Timing and TPS adjusting issues (searched)
 

Hi,

First of all I went through the entire FSM, 2nd gen timing and tps thread through search. None of them seem to have similar issue as mine.

Now here is the spec of the car
1988 Rx7 Turbo II S4 turbo engine
- rats nest delete, ACV delete, OMP delete, Air pump delete
- has BAC and ASV (bac idle screw is gone and plugged with a bolt)
- precat and cat installed and a 3 inch catback
- stock air box
- Stock s4 turbo
- installed boost gauge
- ported wastegate
- installed FCD
- 550 High impedance injectors (later model N333)
- Car runs very rich
- Turbo glows after 30 minutes of cruise (no boost)
- stock bov shoots oil
- o2 sensor never replaced

Few issues..

-When I set the TPS, the best I can get is to 1.7 DC Volt, it won't go down any further without adjusting the fast idle screw. If I adjust the fast and let TPS be set at 1.008 DC Volt, the idle maintains steady at 1.5k rpm.

- When I adjust the timing, rpm set at 750 using fast idle screw. (Initial set coupler jump does not let the car drop back down to 750rpm) And when I hook the timing light to L1 and set the timing yellow mark at 5 degree, then I hook up to T1 and check the timing. Red mark is at 4 degree. Car idle hunts slowly. If I set red mark to 20 degree, the yellow mark jumps all over the place around the pin and car has rough idle.

I'm pretty sure the rich condition is causing the turbo to glow, so I searched the forum and Aaron cake said to check timing. Now that I checked timing. I find that I can't get them to line up right. Either yellow at 5 and red at 4 or yellow everywhere and red at 20. I also can't bring the idle down to 750 unless I adjust the fast idle screw and messing up the tps adjustment.

Any input is appreciated.

I am not clear on why you cant set the TPS to 1v. Does the mechanism not have enough adjustment?

I have never had to move the idle screw to set my TPS.

I set idle with the idle screw. I believe you can unplug the TPS for this. Then I set the timing. Then I adjust the TPS to 1.0v.

I don't think I answered your question, but I am unsure why you need to adjust the idle to adjust the TPS.

Also, was teh car fully warmed when doing these procedures?

Rob R.

Yes the car is fully warmed. Yes the mechanism will not go any further, I screw the tps adjustment screw clockwise as far as I can and the tps reads 1.7 dc volt, if I screw it counter-clockwise the voltage increases. What does unplugging the tps do? Shouldn't the position still be the same even if it's unplugged since the mechanism is still touching the sensor?

I had to adjust idle to adjust tps because for some reason when I got the car, the bac valve had no adjustment screw and instead it just has a bolt screw into it to seal the hole. So I had to adjust the fast idle screw which is the screw that sits on top left of UIM near the firewall. As I turn it clockwise, the screw pushes down and turns the shaft on throttle body that turns both the butterfly as well as the tps mechanism. If I could just use the tps adjust mechanism that would've been the end of story, but the tps screw is all the way in already.


bbtw the thermowax functions normally, the piston pushes up when car is warmed, but i guess the ghettofied bac could be the culprit of my high idle..

okay, I gotcha.

The reason for unplugging teh TPS was to make sure it had no impact on your idle (while setting idle).

Let me look into that adjustment for idle. I don't think that was the screw I used for idle adjustment.

Be back in a few.

Is this the screw you are using to adjust the idle?

If so, I can't see how it would have enough adjustment to make the TPS not have enough adjustment.

Essentially that would mean that you have to hold the throttle kinda far open for it to idle.

If this is the case, I would get the car warm, disconnect the TPS (because if it is ready high than it is having an effect on idle speed). Then re-set your idle speed.

You can also play with the variable resistor to help your idle smooth out.

Then I would check teh timing. Finally, I would hook the TPS back up and re-adjust.

The picture is really small, and it's hard to see. Which variable resistor are you talking about? Be back in a few.

Could you elaborate on this fast idle screw you mentioned. Is this the upside down screw that presses against the fast idle cam or are you talking about some other screw. Also, what happens if you gently squeeze closed the hose supplying air to the BAC?

Pics of the various screws related to idle speed.

https://www.rx7club.com/2nd-generati...-657023/page4/

Whoops, sorry about the pic. The screw I was trying to show has an 8mm jam nut on it on the backside of the engine. You would access it from the passenger side.

The variable resistor is by the passenger side shock tower. It has an R and an L on it. This is for rich and lean. It helps to set the AFR at idle.

Rob R.

Here are some pictures.

fast idle cam screw
Attachment 694562
Attachment 694563

As you can see here the vacumn line from bac is connected directly back to UIM
Attachment 694564


glowing turbo killed the oil seal. The turbo is not smoking yet tho...
Attachment 694565

and the ghettofied bac valve
Attachment 694566


Amazingly the car still pulls hard.

I didnt know that they came stock with a bov?

One thing I start to realize is that one of the best thing a person can do to a car is return it back to stock.

Yes, the stock bov does the job if you are running stock boost. the sound is not noticeable if you still have the airbox.

These pics should be better.

It looks like your screw is different, but in the same location.

Have you tried adjusting the idle with the TPS unplugged? If not, you may be fighting yourself.

What I mean is: when you adjust the idle with the TPS plugged in, it can act upon the TPS. This can cause the computer to think you are pushing on the gas pedal. This would then change the fuel quantity going to the engine. The fuel quantity changing would then effect your idle. You would then have to change the idle screw again.

* This is only true if in fact the computer will change the fuel amount based on TPS readings only.


Wait.... I just reread your problem statement. The screw that I included a picture of is the screw you should use to adjust idle (unplug your tps). Once you get your idle adjusted, adjust the TPS (using only the TPS adjustment screw).

In your first post it sounds like you are using the idle screw to adjust your TPS.

You said you adjusted teh fast idle screw out of teh way and set the TPS to 1.00V. But that made your car idle at 1500 rpm. Okay, when you have teh TPS set and the car is idling at 1500 rpm, turn the screw I have pictured counter-clockwise until your idle is 750-800 rpm. Then you can set your timing.

Rob R.

To be clear, the TPS and idle adjustment screw are independent of each other.

Set idle the way you were, then set TPS. Move the variable resistor screw around until the motor sounds best.

THEN do your timing. Make sure the timing light is only touching one spark plug wire. Make sure that one wire is not touching any other wires.