RX7SIGN

Late boost, my most recent problem with my 7. My boost enjoys kicking in around 5,500 6000 rpm consistantly thru 2-5th gear. 1st gear switches over anywhere between 6-almost redline. This leads me to believe that 1st gear being the fastest to run thru the rpms isnt giving enough time for the actuator to switchover. The only catch is sometimes the car will switch over almost at 4,500 but rarely and never in first gear. This leads me to believe that it could be the flap inside the actuater which is still doing its job but its delayed. Its switching over late because possibly the flap needs to be lubricated, or just stuck or stiff. Anybody agree?

dgeesaman

iTrader: (7)

That's possible. I would try the KOKO test and see if those actuators are moving smoothly.

Dave

RX7SIGN

KOKO what is this technique Dave? I went over it once but I completely forgot.. There was a link for it, unfortunatly I lost it.

weetbix13

RX7SIGN - i had this same issue... look towards your throttle position sensor first.
if you are outside normal readings the car won't even run the actuators for transition until late.

FACT: at low throttle input levels the FD will delay transition to 5,500rpm or so. it's because you are stating the EXACT late transition point that makes the TPS the first culprit in my mind.

level7

iTrader: (3)

Key on, key off. (KOKO)

http://www.fd3s.net/boost_test.html

^ Check vacuum tank storage ability with the engine off.

RX7SIGN

RX7SIGN - i had this same issue... look towards your throttle position sensor first.
if you are outside normal readings the car won't even run the actuators for transition until late.

FACT: at low throttle input levels the FD will delay transition to 5,500rpm or so. it's because you are stating the EXACT late transition point that makes the TPS the first culprit in my mind.


So what is it hear I need to do to fix this problem.

dgeesaman

iTrader: (7)

Measure the TPS sensor and adjust it if required. There is a thread by Damian about it that describes the procedure very clearly: https://www.rx7club.com/3rd-gen-archives-73/fixed-my-idle-problems-backfiring-bucking-more-242321/

Dave

RX7SIGN

This definitly seems to be my problem..TPS never would have guessed. This has to be it because I get bucking problems sometimes. it seems like alot of work to fix though, hopefully I will get the time to do it this weekend. Thanks guys

7THSIGN

Well the TPS issue explains the hesitation we were feeling, but is it the cause of the late switch over? Interisting.

dgeesaman

iTrader: (7)

Well the ECU triggers transition, but the TPS and CASs tell the ECU what the engine is doing. I've not seen the TPS cause this problem, but it's a fundamental part of the engine control system and I believe it's worth getting correct before moving on.

Dave

7THSIGN

Definitely, he will most likely drop it off with Ray since my Supra will be up there soon as well.

But I am just trying to figure out and understand what caused the TPS to go bad like this?

weetbix13

The TPS (internally) is basically a spring sensor that is pushed around by pins on the sensor side - mine, during the rebuild had basically come completely unstuck and did all sorts of BIZARRE things.
thats an extreme cause of the problems with TPS, normally it'll be something like a slightly loose bolt and someone knocking it out of alignment.

it is so easy to fix it isn't funny though - i followed the Damien thread to recalibrate mine.

the transition in the FD is delayed until higher revs if throttle input is not over 40% - if the TPS is sending incorrect voltages to the ECU the transition will be delayed.

7THSIGN

Just for future reference, the problem was found, it was the check valve.