glad to see it was the idler pulley. one down, one to go.

 

hmm

i was just reading, the o2 sensors ONLY read excess oxygen, not extra fuel.

which means, when I misfire, the o2 sensors would read the extra oxygen, think its running lean, and try to compensate.

so, when we pulled BLM's of 109-110, how does the above theory work?

i'm confused

 

the higher the o2 volts, the more unburned fuel (or less oxygen) there is in the exhaust. a misfire means no or little fuel was burned. and that matches the 109-110 blms. it means the computer is taking fuel away to adjust for the unburned fuel in the exhaust.

 

I don't believe this is correct.

A misfire means no or little fuel is burned, which means no or little oxygen is consumed. Since the O2 sensor only measures oxygen (not fuel), it'll report a false lean condition (low mV reading) because the oxygen wasn't consumed by combusting the fuel.....it was just pushed right out of the exhaust port to the O2 sensor. The PCM will interpret this as a LEAN condition and INCREASE the BLMs to increase fuel delivery.

Rob
95Z28

 

it is correct. the higher the o2 volts the more unburned fuel is in the exhaust. the lower the blm the computer is cutting fuel back to get to the 14.7:1 ratio.

 

In a sense, yes, BUT the O2 sensor does not measure fuel, it measures oxygen.
The less oxygen - the higher the O2 volts (rich).
The more oxygen - the lower the O2 volts (lean)

If you pull the plug wire off the sparkplug to create a misfire, you'll have unburned fuel dumping into the exhaust. What happens to the unused oxygen that was sucked in on the intake stroke?....it gets pushed out the exhaust too. The O2 sensor sees this OXYGEN and generates lower O2 voltages. The PCM sees the lower O2 voltages, and INCREASES the BLMs (adds fuel) to correct for the "false" lean condition.


I agree that is correct.

Back to the symptoms of the problem (low BLMs), anasazi....what are your mods? Is the vacuum line connected to your fuel pressure regulator? What is your fuel pressure? Is your air filter clean? Is the MAF clean?

Rob
95Z28

 

yes the o2 sensor measures oxygen. so more unburned fuel means less oxygen right?

his compter is seeing higher o2 readings and thus lowering the blms. not raising them. pulling a spark plug wire would raise the o2 volts, not lower it. the unburned oxygen is being covered up by the unburned fuel. believe me on this. when i put the pills in backwards on my friends n2o on a TBI car, the o2 went to 1.02 volts. on a TBI car, they want the bigger pill on the n2o side, not the fuel side. opposite of a carb car, that's why i put them in backwards. happens when you don't read the instructions entirely. according to your logic it is a false lean condition? how's that?

The O2 sensor sees this OXYGEN and generates lower O2 voltages. The PCM sees the lower O2 voltages, and INCREASES the BLMs (adds fuel) to correct for the "false" lean condition.

you keep talking about lower o2 readings. he has high readings.

i'm not the smartest guy in class by all means, but i see only half the logic you are putting out. but i can't keep these blm and int definitions right in my head either. but, the lower the blm, the more the computer is trying to lean the mixture,. and vice versa.

 

Yep, fuel pressure regulator is plugged in.

Fuel pressure is about 38psi at idle, 48 at WOT (fuel pressure regulator unplugged), and 42'ish with just key in "on" but engine off.

the air filter i believe is clean, i havn't checked that since it was installed. i'll check this tomarrow when i have it apart for the opti.

the MAF is clean. it used to be dirty (probably from the K&N) but awhile ago i sprayed it off with electronics cleaner... so its clean as i can get it but my problem persists. possibly might want to switch the MAF out with a working MAF just to double check.

my mods are:
160 t-stat
tbody bypass
hooker catback
K&N CAI
polly tranny mount
Accel coil
MSD 8.5mm wires
descreened MAF

the symptoms were before all of these mods I think, its been around for awhile but is becomming more aparent.

whats happening exactly:
The car is sometimes hard to start, especially after sitting for ~4 hours, or sometimes after sitting for a few minuites (rare though). it used to be hard to start when cold but i ran some injector cleaner through and it helped a tad. when the car is warm, generally it is very easy to start. sometimes when it starts, it'll act like its stumbling for a few revolutions but then fire right up.

when sitting idle, generally it'll feel a little rough, and every once and awhile it'll feel like a sudden burst of roughness, sort of like feels like a cylender fires stronger or weaker than the rest. i'm not sure if this is what is happening, this is just as best as i can describe.

when accelerating, at about 1.5k RPM's in 1st or 2ed gear, the RPM's will start to fluxuate and the car will sometimes lurch. you can definantly hear it reving. it does this till about 2.1k RPM's when it takes off like a bat out of hell. i guess the best way to describe this is like someone is sitting there lightly tapping the gas as you accelerate. the same happens in park.

when i push down the throttle body and hold it at a low RPM's you can actually see and feel and hear the engine revving up and down, but your finger isn't moving.

just tonight, i noticed as i was standing behind my car that there was a ting ting ting sound randomly comming from the exhaust pipes. it was fairly hard to hear because of the muffler, but could be clearly heard if you bent over behind the car. after i shut off the car for about 2 or 3 minuites and turned it on the noise was gone???

the symptoms generally seem to manifest themselves the greatest when the car is warm. in the morning when its cold from sitting overnight, the problem does not apear hardly at all, if its even there.


i've tried looking for arcing wires, but these are new wires and it did it with the old stock wires. the car has 60k miles on it. it had the intake oil leak in both the front and the rear, and the whole front of the engine is basically covered in oil, including the opti. when i changed my plug wires the ends of the wires on the opti were soaked with oil and they were actually soft to the touch.

tomarrow i'm installing a brand new opti, and while i'm at it i'm going to get a new mechanical waterpump at Central AutoParts. I might also get a new altinator, even though the one i have is a week old i don't think its charging correctly cause at idle after the car is warmed up the volts drop to about 10.9 - 11.1 volts !

i'm trying to find a MAF screen, to see if my car is one of those that doesn't react well to no MAF screen.

if the new opti does not do the trick, wed. i'm going to try to get over to norris motorsports and see if we can get the tech2 on it and see what it finds out.

i REALLY REALLY hope its the opti... this is getting very annoying, and expensive.

ok, i think that describes it accuratly, if not i'll add to it. i hope what i wrote makes since, i'm fairly tired.

[edit]
this afternoon at work in the parking lot it was doing the surging RPM's at about 1.7k RPM's and for the heck of it i gave it gas... didn't go WOT, but probably 3/4 throttle. i nearly gave myself wiplash and i had a headach for 3 hours from my head hitting the headrest... so its not loosing power that i can tell

and i ran 13.9 pretty much stock with this problem, but it wasn't really too terribly aparent back then, but it was definantly there.

 

yes the o2 sensor measures oxygen. so more unburned fuel means less oxygen right?

I don't think so, at least not in every case.
If you've got good spark (no misfire) and enough fuel, but not enough oxygen, the O2 sensor will read high (rich). BLMs will decrease.

If you've got good spark (no misfire) and enough oxygen, but not enough fuel, the O2 sensor will read low (lean). BLMs will increase.

Here is the case where I think your statement is in error:
If you've got no/little spark (misfire) the fuel and oxygen will not combust. Both will be pushed out the exhaust, the O2 sensor will read low (lean) due to the unused oxygen. BLMs will increase.

his compter is seeing higher o2 readings and thus lowering
the blms. not raising them.

That makes sense and that's the way it should work. I don't think his symptoms are indicating a misfire but I am no expert for sure!

pulling a spark plug wire would raise the o2 volts, not lower it. the unburned oxygen is being covered up by the unburned fuel. believe me on this.

This is why it is important to understand that the O2 sensor measures oxygen, not fuel. The O2 only cares about oxygen and unburned oxygen can't be "covered up" by the unburned fuel.

when i put the pills in backwards on my friends n2o on a TBI car, the o2 went to 1.02 volts. on a TBI car, they want the bigger pill on the n2o side, not the fuel side. opposite of a carb car, that's why i put them in backwards. happens when you don't read the instructions entirely. according to your logic it is a false lean condition? how's that?

Let me first state that I know nothing about N20, or carbs for that matter!:-):-) If I understand you correctly, you increased fuel and decreased N20. You had adequate spark, consumed all the oxygen available, had unburned fuel left over, and created a rich condition (higher O2 readings).

you keep talking about lower o2 readings. he has high readings.

Exactly! I don't think the symptoms are indicating a misfire.

i'm not the smartest guy in class by all means, but i see only half the logic you are putting out. but i can't keep these blm and int definitions right in my head either. but, the lower the blm, the more the computer is trying to lean the mixture,. and vice versa.

I am by far not the smartest guy either! I've been learning a lot as I go and I will admit this discussion really has my brain churning. The inverse relationships are confusing and I have to re-read my replys several times to try and make sure I didn't screw up! Is my logic in this post any clearer?:-)

Rob
95Z28

 

i'm personally still betting on the injectors. we just replaced some on my friends 88 formy. real hard start, smoke coming out at start up, rough idle, bad fuel economy. pulled his injectors out. seven were kinda blackish. #7 injectors clean as a whistle form being stuck open. now it starts right up, no smoke, better fuel economy.

 

we could toss theories all night long. both being right. also i think we are both pointing to injectors as being the problem. not the opti.

 

Do you know anyone close by with Datamaster? Logging things can provide some great troubleshooting data.

How does it run if you unplug the MAF? Do the BLMs fall more in line? Something to look in to.

What about the Idle Air Control (IAC).. .how does it look at idle?

Rob
95Z28

 

I'll go as far to say I don't think it's the opti. I think it's air or fuel related and injectors are a possibility.

If the cleaning didn't help, the next best thing I know to do to rule out the injectors is to pull the fuel rail from the intake manifold (don't disconnect the fuel lines) and turn the key on. See if any of the injectors leak.

As far as the fuel pressure, I don't think 48psi is where it should be but I can't recall what it should be. I'm thinking 43.5 or 46.5 psi.....I just can't recall! Maybe search LT1Tech?

 

he's cleaned the IAC and MAF. also he said with FI cleaner it help a little. he mentioned somewhere about the #4 injector. found it.

but if the cleaning doesn't help, then i'll be doing the opti. if the new opti doesn't help, then i'm going to move that fuel injector on cylender 4 to a different cylender with a clean plug and run it for a few weeks and see how that clean plug looks after that. if its dirty and the plug in #4 is clean, then its new injector time... otherwise i'm back to the drawing board.

 

yea, i dissassembled my throttle body, the lower part with the coolant passage and the IAC motor. took it all apart, cleaned it out with car / intake cleaner, put it back together with new gaskets.


when i pulled all of my plugs last weekend, 3 were PERFECT, literally looked like i just put them in, except they had a little bit of dirtyness on them which i'd consider normal for spark plugs

4 of them had a little black mark on the white (insulator?) part... where the lower electrode thing comes out of

1 plug, the entire white part was black except for maybe a very small part i think. and when i tried to scrape it off with the tip of a safety pin, it wouldn't scratch off very easilly.

tomarrow morning before i do anything, i'm going to take my fuel rail off and prime the system and check to see if any are leaking. then once i get back to where i'm actually going to do the procedure, i'll take it off again and check it again, i'll also double check the air filter.


would it be advisable to remove the starter relay and maybe ignition relay then try to start the car, with the fuel rail hanging inside a plastic bag or something? something like to test to make sure the injectors are all firing. just a thought, this could be a horribly bad idea.