1996 Geo Tracker P0300

[gorkyb]

Fellow Trackickers, I hope is all going well with your rides.

This morning my Tracker took a little more cranking than usual to start. After I've got it started I took it out for a spin and upon acceleration between first and third gear it hesitated twice.

Code P0300 stored. I've got fairly new plugs, wires, cap and rotor on this car. I did noticed a very small piece of wire insulation peeled off from one of the wires on the connector that plugs into the distributor base. Due to recent service I did to the car I can say with confidence that everything is fine in the timing area, meaning crank key is intact, it has a brand new crank gear, belts are not over-tightened.

I inspected all spark plugs for flooding and they all looked dry and did not smell like fuel. Gauge mounted on fuel rail shows no loss of fuel pressure neither.

I put everything back together and the car ran normally, I test drove it for about 20 miles. I then erased the P0300, test drove it again and P0300 is back as a pending code. I have a spare distributor so I'm going to drop that in today and will check that all injectors are clicking with the stethoscope.

Anything else obvious that I'm forgetting to check?

[fixkick]

oops clearing the code, cleared the freeze frame, but.. next time....
freeze frame shows you when the random all 4 cylinder misfire happened, speed,rpm, load, etc. is the misfire cold only? or hot, both, or idle, or , cruise?
if you knew the when you could watch O2 and see whats happening live/
bad coil
lean mixtures

id plot the 02 front sensor as graphic and drive and see if its going lean.
if its rich misfire, the o2 goes lean when not. do to air slugs.
if the coil fails, all 4 misfire, and you get 4 air slugs of 20% oxygen to the header. the 02 rails the hard lean, stuck at 0 volts.?

good luck to you !

[gorkyb]

I took it all down again to inspect proper timing (not jumped belt) and to inspect rubber on crank pulley, the rubber looks a little cracked but it doesn't seem to be completely separated from the center part. I was able to time it with the strobe light afterwards. Between all this I tried a spare distributor I have but the car lost power to the point where it could barely move, I figure timing was wrong so I tried several times and I was either too advanced or too retarded but never right on like the other distributor I had in there, is it possible the gear at the bottom of the distributor slipped? anyway, I put back the old one, made sure I inspected everything I could imagine, HV wires, spark plugs and their wells, wiring to TPS and distributor, all contacts under fender fuse box, injectors (connectors and clicking sound), sat there for 20 minutes from cold until it warmed up watching the scanner and all readings are within specs, o2 sensor is hunting and MAF is near .3v at idle at it goes up when depressing gas pedal. I felt very little or non misfire (I think is mostly in my mind now since no P0300 has come up pending or stored) P0420 came back as pending. P0400 came up as stored but I think it was because when checking for leaks in the induction I left the vacuum hose from the egr to the VSV unplugged by accident. Engine runs fine at idle and under load, closes loop shortly after starting the engine. Everything seems fine so far. I keep thinking the issue is electrical, a "spark" noise (very distinctive) can be heard when the misfire was happening before, I'll have to wait and see when it comes back (I hope it doesn't)

Does the way the HV wires are laid out make a difference? meaning crossing over or under another wire?, assuming the insulation is still good, otherwise it is obvious they'd short out.

I'd still like to make my spare distributor work, I just haven't had time to look into it. I'll plot the o2 sensor while driving and look for the signs.

[fixkick]

Bad gas? nah.

[quote='gorkyb' pid='440' dateline='1372858697']
I took it all down again to inspect proper timing (not jumped belt) and to inspect rubber on crank pulley, the rubber looks a little cracked but it doesn't seem to be completely separated from the center part. I was able to time it with the strobe light afterwards. Between all this I tried a spare distributor I have but the car lost power to the point where it could barely move, I figure timing was wrong

so I tried several times and I was either too advanced or too retarded but never right on like the other distributor I had in there, is it possible the gear at the bottom of the distributor slipped? anyway, I put back the old one, made sure I inspected everything I could imagine, HV wires, spark plugs and their wells, wiring to TPS and distributor, all contacts under fender fuse box, injectors (connectors and clicking sound), sat there for 20 minutes from cold until it warmed up watching the scanner and all readings are within specs, o2 sensor is hunting and MAF is near .3v at idle at it goes up when depressing gas pedal. goes up means little, how far at what load , only has meaning.
If spark is good, and compression over 170, then its fueling. (lots of ways to have that go bad, even bad gas)
is not , .3v wrong? the scan tool shows Gram/ sec?
keep in mind the ecu only warns of a bad maf, when TOTALLY DEAD and never ever warns ( directly) that it is way OFF spec.
The MAF must work, if not , there will be no power, the MAF is the KECSTONE to the whole system. (injections)!!
unplug it and you get back 1/2 the power, (limphome)
best i can tell, here is suz spec , MAF OUT.
[color=#FF0000]off = 0 volts
keyon (only) 1.0

[gorkyb]

Thank you for the pointers. I finally will have some time to work on the car tomorrow. I'll make sure MAF works properly and will plot the readings with the scan tool.

[fixkick]

good luck in your search , ask for help, if you need it.
cheers.

[gorkyb]

Found broken pieces of gasket on distributor body, I think water and humidity were getting in there, took distributor apart and resealed it with permatex, it hasn't misfired again, I did not have a chance to log readings on scanner but will do it hopefully this upcoming weekend, weather permitting it's over 100 F over here.

[fixkick]

ouch, that is an odd failure. yes, ive had water in and mix with dust and make mud that conducts. its a real pain that.
so was spark, 300 sure can be. but usually you can feel the violent misfire of spark (like chain saw, loading up...., unlike , lean bog misfire.

[gorkyb]

I doubt it but I'm sure that wasn't helping, like you said my misfire feels like lean mix so I still have to troubleshoot, I'm workin on replacing my cat for now

[fixkick]

i can send back your old china maf, no problem. (i think if fixed it...)
a dead maf (or way off, ) is very hard to troubleshoot.

just keep in mind, 300s means all 4 cylinders, the piston slowed down. randomly.
1: lost spark. at all 4 spark plugs.
2: all injectors weak at ll 4 ports or too rich. ( or maf) keep in mind you can unplug the maf, & use limphome to see if it recovers some power.
3: compression weak on all 4 , no.
4: cam to crank bounce, loose timing belt. nah.