Mjedi

I finished rebuilding my 86 FC and I initial opened the hard idle set screw so the motor would idle (rough). I've been running the motor for days with no problems starting it (a little hard, but timings out), but now I'm trying to time it. The motor has never held a steady idle bounces about from about 2K - 1500rpm (when warmed up). When I turned the hard idle screw back down the car will stall. I turned the crank angle sensor but I cannot find top dead center were the motor idle would smooth out enough allowing me to time it. I've made and connected a error code diagnostic reader, and I'm getting no lights. I've also checked for leaks, compression, the throttle position sensor and fuel pressure, all are ok. Am I over looking something ? What should I check next?

diabolical1

iTrader: (3)

if turning the CAS doesn't bring the mark into sight while it's running, then it's probably a tooth off.

Mjedi

Then should I turn the motor over to top dead center and pull the Crank angle sensor out and realign the gear teeth on the CAS?

misterstyx69

iTrader: (142)

align the pulley to it's mark(forget the color..brain fart.sorry)
then pull the CAS and align that dimple on the bottom to the mark on the shaft and hold the Internals while placing the CAS into the hole.
That should be close enough for the engine to start and run.
With a Timing gun you can then move the CAS and get the engine dead on stock timing.

adprokid

good luck

Mjedi

Try this... marked the tooth at TDC and my timing was way off I can at least see the yellow and red marks on the pulley now (with motor running & timing light). Still cannot time the motor because of the idling problems is there anything else I can try?

satch

iTrader: (1)

You need to get the idle lower to time the engine and you should be able to set the CAS manually to get the idle to be low enough to set w/a timing gun. If this is not working for you then you obviously have the primary throttle plate(s) open too much from fiddling around w/the "hard idle screw" so unfiddle it. You also have the idle set screw on top of the engine you can play with in addition to the Variable resistor.

Mjedi

Satch ..... I will un- fiddle the "hard idle screw" when I get back to the car Saturday. Does the hard idle screw directly effect the idling quality (bouncing open and down)? Does the set idle screw also effect quality of idle by 500 rpm? (I thought it was more delicate than that).

satch

iTrader: (1)

The TPS or a vacuum leak would affect the bouncing but you need to drop the idle before setting the TPS. Sure, some things only delicately affect the idle but all things set properly in concert only serves to help things along.

Mjedi

I'm going to need to re set the TPS? I had previously test the TPS using this method RX-7 Throttle Position Sensor (TPS) Testing / Adjustment : 13B Etc - Mazda RX-7 Parts And More before. It was reading 1014 Ohms at idle and I did see any dead spots. Is there a better method?

satch

iTrader: (1)

1014 ohms is equivalent to approximately 1K ohms which is precisely what it should read so when checking ohms chances are you had your meter set to the 1K setting such that a 5 would read 5000 ohms and .5 would read 500 ohms.

Mjedi

If I remember correctly I had it set to 1K ohms. But this would indicate NOT a TPS problem right? Could it be an ECU problem?

satch

iTrader: (1)

Checking a TPS for 1K ohms is just to see if it is in spec and has nothing to do w/the ECU for this test is done w/no key in the ignition.

Mjedi

I don't have to warm up the car first to check TPS? Any else I should check when I get back to the car?

satch

iTrader: (1)

^yes

Mjedi

Satch - Before starting the motor the TPS was reading 1.9 ohms on 2K ohms setting. I set the the TPS to .997ohms and un fiddled the 'hard set screw'. The car ran better but the rpms still was bouncing and I had to keep my foot on the throttle for it to stay running. So I did until it warmed up. I notice that the less I was on the throttle (once the car warmed open) the less the rpms were bouncing, at one point I was barely touching the throttle and it wasn't bouncing at all. I let off the throttle and it died. I turned the 'hard idle screw' back 1 turn but now the car won't start. I rechecked TPS ( the motor is still warm) and now its reading .337 ohms I was think about adjusting it it back to 1K ohm to get it to start again?

satch

iTrader: (1)

You have to take TPS readings immediately after the engine is turned off. If you wait too long then the Fast Idle Cam starts to open the primary plates and it changes the TPS reading. And you might have a vacuum leak thrown in there in addition to having the idle adjustment screws off some. Taking a reading beforte starting the car is rather irrelevant unless the engine is as hot as it can be. Again, the idle cam affects the positioning of the throttle plates which affects the TPS plunger which affects the TPS readings. And testing the ohm reading of the TPS is supposed to be done w/the TPS unplugged.

Mjedi

A leak hunt ...... gggggggreat! I set the TPS to 1004 ohms immediately after running.

satch

iTrader: (1)

Engine needs to be as hot as it can possibly get to set the TPS. We're talking about a 20 minute drive.