ShiftRX7

Hi everybody, i have been experiencing this weird issue with my FD but was not able to find anything similar in past topics...so i hope some of you will be able to help me a bit.

Here is what happens: as soon as coolant temp reaches 104°C (PFC reading) idle starts bouncing heavily from normal rpms (900) to approx 3000rpms and then back to normal, giving the same feel as if i were pushing on the pedal and immediately releasing. This happens both on startup and if i am already cruising. Only way to stop it is let the engine cool down a bit and have the temp below 104°C.

Temps dont usually run that high but since this summer is particularly hot (>100F everyday!) it can happen if im using A/C and im stuck in traffic for a long period of time. Also it may happen when turning off the car at normal operating temp and then starting it again after a few minutes (PFC will read a high temp, but it will be adjusted down only after a few seconds).

My car runs PFC, DP-MP-CB and no airpump with all the boltons

Do you have any idea of what can be causing this?

Thanks in advance for your help!

1QWIK7

iTrader: (33)

Could be the AIT sensor. Its located underneath the upper intake manifold.

For some reason, mazda thought it was a great idea to put an air intake sensor in probably the 2nd hottest area of the engine lol.


Some people relocate the AIT and get better intake readings and eliminate those weird hot start idle problems and/or the weird action if sitting stationary for a while, then you go and try to boost etc etc.

ShiftRX7

Thanks i'll give it a check this weekend!

adam c

iTrader: (2)

I would set the pfc to turn on the fans sooner. Mine is set at 85 degrees. This won't fix your problem, just a general suggestion.

ShiftRX7

i will be doing that as well as installing the FC sensor (that i just received some days ago)...just needing to find some hours to work on my sweetie

arghx

iTrader: (3)

The idle circuit is probably flipping out when the fans come on. They are set for 105C (which is really 104C) by default in Settings 3 tab of the Datalogit software. The fans trigger the electrical load idle control logic which uses different ignition timing values and ISC valve duty cycle. The idle control is based on the throttle body adjustment as well as the settings under the rev/idle screen of the commander.

See https://www.rx7club.com/3rd-generation-specific-1993-2002-16/how-make-your-untuned-pfc-basemap-safer-idle-better-no-datalogit-needed-841706/ . Especially look at posts #1, #27, #28

rotarymaz

iTrader: (1)

I had the exact same problem when I first install my Power FC. Idle would go crazy if car hits ~104 F or above, which it really shouldn't happen if all my cooling system was working properly, even in 110 F summers here in PHX. It turns out one of my radiator fan was broken and I wasn't getting proper air flow. I replaced the broken fan and make sure I activate the fan if temp hits ~98 F, once the fans kick in, it usually bring temp back to low 90's even in stop and go traffic. So, I would suggust checking you cooling system to make sure everything is working and try to keep temp below that 104 F point.

1QWIK7

iTrader: (33)

Fixed for ya.