94 rx7 wont pass 4500 rpms
 

hey, i gotta 1994 rx7, chasis has 129k but the motor has about 6k on it with a rebulid from chris sanders of banzai... vaccum lines have been replaced along wit most hoses with silicone and the only mods i have are blitz intake, blitz bov, 3" downpipe with stock exhaust (for now), im runnin on 11psi (stock boost) and my car will not pass 4500 rpms... whenever i punch the accelerator, the car only goes up to 4500 rpms and then bogs and the boost drops and the rpms do not pass 4500 rpms... when i dont punch it and i accelerate slowly, the car goes up to 6500 rpms (but thats when i dont punch it) ... i tried toppin my car to see how fast i can take it on the highway b/c i knew my car would not pass 4500, i took it all the way to 5th gear by shifting early on each gear and the car topped off at 125mph and stayed on that since my rpms were still on 4500...

im not sure what can be wrong with my car, :confused: i am new to rotary and i am still learning more and more things about the car, so im still a newbie...so i have no clue what and why my car is doing this... so if any one can help me out, id really really appreciate it, id liek to get this fixed and run my car on the track but i cant do so cuz i cant go past 4500 rpm...when ibought the car, i was told that the turbos still have life in them but they are going out (they have 129k on them) stock twins... also, i was told to replace the fuel filter...im not sure if its b/c of that, i could perhaps be the turbo, but i am unsure.... :( please help! thanks.

Your problem has nothing to do with your turbos themselves, most likely an electrical or fuel issue.

mine was doing that b4 i changed my plugs. didnt think that was my problem.

pull codes and fix problem then reset the ecu.

if you don't know how to do any of that stuff, use the search...it's helpful and goodluck and welcome.

to reset ecu: disconnect neg battery cable. step on brake. reconnect.

My money is on plugs.

hey, thanks alot .. ill try replacing my spark plugs and go from there .. will i need to reset the ecu after replacin the plugs?

Change your plugs if you want, but I don't think that is going to fix this problem...

It sounds like a boost-related issue, because 4500RPM is where the secondary turbo engages.

Could be the charge relief valve, not closing when charge control opens to engage the secondary turbo. Or it could be a blown secondary turbo. In any case, it sounds like a loss of boost pressure when the secondary turbo is engaged. It could even be a crack in the rear section of the Y-pipe.

Right, 4500 rpm is where the second turbo kicks in, but that has nothing to do with the engine revving. The engine can rev regardless of the condition of the turbos or their control system. It is most likely not turbo related.

the cat may be cloged. or it may be elec. slowly getting to 6,500. when was the last time the fuel filter was changed?

changed the spark plugs, no improvement, still bogging...

the fuel filter has not been changed for a long time (that's what i was told by the previous owner) and he had the engine rebuilt but advised him to changed the filter, im gtonna do that next...but like i said, when i drive the car and rev it up in any gear, the car hits redline, so the engine is reving up but when i go full throttle, thas when it bogs, after 4500rpms... the car wont' pass 120mph since its hitting 4500 at that time in 5th gear...

im thinking its fuel related, b/c i was driving my car when i was really low on fuel and the car was boggin exactly the same way it bogs normally, instead of boggin at 4500, it was boggin at 2500, once i filled my tank up it started to bog at 4500 again .. any comments? should i add a bigger fuel pump? or my secondary injectors? when i bought the car, the guy told me the turbos will be needing a rebuild..so do you think it is my second turbo?? any suggestions? please help, thanks.

do you hear anything inparticular when you reach 4500 RPM's, does it feel like you hit a wall, do you have a boost gauge to see if you making positive boost at 4500 rpms, if you floor it to 4500 and then ease off the throttle will the engine rev higher then? my guess would be on a vacume line issue

Why don't you quit guessing and just replace the fuel filter? It's in obvious need of doing. Your fuel pump pickup may be faulty as well. This is obviously a fuel-related or electrical issue. I also suggest not going 120 mph until you figure it out....:o:

This has nothing to do with boost guys, as I and others stated above. You can redline the bejesus out of the car without boosting, just fine....

did you reset the ecu?

my car was doing something like that...the vacuum line for the boost sensor came off...its by the throttle body

Ok, I got one for ya then. You can rev the car all they way to 8000rpms or whatever, but when you drive off the boost it wont go above 4500rpms? Similiar to this problem...

We found that the actuator on the turbo was off(little horse shoe came off, and the rod came off), I dont know know if that was the problem, we put it back together and 4.0 (works great).

Re: 94 rx7 wont pass 4500 rpms
 

When you do this, the car doesnt chug, fart, pop and backfire?

If not hummmm

i reseted the ecu, spark plugs changed (looked liek they needed to be changed)...

i was checking the rpm again and its jerking at 5000rpms now, i get full 11psi on my boost gauge until i hit that rpm, all vaccum lines on my car have been replaced with silicone so i know it isn't that, im gonna change the fuel filter next... does a fuel fiter really effect a cars performance that much?? i hope its the filter, if anything, im gonna add a upgraded fuel pump... hopefully it'll work...

the car jerks and thats it, just a big jerk, and a pop noise, but that could be the car jerking...

get you fuel filter changed!!! if i remember correctly you need to change them every 30k. and if it hasn't been changed in a long time it could be cloged.
it sounds like your running out of fuel. if you fliter is cloged then it will only let so much fuel through it. hence the reason why your car is craping out at 5k. not enough fuel.

and yes the fuel filter does matter that much. if it is clogged it will only let so much fuel through it to the motor