1987 Pathfinder - flooding?

maier65 · Mar 1st, 2004, 11:51 AM

Hello,

I have a 87 Pathfinder that won't start. It has spark and is getting fuel, too much fuel I think. When the ignition switch is in the "on" position the fuel injectors start clicking on and off. The "on-off" click happens about once per second and doesn't stop as long as the ignition key is "on". Fuel is definitely coming out of the injectors since i can stuff a paper towel down in throttle body and absorb some.

I've checked the fuel pressure and it is okay(~35psi), the fuel relay is also okay.

I took the air mass module out and measured the resistance across the two small coils/sensors and they both read less than 100 ohms. I don't know what they are supposed to be, but i'm assuming if they aren't shorted or open then they are ok.

The emission reducing system on this thing is definitely not working correctly since a couple of the components are out of the loop completely and just plugged to keep the vacuum. So i'm sure that doesn't help, but it's been that way since i've had the beast(bought in 1999) and it hasn't been a problem.

When I look at the computer in the diagnostic mode, the red LED just blinks at the same rate as the injectors. I'm guessing the computer is confused or bad.

It's getting close to fishing season and i need this thing to pull my boat (that also needs some work!), anybody out there have a suggestion?

89PathSE · Mar 2nd, 2004, 01:00 PM

My '89 did this crap one time.... try starting it again and give it different throttles with the gas pedle while you try to start it.... see if you cant coax it to kinda kick and sputter to run (it'll prolly run like crap and, and prolly have to keep messing with the throttle to keep it running). Why I am telling you this: Its most likely the mass-air sensor.... see, when the sensor dies, the computer goes into limp mode and just starts dumping a fixed amount of fuel in (why its dumping fuel even when the engine isnt running), regardless of anything.... its designed that you might hopefully be able to figure out how to keep it running enough to limp home (where the finessing the gas pedle comes in). You see... by adjusting the throttle, you can kinda "match" the air your letting in to the fixed amount of fuel being dumped. I know its weird, but just try it and see if you cant get it to react. The only other sensor it will do this for is the crank angle sensor... same thing, wont, or barely wont run, and dumps fuel constantly. Also afterwords, try unpluging the - battery terminal to reset the ECU. Let us know what happens.... I got other ideas at that point in time.

maier65 · Mar 2nd, 2004, 04:04 PM

thanks, I'll try that after work today. Do you know how to check the mass air flow sensor?

89PathSE · Mar 2nd, 2004, 09:35 PM

There's not a specified check routine... but the ECU will pick it up hands down if its malfunctioning... its the single most important sensor asside from the crank angle sensor in the whole engine.

maier65 · Mar 3rd, 2004, 09:14 AM

I tried messing with the accelerator to start it, but it only farted and then wouldn't do anything, almost as if the spark was gone. I guess i just flooded it bad.

I also checked the crank angle sensor (following the directions in my Haynes manual) and it is okay. So, do you think the mass flow sensor is dead?

89PathSE · Mar 3rd, 2004, 12:29 PM

Its possible at this point that its a faulty MAF... the trouble is that it is such an expensive part you gotta be sure that is what is going on. Are you sure your doing the ECU diagnostic correctly?...

-put key in and turn to the ON position

-flip little switch on the ECU under the passenger seat towards the rear of the truck....

-watch red and green LEDs... both flash once (mode 1), pause, two flashes (mode 2), pause, 3 flashes (mode 3, the one you want), pause, 4 (mode 4), pause, then five (mode 5), pause and repeats again at 1....

-at the moment it does the 3 flashes... flip the switch back towards the front of the truck...

-has a short pause... then starts flashing codes.... if it flashes 5 red and 5 green, then its reported as ok.... if not, it will flash codes one at a time with pauses in between, and repeat when it has shown the "list" of stored codes.

Anyhow, I just wanted to make sure it was being done correctly. If so... what exactly does it say... it should not just constantly flash red... if you do the above steps, and it still flashes only red... there is a problem. Most likely it will be a dead ECU (water damage, blown capacitor, or electrical damge (ie. trying to weld on your truck with the ECU still plugged in)) The other thought is that it has an electrical problem somewhere in the wiring harness that is causing the anomalie. Typicaly, the flashing red lights only run when you have an error code on the computer or a major malfunction and it is NOT in a diagnostic mode... ie, that is the "check engine light", not the diagnostic mode.... so thats why I wanted to make sure you were doing it correctly.

maier65 · Mar 3rd, 2004, 01:59 PM

thanks for the instructions. I'll try it again, but the last time I checked for the codes I think i was doing it right.

maier65 · Mar 3rd, 2004, 06:21 PM

Well, I tried reading the codes again and with the key in the "on" position and the ECU diagonstic switch off, both green and red LED's blink at the same rate as the fuel injectors. When I flip the diagnostic switch on, the green LED goes out and the red LED blinks at the same rate as the injectors. I took the ECU out and looked for corrosion or burned out components on the circuit board, but found none of either. I blew it off with some compressed air, put back in the truck and it still clicks away and won't start.

I also disconnected the MAF and tried starting the truck, but to no avail.

I'm all ears for your next suggestion. I really appreciate your help thus far. Have a good one.

89PathSE · Mar 3rd, 2004, 11:31 PM

OK... its not a switch really... its a mode selector. You cannot just leave it in one position. The position that it starts flashing the red and green lights at you.... those are the modes. Watch it closely for pauses between "sets" of flashes. You have to flip the switch BACK when its on mode three. Like I said, it will flash them both once, pause, flash them both twice, pause, flash 3 times, pause.... and on to 4, 5, and repeate it again. On the one where it flashes them both 3 times together, you quickly flip the switch back.... THEN it will display the codes. You gotta pay close attention to it. BTW.... the injectors fire so quicly it cannot be flashing with the injector pulses.... it'd be one blur of a light. Sorry man, I just really think you arent quite gettin the procedure correctly, no offense. If your sure you are doing it right, then I would say its time to get or borrow somebody's ECU and see if you can get your truck runing.

maier65 · Mar 4th, 2004, 11:48 AM

Like I said previously, the green LED is off, and only the red is flashing. There are no pauses when the LED is flashing. And if i watch the LED and listen to the clicking coming from the engine compartment the noise and flashing seem to be synchronized.

I can stick my ear in the throttle body and hear the injectors clicking, (remember the engine isn't running), the frequency isn't really that high, about two pulses per second.

Guess I'll try and get new/used ECU.

Thanks again,

maier65 · Mar 9th, 2004, 01:39 PM

Hey,

I just bought a used ECU and will install it after work today. I'll let you know what happens...

maier65 · Mar 10th, 2004, 11:22 AM

Hey 89PathSE,

If your still looking at this thread, I'm getting closer to the end. The ECU was bad. Now the new ECU is blinking the codes correctly as you said it should and telling me the water temperature sensor is bad. The problem i have now is that the connector for the water sensor is melted and on the other end the wires are broken so i need to find a new harness or rig one up. Not a big deal really, but the sensor is in a not so nice place and I'll probably have to order the harness from the dealership.

maier65 · Mar 11th, 2004, 10:04 AM

Finally got it running yesterday. The temp sensor actually was okay,after i hooked up a temporary wire harness the code for a "bad" temp sensor disappeared. But now the ECU is blinking a code 44. In my Haynes manual a 55 means everything is okay, but they don't list a code 44. Any ideas? I'm guessing Haynes has a typo.

pstephens1 · Feb 2nd, 2007, 12:18 AM

My manual stated code 44 is normal operation

**88pathoffroad** · Feb 2nd, 2007, 11:45 PM

Ditto. Board Message