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Old 03-04-2015, 07:18 PM   #21
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Quote:
Originally Posted by stratosteve View Post
Electronics can do random things when failing due to heat. I threw parts at the saturn and nothing worked. I would have never thought to look at the cps, due to the symptoms. I figured it was a work/no work sensor. I got lucky with a phone call to a local saturn dealer, who pointed me in the right direction. He was just the parts guy but went above and beyond.
Steve, I'm not discarding your suggestion. I'm trying to find out how I can check it out. I live overseas and it's not that easy for me to get a part like that one. I've been googling it to see what I find.

Thanks for the help.
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Old 03-04-2015, 07:22 PM   #22
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I am not familiar with where the cas is located on an NA. Is it possible to add some heat resistant tape/foil/something to reduce the heat?
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Old 03-04-2015, 08:26 PM   #23
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from m.net:


"STO962
Third gear

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Quote:
Originally Posted by Jim (Pop VII) C
Do not see a real practical test for the CAS. It is an optical sensor and has a rotating disc and light inside. If the voltages are correct does not mean it works.

The only practical way I see is to swap it out with another 1.6 unit.
If the voltages are correct, it has to work. The ECU is looking for a square wave signal from the two sensors and as long as it is seing that, it should work. Ideally, an oscilloscope is the best way to test it but a voltmeter will do in most cases.

I think I know what you mean though, as these can fail intermittently. The sensors can suffer from heat/temp induced failures. I have also seen the optical sensors have problems due to oil contamination from internal seal leakage. The oil will block the optical sensors. In this case it may check good while you're testing it but it will still have problems in operation. However, if the test is done correctly and it fails, you can pretty much bet on it being a bad part.

Thanks hsue for clarifying the wire colors for each signal. You're also right about the optical and the magnetic (Hall Effect) sensor being electrically identical as far as testing. They both switch the 5 Volt signal on and off, they just go about it in different ways. The same test works for all NA models.

Back probing the connector is the tricky part for getting an accurate test. I have much better results using test leads with a "bed-of-nails" type alligator clip."



I'll try this tomorrow.
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Old 03-04-2015, 08:43 PM   #24
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Everyone keeps saying coils. Did I miss when you checked spark when it was disabled on the side of the road? My guess is your CAS and coils are working fine, you need a new temp sensor in the back of the head, or the wiring to it has failed.

This happened to an old truck I had, and when they fail they often read -40 degrees, and the ECU gives it an inappropriate amount of fuel.
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Old 03-04-2015, 09:46 PM   #25
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Everyone keeps saying coils. Did I miss when you checked spark when it was disabled on the side of the road? My guess is your CAS and coils are working fine, you need a new temp sensor in the back of the head, or the wiring to it has failed.

This happened to an old truck I had, and when they fail they often read -40 degrees, and the ECU gives it an inappropriate amount of fuel.
Thanks curly.

Us old guys have to help one another

I'll check it tomorrow and if it's not working properly, I'll get a new temp sensor tomorrow.
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Old 03-04-2015, 09:52 PM   #26
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Just bring some plugs with you for a drive. As soon as it stops, plug them into the wires and crank to check for spark. If they fire I bet it's fueling related, because of a temp sensor. Or if you have a wideband, I bet it's going full lean.
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Old 03-04-2015, 11:04 PM   #27
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I'm still guessing the coils or a sensor are failing when they get enough heat in them.

Coils and magnetic sensors have many windings of small diameter wire in them and when they heat up, they expand slightly. If there is a break in a wire in the windings it may work well when cold but upon expansion due to heat it may grow enough to pull the broken wires apart causing failure.

Similar things can occur with printed circuit boards on rare occasion.

I hope this is at least useful information to you, my friend.
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Old 03-05-2015, 11:17 AM   #28
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So, we decided the issue was fuel related and decided to concentrate exclusively on that.

We think (emphasis on "think") that we may have found the culprit in the TPS. We tested the car with a borrowed one and it worked flawlessly. I'm lucky that some time ago I bought another throttle body from an mt.net member and we're about to test the car with that one.

I'll post the final results.

Many thanks to all who assisted.

Rafa
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Old 03-07-2015, 11:13 AM   #29
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Back again.

I'm driving the car back from the shop. No cooling issues whatsoever.

The only issue left has to do with fueling. My mechanic could only avoid the problems with the car stalling by combining the new TPS with a 255 Walbro fuel pump. At low RPMs the car will basically use fuel like a V10 engine and the engine is overwhelmed by so much fuel. It sputters quite frequently and the car bucks; from 3,500 RPM on when the car is working at the correct temperature, the engine is perfect.

I'm seriously considering purchasing an MS3 from Reverant and working out those kinks that way.

Do I have any other options to try with the OEM ECU in the meantime?

Thanks,

Rafa
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Old 03-07-2015, 12:09 PM   #30
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So what your mechanic has done is overwhelm the stock fuel pressure regulator and the injectors, to increase the FPR's psi, and the injector's flow rate.

I'd suggest putting in a 190, since the 255 overwhelms even a proper working fuel system. Then send some 99 injectors out to RC engineering, as they only flow a little bit more than stock so the OEM computer will handle them, and will be a great upgrade for when you install a MegaSquirt. Then check the resistance values of your coolant sensor and replace if needed, and test fuel pressures of the FPR. If all of these are old, they're fairly cheap, so you could also just ditch the tests and replace them.

I've had one NA that stumped me completely, it would refuse to start well when cold. Never tried a new temp sensor, I ended up putting a small worm clamp on the return line. This increase fuel pressure and gave it enough fuel to start properly.
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Old 03-07-2015, 12:38 PM   #31
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Quote:
Originally Posted by curly View Post
So what your mechanic has done is overwhelm the stock fuel pressure regulator and the injectors, to increase the FPR's psi, and the injector's flow rate.

I'd suggest putting in a 190, since the 255 overwhelms even a proper working fuel system. Then send some 99 injectors out to RC engineering, as they only flow a little bit more than stock so the OEM computer will handle them, and will be a great upgrade for when you install a MegaSquirt. Then check the resistance values of your coolant sensor and replace if needed, and test fuel pressures of the FPR. If all of these are old, they're fairly cheap, so you could also just ditch the tests and replace them.

I've had one NA that stumped me completely, it would refuse to start well when cold. Never tried a new temp sensor, I ended up putting a small worm clamp on the return line. This increase fuel pressure and gave it enough fuel to start properly.
Thanks curly. These options sound like a solid plan. I'll try the worm clamp on the return line first while I wait for the 190 fuel pump to get here.

Local mechanics are generally good for regular engine maintenance routines but not for much else. He even told me my Miata didn't have a FPR.

Last edited by Rafa; 03-07-2015 at 12:38 PM. Reason: use of proper grammar
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Old 03-07-2015, 12:39 PM   #32
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Yeah, get your Miata out of there.

Don't do the worm clamp with the 255, it'll just make things worse at idle by increasing the fuel pressure. It's a trick for a stock pump.
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Old 03-07-2015, 12:45 PM   #33
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Hey Rafa! I hope you are doing well, long time no talk!

I read your post, as mentioned next time it dies, pull over and hook a spark plug and wire up and see if you are getting spark. also, look at the tach too. If you spin the motor over, it should spin around 300 RPM on the starter motor, and your tachometer will show this.

IF the CAS if failing, when it dies on you, the tach will not show any RPM as it won't know the engine is spinning over, and of course no spark since it doesn't know the engine is turning.

If it's a coil, tachometer will show RPM on the starter, but no spark. If it ran on 2 cylinders when this happened, it could be a coil as the car will run on 2 cylinders if one coil fails.

Thus if it's ignition related, I'd say 95% chance it's the CAS, and yes they can fail only when hot, but work fine when cold.

Regarding fuel pressure, you could hook up a fuel pressure gauge in the car, they are not expensive. Then you could check the pressure at any time and KNOW what it is and if it's not right.
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Old 03-07-2015, 02:42 PM   #34
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Quote:
Originally Posted by curly View Post
Yeah, get your Miata out of there.

Don't do the worm clamp with the 255, it'll just make things worse at idle by increasing the fuel pressure. It's a trick for a stock pump.
I'll try to buy the OEM fuel pump locally then and try it. It's harder to source the 190 Walbro and the 99 injectors locally than the stock fuel pump.

One last question: would you suggest the worm clamp in the return line with it?

Thanks
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Old 03-07-2015, 02:44 PM   #35
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Hey Pat; long time no speak. I see your car is up in jackstands too. Sorry to see that.

I'm pissed with mine. hehehe.
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Old 03-07-2015, 08:08 PM   #36
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Quote:
Originally Posted by Rafa View Post
Hey Pat; long time no speak. I see your car is up in jackstands too. Sorry to see that.

I'm pissed with mine. hehehe.
Yeah mine is for sure! I'm hoping to have it running by May 1st. I'm making good progress but everyday there's a few little things I can never predict that pop up that take up time and I don't get everything done that I wanted to.

If you need anything from US I'll send it to you as a gift, just let me know.
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Old 03-07-2015, 11:06 PM   #37
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Yeah mine is for sure! I'm hoping to have it running by May 1st. I'm making good progress but everyday there's a few little things I can never predict that pop up that take up time and I don't get everything done that I wanted to.

If you need anything from US I'll send it to you as a gift, just let me know.
Thank you Pat.
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Old 04-02-2015, 04:40 PM   #38
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So, I decided to keep on using this thread to get assistance for my engine's ongoing issues.

The cooling is finally fixed and working properly so now I want to address my fueling issues.

Following a suggestion made by shooter in another thread, I ordered a DW100 fuel pump (equivalent to 165 psi) and finally got it last week. I took out the Walbro 255 that was in my car and replaced it with the DW one. The fueling is better but it still not working properly.

I decided to buy an MS2 that was up for sale on m.net. I will receive it by the end of April. In the meantime, I wanted to know 2 things:

1) besides an IAT sensor and a wideband o2 sensor, what else do I need to install the MS2?

2) is there anything else I can do in the meantime with the OEM ECU to improve my car's fueling issues?

The IAC valve won't compensate when I use the AC and the engine bogs down and backfires once in a while. It seems like this happens when I try to floor the car. These symptoms improve when the engine is working at the correct operating temp but they don't go away all together.

Thanks,

Rafa
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Old 04-02-2015, 07:19 PM   #39
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That's weird. I wonder if the mechanic did something funky to it?
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Old 04-02-2015, 08:12 PM   #40
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I'd address these issues before installing the MS. There's something wrong with the engine and it's probably not the ECU. Adding th MS will just add new problems and lack a tuned map.

There have been some good diagnostic tests suggested that'd I'd follow through on before putting hose clamps and ecus in the car hoping one makes the problem go away.
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