Lean Fuel Codes, Need Some Help

Folks,

I'm in need some advice from the experts. I got my wagon a while back with a warning that it runs terribly after warming up. the Service Engine Soon light would sometimes come on, sometimes no. I asked my neighbor to change parts for me and down load the fault codes since I am out of commission from a motorcycle accident (the reason I have the wagon now). He never did check the codes but did change the following parts (all AC-Delco except the wires:

-Optispark and connector
-ICM
-TPS
-Coil
-Water pump and sensor
-Fuel pressure regulator
-EGR
-plugs
-MSD wires
-O2 sensors

He noted that the exhaust system was in pretty bad shape, so I had that replaced professionally with Magnaflow cats and mufflers.

The car seems to run even worse than before.. A lot worse. It barely gets out of its own way...if it can start in the first place. I was pretty upset about not getting any fault codes from him, so I got them from the A/C panel. The only code I would get is a 44, lean left bank. We did a fuel pressure test and only had 19 PSI. So a new fuel pump went in and now the pressure is 49 PSI. That's good and seem to drive better, but then it would kick the code 44 again, but seemed like it would still drive....but that only lasted a day...

The day after changing the fuel pump I lost all power again, barely ran but this time it kicked a 55. Even after sitting for a while, there's been no change, so I replaced the MAF sensor blindly. And that didn't fix it either. I'll attempt to start the car in the AM to see if it works, but yeah, it's un-driveable until I solve this. I told my neighbor he had his chance and now I'll fix it, even if I'm still using a walker.

My next step is to test and replace the MAP. I would also like to do a vacuum test on the engine, but I don't know how, which brings me to what I request help with:

How can I vacuum test the LT1? Should I also test the EGR? And what should I be looking for to repair this poor running engine and fault 55? Am I on the right track?

Thank you for taking the time to read this and help. I'm getting pretty frustrated. I never had to rely on shops or mechanics before. Not even with my E93 Bimmer or Ducatis, but after being hospitalized and and the need for rehab for the next year or two, I didn't see a choice. **** that though, I'm done with outside mechanical help. I just need internet help now.

Oh, air and fuel filters were changed too.

maf and map almost never go bad.

what brand O2 is in there now ? what brand opti ?

Throwing parts at it probably isn't the most efficient way to go.

O2s are AC Delco. The Opti is also AC Delco with an MSD cap and rotor. New and sealed plus it was tested at 180 degeees with an osciliscope.

My plan today is to test the MAP. Search for vacuum leaks and then investigate/inspect the left O2 wiring. Being f**ked up though, I'm not sure if I can crawl under the car to reach the O2 sensor harness, but I'll try. Any thoughts?

O2 sensors provide a signal to trim the fuel, but even when dead won't give the kind of drivability issue you are having.

A cheap test is to switch the sensors side-to-side and see if the lean code moves with them.

Sounds kinda like a bum injector.

Brandt51 wrote:

Any thoughts?

check the O2 mV with a scanner.  
both codes are for lean exhaust.  Keep in mind that bank might be leaning out cause the other one is too rich.  I'd follow the [You must be registered and logged in to see this link.]

ensure the [You must be registered and logged in to see this link.] is in good shape.  You can get a new one at a harley davidson dealer.  Wouldn't make the car run as poorly as you describe though.

MAP tested good with a vacuum pump...no surprise. Seal seemed ok, looked like it was OEM

O2 sensors are new, so yeah, I really wish I knew what the codes were before we changed parts. I'm kicking myself for that.

I unplugged the MAF to get the car started. Then sprayed carb cleaner around the engine looking for a vacuum leak. I think I found a small one on the passenger side. I need to look into it more.

I am fairly certain I have it figured out, but not happy about it. I have an exhaust leak on the drivers side where the manifold mates to the head. This has me worried. According to the link above that references the service manual, this could cause the issue. Why it affects the car some days more than others is a mystery, but I sprayed some carb cleaner around the manifolds and I think some was sucked in because the pipes kicked out fluid that later evaporated. This is just a broken bolt in the block waiting to happen. I'm thinking the right is similar, just not as bad.

Do the manifold heat shields come off easily or what? I'm considering a temp sealant fix to avoid the inevitable broken bolt in the head, but yeah, open to suggestions and options. BTW, motor has 206k miles, so a temp fix would likely last until the motor was done. Thoughts?

Check your PCV valve and associated lines, including the port. PCV system faults can cause all kinds of weird symptoms.

Copy that. I got a new one to swap in.

If I disconnect the Left O2 sensor, the car will run in open loop right?

Everything with this car is done except I just need it to run right. I might replace the manifolds with replacements or headers (I like headers) to cure the small exhaust leak. It doesn't start with the MAF connected though. Symptoms are still slightly changing and getting me off track. Before it would still run and there was a noticible difference in the sound when the SES light comes on. Going back to open loop I assume? Here is my current plan:

Diagnose and repair small vacuum leak.
Verify egr circuit is good (vacuum line looks sketch, but didn't get the car up to temp yet)
Replace PCV
Real time read of O2 sensors (to further confuse myself)
Replace exhaust manifolds to repair small exhaust leak.
Flow check/clean injectors

Thoughts and suggestions?

This car is totally bad ass other than this sketchy obd1 LT1.

Thanks so much.

""Do the manifold heat shields come off easily or what?""

The shield halves are held together by rivets and/or upset (pressed) connections . The shields are fastened to the manifolds by drive screws.

Copy. It's sunk in that I need to tackle the manifolds. At least the left one. I looked at replacing them with BBK headers, but I'm not interested in doing that. I don't care about this car being fast. I think I'll attemp to replace the gasket with an Earls one as well as using ARP bolts. This all theory for now. I need to gather my strength. I'm still using a cane or walker and the first time in six months sitting on the ground form me was to crawl under this boat.

Thanks for the advice.

I guess the advantage of headers is that you don't use the outer bolts. Usually aft bolt breaks off in the head. If you're lucky, there's enough sticking out to get vise grips on it. If not, it's either a shitty session with an easy-out or weld on some stainless rod to remove it.

If you put the manifolds back on you don't need earl's pressure master. Great gasket but overkill for manifolds. Percy's is good and a bit cheaper. If you don't fix the bolt issue, any gasket you use will leak.

Grade 8 bolts are recommended as replacements, and make sure you reinstall the thick washers.

""as well as using ARP bolts.""

This solves the manifold leak issue permanently. In addition to the standard ARP SB exhaust manifold stud kit, you will need several of their longer bolts for accessory mounting.

Ah, thanks. I'll go with a different gasket then like suggested. If I break an outer bolt, I'll probably put headers on to avoid dealing with it. FML, I didn't want to do performance stuff, but it just follows me. It has a brand new 2.5 inch exhaust system with high flow cats and mufflers. I got it done for a sweet price, but I'll have to back track on it a bit if I put headers on. I think I'll leave the pipe connected and just pull the manifold back enough to drop in a new gasket...I hope.

Longer accessory mount bolts are needed? Only if I dick around with headers though yeah?

What I should have done is dropped an LS in this, but for being a my replacement budget beater car, it's getting expensive real fast. Hahaha.

After some more reading on this site, a post led me to check the tightness of the manifold bolts...well, I only checked two and the back drivers side (around where my leak is) was loose. So, my new plan is this:

-Tq check all manifold bolts
-Diagnose and repair small vacuum leak.
-Verify egr circuit is good (vacuum line looks sketch, but didn't get the car up to temp yet)
-Replace PCV

If it's still running poorly, then I'll do the two other things that I need hardware and software for:
-Real time read of O2 sensors (to further confuse myself)
-Flow check/clean injectors

No matter what happens, I'll update this thread with the results and hopefully the solution soon too. Nothing is worse than people asking for help on forums, getting answers and then not closing out the thread with what the fix was. That's just as bad as leaving your shopping cart in the middle of the isle.

""Longer accessory mount bolts are needed?""

There is some bracketry that mounts off of the passenger side manifold bolts. The ARP exhaust manifold studs have to be replaced with longer bolts (ARP) in these spots.

Ah, copy.

So here's an update. I tightened that loose bolt on the back of the driver's manifold. Repaired the leaking vacuum line that was pretty brittle and broke more. It was for the HVAC system. The PCV wasn't seated all the way, so I pulled it out and changed it. While doing so, I replaced that short section of vacuum line from the hard line to the PCV valve. I installed the original MAP with the worn gasket...more to come with that...

So, I go to start the car. It takes several attempts of cranking for it to finally light off. Very strange. Once running, it did not idle well and died several times. Once I got it running by revving the gas and letting off when it stumbled, it finally started to run fine in idle...no codes yet. Any attempt to throttle it up, it stumbled. After it idled for a while, it finally started to idle nice, but still stumbled when I got on the gas. Several minutes later, the SES light came on with the same 44 and a noticeable change in the engine idle sound. After it warms up, it still doesn't want to start easily. So, these are my new symptoms:

Hard starting hot and cold.
SES light with fault 44 (lean left bank).
Stumbles and dies when revving off idle.

I feel like I'm chasing my tail. It has a new fuel filter, pressure regulator and fuel pump.

So my next step is to solve the hard starting/stumbling issue. I'm going to pressure test the fuel. Perhaps there's a relay issue involved with that.

Even though I changed the MAF, I'm going to attempt to test it, I need to find the procedures. I got a bad ass multi meter though.

I also need to replace the MAP seal I think. It might help some with the stumbling issue maybe?

Thoughts? Am I on the right track or off the path?

Have you taken the temperature of the exhaust manifolds at each exhaust port? That the problem is reporting in the left bank is interesting.

Get a laser heat tempt gun from somewhere like Harbor Freight. Take the temps right at the head on the exhaust manifolds. Are you are getting a reading that is cold in proportion to the other three cylinders? A few degrees is no big deal, 100 degrees is. Since "lean" is fuel related, it may be a bad injector,  particularly that it is only on one side, and not both.

Got a way to see AFR or voltage off the left bank O2 sensor. and compare it to the right during the same run time?

Also of interest. Reporting that it runs terrible AFTER warming up could mean that it is OK during the open loop table portion of the program, but as the temp rises to meet closed loop requirements and go onto the sensors that you have issues.  In open loop the ecm uses specific AFR vs load tables. In closed loop it switchevcs to rpm vs load tables and other modifier tables.



Have you reset the  minimum air screw  on the thottle body? Reset the  IAC ( Idle Air Control)

I'm also starting to wonder if either the PCM is bad or someone played around with the tuning and didn't tell you.

At this point I'd suggest focusing on communicating with the PCM. Fortunately you can do this, and reprogram it to your heart's content, for the cost of a communications harness.  You can build a USB-TTL converter pretty cheap (like $30 or less) if you go to [You must be registered and logged in to see this link.].

[You must be registered and logged in to see this link.] is an amazing data logging tool and even allows some real-time adjustment of target AFR and spark timing.  You might try this thing out and change AFR in real time and see if that cleans up the behavior.

Sending you a PM as well.

Another thought - every healthy LT1 I've ever driven always starts in 0.5 seconds every time. Unless it has a bad coil, bad optispark, or bad optispark sensor harness.

After a short run after a cold start, what do the spark plugs look like?

Rev Bob wrote:

O2 sensors provide a signal to trim the fuel, but even when dead won't give the kind of drivability issue you are having.

A cheap test is to switch the sensors side-to-side and see if the lean code moves with them.

Sounds kinda like a bum injector.

Did you have opportunity to swap sensors as suggested? Does the code follow the sensor.

I love excuses to buy tools. I'll get the IR temp sensor. My other neighbor is lending me a Motus or something rather to realtime them O2s and such. Or so I hope.

I haven't swapped sensors yet. I will though or replace the left since I have a spare. Wiring would still be questionable though, sonprob better to swap. The car side wiring looks safe and the sensor wires are zip tied away from the exhaust. I don't want to short cut stuff, but I'm cautious about over working myself.

I hope that PCM is stock. I thought this car was unmolested, but I'm finding evidence of shaddy work done. It has slotted and cross drilled rotors, but I didn't think much of that at first. When I removed the steering wheel to replace it, it was def not the first time it's been off. That was odd because the wheel was garbage. There's also a JB weld fix on the fuel tank too and it had shitty rear shocks on it too. The more I fix, the more I find.

I'm betting on injectors now, but I gotta do the pressure test and then follow all of your suggestions before I make that call. I'll report back soon. Thank you all for the help. I really appreciate it.

Keep in mind the O2 sensor is measuring unburned oxygen , not full. So a lean would indicate unburned O2. Make sure there are no exhaust gasket leaks as well. I had always thought the gas would escape out the loose gasket.

Others have told me it can suck air into the exhaust stream by venturi effect therefore be a source of unburned O2 . The false reading can cause MORE fuel to be injected, because of the lean indication that the unregulated air is causing. SO make sure there are no exhaust leaks.

Typical culprits are cylinders 7 and 8 as they seem to take the most stress from weight and vibration of the exhaust system. And of course they are the biggest pain in the butt to deal with.

Ethanol fuel is tough on 20 year old injectors ,..if the plug wires are crossed it plays havoc too
5-7 are most common problem,.

So....I attempted to test the fuel pressure, but the ghetto Autozone kit didn't have the adapter that pushed the schrader valve down...But, the fuel pressure has been checked good before. So because I can and don't have a lot of patience, I bought a few things:

-Longacre IR pyro gun (plus tire probe for my other hobby) to shoot at the engine.
-My own fuel pressure test kit.
-Percy manifold gaskets and ARP bolts. (I think that part is fixed, but I'm betting I'll need it sooner than later).
-Stock rebuilt 24lb injectors from Injection Connection.
-I was attempting to get a Blue Point fuel line kit to for removing the rail, but it expired too soon, so the search continues for that.
-A heater core flush kit, because Roadmaster problems.

While waiting for the parts, I'm going to swap the 02s and ohm out the stock injectors. If no change, I'll get the the injectors ready to change. I also have the Snap-On Modis, but it doesn't have the OBD1 adapter, so no dice on reading the O2s with it. I am totally shotgun blasting stuff, but after I get tired and have a computer in front of me, I get impatient and buy stuff on the internet. 1st world problems.

BTW, this car did have low fuel pressure and only after replacing the pump, filter and pressure regulator did the it really start running poor and stumbling off idle. If I had to guess, the issues just flowed down to the end and the 22 year old injectors couldn't handle 47lbs of fuel pressure all of a sudden.

Thanks again. Standby for updates.

That's why I suggested getting the temps at the exhaust ports. It would help determine if an injector is frirng. If you have a comparitively cold port, that would be a suspect injector.
To my limited knowledge, If a spark plug is not firing, you would be getting a rich condition, not lean due to the unburned fuel. But the unburned fuel can also have a cooling effect on temps, so the lean code is key, not just the temps.

Keep us posted.


Dave.

You may also have a cracked exhaust manifold. I think the right side was more commonly cracked. Dorman makes a replacement, I believe.

I would not bother with removing the heat shields; they're just "part of the deal".

Whelp, got my fuel pressure test kit in today. Checked fuel pressure again. 10 f'n PSI. So yeah, I'll need to replace the fuel pump again most likely, but I think I'll try the filter first, even though it's new. I am pretty hot right now with my neighbor who's been 'helping' me, or so I thought. That's another issue. So, I'll have some spare fuel injectors around, but there's nothing wrong with that.

Las time the tank was down, we found some issues on it, so I'm going to look for a replacement as well. Stay tuned...if you're that bored.

I'll bet you wish you had a drain on that tank.

While the tank is out, if it gets used again, put a drain in the bottom of it. Use a fuel proof sealant on it.
Transmission pan drains work and are both cheap and available at most auto parts centers .

Hey Sam, make sure you check it under a variety of conditions. Ignition on / engine off, initial spike, where it settles to, what it does while running, does it go up or down when you jerk the throttle body open, etc.

Given what you said about the quality of repairs on the car in other places, I'd want to make sure there's no restriction in the lines or perhaps another bad regulator before dropping the tank again.

Good thoughts. I buying a new tank because of the previous tanks's condition. That 10 PSI doesn't move much at all. We're going to pressure test it at the fuel filter too. Probably needs the lines cleaned out, so that's on the list of things to do. I AM NOT installing the new injectors until I verify the lines are clean.

It's possible the pipe connections on the fuel pump came loose. Take a close look at the top of the fuel pump when you drop the tank.

lakeffect wrote:

I'll bet you wish you had a drain on that tank.

While the tank is out, if it gets used again, put a drain in the bottom of it. Use a fuel proof sealant on it.
Transmission pan drains work and are both cheap and available at most auto parts centers .

I wouldn't do that.

Using a fuel proof sealant helped to eliminate leaks for the past several years. Maybe not the smartest move in the world, but because of the need to have to drop the tank several times over the years, it proved handy.

How often do these pumps go bad? I saw one fella cut his floor to do it while on the road.

It only takes one to strand you.

In all my years of driving these cars I never ever had a fuel pump failure. Rather than spending all the time to cut up my floor I'd just keep some money saved away for the tow and repair and call it good.

Wish I could say the same.

The biggest contributor to turbine fuel pump failure is running out of fuel. The little jewel spins at very high speed and quickly overheats the bearings, windings, and seals when running dry.

This is why dual-tank setups like used on the Corvette use a no-moving-part jet pump on the side designed to empty first.

Quick update, replaced the pump again and I'm back on the road. I still get a fault 44, but the car runs great. I have the injectors to replace, but I still want to look into that O2 sensor on the drivers side first. A quick look of the wiring did not reveal any damage, but I'm going to inspect it with a more critical eye and try a different sensor.

Presuming the code tells you what side the problem is on, swap sensor to the other side, of the code changes, you know its the sensor.

OR, follow the diagnostic flowchart provided above

jasonlachapelle wrote:

OR, follow the diagnostic flowchart provided above

Totally. I got the IR gun to shoot at the manifolds tomorrow. Then to the O2 sensors if the manifold temps are uniform. I never found a Tech 1 or MT2500 for a price that made it worth it for me.

I also need to flush the core at some point and thanks to this site, discovered that the T-fitting might be sketch, so I got a new GM kit on the way to make sure I don't get stranded.

And after all of that fun stuff, I need to replace the plastic window regulator guides in 2 windows.

I forgot to note I got a new tank from BuickNut that was in excellent shape. My original tank had a JB weld fix to the filler neck and the mounting flange was cracked after what I suspect, several fuel pump changes. The new tank from BuickNut was very nicely packaged. That dude doesn't mess around and will make sure you're happy with the condition of the parts before taking payment.

Another note, with 38% tint on the windshield, the Twilight Sentinel is on all the time. Las Vegas problems.

This car is bad ass though. Always draws compliments. When I get the wood re-wrapped, I imagine the panties will start flying.

Thanks for all the help, I'll be sure to keep this thread updated on the engine code issue.

Yup,new wood wrap,and the panties will start dropping. Works every time...

I wouldn't waste my time or money on a tech 1 or any other scanner. Laptop, numerous free software titles and a cheap cable make much more sense. Plus they can do so much more than an overpriced scan tool.

Andebe wrote:

Yup,new wood wrap,and the panties will start dropping. Works every time...

Andy, the problem starts when the realization is that the panties were worn by someone named Ralph.  

And....the fuel pump died again, this time on my way home from the base hospital where I got a nifty award by a patriotic group of bikers, but that's another story. The pump was Delphi unit and the 2nd one I've installed. F'n A these are garbage. At least I got just under a half tank this time at least. I read on this forum that another person went through a couple Delphis in short order as well.

I did check the fuel relay and jumped the contacts...still had a whopping 9 psi. I was hoping it was a FUBAR'd relay because the case was cracked, but no such luck. Anyways, I was torn between Spectra and AC Delco...about $180 swing, but I chose Spectra because it gets here faster....and if AC Delco was so good, I don't think there would be so many threads about fuel pumps. Thoughts on that? I could care less about buying another pump and keeping the Spectra as a back up.

Thank God SEMA is coming up (no appointments) and preventing me from getting my panty dropping wood grain wrap done, I'd be pissed if I had an appointment set up and was held back because of it.

Anyways, thanks for tuning in, I'll report back when this bitch is running again and go from there.

lakeffect wrote:

Andebe wrote:

Yup,new wood wrap,and the panties will start dropping. Works every time...

Andy, the problem starts when the realization is that the panties were worn by someone named Ralph.  

Ralph can be a girls name right?

""and the 2nd one I've installed. F'n A these are garbage.""

Same pump as used in tens of thousands of cars. Usually multiple short time failures of anything are caused by something else contributing.