Spark Knock

[00 Expy Police]

Hello All, I got a 00 Expy that i bought with a blown eng and had a hole in the side of the block the size of ur head,,I bought a motor minus intake timing cover and pan,,basicly i had to put all my stuff on,,well the motor i got is an 03 and after getting it all in,i changed all plugs and coil wires,ran fine for 2 days and detected misfire in cyl 1, that new coil was bad and I put old one back on and its fine,,now when i start up and leave for work in the morning soon as i get out and moving it will start spark knocking right off the rip,i throw it in nuetral and restart and its fine,,soon as i come to red light and restart moving or try to pass on eway it will spark knock and no eng light or codes,whats the prob here never seen something like this,,i even ran 93 octane and injector cleaner thinking injectors were dirty,pulling my hair out trying to get past all this other than that shes got some power

Thanks

 

[JUST4FUN]

possable egr problem ports are clogged??

 

[JUST4FUN]

are you running a 3 valve motor in a 00

 

[00 Expy Police]

are you running a 3 valve motor in a 00

no its a 2v

 

[00 Expy Police]

the guy i got the motor from said it came out of an 03,also valve cover said 03

 

[00 Expy Police]

possable egr problem ports are clogged??

could it be that i got the wrong plugs in it,,auto zone says i need platinum plugs i put copper plugs in it?

 

[designit]

is a spark knock different than a general misfire?

 

[panda24619]

go with, what are they, motorcraft? plugs. thats what these motors like. switch them out and that should help.

 

[toms89]

Spark knock to which I believe the op is refering to is pre-ignition. Not the same as misfire.

I believe the reluctor wheel is different on post 2000 expys and possibly the sensor?? Maybe this can cause issues on earlier processors... doubt it buy maybe. Other than that I would say maybe one of the sensors the computer uses to adjust timing and fuel. I know... thats most of em. IAT sensor, coolant temp sensor, mass air, 02 sensor... etc.

I would say maybe bad fuel but it sounds like you put new fuel in. Check for vacuum leaks.

 

[toms89]

Oh yea..... too hot a spark plug range could cause pre-ignition or if it protudes into the combustion chamber differently that stock. Type of plug should not matter as long as it is correct for the application.

Forgot to mention fuel pressure...... maybe its low due to fuel filter or pump problems.

After rereading your post a few times I think you said it did not start to ping until a few days after you got it running. If this is the case my best guess would be the o2 sensors. The computer readjust the spark and fuel tables based on input from many sensors and this is adjusted based on o2 sensor readings. So over a few days as the computer adjust from the base program it may have it running too lean. You can easily test this theory by reseting the computer.

 

[designit]

ahh, thanks toms.. That makes sense I guess... Hot pre-fire on a wrong plug?

Gap maybe? -- just weird he had it running fine for a couple days... very well could be plugs?

But wouldn't a prefire "be" a misfire in terms of timing? -- which the computer would pick up and post a code?... He ain't getting any codes either?...

 

[toms89]

ahh, thanks toms.. That makes sense I guess... Hot pre-fire on a wrong plug?

Gap maybe? -- just weird he had it running fine for a couple days... very well could be plugs?

But wouldn't a prefire "be" a misfire in terms of timing? -- which the computer would pick up and post a code?... He ain't getting any codes either?...

I consider misfire - no spark condition intermittent in nature.

Too large a gap would cause misfire but no spark knock. Too small a gap and it would just be less efficient combustion.

I grouped detonation and pre-ignition together which is technically not correct. Pre-ignition cannot be caused by too much timing advance. That would be detonation. While lean fuel and hot spots can cause pre-ignition. I know the difference between the two but I still tend to group them together..

The knock sensors are tuned to a specific frequency. They may or may not pick up all forms of spark knock.

http://www.streetrodstuff.com/Articles/Engine/Detonation/

 

[designit]

I consider misfire - no spark condition intermittent in nature.

Too large a gap would cause misfire but no spark knock. Too small a gap and it would just be less efficient combustion.

I grouped detonation and pre-ignition together which is technically not correct. Pre-ignition cannot be caused by too much timing advance. That would be detonation. While lean fuel and hot spots can cause pre-ignition. I know the difference between the two but I still tend to group them together..

The knock sensors are tuned to a specific frequency. They may or may not pick up all forms of spark knock.

http://www.streetrodstuff.com/Articles/Engine/Detonation/

Well holy 14deg BTDC burning combustion chambers batman... See there, that's why we come.

Good link, read a little but I got a headach from the basketball game!... Read later though... Great techie garb..

 

[NewbieVet]

Well holy 14deg BTDC burning combustion chambers batman... See there, that's why we come.

Good link, read a little but I got a headach from the basketball game!... Read later though... Great techie garb..

what he said ^^^

 

[00 Expy Police]

ok i changed out the plugs to double platunims (autolite),also changed out the idle control valve cause it popped a code,,road test and after 30 mins it still sparked knocked so back to drawing board,i was told to unplug the vacum from EGR valve and plug end of hose,cleared computer and this morning all the way to work and back 110 mile trip ran perfect check eng light decided to pop on 1 mile from house so im going to put it back on scanner in lil bit to see what code is,,im going to guess cause it ran smooth that the egr is plugged like Just4fun said above

 

[toms89]

I having trouble following what you did. If you disconnected the vacuum from the egr valve it cannot work which in effect would be the same as if it were clogged. Maybe I just misunderstood what you did.

The egr recycles exhaust gas back to the intake for emissions purposes. This is supposed to reduce combustion temps because the recycled exhaust will not burn. This has the effect of reducing spark knock which I am sure why Just4Fun mentioned it.

On the chance that the knocking returns I would suspect the 02 sensor(s) as it sound like it runs fine when you reset the computer. As the computer adjust for o2 readings while in closed loop mode it may be leaning out the fuel to much.

 

[00 Expy Police]

I having trouble following what you did. If you disconnected the vacuum from the egr valve it cannot work which in effect would be the same as if it were clogged. Maybe I just misunderstood what you did.

The egr recycles exhaust gas back to the intake for emissions purposes. This is supposed to reduce combustion temps because the recycled exhaust will not burn. This has the effect of reducing spark knock which I am sure why Just4Fun mentioned it.

On the chance that the knocking returns I would suspect the 02 sensor(s) as it sound like it runs fine when you reset the computer. As the computer adjust for o2 readings while in closed loop mode it may be leaning out the fuel to much.

I dont know for sure what it does by disconecting the vac hose but i do know it runs smooth,after sitting for for a while i connected the vac hose back to EGR and right away it spark knocked,while it was running i disconected it and drove away fine so im on my wat to get it scanned for code,,,,but what are chances of the code being the EGR valve cause it was unpluged?

 

[00 Expy Police]

i give up,i put new egr valve in it and still spark knock,,,any thoughts?????

 

[designit]

I'll just toss this out for now... I'm beating a dead horse into dust but try a full bottle of seafoam through the brake booster hose... Then stick another bottle in it & let it sit for about 45 mins...



Did you build the motor from the ground up?.. or was it sitting around for a couple years & you have a dead mouse in one of your holes that created a carbon layer 1" thick causing crazy compression? (I'm joking of course with that but geez... Any history on the motor?

 

[00 Expy Police]

i bought the motor minus the intake manifold,oil pal,timing cover,when we got home i dug into to it deeper and all looked good,under valve covers looks nice and clean,lookied down intake runners and looked clean,front timing set looked clean,even took a few rod and main caps off and bearings were perfect,everything else came off old motor that cam with the truck,other than the guy told me it ran perfect when came out i dont know much about it