the least expensive to fix, are not enough fuel flow and ignition problems.
I would check the fuel filter and change it if its been awhile. You need to be able to watch the fuel pressure as you rev the engine up, but that can be tricky on some engines.

As for the ignition, I would change the plug wires if they are as old as the plugs. It used to be that you could get by with a couple of plug changes per wire set.
But these days the plugs last so long that the wires are pretty much at the end of their life by the time you need plugs.

While you are under there, pull the dist. cap and look for trouble.
Anything that looks hinky, replace it. Grab the rotor shaft and push it from side to side. If it wobbles, then a new dist. goes on the shopping list. If you have the top mounted coil, it needs to come off and inspected for rust or corrosion underneath.

If yours uses the little control module on the dist., consider getting another one of those.
They can cause all kinds of strange stuff when they start going bad.
If you change it, be sure to put the heat sink compound under it. Plus, if you suspect it might be your problem, I recommend just changing it instead of having it tested. I'm not sure I have ever heard of one that was just having problems instead of being dead not passing the tests they do in the auto parts places.

Unless they are completely dead they usually pass, but wind up getting changed.

And, if it turns out the old one was good, it goes in the glove box to get you home some dark night when the other one goes out.
 
How do you know it's running like crap if it's missing? :haha:

Seriously, you might have mixed up the plug wires after you changed plugs (assuming you pulled all the wires off at once). My suggestion is to do a compression test, this will rule out any internal engine issues.
 
Had same type of trouble with same type of truck. Fordum hit it with his last post. The ignition module can play hell with having misfires if it is on its way out, but I would say a full tune up is due (cap, rotor, wires) and depending on milage coil and module. You may want to put a timing light to it also. Check with a good local mech than can guide your atc or btc for your altitude because the books are always sea level and I find just a jumping off guide line.

Any perfomance mods can change your timing needs for a properly tuned engine also(i.e. intake, cam,air cleaner, exaust).

Keep us posted if you find what it is.
 
well, I have replaced The Cap. rotor. Plug wires. Plugs. and plugs again. Got some ac delco PN#CR43TS. And as far as the wires go, I Pulled one off at a time. and put it on the New Cap.. and now. I Tried to start the truck, Its cranking cranking cranking. then BOOM! sounded like a 12 gauge going off. and white smoke EVERYWHERE. Little looking around the motor after the smoke cleared. and the driver side Valve cover had Blew half way off.
Does that sound like a timing issue now? Besides me needing a new valve cover.
 
Shame you are not closer. I'd love to get a video of you cranking the motor......

But, timing can cause weird things, but I'm not totally sure it can cause that.

Usually putting the dist. in 180 degrees out will cause backfires, mixing plug wires will sometimes cause them too if the plug fires with the intake valve open, so be sure to double check the firing order.

But, to blow the timing cover off.............Was it the one with the PCV valve? I'm thinking that gas fumes got under the cover from somewhere, but not sure what would have ignited them.

And white smoke is usually gas steam caused by gas hitting a hot surface. But there should not have been anything hot if it had not cranked.

I'm sure someone will have an idea, but personally, I'm gonna have to think about this one for a little while....
 
My first thought is timing is off and it flooded then had enough umph to ignite.
Those plugs are great plugs.
What does it sound like if you turn it over again. Any knocking or banging noise?
 
OK, stupid question. Did the dipstick blow out?

If you had a build up of gas fumes in the crankcase, which ignited, then the blast could have come up around the oil drainback holes and what have you.
But, as the pressure was building up under the valve covers, it should have tried to vent through the dipstick too.

If the explosion was under the valve cover to start with, it would have been less likely to blow back down and pressurize the crankcase that much before the valve cover gaskets let go.
 
Fordum said:
Shame you are not closer. I'd love to get a video of you cranking the motor......

But, timing can cause weird things, but I'm not totally sure it can cause that.

Usually putting the dist. in 180 degrees out will cause backfires, mixing plug wires will sometimes cause them too if the plug fires with the intake valve open, so be sure to double check the firing order.

But, to blow the timing cover off.............Was it the one with the PCV valve? I'm thinking that gas fumes got under the cover from somewhere, but not sure what would have ignited them.

And white smoke is usually gas steam caused by gas hitting a hot surface. But there should not have been anything hot if it had not cranked.

I'm sure someone will have an idea, but personally, I'm gonna have to think about this one for a little while....
Click to expand...

the valve cover, was the one that had a tube going to the air filter housing.
 
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