Ark1

Currently I am no farther ahead than I was a week ago after swapping out parts from my son's 85 GSL SE and the donor parts car.

As suggested I jumped the fuseable links, no difference, I checked the voltage at the ignition coils and it is at battery voltage. I then jumped the + coil directly to the battery still no change. TPS is set with the 2 light method at the Green connector. The engine surges at idle from 1000 to 1300 rpm. The engine surges at all sustained RPM. Depressing the clutch allows the engine to level out at 1000 RPM but it now sounds like a miss fire is continually happening. Punch the throttle and the engine spools up smoothly with out a miss.

The engine does not want to hot start, too lean and I must put a shot glass of fuel into the mass air flow sensor to get it to catch. Installing a vacuume gage show a fluctuation in sync with the surging of the engine. Punching the throttle at surging idle drops manifold pressure almost to atmosphere and the engine spools up nicely, once vacuume builds the surging starts again.

On piston engines one may suspect a timing chain that is loose that continually advances and retards the timing, but I have my doubts about the rotary if this applies.

I have removed the bolt from the dizzy and while the engine is surging and idlining moved from advanced to retarded only noting of how quickley the surging is. Meaning quicker when advance and slower when retarded.

It is almost like the engine runs up and something is telling it to shut down then tells it to run up again.

On Friday I go to Hawaiia for my 30th aniversary and my son will have to drive my 4 door Dodge truck for 11 days. Any thoughts fellows and I mean any thoughts. I have been working on piston engines since I was 12 years old and have never had a problem that has lasted so long without a resolve.

I am listening.

Thanks for your consideration

TonyK.

Rx-7Doctor

iTrader: (13)

Tony,
I have owned and worked on my own SE's for many years and it is never the same thing twice it seems.
Have you done a pin test at the ECU to see if there is any out of range readings?
I would be interested in the reading for the coolant temp sensor.

Ark1

RX7 Doctor.

I think you are refering to the ECU under the floor mat on the passangers side.

I do have the 85 Haynes manual that gives the pin voltages but have not ventured to take readings yet, it looks like this will be the next item pending.

I am working full time and have 3 more days before I leave on vacation. This will most likely have to wait until I get back. I called a Mazda mechanic that worked on these cars years ago and promised that I would not tell his wife I was going to Hawaii if he came down to my place and took a look at the car. He agreed.

Is there a manifold absolute pressure switch on this engine? Just a stab in theory. The senor could by bad or gets stuck then tells the engine to ramp back, it does the sensor now clicks the other way and tells the engine to spool up and thus the cycle continues.

Slow acceleration of the engine is rough like a miss fire. Put the throttle anywhere like 2000, 3000, 4000 RPM and it surges.

My buddy told me these pre ODB engines were a nightmare to work on, no direction, just swap out parts and hope. So time consuming.

I will try the pin out test and make notes and get back to the form. Can't promise it will be before the 20th of the month.

Thanks again and should anyone think of something worth trying I will do it.

And if I figure it out this form will be the first to know what the problem was.

Thanks for all your help.

TonyK.

Ark1.

Rx-7Doctor

iTrader: (13)

Tony,
There is no MAP sensor.
If you can take detailed pictures of the top of the engine. Including all areas of the manifolds and also of the passenger side firewall area I can look at them and see if I can spot anything that does not look correct.

I'm looking for mis-routed vacuum hoses. Or non-hooked up ones.
If you can take pictures and down size them before posting. I'm on dial up so if you don't down size it takes too long for me to view I will do my best to come up with an answer.

I also remembered that you stated you jumpered the fuseable links. Does that mean you took a jumper bypass and put it in place of the 2 top fuseable links?

Ark1

RX7 Doctor,

I went from the + of the battery to either side of the terminal of the fusable links with no change.

I was looking through the Haynes manual and it states that fuel pressure at idle should be 29 psi, then with the vacuum hose removed from the pressure regulator it should be 38 psi. When I have tested the fuel pressure with a T on the supply line it was 38 psi. I know this next statement is a stab in the dark but if the fuel regulator is shot or a vacuum line is incorrect then would the low manifold pressure along with the high fuel rail pressure be too much for the injectors to open at idle. At near atmospheric pressure the engine runs smooth but as it spools up vacuum increases and the engine surges.

Keep this thought, high vacuum in the manifold engine wants to die, low vacuum in the manifold engine is smooth, the cycle continues.

I can send some reduced pictures latter tonight.

Thanks for your efforts.

TonyK.

Ark1.

Rx-7Doctor

iTrader: (13)

Looked at the pictures and can't see anything abnormal.

I need you to remove the 2 fuseable links at the top of the block. As stated before 1 is for the computer, the other for the injectors. Take 2 good ones from the headlight links below and put them in. Start the engine and see if anything changes, while it is running wiggle the links around in the housing and see if there is any change.
Also against the passenger side firewall are 2 solenoids. From those solenoids vacuum hoses go to a tee. You need to verify that the tee has not cracked or a vacuum hose has come off or is cracked. Check all hoses from the tee. Also the hoses at the top of the solenoids.

Check and make sure that the coolant temp sensor connector is tight at the back of the water pump housing.

After checking all of those if you do not find a problem then you need to atleast check the ECU and pins E and H I believe, I will have to double check. It does not take long. Just pull up the carpet and the ECU covering. You are looking to see if there is 12 volts at those pins or with a test light insert into the the backside of the connector and see if it lights up. Remember the connector stays plugged in with the ignition at the on posistion.

Ark1

The 2 solenoids on the passanger firewall have a vacuum supply that also leads into the cruise control. At the cruise control I disconnected the vacume line and attached my gauge. Vacuum cycles at that supply line. I have disconnected each electrical connector at the solenoids while the engine has been running without change. I have lifted each hose at those solenoids and no change. The engine continues to surge. I have also squeezed each hose with a pair of pliers to crimp it off, still no change.

I will swap out the links tomorrow from the donor car. A check at pin A and B would see if the unit is getting full voltage. Maybe the wire harness has a bulk head connector that is corrodied? I have wiggled and cleaned the connections at the links. I have not touched the coolant sensor that you have mentioned will attempt tomorrow. It has a connector that is similar to the injectors with the wire clip.

As for the ECU check, okay, I have to start packing for my trip soon, wife wants to leave too, I am either in the barn working on the car or on the computer. You state must have key on, but engine not running? Test light or volt meter? Engine warm or cold?

Thanks for the guidance. I like a challenge and know that what ever it is we will come across it, laugh and I will feel stupid but satisifed. In the process I have been learning a lot about this engine, still not as comfortable as a piston engine, but learning.

TonyK.

Rx-7Doctor

iTrader: (13)

You don't need a donor car. Just remove 2 of the 3 on the existing vehicle from the headlight system. Leave the middle one that is for power to the vehicle.

The only pin test that I am interested in is the two for the injectors at the ECU. Also the CTS would be a good idea also. The engine should be at operating temp then shut the car off. The turn the key to the on position. Test light is fine for the 2 pins for the injectors since they need 12 volts. If they do not light up then there is less than 12 volts there. For the CTS a OHM meter is needed to check resistance.
With the symptons that you are describing you can disconnect every solenoid on the engine and it would not affect it. Also if you removed vacuum hoses from the intake the idle would rise at first but should vasilate if it is losing vacuum to the BACV.
Another thing that I spotted that you did was take apart the Throttle body. It's almost impossible to take it apart and reposition everything correctly and have it function properly.
If you have a non-molested T/body, you need to put it on. If you don't then while the engine is running just take your finger and press down on the throttle linkage to close it. If the surging goes away then the butteflies are binding.

Rx-7Doctor

iTrader: (13)

Amendment.
2 pins for ECU are F and H. Both should have 12 volts at them.
C which is the CTS should be 1-2 volts with warm engine.

Ark1

The reason I changed the throttle body was because the old one was binding. And would not always go back to the stop. The one that I changed was in better shape, it was sand blasted and painted. I also looked at the shaft bores for wear and possible air leakage. When pressing the throttle body linkage to the closed posistion ( close to forcing) only when the engine is cold will it drop to a near but rough idle. I have even lifted the linkage off of the thermo wax to get it to close when the engine is cold. Idle drops to 600, is fairly smooth and then starts to drift then surge. Lifting the vacuume line to the BAC allows a lot of air into the manifold but surging continues.

I can put the old throttle plate back on but, there was no difference between this one and the old one as surging was there too. The only difference is that the throttle plates were binding and for a short time I added a spring to force it back to the idle stop.

What does CTS stand for.

Will do the link change tonite when I get home. As for the throttle body plate change going to have to wait. Will read the voltages at the ECU as well.

Thanks.

TonyK.

Rx-7Doctor

iTrader: (13)

Coolant temp sensor.

Ark1

Yes! Thank you!

Tried your suggestion of moving the fuseable links from the lower portion of the car. Started the car, smooth idle, fuel pressure constant at 29PSI engine spools up smoothly, no surging. A bit at idle but reset TPS with the 2 light method. Advanced timing slightly, 800 RPM idle.

Many, many thanks. My error was using a voltmeter to check voltage at the fuseable links. I suspect a back feed that allows the engine to start but run poorly and shows voltage at the upper link. Once running, I removed the link and all symtoms reappeared.

So simple and so frustrating. Boy do I feel good. The beast has been beaten.

Thanks so much.

TonyK.

Rx-7Doctor

iTrader: (13)

Your are very welcome Tony.

Like I stated before I have gone thru and tested everything there is on a se at one time or another.

What I have learned is to disregard alot of the FSM things along the way. I have never not been able to figure one out yet. The only problem is that it always seems to be some variation. lol.

Forgot to add. Dump those fusable links and buy some 2nd gen fuses to replace them. They fit right into the same link area.