Anakhoresis

iTrader: (1)

Well my 'weekend' didn't go as planned, but finally got the different alternator in, it's working at 14.4v. The other was plugged in properly and everything, must've just had a bad voltage regulator. I was always a bit suspicious about it after I got it rebuilt a few months ago.

After putting the new alternator in, I took the RX-7 out for a drive, and at the very least, it went 17 miles without even being overly hot on the temp gauge like before. Last time I took it out it went about 10 miles before having an issue, if I remember correctly. So it's not a certain fix.

I'm kind of confused. I'm going to try taking it out for a longer drive soon hopefully, but I'm not really sure how this could have been the root of the problem? Or do you think there's something else that just hasn't resurfaced yet?

Anakhoresis

iTrader: (1)

Figured I might as well resurrect this thread since I'm still experiencing the same problem, no point making a new one.

Went through a number of alternators, found out that the tester was incorrect in the first place, alternator was fine (Go figure, spent an annoying amount of money on 'alternator issues' before finding that out), and of course, after finding that out, a day after throwing a working alternator on, original issues resurfaced.

I did a compression test, engine is very healthy as I suspected seeing as it has about 12,000 miles on it. Both rotors above 110 PSI, all even bounces using a piston compression tester. Set the TPS first using voltage method, then fine tuned with resistance method.

My guess right now is leaky injector(s). By all appearances it's choking itself out on too much fuel. I'll start it, leave it idling, and after a while it will start to lope, sounding like it's misfiring. There's a strong smell of fuel, and sometimes it will backfire (either when pressing the accelerator, or trying to start it again). Pressing the accelerator will result in it attempting to rev higher, generally will go no higher than 3-4 thousand RPM and sounds absolutely terrible doing it. After a while of loping it will eventually kill itself. If trying to restart it seems flooded, but also very difficult to restart. I have a fuel cut off switch, and if I shut off the pump, it will start on what fuel is left in the chambers, but if I switch fuel on again, it usually dies again without actually starting and running.

Any other thoughts besides injectors? I have a set of 86 TurboII injectors that I believe are okay that I'm going to clean up and throw in to try, in theory it would use more fuel but, if they work, won't exhibit the same problem, correct? If that did work I'd send off the original injectors to a cleaning shop and put them back in when they got back.

Or could it be the fuel pump? I also have a spare TurboII fuel pump I can try, or if there's a test with a multimeter I can do that.

Anakhoresis

iTrader: (1)

Never did get to test out the fuel pump unfortunately, for which I am kicking myself now.

I'm fairly certain it has something to do with the fuel system, and at this point I've saved up a bit of money and I'm going to start replacing things. I replaced the fuel filter a little while back and it definitely ran better... For a little bit. Then back to same old. Next step I'm going to replace the fuel pump with a new Bosch pump with fuel sock. If that doesn't work I'll remove the injectors and send them off to get them flow tested and cleaned if necessary (I do suspect if it's not the fuel pump it might be an injector stuck open).

If it's not THOSE... Well, I'll cross that bridge when I get there.

Unless there's any other suggestions? I'll hold off on ordering a fuel pump until mid-day tomorrow to see if anyone has ideas.

dwb87

iTrader: (22)

You can always secure the injectors to the fuel rails, unbolt the fuel rails (Put something under the fuel injectors to catch any fuel that may spew while performing this test.), jumper the fuel check connector near the passenger side strut tower, turn the key to "ON"... Not to "START". You'll be able to hear the fuel pump running. Check to see if there is fuel spewing out of your injectors. If so, your injectors are stuck OPEN. (There is a great example of this in the FSM. Fuel and Emission Control Systems E.G.I. > Section 4A - Page 70.) -> 1988 FSM: N/A Fuel and Emission Control Systems

Anakhoresis

iTrader: (1)

I tried to do that but my fuel lines were too short to move the fuel rail with the injectors on them... I may have been doing it wrong, and may be worth another shot after today.

So now have a brand new fuel pump and fuel filter and still the same problem. Does injectors sound like it could even be the problem? It seems to encounter the issue pretty much once it's fully warmed up.

satch

iTrader: (1)

Check the voltage of ECU pin 2I, Green/White wire, which is the Water Thermosensor. It should be 2 to 3 volts cold and .4 volts fully warmed. Sensor helps to decide how much fuel is required relative to the engine temp. More for a cold engine, less for a hot one.

Anakhoresis

iTrader: (1)

Finally got out there to check it. We may have a culprit?

At key to on, it was 2.8V, which is above FSM specs. Then started, it was 2.8V, which was okay, then it jumped to 4.95V for a second, went back to 2.8, started lowering as it got warmer, occasionally spiking to 4.95V, finally went back down to 1.2V as it was about halfway warm, spiked to 4.95V again, went slowly down to 4.8V and then sputtered and died.

satch

iTrader: (1)

Cold engine will be between 2 to 3 volts. Secondly, if it jumps to 5 volts then it's likely that either of the two wires in the plug are pulled back and not making good contact w/the sensor.

Anakhoresis

iTrader: (1)

Kind of confused. Is this the water thermosensor? (not my engine, found this picture on the forum)



If so it's only got one black and green wire coming from it. I can't trace where it goes, as the engine is hot at the moment and it disappears into a bundle of other wires.

satch

iTrader: (1)

Nope, but it's close. It's located on the backside of the water pump almost underneath the alternator. It has a plug which looks like an injector/BAC plug (this is the dead giveaway). G/W and a Black ground wire.

Anakhoresis

iTrader: (1)

Ah, found it. It was actually very slightly unclipped. I pushed it firmly back in, but the voltage still ended up going back to 4.6-4.8 and dying. The wiring to the sensor is in a rubber cover though. Unfortunately it's dark and raining outside so can't do any more tonight. I guess next step would be to remove the plug and clean off the contacts?

satch

iTrader: (1)

There are two contacts inside and make sure that both are not recessed/pulled back as this is likey the cause, and occurs fairly often it seems. And the plug could be as snug as possible, but that doesn't mean that one of the wires is not pulled back in the plug.

Anakhoresis

iTrader: (1)

I popped out the sensor today, and the contacts inside were fine. No play, not recessed. A tiny bit grungy, so I cleaned them off, put it back on, clipped on the plug, and while it seemed a little better, as it got down to .67V while warming up (though flashing to 4.95 twice again), at .67V it went up to 4.95 for a third time and chugged and died again.

satch

iTrader: (1)

If the plug connection is good and the sensor was good, which you can test using the method in the FSM, then the possible cause would be the G/W wire is damaged as it meanders its way back to the ECU or the ground wire is faulty. And when you say the contacts inside were fine are you referring to the plug or the sensor?

You can take a ohm/resistance reading on the G/W and see what that reads and this is done w/no key. You can also turn the key to on and measure the voltage on the ground and w/respect to the ground you can also place one meter lead on the ground wire and the other meter lead to a good ground and w/the meter set to ohms see what you get as it should be a rather low reading and this is also done w/no key. You can also jiggle the wires that this harness runs to when taking these measurements to see if you get a range that would indicate that it is okay at one moment but not another.

Anakhoresis

iTrader: (1)

I can't test the sensor yet, I'll see if I can pick up a thermometer tomorrow (Sadly don't have one lying around), but I did get the resistance/voltage readings.

I had the setting on the multimeter at 200 ohms, wasn't quite sure if that was correct, but it provides reference.

G/W resistance: 1.2
Ground resistance: 1.2
Ground voltage: .02

Also just to make sure, to get the ground voltage I put one end on the ground tab then the other on a good ground with the multimeter set to volts, correct?

Wiggling around the wires made it vary between 1.1 and 1.2 occasionally.

satch

iTrader: (1)

In the meantime you can try starting the car and as it warms up and gets close to .5 volts on the G/W wire before it konks out disconnect the plug to the Thermosensor and the ECU should default to a warm engine temp and this should allow the car to run properly w/o any interference from the ECU. The sensor in a normal situation sends a resistance reading to the ECU which reduces the voltage on the wire and the ECU then uses this reading to help identify how much fuel is needed based on the engine temp. Now the ECU uses a voltage signal sent to a group of sensors such as the TPS and AFM for example and it's referred to as the voltage reference or Vref which should be 5 volts. You might want to measure pin 2A (should be a Brown based wire) w/key to on and while running and see if it reads 5 volts.

Anakhoresis

iTrader: (1)

Alright, so I started the car, couldn't actually tell when it got to .5 because it leaped to 4.95 in about a minute and then slowly went down to 4.76 and died. It fortunately started right back up with no chugging (pretty rare for it to do that), unplugged the the sensor, and it's been running a good 20 minutes now and is still running, at full warm temperature.

The brown wire read 4.95 the entire time.

satch

iTrader: (1)

As long as the engine is close to warm the car won't really need the sensor, but it might run a little rough after starting a cold engine and the car could easily have a difficult time starting if the engine is cold to begin with w/o the sensor. You'll want to still test the sensor itself, but could you explain the method used to test the resistance on the G/W wire?

Anakhoresis

iTrader: (1)

I backprobed the G/W wire on the ECU, then ran the other end to the plug under the hood. Since it was covered I couldn't actually tell which was ground and which was the G/W wire, but I guessed that since only one gave me a reading when plugged to the ECU, and one gave a reading when grounded, that signified which was which.

Not exactly an expert electrician so hopefully doing this correct. I'd definitely welcome advice on how to do better.

satch

iTrader: (1)

The plug to the ECU, housing the G/W wire, needs to be disconnected before measuring the resistance on the G/W wire that is backprobed.

Anakhoresis

iTrader: (1)

Okay, I went out and did it again with the ECU plug disconnected but it still registered as 1.2.

satch

iTrader: (1)

And if you want to make sure you are measuring the correct wire on both ends then you can do a continuity test and if it rings out you then know you have identified both ends to a segment of wiring.

Anakhoresis

iTrader: (1)

I'm kind of confused. Is a resistance test the same as a continuity test? It rather looks like that from what I've been reading.

Going to try and get my hands on a thermometer to test the thermosensor tomorrow. I'm also kind of confused on that as well though. When this first happened and a few times after that as well it was on a fully warm motor. The first time it happened I had been driving g for 40 minutes. If it should sword to different sensors when warm is there something that could make it swap back to the thermosensor which seems like it's having issues?

satch

iTrader: (1)

Not sure what this means. And the ohms test is a bit different and uses a different setting on the meter. Ohms would normally have the Omega symbol which looks like an upside down n w/feet and the continuity symbol is usually a sound wave looking image (V shaped like a tornado).

EDIT: If you place both meter leads together while set to continuity, the meter will emit a solid beep. And when using the ohm setting it is normal to first touch the meter leads together to reset the meter to 0 ohms.

Anakhoresis

iTrader: (1)

Wow, autocorrect messed that sentence up and I didn't notice. What I meant to ask was "If the car switches to a different set of sensors when warm, what could make it swap back to using the thermosensor which seems to be having issues and thus causing the issue?"

Also my multimeter doesn't appear to have that feature. It's a pretty simple one, AC, DC, and Resistance.