Ping maybe knock?

**jetaws6** · 09-23-2010, 05:30 AM

I just finished up a heads and cam swap in my car and I had it on the dyno for the first time last saturday and it was ping/stuttering/knocking or something on wot right at 4 grand every time.

My tuner couldnt figure it out but he said it might be a bad plug or a blown head gasket. A mechanic I know told me to smell my oil for coolant and there was no hint of coolant so I don't think the head gasket is the case

Do any of you guys have any suggestions of what this could be? I also heard from someone that my rev limiter might be f'd up and its trying to kick in at 4 grand. Never heard of that but its a possibility.

**shady milkman** · 09-23-2010, 10:29 AM

4 grand is just about the time that a change in the computer happens..i cant remember for the life of me what it is...i want to say VE tables are used and the maf is ignored or something to do with the fuel trims(dont hold me to that)...there is some transition that takes place around there

**jetaws6** · 09-23-2010, 11:51 AM

Originally Posted by shady milkman

4 grand is just about the time that a change in the computer happens..i cant remember for the life of me what it is...i want to say VE tables are used and the maf is ignored or something to do with the fuel trims(dont hold me to that)...there is some transition that takes place around there

So how would I go about to fixing that? The tuner said my air to fuel is right where it should be so that eliminates that.

**shady milkman** · 09-23-2010, 12:28 PM

Originally Posted by jetaws6

So how would I go about to fixing that? The tuner said my air to fuel is right where it should be so that eliminates that.

who is your tuner ? id have him give you a digital copy of the tune..if he is using hp tunners..and post it over at hp tuners forum and ask the question .

**shady milkman** · 09-23-2010, 12:28 PM

does it studder etc past 4k ?

**jetaws6** · 09-23-2010, 12:47 PM

Originally Posted by shady milkman

does it studder etc past 4k ?

it studders once at four and then a few times past it I think. The dyno chart wasnt smooth past 4k. It had a big drop off at 4k and then a few more stutters to 6

**LSXZ28** · 09-25-2010, 02:47 PM

Could be a bad plug or wire... could be a valve spring issue... maybe you were off a tooth on the cam... could be a bunch of things. I would start with pulling all of the plugs and seeing if any one or more cylinders show different (rich, not burning, etc) and go from there. You sure the tuner knows what he is doing??

**shady milkman** · 09-25-2010, 06:40 PM

Originally Posted by LSXZ28

Could be a bad plug or wire... could be a valve spring issue... maybe you were off a tooth on the cam... could be a bunch of things. I would start with pulling all of the plugs and seeing if any one or more cylinders show different (rich, not burning, etc) and go from there. You sure the tuner knows what he is doing??

X2 ..while I got you..what happens at 4000rpm..is it the maf is the only thing referenced or something?

**LSXZ28** · 09-26-2010, 04:22 AM

Originally Posted by shady milkman

X2 ..while I got you..what happens at 4000rpm..is it the maf is the only thing referenced or something?

Not really - if you are running a MAF tune, the MAF has more "influence" on the fueling as the RPMs go up - is really the way to look at it... but its not like a switch is flipped and it happens - it is due to the way the tables are set up. The MAF table has less influence at lower flow values and more at higer flows - but the MAF and VE will both effect fueling throughout the entire range...

**shady milkman** · 09-26-2010, 01:35 PM

Originally Posted by LSXZ28

Not really - if you are running a MAF tune, the MAF has more "influence" on the fueling as the RPMs go up - is really the way to look at it... but its not like a switch is flipped and it happens - it is due to the way the tables are set up. The MAF table has less influence at lower flow values and more at higer flows - but the MAF and VE will both effect fueling throughout the entire range...

ahh ok

**jrgswhitels1** · 09-26-2010, 02:05 PM

.....dont think its a fuel mapping issue, it sure sounds like a timing issue of advance in that gear! Provided the fuel is not cheap and is not a watered down 87 octane. Try improving octane rating or drop timing a bit. Any KR with it?

**LSXZ28** · 09-26-2010, 02:26 PM

Originally Posted by jrgswhitels1

.....dont think its a fuel mapping issue, it sure sounds like a timing issue of advance in that gear! Provided the fuel is not cheap and is not a watered down 87 octane. Try improving octane rating or drop timing a bit. Any KR with it?

What??? Where the hell did you come up with that...

jetaws6 - Do you have any way of logging it? You are about an hour north of me - do you ever get down around Crofton? If you do, I could log it for you and see what we can find...

I still say pull the plugs and take a look at them all - they usually tell a story...

**jetaws6** · 09-27-2010, 04:39 AM

Originally Posted by LSXZ28

What??? Where the hell did you come up with that...

jetaws6 - Do you have any way of logging it? You are about an hour north of me - do you ever get down around Crofton? If you do, I could log it for you and see what we can find...

I still say pull the plugs and take a look at them all - they usually tell a story...

Im planning on ordering new wires wires and hopefully going to pull the plugs on friday. I could make it down to Crofton whenever, if the plugs and wires dont do the trick I will deffinitly take you up on that offer.

Andrew at complete street performance is tuning it for me. Hes a good guy and I have heard a lot of positive things about his work. When we were trying to figure it out the guy that he works with that does all of the diagnostics wasn't picking up his phone