has anyone experienced this?

[terminaltsi]

while under load and over 4500 rpm, i get a severe stutter. i also notice the EGT's dramatically drop to about 450*C while this is happening. at first i thought it was too rich, so i leaned it out some witht he SAFC, but then i found my knock to be rising when i had none before.i tried very small increment, but nothing seems to smooth it out.
i'm running a 255, 650 inj., afpr, safc for tuning.
any ideas?

 

[2.4 turbo Hyped]

Boost leak. Too much gap in spark plugs. Cant think of anything else right now.

 

[terminaltsi]

Boost leak. Too much gap in spark plugs. Cant think of anything else right now.

plugs gapped at 030, but i do need to check for a boost leak tomorrow.

 

[Defiant]

Used-up plugs and/or wires.

 

[Kevin Jewer]

Thousands of poeple have experienced this Typically a stutter at boost worthy rpms is ignition related, and a over rich misfire/stuter will happen anytime, even reving in nuetral.

 

[laserspeeddemon]

Wow, those are exactly my symptons, maybe I should check those other problems first. Before installing the VPC.

 

[terminaltsi]

well, i have less than 5k on the plugs and wires, the plugs look like they are burning properly. will check for boost leaks today. anyone think the fuel pump might be at fault? i bought it used....

 

[LandoAWD]

well, i have less than 5k on the plugs and wires, the plugs look like they are burning properly

What kind of plugs? A visual inspection might miss wire issues.

will check for boost leaks today. .

Always do this first.



Also, for the love of god, please use descriptive thread titles. The next guy with stuttering issues might not search on "experience before" when looking for a solution.

 

[terminaltsi]

ok, so , no boost leaks found. coil pack and ignitor substituted for known good parts.
plugs are new. plug wires are new.
EGT's drop to 350*C when stutter occurs, while a/f ratio drops to the lean side. that's what i don't understand. why would egt's get cold while it's running leaner? how is that possible? the typical rich running car would show a/f as rich while egt's drop.

 

[2.4 turbo Hyped]

Dead fuel pump. Hows your fuel pressure??

 

[Kevin Jewer]

When the motor is misfiring the air-fuel mixture isnt burning, so it doesnt get very hot That could explain it. Also keep in mind that high EGTs can be from being too lean OR too rich, its not as simple as people want to make it. In fact, on diesels with high EGTs (over 1300 degrees F) you take fuel out! Or add air, or nitrous. Basically you add as much fuel as you can without going over 12-1300 degree EGTs. I also put up a lengthy post about EGTs a couple years ago.

 

[terminaltsi]

Dead fuel pump. Hows your fuel pressure??

FUEL pressure is fine at idle ~42psi, but i have no idea what it is under load due to my fp guage being hte underhood type.

 

[terminaltsi]

When the motor is misfiring the air-fuel mixture isnt burning, so it doesnt get very hot That could explain it. Also keep in mind that high EGTs can be from being too lean OR too rich, its not as simple as people want to make it. In fact, on diesels with high EGTs (over 1300 degrees F) you take fuel out! Or add air, or nitrous. Basically you add as much fuel as you can without going over 12-1300 degree EGTs. I also put up a lengthy post about EGTs a couple years ago.

what about the lean condition while the egt's are dropping like a rock?

 

[2.4 turbo Hyped]

You need to find out what the fuel pressure is doing at load.

 

[terminaltsi]

You need to find out what the fuel pressure is doing at load.

any idea how to do that besides buying another fp guage?

 

[Kevin Jewer]

what about the lean condition while the egt's are dropping like a rock?

You have no way to know that there is a lean condition. The O2 voltage drops because oxygen content goes up, again, the mixture isnt being burned in a misfire. In fact, thats how I spot misfires with DSMlink, downward spikes in O2 voltage (obdii loggers typically arent fast enough).

As I said before, msot likely ignition reltated misfires, all independant of fueling, and the readings from the EGT guage and O2 voltage are useless if you dont know how to interpret them. Have you tried swapping any ignition related parts like plugs (properly gapped) and wires? If not there is no point in continuing this thread.

 

[Defiant]

Which plugs and what gap? NGK BPR6ES, .028"

 

[laserspeeddemon]

Found the boost leak, looks like the coupling coming from my turbo to the ghetto IC kit I made was to close to the E. manny. Melted a hole right through it..... the funny thing is I never felt like spool time was any slower. And I still am hitting 15 psi....

Oh, I also found a hole in my ignition wire. How that happened I have no idea. So I ordered another set of Magencore 8.5mm wires, NGK BPR6ES, and a fuel filter just for kicks! :laugh:

 

[terminaltsi]

You have no way to know that there is a lean condition. The O2 voltage drops because oxygen content goes up, again, the mixture isnt being burned in a misfire. In fact, thats how I spot misfires with DSMlink, downward spikes in O2 voltage (obdii loggers typically arent fast enough).

As I said before, msot likely ignition reltated misfires, all independant of fueling, and the readings from the EGT guage and O2 voltage are useless if you dont know how to interpret them. Have you tried swapping any ignition related parts like plugs (properly gapped) and wires? If not there is no point in continuing this thread.

gotcha on the misfire.
i think i've solved it, pulled a hell of a lot of fuel out to -38% at high.

 

[Kevin Jewer]

Injectors compensation alone should have you at -30-31% (650s in your vehicle profile). So you are only 7% leaner than that, which is perfectly reasonable (assuming fuel pressure, air metering, injector flow are all normal or course). For reference, I shoot for 11:1 for regular pump gas settings, which is 10-11% below injector compensation. Anyway, the point is, thats not taking out a lot of fuel, thats pretty much right where you should be for 650s.

 

[terminaltsi]

MY fuel press. is 42 psi, so tha tmight account for the extra 7% i'm taking out.

 

[laserspeeddemon]

Found a hole in one of the couplers for my IC piping, fixed it.... no more buh-gogging.

Also ordered,
new set of Magnecore 8.5 mm wires, NGK pugs (7ES), and fuel filter.