mkvevil

I have a 87FC and for some reason when its cold it will not idle? but if i run the car that way she will pull like crazy. As soon as the car warms up though she will idle but when i hit the gas it runs so slow. It feels like its hesitating but i dont know y? can anyone help?

LikeThunda

iTrader: (1)

Redline that Beezy... Clean out the Carbon..check ur sensors...Filters..sparkplugs..Coils.....

that should work... as for the Idling... check sensors...right by the throttle body

PnoyRx7

iTrader: (3)

wrong, dont redline the car while cold, thats a big no-no. also if you step on the gas after its warmed up and it feels like it hesitates its the 4k rpm hesitation, i fixed this by re grounding the some wire and my friend re-soldered my ecu, it fixed the problem about the hesitation.

rxmadness

iTrader: (1)

sounds like when it gets warm the MAF sensor is richining the engine. not sure what fc's use but your problem sounds like a MAF or mass air flow sensor you can usually borrow a scanner from a parts store and check the voltage on the mas and it will tell you what it should be..ask the parts guy for help. i really dont know about the FC's but a normal MAF sensor should read about 1 volt at an idle and 5 volts while revving
if its not reading right replace it or clean the terminals and bottom end of it with electric cleaner or parts cleaner.

if that isnt it check plug wires, plug gaps, also while the engine is idleing try tapping the MAF, IAC(if there is one), and coil packs lightly with a screw driver or somethign and see if that helps

mkvevil

I have grounded the Wires in the engine bay pero nothing. and i havent messed with the ECU but i am Having a friend bring a MAF and an ECU so i will see which on fixes it. thanx for the reply's though i will let u guys know what works.

diedxjustxyesterday

he prolly meant reground the pressure sensor and ecu grounds within the cabin. the 4k hesitation is pretty common on s4's without this modification done. also i believe mazda added a ground for it on the 87.5 cars to rectify this. so if yours doesnt have it could be the problem,

mkvevil

reground the pressure sensor and ecu grounds within the cabin. I really wouldnt know where to find these in the cabin? maybe a picture or a tom tom to point it out for me?

diedxjustxyesterday

the pressure sensor is in the engine bay on the passenger strut tower should have a sticker that says n 326 or n327 check the factory service manual and find the ground wire within the wiring diagram. also in the cabin the ecu is located beneath the front of the carpet on the passenger side. the wiring diagram will also identify the ground wires for that as well. make sure to crimp and solder any connections you make, shrink tubing doesnt hurt either, also use dielectric grease on any metal points of connection to the chassis.

PnoyRx7

iTrader: (3)

THIS , this guy knows what he is talking about. thats what i did and it fixed my hesitation but not completely, ovbiously there is something else wrong with my 7 .

diedxjustxyesterday

also wouldnt hurt to check the ground on the engine block as well clean and re dielectric grease the main ground at the drivers side strut tower as well

mkvevil

Ok cool well i will check those grounds atleast i did the one on the block first so i dont need to do that again but the others i will find and let u know what happens.

HAILERS

The ECU ground is located on the rear ROTOR housing and cannot be accessed unless the upper intake is removed. IF you fixed some gnd without removing the upper intake.......you done did the wrong gnd.

The ECU grounds are on pins 3A, 3G, 2R and 2C. The 2c is the gnd wire for all the sensors in the enigne bay....afm, boost, tps you name it.

They all come together inside the EM harness inside the passengers foot well about a foot from the plugs on the ECU.

See the free online FSM and wiring diagrams located on this site.

Also read the several hundred threads dealing with *hesitation* and grounding the ECU's internal circuit.

mkvevil

Well good i did take the intake off to do that ground so i guess that was right. but i am going to locate the 2c one that u recommended and see what happens. Also i cannot find any wiring diagrams on this site can anyone help me locate them?

HAILERS

Wiring diagrams can be found on the 2ND GENERATION site and is located in the FAQ thread there.

I'd do the other gnds other than 2C also.

HAILERS

https://www.rx7club.com/2nd-generation-specific-1986-1992-17/frequently-asked-questions-2nd-generation-rx-7-faq-fc-494667/

mkvevil

OK, cool i got it lets see if they work. THANX