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Motor running lean

JohnAllen

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JohnAllen,

A 86-87 2.9L t/b is larger but nowhere near a 4.0L's t/b.

If you want your 2.9L to run well, use the stock rated injectors with the 86-87 T/B, then start troubleshooting.

RonD is 100% on the money; the t/b and 14# injectors are not your problem. For the minimal amount of effort, put the original T/B and stock injectors back on and retest. If it runs correctly, then make only 1 change at a time to determine the fault (just keep those 19# in a box in a different room).
Also, what would cause it to idle better with the fuel pressure regulator vacuum line unplugged and the port for the intake plugged back off allowing it to have the full 41 lb of fuel pressure on the rail constant. I could be wrong but to me that saying that I increased my volume to the fuel injectors therefore allowing it a more efficient spray and allowing it to idle a lot better. But like I said my thinking on this could be wrong.
 


gaz

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John,

When I first decided to try and improve the efficientcy of this engine, I thought it would need larger injectors too. I spoke with several mechanics, several engineers, even injector specialists/authorities. I was assured beyond any shadow of a dought, unless I was making in excess of 225 hp, I should use the stock #14 injectors.

Troubleshooting can be a nightmare. My best results are often obtained by undoing the last change I made. I recommend starting that way, to learn what is causing this issue.

When you swap those #14's back in, use all new gaskets, o-rings and hats.
 

JohnAllen

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John,

When I first decided to try and improve the efficientcy of this engine, I thought it would need larger injectors too. I spoke with several mechanics, several engineers, even injector specialists/authorities. I was assured beyond any shadow of a dought, unless I was making in excess of 225 hp, I should use the stock #14 injectors.

Troubleshooting can be a nightmare. My best results are often obtained by undoing the last change I made. I recommend starting that way, to learn what is causing this issue.

When you swap those #14's back in, use all new gaskets, o-rings and hats.
Okay. I'll give it a shot.
And yes, trouble shooting is a nightmare, lol.
 

superj

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My credo
Grew up in the 70s, 80s, and 90s
does it have two fuel pumps because one is an in tank lift pump and the other is the higher pressure pump that actually pushes the fuel through the system?
 

JohnAllen

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does it have two fuel pumps because one is an in tank lift pump and the other is the higher pressure pump that actually pushes the fuel through the system?
No sir it doesn't. That's why I was wondering about the volume of fuel running through the rail. Being how it's basically set up like an 86 or 87, just with no egr valve, if I shouldn't be running a second high flow fuel pump, and if so, what size I should get to help the rails maintain the right volume to keep the injectors properly supplied to preform right.
 

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I have my doubts about the larger throttle body actually increasing the flow of air to the motor...

I'm willing to bet the stock TB can flow more cfm than the motor would pull at full chat.
 

RonD

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Lean code does NOT mean engine is running Lean, you have to get past that
Pinging/knocking means engine is running lean

Lean code means computers calculations were off so it is having to correct them, the code is to let operator know there is a computer calculation ERROR
OBD codes rely on a human to diagnose actual problem

So ignore the code and work the problem that is occurring, which I assume is stumbling or rough running
 

JohnAllen

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Lean code does NOT mean engine is running Lean, you have to get past that
Pinging/knocking means engine is running lean

Lean code means computers calculations were off so it is having to correct them, the code is to let operator know there is a computer calculation ERROR
OBD codes rely on a human to diagnose actual problem

So ignore the code and work the problem that is occurring, which I assume is stumbling or rough running
Lean code does NOT mean engine is running Lean, you have to get past that
Pinging/knocking means engine is running lean

Lean code means computers calculations were off so it is having to correct them, the code is to let operator know there is a computer calculation ERROR
OBD codes rely on a human to diagnose actual problem

So ignore the code and work the problem that is occurring, which I assume is stumbling or rough running
There are no pings or knocks. It just idles a little rough literally sounding like it has a mild cam sometimes so I guess you can say it lopes. And then around 55 mph or faster when I push the pedal all the way to the floor in 4th or 5th gear show shutter every once in awhile but not often. And when none of that is going on she'll run like a dream. No hesitations no loss of power or nothing. But when it's doing that shutter thing it feels like I've lost power.
 

RonD

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A misfire can set Lean code

O2 sensors can only see Oxygen, not fuel, this why people get confused about "lean" and "rich" in this context, they think lean means too little fuel, and rich means too much fuel, and it does if you are talking about fuel, but thats not what lean/rich codes are talking about, they are talking about Oxygen

When a cylinder misfires no Oxygen is burned up in that cylinder, and all that Oxygen is dumped into the exhaust, where the O2s are
O2 sees that extra oxygen and that's what sets the lean code, too much oxygen not too little fuel
Other cylinders are running fine, not lean or rich, but the misfire causes computer to see extra oxygen so it adds more fuel using the injectors on that bank trying to "fix it"

But if the misfire was not fuel related.......................well you still have the misfire and now you have other cylinders running too rich

Misfires can be spark related or compression related
Compression test is the first test to do because its not a "grey area", cylinder compression is good or bad
You need to test all cylinders at one time, so all things are equal
Then compare results

Many chose to do new coil, wires and plugs first, which is fine, these all wear out so not a waste of money
But compression test first is always what I do, so I don't end up chasing my tail on spark and fuel if its a compression issue
 

JohnAllen

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A misfire can set Lean code

O2 sensors can only see Oxygen, not fuel, this why people get confused about "lean" and "rich" in this context, they think lean means too little fuel, and rich means too much fuel, and it does if you are talking about fuel, but thats not what lean/rich codes are talking about, they are talking about Oxygen

When a cylinder misfires no Oxygen is burned up in that cylinder, and all that Oxygen is dumped into the exhaust, where the O2s are
O2 sees that extra oxygen and that's what sets the lean code, too much oxygen not too little fuel
Other cylinders are running fine, not lean or rich, but the misfire causes computer to see extra oxygen so it adds more fuel using the injectors on that bank trying to "fix it"

But if the misfire was not fuel related.......................well you still have the misfire and now you have other cylinders running too rich

Misfires can be spark related or compression related
Compression test is the first test to do because its not a "grey area", cylinder compression is good or bad
You need to test all cylinders at one time, so all things are equal
Then compare results

Many chose to do new coil, wires and plugs first, which is fine, these all wear out so not a waste of money
But compression test first is always what I do, so I don't end up chasing my tail on spark and fuel if its a compression issue
Okay this motor has been in my truck for about a year now. Bought it brand new and took it to a shop to have the valves readjusted after the break-in period. Could it be possible that the valves was not adjusted properly?
 

JohnAllen

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A misfire can set Lean code

O2 sensors can only see Oxygen, not fuel, this why people get confused about "lean" and "rich" in this context, they think lean means too little fuel, and rich means too much fuel, and it does if you are talking about fuel, but thats not what lean/rich codes are talking about, they are talking about Oxygen

When a cylinder misfires no Oxygen is burned up in that cylinder, and all that Oxygen is dumped into the exhaust, where the O2s are
O2 sees that extra oxygen and that's what sets the lean code, too much oxygen not too little fuel
Other cylinders are running fine, not lean or rich, but the misfire causes computer to see extra oxygen so it adds more fuel using the injectors on that bank trying to "fix it"

But if the misfire was not fuel related.......................well you still have the misfire and now you have other cylinders running too rich

Misfires can be spark related or compression related
Compression test is the first test to do because its not a "grey area", cylinder compression is good or bad
You need to test all cylinders at one time, so all things are equal
Then compare results

Many chose to do new coil, wires and plugs first, which is fine, these all wear out so not a waste of money
But compression test first is always what I do, so I don't end up chasing my tail on spark and fuel if its a compression issue
Also just to store this knowledge in my head you're saying when no oxygen is burned up the O2 sensors will read lean and that the O2 sensors don't pick up on fuel it just reads the oxygen, so then how does it get a rich code? Just out of curiosity.
 

RonD

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Yes, O2 sensors only see Oxygen

"Rich" for an O2 sensor is low oxygen in the exhaust, as an example ALL properly working exhaust systems with Cat Converters run RICH, as far as rear O2 sensor is concerned

O2 sensors make their own voltage via a chemical reaction with Oxygen(which is why O2s wear out, they run out of chemicals)
O2 voltage
0.10 volt is High Oxygen, "lean"
0.90 volt is Low Oxygen, "rich"

The upstream O2 sensor gets exhaust straight from engine
The computer cycles injector open times to try and keep O2 voltage at around 0.4 volt, optimum oxygen level that means good burns in cylinders

Downstream O2 sensor(after Cats) should run at 0.7 to 0.8 volt, so "rich"
Cats use up most of the Oxygen left in exhaust to burn up pollutants in the exhaust, so there should be Low Oxygen levels in the exhaust After the Cats, so "rich" exhaust, but not really, lol


Now when a cylinder misfires the unburned oxygen makes the O2 sensors voltage drop(0.1v) on that bank/side of the engine
So computer responds by opening the injectors longer, this causes all the cylinders on that bank to have a rich mix, say there are 3 cylinders(V6)
Well the 2 working cylinders will output less oxygen because of the NOW rich mix, too much fuel, which compensates a little for the misfiring cylinder that's outputting too much oxygen
And computer will set Lean code because it is opening injectors longer than it calculated to compensate for the higher oxygen level on that bank
So Lean Code means too much oxygen on that bank, not too little fuel

When a cylinder/engine, is actually running lean on fuel it will ping/knock, and it will smoke if its running too rich on fuel

So lean code is about oxygen in exhaust at the upstream O2 sensor(s), not downstream
That can be caused be an exhaust manifold leak as well or loose O2 sensor, it sucks in oxygen
Or partially blocked exhaust, it holds in the oxygen at the upstream O2s
And of course misfires and partial misfires, not as much oxygen is used

And then of course the usual suspect, intake air leaks, computer calculation is off because of unreported air coming in
 
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JohnAllen

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6"
Tire Size
33x10.50r15
Yes, O2 sensors only see Oxygen

"Rich" for an O2 sensor is low oxygen in the exhaust, as an example ALL properly working exhaust systems with Cat Converters run RICH, as far as rear O2 sensor is concerned

O2 sensors make their own voltage via a chemical reaction with Oxygen(which is why O2s wear out, they run out of chemicals)
O2 voltage
0.10 volt is High Oxygen, "lean"
0.90 volt is Low Oxygen, "rich"

The upstream O2 sensor gets exhaust straight from engine
The computer cycles injector open times to try and keep O2 voltage at around 0.4 volt, optimum oxygen level that means good burns in cylinders

Downstream O2 sensor(after Cats) should run at 0.7 to 0.8 volt, so "rich"
Cats use up most of the Oxygen left in exhaust to burn up pollutants in the exhaust, so there should be Low Oxygen levels in the exhaust After the Cats, so "rich" exhaust, but not really, lol


Now when a cylinder misfires the unburned oxygen makes the O2 sensors voltage drop(0.1v) on that bank/side of the engine
So computer responds by opening the injectors longer, this causes all the cylinders on that bank to have a rich mix, say there are 3 cylinders(V6)
Well the 2 working cylinders will output less oxygen because of the NOW rich mix, too much fuel, which compensates a little for the misfiring cylinder that's outputting too much oxygen
And computer will set Lean code because it is opening injectors longer than it calculated to compensate for the higher oxygen level on that bank

When a cylinder/engine, is actually running lean on fuel it will ping/knock, and it will smoke if its running too rich on fuel

So lean code is about oxygen in exhaust at the upstream O2 sensor(s), not downstream
That can be caused be an exhaust manifold leak as well or loose O2 sensor, it sucks in oxygen
Or partially block exhaust, it holds in the oxygen at the upstream O2s
And of course misfires and partial misfires, not as much oxygen is used

And then of course the usual suspect, intake air leaks, computer calculation is off because of unreported air coming in
Well definitely leaning towards the misfire now. Because there are absolutely no leaks of any kind. Exhaust side and intake side. All of those have been thoroughly tested. Could misadjusted valves cause a misfire?
 

gaz

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FYI,

"Adjusting the valves" = adjusting the hydraulic lifter preload.
 

JerryC

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Off the wall thought. The TB is not adjusted or working properly. It is opening farther than what is reported to the ECU.

Second thought, an exhaust leak makes an 02 sensor read incorrectly, but I don't remember it reads lean or rich.
 

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