Mattimus Aurelius

Somebody please help ! I just bought a 93 FD and already messed something up when I was only trying to tune her up. So here's the story...

I changed the plugs and the car responded really well to the new plugs. Started right up and the was the first time the car actually revved up to 3000rpm momentarily before dropping back down (I read this to be a normal condition) and purred really smoothly at normal engine idle 750-850rpm when warm. Next I changed the fuel filter which was a task hahaha. After that the plug wires... This I struggled with trying to avoid removing the throttle body because I heard that these cars are extremely difficult to bleed air from the cooling system. Well I failed and eventually caved and removed the throttle body. What I noticed when I removed the throttle body is that what I am assuming is the throttle position sensor one of the prongs on and inside of the actual harness side were corroded pretty badly. Again, the car ran fine before I messed with this. I also noticed that coolant ran through the throttle body which I assume is the ISC Idle speed control or the IAC intake air control? At this point I pretty much knew I would have to bleed the cooling system for the sensor (ISC IAC) to function properly. I then finally get the wires hooked up go back together with everything (attempt to clean the connector and sensor). I also change the air filter....

I bleed the cooling system (from a procedure that I am pretty sure I found on this site actually) Which pretty much involved setting the level in the exp tank, filling the filler neck until the ast was full and then run it and burp the bubbles out of the filler neck with a coolant bleed kit which I did.

So the cooling system seems to be functioning properly and maintaining cooling system pressure and temp without having to top off after cool down.

The problem lies here....

Upon even first start up the idle freaked out and my check engine light came on as if I forgot to hook up a sensor (I checked all the sensors and vacuum/coolant lines all appeared to be okay) Once I bled the air from the cooling system the car ran better but as it warms up the idle never drops back down below 1500 rpm as if it is still running on the cold engine start up circuit or something? Is this because there is air trapped in the ISC/IAC circuit ??? I've even drove the car around to see if I could get if any air to burp out through the AST cap but the only time the idle drops down to normal when its running is when I put in the clutch and the car into gear, other than that if the car is in neutral its staying steady at 1500rpms. The car seems to run fine when driving, it produces good boost and operates as it should. For the life of me I can not figure out why the idle is still so high. I checked the map sensor (which causes completely different symptoms than I am experiencing), vacuum lines, electrical connectors (including the tps again). I pulled everything apart again in attempts to better clean the tps attached to the throttle body. The check engine light kinda of flashes on warm up a few times but eventually goes out???? I dont have an obd 1 mazda scan tool any suggestions there ?? I understand automotive theory and just spinning my wheels here. Someone who has experienced these same symptoms please I beg you help. Once the car has warmed up it runs fine except the high idle. You can hear possibly the IAC or ISC maybe trying to correct the high idle when its warm upon first start up, it will try an drop, then rise, then drop, then rise and just stay there. I assumed this indicated a vacuum leak (manifold vacuum 30psi/hg?) at idle. I sprayed the engine back with carb cleaner and got no real obvious engine rpm changes. I am at a loss here....

ROTORNEWB

When you removed the throttle body you might have bumped the TPS sensor out of whack. That has quite a bit to do with the idle. You can also adjust the dashpot, air intake screw in the throttle body, screw on the top of front side of the throttle body facing the front bumber where the 2 butterflys are.

Does the car have any mods?

https://www.rx7club.com/3rd-generation-specific-1993-2002-16/fixed-my-idle-problems-backfiring-bucking-more-170731/ << TPS adjustment.

Gringo Grande

iTrader: (97)

My first guess is TPS. Easiest way to adjust is PFC Commander. You can watch the voltages change as you have someone adjust the TPS.

RX7 tuga

Hi mate, did you try to see if it shows any engine code error?
Don't forget first to reset the code error memory, unpluging the battery and depress the brake pedal for about 20 seconds...

Mattimus Aurelius

Thank you everyone for your suggestions as to helping me with my high engine idle problem. I think I found out the solution to my problem..

When I removed the throttle body to service the ignition system I also cleaned the throttle body with carb cleaner and think I created air gaps between where the butterflies once rested. Once I started messing around with the throttle linkage stops (not the cable itself) and idle speed screw I was able to dial the high idle back down to factory spec. I did have check engine codes stored for my tps being out of range so I tested it with my DVOM and set it both closed and wide open back to manufactures specification. Now the only other thing I have left to figure out is why the car only does its accelerated system warm up at night??? haha Regardless of the coolant temp it will only shoot up to 3000rpm on cold start at night. Any ideas? Thanks everyone

Mattimus Aurelius

yeah you guys are great thanks again you guys have been amazingly helpful