1st Generation Specific (1979-1985) 1979-1985 Discussion including performance modifications and technical support sections

GSL-SE ECU voltages

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Old Sep 8, 2004 | 01:12 PM
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GSL-SE ECU voltages

Still running way too rich. I'm pretty sure it's not the injectors because it starts right up every time (no flooding). Idle speed is good and steady. Compression is good, power is good, throttle response is not bad. Plugs are about 2 months old (br9eq-14), wires are a year old, cap & rotor are about 8 months old. I think it's gotta be either a sensor or a valve (or a combination of these), or a timing issue. The Haynes manual shows the ECU terminals and the correct voltages for each one. Would this be the best way to find a faulty component?

Is it possible that my ECU could be faulty altogether? For some reason I think that with a faulty ECU, the car probably wouldn't even start at all... has anyone had any related experiences?

The R-L variable rheostat has definitely been tampered with, but I have no idea where it should be at. I tried following both the FSM and the Haynes' instructions on this but they don't make much sense to me. If I go clockwise (rich) the rpms will slowly decrease, while counterclockwise (lean) will make the rpms go up (also very slowly)... this is pretty much the opposite of the manuals' prediction.

Going on 5 months driving w/o registration because of emissions test... I'm really pushing my luck here.

Thanks
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Old Sep 8, 2004 | 01:21 PM
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do a google for "solving GSL-SE idle problems" you will come across a walkthrough for setting the rheostat.

How rich are you, what are the numbers from the e-test? What have you tried?

Everything from "plumb your air pump into your cat" to "trick the engine into thinking it's hotter than it is" to "run methanol" will help, it all depends how far out you are.
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Old Sep 8, 2004 | 01:23 PM
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http://www.nellump.net/peri/epi/firs...gslseIdle.html

there, saved you the trouble.
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Old Sep 8, 2004 | 01:24 PM
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Should be left till motor starts starving for fuel then back right just a hair. Yea I know how much is a hair? Till the motor sounds right, but just easing it over. Mine sits about 10:30 - 11:00 position if that helps. You want it to be more to the lean side.
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Old Sep 8, 2004 | 01:25 PM
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So when you tested the ECU, there were no codes, correct? What symptoms are you getting indicating rich mixture (black smoke, increased fuel comsumption, black plugs, etc.)? Is it rich all the time or only at idle? Have you replaced O2 sensor (this won't effect idle or near WOT, but will effect cruising)? The R-L pot will only impact mixture near idle.

I would say that if you have access to a DMM, I would definitely test the ECU voltages to eliminate that possibility. It doesn't take much time (probably less than a half hour). I remember reading about another SE owner that was having all sorts of problems getting there SE to run right. It turned out that the ECU got water in it and messed it up. He found this out by testing the injector voltages (also on the ECU) one was at 12v (like it should) and the other was at like 7v. He replaced the ECU, and there were no more problems.


Kent
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Old Sep 8, 2004 | 01:27 PM
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I've had that document for months now, and I'm very familiar with it. I don't have an idle problem, but rather a stoichiometry one. My HCs are 2300 ppm (limit 220), and CO about 6.5 (limit 1.5 or so). Obviously the engine is getting more fuel than it needs. My gas mileage has gone significantly down over the past year.
Plumbing the air pump, tricking the engine, and such other ideas might help me pass the test, but I want to find the problem as well.
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Old Sep 8, 2004 | 01:32 PM
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From: LOS ANGELES
Did you change your airfilter?

I tried running another airfilter with a hose running to the front of the car. The hose was too small and my car was being restricted making it run rich.
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Old Sep 8, 2004 | 01:35 PM
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Kent,

I haven't tested the ECU yet, but based on your generous reply, I think I just might try that first. I do have a DMM, and it does seem like a very straight forward procedure. My e-test is only at idle, but I think I'm rich all the time based on my poor gas mileage. The 02 sensor is brand new and the cat (Bonez high flow) is not too old. I don't get any black smoke (only the normal blue puff on start-up), but I do smell fuel coming out the exhaust, and the plugs do seem to get black rather quickly.

It is highly possible that I too could have had water reach my ECU, since I used to have a hole in the botom of my passenger floor, and the metal plate covering the ECU was very rusted through (I recently 'fixed' the hole and replaced the metal plate). I'm cusrious, though, when your friend noticed the unusual injector voltages, what made him think that it was actually the ECU, and not the injector?

Air filter's a K&N, and It looks pretty good. I think a small air obstruction wouldn't throw my HC 10 times over the limit, though, and I would probably notice it in the idle quality.

By the way, thanks for the fast responses so far!

Last edited by riofrio; Sep 8, 2004 at 01:37 PM.
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Old Sep 8, 2004 | 01:57 PM
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Well, it wasn't a friend that had the problem, but someone that I read about on the internet. Usually if an injector fails it will either stick partially to fully open or could just be leaking. It is possible that you have a leaking injector, but usually that will cause flooding after the car has sat a while (the injector leaks into the engine while the car is off until the fuel system pressure drops).

Fuel injectors work by applying a constant 12v to one connection and the other side goes to the ECU. This is should also be 12v when the car is not running. The ECU fires the injectors by pulling its side from 12v to ground. This put 12v across the injector causing it to open. Fuel injectors are essentially solenoid that switch the fuel either on or off. The amount of fuel injected per squirt is controlled by how long the injector is held open, not by opening the injector partially (like a valve). Injectors are either on or off type devices. Because the person had 7v when the car was not running, the injector was partially opening with the 5v or so differential across the injector, so it was injecting some fuel during times that it shouldn't.

By testing the ECU, you can at least eliminate it as a problem. If it checks out, I think that I would check the AFM next. It is also a pretty simply proceedure (testing resistance across various pin with the door open or shut). Is your AFM flapper closing correctly? If it is sticking, you will get a rich mixture at low throttle/ idle.

I would also test the ACV if the car is not passing emmisions. You are welcome to PM me if you have further questions or you need some clarification.

Kent
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Old Sep 8, 2004 | 02:09 PM
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Thanks man, now I feel like I'm on the right track. If I have time this weekend, I'll try all that. I'll test ECU voltages, AFM signals, and the ACV as per the Haynes Manual. Hopefully I'll be able to get to all that within a day. I'll let you know how it goes.
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