JEFF1988RX7SCOTTSDALE

Hello Everyone,
I did post a few pics in an album if anyone is interested. I didn't go crazy yet, because I wanted to see how it works but, at least a few are there. I still need to detail the interior and finish the paint clean up....better pics to follow.

But at this point I'm in need of some further specific advice on the TPS adjustment. (I don't think things are quite right with the idle and therefore I'm trying to be thorough before I attempt to go through emissions).

Anyway, the idle usually starts out at about 3000rpm when cold and comes down to about 800-900 depending on how long you allow the car to "settle" down. After driving it seems to climb to about 950. But, just lately I noticed it will surge for a few minutes or until you start to drive the car.

So, also I know I have code 7 coming up with the key on reading my 2 red LED lamps (dash, dot, dot, pause). Basically the Boost Sensor. I checked the vacuum to the device (vacuum hose is replaced). The device holds a vacuum just fine. The FSM describes checking voltages etc. at the connector, but I'm still figuring out what pins are what.

Basically, I'm wondering if the Boost Sensor affects the idle and if so, I'm assuming I need to fix/replace it before I go further. (cost?/supplier?) Other than that I'm wondering the following:

---I get a smooth increase from about 2600 Ohms to 6200 Ohms by manually opening the throttle (stop to stop), measuring from pin A to pin B on the TPS connector. I was expecting to see around 1k ohms at idle (is this what I'm supposed to adjust to 1k ohms at idle?). Am I measuring the right pins? I'm reluctant to try to change the throttle position setting that much since the car seems to running close to right. Also, is this the first adjustment to make? I have not touched the air/fuel adjustment on the top of the plenum and I haven't touched the variable resistor adjustment by the air box. What should I do first? I'm assuming my O2 sensor is doing something right because the green lamp is on at idle, on during acceleration and off during decelleration, can't remember if it is flashing at cruise...I think so.

Sorry for the long post, but I have read several checking methods for all of this, but I'm not clear on which ones can be done in what order. Does the initial set connector allow me to check some things without worrying about other systems?

Thanks in advance, Jeff

arghx

iTrader: (3)

You have to test the TPS with the engine warm or the fast idle cam physically rotated away

HAILERS

The series four boost sensor has four wires.

Key to ON.

Unbolt the boost sensor......remove the vacuum line..........turn it upside down so you can access the wires in the elect plug that you leave connected to the sensor.

Black/white wire.....12vdc

Brown/white wire.........approx 4.5 to 5vdc

Black wire.......ground

Brown/red wire...... 2.3 to 2.7vdc if this car is a TurboII. Non turbo is different.

This is done with engine off. If for some reason the engine is running, then be sure to disconnect the vacuum hose and plug that hose. If the hose is on the sensor and engine running, the figure won't be 2.3 to 2.7vdc.

Actually your doing yourself a diservice checking it at the sensor. You should be back probing pin 2B at the ECU instead. Enine off.

If you decide to go to the ECU, then while your there (with a fully hot engine) then take a moment and check out the TPS output voltage at the ECU. Pin 2G. At idle with a fully hot engine, the reading should be approx 1vdc. IF not that figure, then turn the TPS screw til the reading is 1vdc with engine running and fully HOT.

Approx 1vdc means it can be 0.95 or 1.05vdc and still be correct. Actually even further off than that, but why not do it right? and make it one volt.

That 1vdc will be higer with a COLD engine because the water thermowax will move the throttle linkage open more and therefore effect the TPS reading when cold.

Actually from your description, I'd suspect the water thermowax fast idle cam isn't seperating from the roller. See FSM, Fuel and Emissions section for how to set the waterthermowax.

On a series four car a fault almost everytime can only be triggered if the sensors output isn't being seen AT the ECU. Just my opinion on that.

JEFF1988RX7SCOTTSDALE

Okay, I'll start checking things at the ECU. I'm assuming all things connected to the ECU at conditions, e.g. engine warm, etc. Since the TPS is just a position sensor (off fast idle cam---same as after warm up theoretically), then obviously the voltage test of 1 volt is more accurate because is takes into account the wiring (actual) drop to the ECU.

Will this then change with the lights on at night?, etc. accessories. Bottom line--am I aiming for 1 volt TPS input at the ECU after warm up at idle (off fast idle cam) with accessories off or on, or is that just dependent on how perfectly you want it to idle depending on whether you start the car at night and turn the lights/stereo on, or during the day with nothing else dropping the voltage? OR, should the voltage regulator make the above discussion irrelevant?

As always, TIA, Jeff

JEFF1988RX7SCOTTSDALE

Well,
It seems the boost sensor is reading high in voltage at 100mmHg (4.6V nominal), so the ECU will think lower vacuum and therefore, more engine load, and therefore, create a rich condition at idle.

Please correct me if I'm wrong...I don't have the experience to have a "feel" for this. Anyway, just wondering what I should pay for a new Boost Sensor or should I attempt to fix??

Jeff

HAILERS

No. It'll be one volt with all ACC on and headlights. It should not change.

Something if fishy about the output reading of the sensor. You say 4.5vdc which sounds......fishy. Try this. Put the vacuum hose back on the sensor and start the engine. Watch the voltage at 2B while you rev the engine up and down. It should change.

Tell us, is this for sure a Turbo car or a non turbo? I don't know. Turbo and non turbo sensor outputs are different.

If your meter leads are long enough, pull the plug off the ECU and the boost sensor. Then ring out (ohm out) the brown/red wire from end to end and see if it ohms out ....or not.

The 4.5 sounds roughly like the ref voltage the ECU uses to operate with. Like the wire is open b/t the ECU and boost sensor and your reading the guts of the ECU pin 2B circuit. Guessing. Oh, I've an idea. PUll the plug off the boost sensor and then read 2B at the ECU and see if you still have 4.5vdc. If you do, then I"d guess the wire is open b/t the ECU and sensor.

Also what is the or any number written on the boost sensor?

arghx

iTrader: (3)

are you sure you are checking the correct pin? those diagrams are from the BACK of the connector

HAILERS

.

JEFF1988RX7SCOTTSDALE

Sorry to get back so late. The car is non-turbo, but I may not have been reading the right pin on the connector to the boost sensor. I'm going out to warm up the car and read the voltage at the ECU. The boost sensor says N327 8615 T1..... on it. The voltage I was reading was with a hand vacuum pump connected with 100mmHg set. The voltage goes down to around 2.5 volts if I increase the vacuum to around 500mmHg if I remember. But, again, I may not have been on the right pin so I'm going to warm up the car and find pin 2B on the ECU and get some results.

Jeff

calpatriot

Here are some voltages you can check on the ECU, with their pin numbers and their nominal values. Once you are in there, it only takes a few minutes to check each of the pins.

Sensor ECU pin voltage at idle Notes
Air Flow Meter 2E 2.5 - 3.5
Air Flow Meter Intake Air Temp 2J 2.0 - 3.0
Atmospheric Pressure Sensor 2H 3.5 - 4.5 3.5 - 4.5v at sea level; 2.5 -3.5v at 6500 MSL
Boost Sensor 2B 3.5 - 4.0 2.5 - 3.5v at 3.9" vacuum
Bypass Air Control Valve 2Q 8.0 - 12.0 Pulsed signal duty cycle varies to maintain idle rpm
Bypass Air Relay 1C 12 0v for 17 sec after cold start
Crank Angle Sensor 1N < 1
Crank Angle Sensor 1P < 1
Crank Angle Sensor 1Q < 1
Crank Angle Sensor 1T < 1
Exhaust Gas Recirculation Valve 2N 12
Oxygen Sensor 2D 0.45 - 1.0 Nominally 0.7v at idle, warmed up
Port Air Solenoid 1S < 12
Throttle Position Sensor 2G 1
Variable Resistor 0.5 - 4.5k ohms, pins A-C and B-C

Each of these has a potential impact on the idle of the car

JEFF1988RX7SCOTTSDALE

Okay, I am getting up to speed. I just got my fluke onto the ECU and I adjusted the TPS. It was about 2V nominal and so I ajusted it down to 1.003 where it sat for several minutes and revs. This finally solved the surging (which I think was indicated by the fact the green lamp was not lit at idle...only on accel.) The idle speed settled down to about 800 (cool), and I think I'm getting close.

It now smells like it's running rich, so I checked the O2 sensor at the ECU and I'm reading .7 / .8., and it's bouncing around. I'm going to replace the O2 sensor with a Bosch generic today and check again because the car has 119k miles and I don't think the previous owner did anything....Just to eliminate that.


But, again, I know the boost sensor is reading 4 to 4.5 volts even though I know it has no vacuum leaks to the manifold and the wiring is Ohm'd out. AND, I have the clicking (like a turn signal, BAC??) after the O2 sensor starts to read low (e.g. .2 volts to .02 volts, etc.). I'm guessing the O2 sensor needs to be taken out of the picture.

But, I'm wondering if the boost sensor could cause any of this. After I set the TPS (and it was solid .996 to 1.003 nominal at 850 rpm), should I try to set the idle rpm. Don't really know how to do this?? Is this the small flat screw at the airbox, or should I be setting the air/fuel mixture at the top of the plenum?

What's next??

Thanks in advance, Jeff

HAILERS

This a Non Turbo??

A 02 reading of .7 or .8 is more or less normal for a RX that has no airpump/ACV.

If the car has the airpump and ACV connected, then the 02 reading would be real low. Like .o2vdc or so. Because a car with an airpump and WORKING ACV will send fresh air to the exhaust PORTS which are prior to the 02 sensor area and this airpump air dilutes the exhaust gasses. So the 02 can't help but read low at idle in the driveway.

Did you ever disconnect the boost/pressure sensor AT the sensor and then go to the ECU pin 2B and see if the reading is the same? or not?. 2B has a brown/red wire just like the one at the sensor itself. One and the same wire.

What is the part number on the boost/pressure sensor?

You KNOW the TPS shouldn't be adjusted unless the water temp is fully up/hot? Right.

calpatriot

Both the idle speed and idle mixture are set with a jumper connecting the two pins of the initial set connector. This puts the BAC in fixed-duty mode so it does not try to change the idle speed while you are setting it.

Actually, the FSM procedure calls for you to set the idle speed, idle mixture before doing the tps.

The idle speed is set with the screw at the very top of the throttle body. The idle mixture is set with the screw recessed into the center of the variable resistor, which is mounted on the front of the right wheel well, very near the boost sensor.

JEFF1988RX7SCOTTSDALE

Okay,

I've been trying to follow all of the advice and I'm thinking I'm close. To recap:


88 Non-Turbo Convertible

Boost Sensor: N327 8615 T1.....

Here are the things I've done--

Set the TPS to 1.00 volts nominal (after full warm up, driving for 1 hour min, sitting idleing for at least 10 minutes afterwards, revving a few times to make sure the fast idle cam is off and I'm not putting pressure on the TPS adjustment screw as I adjust).

Measured the Boost Sensor as follows:

Engine Cold:

Ignition on (battery 12.4V nominal with the engine off) , VRef at the boost sensor connector and at the ECU is 4.89 Volts nominal; 5.18 Volts at pin D nominal with the vacuum line disconnected from the boost sensor.

Applying vacuum with a hand vacuum pump and gauge to the Boost Sensor as measured at the ECU pin 2B:

4.65V at 100mmHg 4.19V at 200mmHg 3.62V at 300mmHg 3.09V at 400mmHg 2.55V at 500mmHg

Same conditions as above but measured at Pin D of the Boost Sensor:

4.67V at 100mmHg 4.17V at 200mmHg 3.67V at 300mmHg 3.12V at 400mmHg 2.59V at 500mmHg*

*Note: The above results show a "normal" voltage drop from the Boost Sensor to the ECU, so I'm confident the wiring to the ECU is good.

Starting the engine:

Engine cold--1500 rpm as it warms up--2.6 volts at pin 2B from Boost Sensor

Engine getting warm--1000 rpm--2.8 volts at pin 2B.

Engine fully warmed up--800 rpm -- 3.0 volts nominal at pin 2B of the ECU.

HAVING SAID ALL THE ABOVE, here are the results of the first attempt to pass emissions: (Arizona, 85 degrees F, car fully warmed up, etc.)

Fuel cap and equipment: PASS.

Hydrocarbons: FAIL: 2.93 of 1.60 allowable (most likely the 2-stroke oil (1oz per gallon) in the tank before I could make sure the OMP was working, but I think this is obvious. (About 1/2 tank left of the premix...running it out today and adding 87 octane Chevron to fill up)).

Carbon Monoxide: FAIL: 16.05 of 15.00 allowable (possibly related to above).

Oxides of Nitrogen: PASS: 1.65 of 2.5 allowable (Cat. is probably good).

I have not set the idle speed down to 750 and have not adjusted the air/fuel mixture with the variable resistor, but I thinking the above results don't have much to do with this since the majority of the emissions test was accelerating and decelerating through the gears up to 60mph on the dyno.

Jeff

STILL wondering if the boost sensor is bad, or off, or whatever?? If it is the cause of the rich condition, then where can I get a replacement or is there a fix?? Anyone with this same experience??

TIA

HAILERS

I guess the sensor is bad then.

I don't think the sensor nor the oil in the gas is the problem with whether or not you pass emissions. Either a 02 sensor isn't cutting it or the ACV isn't cutting it or if those two items are good, then the catalytic converter isn't cutting it.

If memory serves the boost/pressure sensors effect on fuel delivery isn't worth talking about. That's from memory and I might be wrong. Do a search using HENRIK and BOOST SENSOR for a idea on how that sensor effects fuel delivery.

Is this a two speed emissions test? LIke one test at 15mph and the other at 25mph?