Stutters at high RPMs...

[SupraDreamPDR]

ok, just got on my car hard for the first time. had to wait on the clutch to break-in. anyways, having some problems with stuttering at higher rpms, in this case anywhere above 5300 rpms the car acts like it wants to quit. if fact i did a pull in 4th gear and the car stuttered at or around 5500 rpm and then the check engine light cam on and the car stalled. so i checked for a code, but there wasnt one. the CEL blinks non-stop when testing it right? so we checked the timing and the timing numbers are hard to read, so i looked them up on here and it looks fine... somewhere between 10 and 12 degrees. so i am now thinking that maybe i have a boost leak somewhere? i have been replacing alot of the old, worn-out hoses and most are just breaking off in my hands. but the funny thing is that i thought that when you have a boost leak you cant build boost? i hit the stock boost of 6-7 psi, as read on my Autometer boost gauge, just fine. so what do you guys think is up? should i post a video of it in action, will that help?
Mods: DDP into testpipe and no cat. back (still waiting on it from HPF!), K&N FIPK, NGK plugs (stock heat range), MSD 8.5mm wires and new clutch/FW. Dont think its a factor in this, but i also just replaced the valve cover gaskets.

 

[McMsk]

I just remebered my car now also has a bit of a stutter sometimes at high rpms. Do you have anykind f tuning in your car already. I believe it might be a week fuel pump you have there.

 

[SupraDreamPDR]

I just remebered my car now also has a bit of a stutter sometimes at high rpms. Do you have anykind f tuning in your car already. I believe it might be a week fuel pump you have there.

edited my post to try and explain problem more and show my mod list.

 

[mixmastermatt]

You have any way to monitor AFR? If not, find something and check it. You're either running lean up top (fuel pump, injectors, poor tune) or too rich (plug gap, poor tune). Also, if you can get a MAF to swap, try that.

 

[SupraDreamPDR]

You have any way to monitor AFR? If not, find something and check it. You're either running lean up top (fuel pump, injectors, poor tune) or too rich (plug gap, poor tune). Also, if you can get a MAF to swap, try that.

hmmm... hadnt thought of that. i did just install new plugs, but i didnt bother to gap them because i was told not to gap the Iridiums? anyone have any info on this?

 

[theDon]

always check the gap on your plugs, even if they come pre-gapped. It only takes a few seconds and ensures that isn't the problem

Also I changed to copper plugs, autolite 3923's, from NGK's and gapped to .031 and my stutter went away instantly.

 

[SupraDreamPDR]

that is probably what i will do... i just bought these damn NGKs though. i removed alot of the plastic hoses and then replaced them and the problem seems to have went away.... although when i got on it hard 1st through 4th gear and then let off in fourth with the clutch pressed in the car died on me. i am just going to mark that one up to the Supra just trying to be a PITA.

 

[mixmastermatt]

that is probably what i will do... i just bought these damn NGKs though. i removed alot of the plastic hoses and then replaced them and the problem seems to have went away.... although when i got on it hard 1st through 4th gear and then let off in fourth with the clutch pressed in the car died on me. i am just going to mark that one up to the Supra just trying to be a PITA.

That would be due to a rich decel condition. Usually caused by your BOV not completely recirculating the waste air.

 

[SupraDreamPDR]

That would be due to a rich decel condition. Usually caused by your BOV not completely recirculating the waste air.

would that be because maybe its in need of replacing or leaking?

 

[mixmastermatt]

I know that the stock hoses on mine were all cracked and leaking, so you might want to check them out. The BOV itself should be ok, just make sure that the vacuum line going to it isn't cracked or loose.

 

[diy guy]

you can still build boost with a leak depending on how big it is. I though you should be making more than 7psi with a ddp though, maybe even hit fc, anyone else?

btw, at what rpm are you spooling to full boost

 

[SupraDreamPDR]

you can still build boost with a leak depending on how big it is. I though you should be making more than 7psi with a ddp though, maybe even hit fc, anyone else?

btw, at what rpm are you spooling to full boost

i was thinking the same thing about having more boost, but i wasnt sure. i think i am building to full boost around 3000-3500 rpm.

 

[IHI-RHC7]

How does the car idle?
I would check your dashpot and ISC also look into making sure the BPV tube back to the acc pipe is in good condition.

 

[SupraDreamPDR]

well, the car idles right around 650-1000 rpm and i am pretty sure that its good to go.

 

[chriso]

I have a similar problem. I am leaning towards the fuel filter since the car sat for about two years and didn't have a drop of gas in it when I put my new engine in it. If that doesn't work out I will investigate boost leaks.