GA16i & ECM questions

[JoeKansas]

1989 Sentra. ECM under the passenger seat- has the 2 led's with the small adjusting screw right next to it for retrieving codes. I have 5 trouble codes on it now- don't have them with me or I'd post them. May have been 12, 23 or 24, 45, and ? Basically ECM, injector, throttle position, and something else- sorry about the lack of info. I am not where the car is setting. The check engine lite isn't on- if it has one at all. I've read everything I can on ecm's/GA16i's on this site and others; have one of the small Chilton's manuals which is some help. As a matter of fact, this site is a fountain of information. It helps me understand things about these engines I could have never found out otherwise. I've got the nissan trouble codes for this engine off that website. What I can't figure out is: 1)- how to change from the default mode 1 on the ecm to any of the other 4 it says it is capable of going to. Not that I need to do that, but I can't seem to get away from just showing the 5 codes......... 2)- how do you erase the codes. I'll erase them and go drive the car and see which ones return to show me current problems, not some I may have fixed! Well, anyway, the engine has started to run rough at times in the last few weeks. I got all the air cleaner off today. I checked and replaced a few vacuum lines underneath it on the engine. One, which I would say was going to what I think is called the A.B. valve-( on the passenger side of the engine near the firewall)- from the manifold was clogged with carbon looking sludge. Cleaned the carbon out of the manifold connection and put in a new hose. Vacuum tested that valve and it moved up and down on the inside ok. The second hose went to a vacuum switch (with 2 wires connected)mounted up on the firewall. Hose looked bad so I replaced it. I am a little hesitant to mess with the injector at this time, cause I don't want to damage something I can't fix. I did put in a new fuel filter yesterday. While I had the line off, I put the fuel line into a bottle and let the fuel pump run, and it seemed to put out a lot of gas. No idea of pressure. Starting the car, the pump runs for about 5 seconds and stops, which I think is normal. I could see down into the throttle body through a little screen towards it front and to what I think is the little filmy wire which is the MAF sensor. That area all actually looked clean. I sprayed Electric motor/contacts cleaner down in there and let it dry. That stuff leaves no residue. I also removed the MAF wiring connector. Had green corrosion on the connector and in the receptacle, also. Cleaned it all out, sprayed it, and put in some dielectric grease to keep it in good shape. I don't think that stuff will hurt anything. Then, I buttoned it all up and started it. Idled smooth, even with the AC going. Took it for a test run. No problem until the engine got up to the speed where the transmission shifts from first to second. Then it acts like either it's starving for fuel or not getting spark. If you carefully hold your foot in one place on the pedal and don't change throttle position, the engine will run a bit, then you can feel it bog down, then it will pick up and run, then bog, and etc. Don't smell unburnt fuel, but I am moving when it is doing this so I am at a disadvantage there. Any suggestions- Throttle position sensor cause problems like that? Injector dirty? I appreciate any suggestion to steer me in the right direction.

[JoeKansas]

Oops, in my second paragraph of the original post, I meant MAF instead of ECM...........

[NISTECH]

Hook up a vaccum gauge and drive the car. place the gauge where you can see it while driving. See if you are loosing vaccum. This will indicate a pugged exhuast system.

[JoeKansas]

It has new exhaust from beneath the oilpan on back. I just went out and drove it 4 or 5 blocks and it starts fine, idles fine, but when you get it up to the speed where it wants to shift, it starts bogging down dying. Pump the pedal and it will perk back up for a bit, then bog down again. Put it in neutral and coast, and it will idle. Thinking out loud, it sounds like starving for fuel, but it very well could be an ignition problem. That's why I'd like to clear the trouble codes and have them reload themselves while I drive it.......... How do you take apart the injector assembly? Or do you just replace it........

[NISTECH]

Yeah dont mess with the throttle body injector. I seriously doubt thats your problem.Do you have a fuel gauge you could rig up in the same fashion as I mentioned with the vaccum gauge? You could see if your loosing fuel pressure.

Then of course there is the old distributor cap breaking down problem. I have seen alot of italy made distributor caps be junk right out of the box. Also there is the old plug problem. If you use anything other then NGK and a couple other exceptions like denso you could have a break down problem with the plug. Autolite, bosch,mighty plugs are all brands of plugs I have seen fail in extreamly short periods of time. The quality of the ignition parts on nissans is extreamly important.

[JoeKansas]

2 days ago I did put in autolite plugs ., but it didn't have NGK or 'denso's in it when I got it. I bought this car from a friend. While she had it, it quit 2 different times. Once was a broke wire in a loom going to the ignition module (don't know how that happened, but I found it and fixed it. The second time was a week later, and when I replaced the distributor- with oily insides- it started right up. I had cleaned the innards of it with electric parts cleaner, but that didn't help. I'm gonna have to rig up something to check fuel pressure, I guess. Is that injector removable as an assembly?

[NISTECH]

Did you buy a reman dist from the dealer? If so I know the caps ok. as it comes with it. If you got used check the cap and rotor.

[JoeKansas]

No, a used one from the junkyard. We haven't had a Nissan dealer here in 10 years. I haven't taken it apart since I installed it months ago. We I do have one bad plugwire- down on the plug end of the wire there is a chip in the plastic at the bottom. Once in a while it will arc in there when I wash out the engine compartment. Other than then, it never misses. I think my local junkyard only had the one sentra- that this distributor came from. If they still have it, I may go out and see what all is left in the engine compartment and try to scavenge some more parts. P.S., I really appreciate your answers to my questions in such a timely manner. I am gonna get spoiled...

[JoeKansas]

This AM the car ran so bad, barely made it uptwon to my shop. Runs good now.....I replaced about all the small diameter vac. lines on the engine. Removed the EGR valve and tested it. The book says that the plunger should stay up for 5 or so seconds after you remove the vacuum, but it didn't. It did move up and down, though, and seemed to seal shut. A valve right next to it, the "BPT" I think, removed and tested and it was ok. Just like the book said. Then the AAV OR AIV, can't remember which. removed and took it apart and put a vacuum to its vacuum pot and it seemed to function ok. Couldn't quite get to the screw at the bottom of MAF sensor, so I didn't take it out. Too many hoses and wires in the way. As a matter of fact, I didn't take any of the sensors on that side of the throttle body. There are 3 wiring harness connectors on the passenger side of the throttle body. 1 for the MAF sensor, and 1 for the throttle position sensor, and 1 other beyond it I can't figure out for what. Took all of them off and cleaned them and put dielectric grease on them to keep out corrosion. I read about a test for the distributor- crank angle sensor and crank position (I think they were). I had my other non working distributor there, so I hooked the wiring loom up to it, like the book said, and did the test. First test failed- crank angle- but the second passed- whatever the name of it was. Put everything back together, and it started right up. Idles good with the AC going, and seems to drive just like it used to. Really have no idea what I fixed. Only thing I replaced were various vacuum lines. I still had the 5 trouble codes and that may be because I can't erase them. Help me figure out how to do that, if you can

[NISTECH]

With the key on rotate the screw and watch your lights blink. It will blink 1 flash pause, 2 flashs pause, 3 flashes pause...up to 5 flashes. after the five flashes rotate the screw back to the normal position and shut the key off. This should erase all the codes.

Each time it flashes it represent a mode, there are... well 5 modes. If you were to rotate the screw back after a set of flashes it would be locked in that mode. I assume you go to 3 flashes and rotate the screw back to check codes right?

[JoeKansas]

I have read that troublecode list and it's instructions- along with other sites with the code info- many times and nowhere does it spell out the process like you just did to clear the codes- or for that matter how to switch between modes. How I thought it worked was: turn the key on, turn the screw on the ecm clockwise all the way. Then the ecm would flash like this:

1 red- 2 green2 red- 3 green3 red- 4 green4 red- 5 green5 red- 1 green

That's where I was getting my codes. Once today, I just turned on the key and watched without turning the screw. It did some flashing but I didn't copy down the numbers- but- it did some flashing. Anyway, I drove the car around some this evening and it never hesitated (like I was expecting). Seems to run good. Tomorrow I wil go out and try this different process with the codes. Nistech, I am in your debt. You're worth more money...........Joe

[NISTECH]

The way I just described how it works I have not seen put in that fasion before. But it is the easier way of how to determine what those lights mean and how they work. I have to be honest with you though it has been a long time since I pulled codes like that on a pre 90's vehicle. At the dealer I only see cars built in like the last 10 yrs, very very rarily do I see something before that anymore.

[JoeKansas]

Went to the shop with the car yesterday and got down under the seat and did it like you explained, and lo and behold, all the blinking I thought was the ecm giving me codes WAS the ecm going through the modes. I went to mode 3, and got the "no problems" code. Makes me feel good to actually get it right for a change.

[NISTECH]

cool, drive it for awhile and recheck for codes, because anytime you let the ecm cycle through all the codes, when you turn it back it erases the codes stored. so the idea is to catch it before it cycles all the way through the first time.

So you know what each mode does.mode 1 is o2 cycles. If you stop it in that mode it will flash back and forth netween red and green. monitoring when the one light means lean one light means rich.[ above and below .45 volts]. The lights should cycle back and forth equally and not hang on one light longer then the other. that would indicate a rich or lean condition.

Mode 2 kinda plays along with one. If you were able to watch both modes at the same time this one would do the opposite. When mode 1 indicates a rich condition mode 2 indicates a lean command. This is you mixture count mode. It displays what the computer is trying to do with the mixture[add or remove fuel] This comes in handy if your mode one results indicate a rich condition then mode 2 should display a lean command. This helps in diagnosing weather you have a foriegn influnce on the system or a misreading sensor.

Mode 3 is codes as you have discovered.

Mode 4 monitiers your on /off signal from the hard idle contacts. when in this mode you should see the red light come on when you very slightly push the throttle pedal.

Mode 5 is real time diagnostics. You use this mode with the car running. It will display a set of flashes if there is a problem happening right then.

[NISTECH]

All modes should be done with the car running but 3 and 4 can be done with it off. modes 1 and 2 should be done with a steady throttle of 2000 rpms. mode five should be performed both at idle and driving above 19mph.