slenderman reporting in...with a @#$% problem

[slenderman]

Hi people...it's been a while...

Back in Feb '13, I was in the process of decommissioning my green '99 GX coupe and putting a '99 black GL coupe on the road...

Well... I got the black one on the road...ran OK for a couple months...then I would get instances where I would be cruising normally, and then it would misfire, stutter and die on me. I would the pull off, crank it, it would start and I would go on. Code: P0200 (injector circuit)

As of now, it will start, run OK for a few minutes, then gradually start stuttering and die. Same P0200 code, along with a generic misfire code.

Earlier, I had replaced an injector or two; and the fuel filter. I had also hit it with some Seafoam.

Any ideas? I'm thinking ECM since the P0200 code is so nonspecific. Kinda seems temp related to me.

[03glgold]

If you keep it held above 1200 rpm does it make any difference

[a.graham52]

use that and ur missfire code to find out what injector/circuit is acting up. maybe a bad connection, corroded wire, breaking wire etc.

[slenderman]

Many thanks a.graham52 for the factory data...looks like I may be on the right track for a change.

03glgold - Regarding the 1200 RPM: yes, it seems to steady out with more RPM; but I'm not sure if that's just more crank rotational inertia helping it along, or the FI's being open longer due to higher demand (lower initial current draw maybe?)

Just to add for historical data: ohm'ed out the FI's, all look OK.

Any idea where the FI ground is located? This car seems to have an above average amount of corrosion.

I will report back any further findings; I will recheck the misfire code and start ringing out the FI harness wiring.

[slenderman]

<deleted, edited above>

[a.graham52]

According to the schematic all the injectors are individually grounded in the ECM. All share 12v from the fuse block and the ECM open and closes the ground to turn them in and off.

[slenderman]

ok, I'm back...thanks for humoring me, it's been nuts lately.
Revisited DTC's, just P0200 as before and a P0300 random misfire.

IGN to ON, no voltage at injectors. Fuel pump spools up and shuts down as expected.
Checked fuse 48 (F/P INJ), was OK.

There is a big lug terminal to the side of the underhood fuse block, should this be getting battery voltage? I checked this, and am getting .5 - 1.5 volts. (it's kinda cruddy)

[slenderman]

Cleaned off terminal and bolt, reinstalled. No change.
Swapped fuel pump relay, no change.

[a.graham52]

Are you testing for power with the key on?

[slenderman]

Yes sir.
I'm thinking of backprobing at the ECM (or the ECU, or what ever they call it these days) to look for FI voltage output.

[a.graham52]

So I'm assuming the car is not running at this point . Have you checked all the under hood fuses to make sure NONE are blown ? Especially the injector fuse

[slenderman]

Replaced one non-related fuze, cooling fan 2 (30A).
Backprobed ECM, 12V is there.
Rechecked injector connector gray wires, the 12v is there (only for a second when IGN is on...duh).
Reassembled everything and started it, stumbled some, then smoothed out into a condition where it runs good with throttle, and surges about 200 RPM when off the gas. One code set: P0200 (random misfire).
Test drove it. Continued the above behavior for about 3 min, then stumbled a lot, kept it running with some throttle. Died on me a few times, restarted and limped it back home with a lot of stumbling, and smelling unburned gas. 3 codes set: P0200, P0300 (as before) and a P0507 (idle air control RPM too high).
I'm now leaning towards the ignition system.

[rocketfast321]

Peeing into the wind here, but have to checked the EGR? Take it off to makes sure the ports are not blocked.

[a.graham52]

it can only be one of 3 things really, bad wires (damaged like mouse chewed etc), bad injector, bad ecm.

with the help of a friend, you may try unplugging one injector at a time. when you find the injector thats not working, engine chracteristecs wont change. for exampe... if you unplug a good working injector the engine will want to stall even more.. or atleast more then the "bad" injector. your friend will have to help keep the car running.

only do this to each injector one at a time. only for a short period because your dumping a lot of unburned fuel in the exhaust. when you find the bad injector, put a test light across the two injector wires and see if it pulsates. then compare with a good injector's harness. if everything elctricaly seems the same then maybe u ahve a bad injector.

like my ASEP teacher always said: "thats the way it is... until it isnt, then it wont be".

[slenderman]

Thanks for the input you guys.

Well...after getting frustrated with the issue, I decided to park it and think it over...for about a year. (I would start it infrequently, just to see what it was doing, and hopefully get more codes.) I did get one additional code, one for the idle speed control (it was 400 rpm high at idle).

A few months back, I gave up and towed it to my mechanic.

And guess what? it was... another injector. (I'm thinking the old gas wasn't helping either.)

Two months later: still doing OK. The idle speed thing seems to have cleared up.
Now on to replacing the mold-ridden smelly carpet (from the previous owner).

Thanks again everybody.

[sleepyalero]

Interesting. Thanks for reporting back, when i have had low idle issues (about 400 rpm) the car with headers and full exhaust didnt even sound like it was running! It was shty IAC sensors.