New engine, popping under boost??

Hey guys,
Just got my customers engine installed in the ol truck and I'm having an issue with it.
I haven't done too much troubleshooting, so feel free to suggest anything.

The truck runs great under normal and non boost conditions. As soon as it hits a few psi 2-3, the truck will start to backfire or pop out the exhaust.

Now when I first got this engine together, for some reason the #5 piston blew a head gasket. I immediately replaced it and now it's back in action.

I gapped the plugs at .025, probably closer to .023 so the 9.5cr doesn't blow the spark out.

Like I said I haven't done anything else, but I figured I'd post up and go through the troubleshooting stages and share.

I guess tomorrow, the process is:

Check plugs for consitency
Compression check - engine can't be hurt, too soon and not any hard runs on it.
Make sure gasket didn't blow again
Change out coils
New plugs

The tune is good enough to not cause anything , so I'm counting that out.

any suggestions?

thanks,
allen

Quote:

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Originally Posted by farmtruc

Hey guys,
Just got my customers engine installed in the ol truck and I'm having an issue with it.
I haven't done too much troubleshooting, so feel free to suggest anything.

The truck runs great under normal and non boost conditions. As soon as it hits a few psi 2-3, the truck will start to backfire or pop out the exhaust.

Now when I first got this engine together, for some reason the #5 piston blew a head gasket. I immediately replaced it and now it's back in action.

I gapped the plugs at .025, probably closer to .023 so the 9.5cr doesn't blow the spark out.

Like I said I haven't done anything else, but I figured I'd post up and go through the troubleshooting stages and share.

I guess tomorrow, the process is:

Check plugs for consitency
Compression check - engine can't be hurt, too soon and not any hard runs on it.
Make sure gasket didn't blow again
Change out coils
New plugs

The tune is good enough to not cause anything , so I'm counting that out.

any suggestions?

thanks,
allen

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I would say it sounds like plugs, wires or coils. Is there any wires that have been nicked or boots that aren't seated all the way? Are you using the stock coils?

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Originally Posted by ramair2002

...stock coils?

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using stock coils, but i'm going to try a set of msd's tomorrow.

Valve float, broken valve spring, poor sealing valve seat, cam advanced or retarded, low fuel pressure, faulty MAF (if MAF tune), CKP failure, loose reluctor, incorrect reluctor....

i say some plug wires burned on the turbo manifold.....like mine did on us.....lol

i have the exact same problem but mine goes completly away when my motor warms up so keep us posted

Bad valve springs? Weak? Wastegates popping early?

Quote:

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Originally Posted by GasGuzzler

Valve float, broken valve spring, poor sealing valve seat, cam advanced or retarded, low fuel pressure, faulty MAF (if MAF tune), CKP failure, loose reluctor, incorrect reluctor....

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valve float at 4krpms and 3psi with good springs, probably not, but i'll check the springs, a bad spring could cause valve float.
could be poor sealing valve, i'll check that.
cam in straight up, runs too good under no boost conditions.
fuel pressure, rock solid! a1000, -10 line everywhere, aero fpr.
no maf
i hope it's not ckp or wheel, that would suck!
i don't think it's the wrong wheel, it would backfire and spit randomly and a lot more often.

Quote:

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Originally Posted by TurboMic

i say some plug wires burned on the turbo manifold.....like mine did on us.....lol

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changing those tomorrow.

Quote:

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Originally Posted by dropem

i have the exact same problem but mine goes completly away when my motor warms up so keep us posted

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Classic lean or low volume fuel problem.

Quote:

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Originally Posted by dropem

i have the exact same problem but mine goes completly away when my motor warms up so keep us posted

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When the engine is cold, open loop, the pcm is using the ve table. If the ve table isn't rich enough, your engine could be experiencing a slight lean condition. When it gets warm, the the maf takes over and patches everything. The ltrims are probably positive, and the pcm adds fuel, which corrects the lean pop.
Or, the fuel pump isn't good enough.

^^^ echo

i had a few issues i found on my setup


first issue i had want seemed to be a 3 bar map but was actually a older 1 bar map..in boost motor would just die and amost stall

second issue was my narrowbands were screwing with the tune. i shut them off and ran OLSD and never had an issue again.

i run un gapped plugs. so .035 and no issues with my combo

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Originally Posted by Quik

i run un gapped plugs. so .035 and no issues with my combo

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x2, i would open the gaps up to .028-032, as for what it could be, tune, coil, plug, valvespring/seat (kinda doubt it), or just a tune issue.

Try a leak down test. Check for valve leaks and leaking gasket at the same time.

Taking the shotgun approach;, changing out heads as we speak, plugs, coils, wires, anything on the heads.

We'll see how it turns out after the install. I'm really set on these heads causing the problem, sticking valve, bent valve, seat, etc, something like that.

The only difference between this engine and the previous one ; are the heads. Everything else is identical.

hope it works,
allen

i would suspect a cracked plug, when installing them sometimes the socket binds on the plug and makes a hairline crack and causes the same conditions.....i have had that before....

a week spring would not cause the issue, it would just bleed off the pressure IE..running fat...

but keep us updated on your results since you've taken it apart...

a bent reluctor ring would pretty much pop the same but on higher rpms.... i had one of those problems too, but it would do it at 5500-5800 all the time...

x2 on quik, i would do a .030 or so gap...unless running high boost 20 + i would do .025-.028

Plugs wires etc the easy stuff.

My truck had all kinds of banging and popping going on, had a bad injector. :(

Quote:

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Originally Posted by flaco

i would suspect a cracked plug....
but keep us updated on your results since you've taken it apart...
x2 on quik, i would do a .030 or so

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I forgot to mention, I did change plugs, but it's getting a new set just incase.

got it all apart and back together again. Just need to get in two plugs and the coils, then let it warm up and top everything off.

i regapped to .030 this time. Thought the smaller gap might cure it, but it didn't. I'm running msd coils just to see if it helps.

I'll keep you updated,
thanks for the feedback.


hey, btw, i did notice something. some of the cylinders had black residue outside of the cylinder bore, like the combustion/explosion escaped pass the head gasket sealing ring. I guess like a head gasket leak.

I know this is a shot in the dark, but maybe if this doesnt work try regapping to .035. I had some bad popping with my plugs gapped at .030. FWIW

maybe your head is warped causing it to leak outside the chambers?

Do you remember when you had mine on the dyno? It ran good until you got on it and started sputtering. Turned out to be a burn plug wire.

Quote:

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Originally Posted by farmtruc

valve float at 4krpms and 3psi with good springs, probably not, but i'll check the springs, a bad spring could cause valve float.
could be poor sealing valve, i'll check that.
cam in straight up, runs too good under no boost conditions.
fuel pressure, rock solid! a1000, -10 line everywhere, aero fpr.
no maf
i hope it's not ckp or wheel, that would suck!
i don't think it's the wrong wheel, it would backfire and spit randomly and a lot more often.


changing those tomorrow.

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fuel pressure regulator? :lol:

At least we won't know what fixed it since have the engine was replaced all at once.....:LOL:

Shotgun approach worked hahah!

I can rule out plugs because I did in fact change those, that's a lot easier than heads I guess.

I installed the same wires and coils.

The only difference are the heads, now I'm upset!

Here's the story; I sent off some perfect condition heads to a shop, I changed my mind and requested my heads be sent back, when I got my heads back, they had been in the vat machine, cleaned and different valves were in there.
I was told they "cleaned them up".

I was always doubting that because the heads I sent off were in perfect condition, came off a running turbocharged truck (with only a few miles on it) and there wouldn't be any reason to clean them up.

I think I got some heads that were sitting in the corner.

So, if the problem are the heads, bent valve, bad seat, etc, what do you think?
Springs are brand new, I put them in there.

let me know,
allen

Quote:

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Originally Posted by farmtruc

So, if they are the heads, bent valve, bad seat, etc, what do you think?

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One of those. Now put them back on and let's do a leak down to find out. :dancenana:

If you have a short block lying around and a beernight you could try them on that. You can also turn the head over with the chambers sitting up and the deck level and pour some solvent in the chambers and look for the valve that drains into the head. This will show a leaking seat. Take that valve out and then check it for straightness. If it's straight, the seat or valve job is the problem.

Sounds like scum to me.. its everywhere

get em allen!

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Originally Posted by GasGuzzler

One of those. Now put them back on and let's do a leak down to find out. :dancenana:

... This will show a leaking seat. Take that valve out and then check it for straightness. If it's straight, the seat or valve job is the problem.

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Ok, I just tore the engine down and I'm going to reinstall the heads to do a leak down, LOL yeah right!

I can turn them upside down and fill the chamber, that's about all the time I have.
I'll just sent them off to the machine shop, have them shaved, reworked, valve job and new valves put in them.
Oh well.

Quote:

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Originally Posted by farmtruc

Ok, I just tore the engine down and I'm going to reinstall the heads to do a leak down, LOL yeah right!

I can turn them upside down and fill the chamber, that's about all the time I have.
I'll just sent them off to the machine shop, have them shaved, reworked, valve job and new valves put in them.
Oh well.

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JR the guy who does the head work up here is freakin awesome. PM jon or kurt an they will get you his info.

i use a guy who build outlaw altred motors in waco, he does amazing work and is very fast

i have the brand new valves out of my 317s Allen if you want them. 0 miles on them. just the factory ones.

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Originally Posted by TurboMic

i have the brand new valves out of my 317s Allen if you want them. 0 miles on them. just the factory ones.

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nice, what did those come out of, that engine in your truck?

i might take you up on this, let me see what i'm going to do with these heads.

thanks a lot!!

You need a way to mark your parts before you send them out!

wow thats shady. Don't worry I just got screwed on a paypal deal too earlier this week

How can you get screwed using Paypal? You can't lose money with Paypal, can you?

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Originally Posted by MikeGyver

How can you get screwed using Paypal? You can't lose money with Paypal, can you?

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it wasnt paypal. it was a spoof email.

Quote:

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Originally Posted by 567234ta

it wasnt paypal. it was a spoof email.

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what he said.

Quote:

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Originally Posted by farmtruc

Ok, I just tore the engine down and I'm going to reinstall the heads to do a leak down, LOL yeah right!

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That was a joke :spit:

Did you try the solvent test?

coil packs... mine did the same thing...
did you try the msd?

crap 4 pages long.... I guess I should pay more attention