Shuttering/Vibration

[Nihil]

My mid and low trims are around 81.5% and I am mostly stock. I still need to set up my piggy back before I can set them to 100 =)

Personal experience from my stuttering issue/idle issue was a combination of fixing vacuum leaks, ECU caps and replacing with a known good MAF; it seems you did all of this already. Are you resetting the battery after each component trade out?

Your only other fuel components you didn't mention are filter and pump; once you get pressure checked should rule this out, but I have a feeling the problem isn't fuel.

ECU is reset each time, car always seems to run perfect for the first 5 or so minutes, fuel trims all 100% then as it learns and adjusts, it goes back to running crappy.

Any ideas/suggestions on a simple cheap way to check fuel pressure? I'm trying to hold off on buying gauges until I get this issue fully resolved, as gauges are expensive and I don't feel buying expensive parts while the car isn't properly running, is a good idea.

I'd guess fuel isn't the issue here, either. I'd guess a sensor, of some sort, coolant temp is new as well...

Only things I can think of are faulty waste gates? or the stock BOV leaking so much it's causing issues? I was gonna pick up an EVO blow off valve and see if that does anything, but I'm not fully sure either of those components could cause my issues

[Nihil]

So, still haven't been able to pinpoint the problem, I've got an EVO BOV on the way and started thinking/wondering about the check valves for the brake and clutch, they seal, but it seems like you have to blow fairly hard before they switch shut or open, so I'm wonderin if its not sealing at lower RPMs and causing issues.

I was thinking of disconnecting the vac lines n test driving, but not so sure about driving with no brake boost...?

[Roybatty]

Don't do the drive w/o brake booster ... Safety issue.

time to look thru list.

I am not aware of a cheap way to check fuel pressure... Harbor Freight kit? I ended up getting 3sx fuel pressure kit w/gauge in engine.

Sent from garage

[Nihil]

So, here's that same list with everything checked off that's either been replaced with brand new OEM or checked and passed. Only ones that seem like they could be contributing causes are TPS, Idle position switch, which is TPS as well, TDC sensor and CAS, which are the same and possibly Vehicle speed sensor, which appears to be the actual gauge cluster itself? Does anyone know how this works? I had issues with the original cluster, RPM's weren't reading correctly so I swapped the cluster from the '93 which fixed the incorrect reading issue. Only other thing listed would be fuel system, which would lead me to buying the underhood gauge setup. Which, I'd only be able to varify base idle pressure.

I added a "key" at the bottom of the list:

[Nihil]

Okay, so doing some searching, found a lot of people having similar symptoms and leading to speed sensor. Anyone have any thoughts on this? Apparently it's a reed switch in the cluster that causes the issue? Can I remove the cluster, disabling the sensor and possibly trouble shoot and confirm if that's indeed the cause? Maybe when I wake up in 5 hours for work, if I'm feeling up to it, I'll pull the cluster before leaving for work, to see what results I come up with...

[OhioSpyderman]

FWIW, my trims are pegged at 81%, always been that way, but my car idles and drives fine.

When I had hesitation/stumbling issues, I found water in my fuel pump relay under the hood (yes, INSIDE the rubber boot). I immediately did the relay bypass and all that went away (except for the 81% crap).

I put a fuel pressure gauge in (temporarily, just to check it) and it was spot on, so I'm clueless as to the cause, but since it doesn't seem to effect anything, I just ignore it

I have a spare ECU, and swapping it temporarily gets the trims looking better (from the reset) but it too will eventually show 81% trims....

My plugs look fine and I get 22 mpg highway/city, so I'm not worried about TOO MUCH fuel (which is what the trims is telling me...)

Bob.

[Alan92RTTT]

My car prior to the 450's and the AFC sat at 100% on the trims. With the AFC and the 450's I'm running in the hi 90's.

IIRC 81% is the min value that the ECU supports. That should not happen with a stock fuel system. Is their any chance that you have larger than stock injectors? I recall John Adams had(has?) 390cc injectors in his red vr4 and the ECU compensated for them by lowering the trims.

[Nihil]

FWIW, my trims are pegged at 81%, always been that way, but my car idles and drives fine.

When I had hesitation/stumbling issues, I found water in my fuel pump relay under the hood (yes, INSIDE the rubber boot). I immediately did the relay bypass and all that went away (except for the 81% crap).

I put a fuel pressure gauge in (temporarily, just to check it) and it was spot on, so I'm clueless as to the cause, but since it doesn't seem to effect anything, I just ignore it

I have a spare ECU, and swapping it temporarily gets the trims looking better (from the reset) but it too will eventually show 81% trims....

My plugs look fine and I get 22 mpg highway/city, so I'm not worried about TOO MUCH fuel (which is what the trims is telling me...)

Bob.

Only reason I'm worried about the trims is because the car isn't running right and that's the tell tail sign, if my situation were like yours, I wouldn't be worried either.

I've swapped 3 different ECU's and same results...

My car prior to the 450's and the AFC sat at 100% on the trims. With the AFC and the 450's I'm running in the hi 90's.

IIRC 81% is the min value that the ECU supports. That should not happen with a stock fuel system. Is their any chance that you have larger than stock injectors? I recall John Adams had(has?) 390cc injectors in his red vr4 and the ECU compensated for them by lowering the trims.

Injectors are flow matched stock OEM from the guy who does EVO Injectors on the other site, came with a proof/spec sheet too.

[Nihil]

Pulled the gauge cluster, no difference, swapped another cluster, no change, unplugged speed sensor on transmission, nothing. I'm ruling that out.

TPS is next in line, but I've swapped 3 different throttle body assemblies, and no difference between them, so I highly doubt the TPS is the cause either, which I think leaves me with CAS and fuel pressure...

[Nihil]

TPS checked out fine, which only leaves CAS and Fuel Pressure...

Was changing out some intercooler piping couplers and noticed rear turbo is blowin oil, not bad enough to make it to the TB but, wondering if that could be the issue? Definitely needs to be addressed soon.

Snowy cold weather is in full affect here and the symptoms have lessened, which I find odd, makes me think the MASS is the issue, though I Swapped in a good one, don't know why colder temps would affect this, other than more dense air to fight against the richness.