[vegas_ss]

That is quite pricey! AC delco fuel injectors are ~$85/ea on rockauto and standard motor products are ~$55/ea. A Delphi, standard or AC delco fuel pressure regulator ranges from $43 to $100 for less than $800 total for all new AC delco parts. Seems like $1000 markup on parts is pretty steep!

Changing the fuel injectors and pressure regulator is less than a 2 hour job (if that)... Are you able to do any mechanical work yourself?

 

[_E_]

Thank you @grandpas wagon.

That is quite pricey! AC delco fuel injectors are ~$85/ea on rockauto and standard motor products are ~$55/ea. A Delphi, standard or AC delco fuel pressure regulator ranges from $43 to $100 for less than $800 total for all new AC delco parts. Seems like $1000 markup on parts is pretty steep!

Changing the fuel injectors and pressure regulator is less than a 2 hour job (if that)... Are you able to do any mechanical work yourself?

I see the parts you mention on RockAuto. I agree that the price discrepancy doesn't make sense. I will make sure there aren't other parts he didn't mention that were included in the $1800 quote. Perhaps there is a harness or similar? A wire kit? Might there be such a component in need of replacing?

My Helm manuals arrived at my PO Box today. I suspect that the labor wouldn't be out of my league, but given that a diagnosis was performed by this mechanic, I think it might be best to purchase the parts myself and let him do the install. Otherwise, he'll probably just recoup sunk labor costs by charging me a lot for the diagnosis anyway. I'll see what my options are.

 

[grandpas wagon]

You say Helm manuals..................Helm does not publish manuals................. or do they? Do you mean FSM which Helm sells?

You are still part throwing. Injectors rarely fail, but they do develop deposits and have leaky seals.

You had a smooth running car, but all of a sudden 4 injectors begin to go south.......hmm

A competent tech could do that labor in less than an hour - very easy on this car, but not a job for an inexperienced DIYer messing with fuel lines.

See post #15 - what were the results of the tests he mentioned? Especially fuel pressure, data logging and fuel trims. A good tech would have a wifi printer capable scanner.

Very difficult to make definitive recommendations without good information.

It's your money.

 

[grandpas wagon]

Is this your daily driver - your only car?

 

[_E_]

You say Helm manuals..................Helm does not publish manuals................. or do they? Do you mean FSM which Helm sells?

You are still part throwing. Injectors rarely fail, but they do develop deposits and have leaky seals.

You had a smooth running car, but all of a sudden 4 injectors begin to go south.......hmm

A competent tech could do that labor in less than an hour - very easy on this car, but not a job for an inexperienced DIYer messing with fuel lines.

See post #15 - what were the results of the tests he mentioned? Especially fuel pressure, data logging and fuel trims. A good tech would have a wifi printer capable scanner.

Very difficult to make definitive recommendations without good information.

It's your money.

I have read in at least one other post from years past that Helm published the manuals on behalf of GM. Is Helm's service manual worth the $$ vs. other...

Regarding post 15, I suppose I can ask the mechanic for the answers to the questions and plug in the answers into a post for folks to read here and advise accordingly.

Yes, it's my daily driver, but I drive very little.

 

[sherlock9c1]

Agree that the stock injectors are junk, but NO WAY on those prices. That's ridiculous. If you can get to a junkyard, get 99-03 GM 5.3 injectors; they will work as drop-ins and are newer designs. Or ones for the Lincoln Mark 8 32V engines; those will also drop in (so I've been told on both). And I would replace injectors yourself. Just make sure the o-rings aren't rock hard; if they are, replace them.

 

[_E_]

I spoke with mechanic #1 today. He insists that the injectors were sent out to be cleaned and inspected, and all of them are in working order. Also, I'd imagine that the injectors wouldn't have all landed on the same cylinders they started on. The initial code was a 304, before the injectors were sent out. Mechanic #2 says injector #4 is in the worst shape. I'm wondering whether he might be making this up, since I told him the initial code was a 304. Thoughts?

Also, I want to shift the attention to the crankshaft position sensor. Nobody has confirmed or denied that this should be of particular interest, since this engine issue started upon the replacement of the rear crankshaft seal. Couldn't it be that this sensor is to blame, and the computer just isn't throwing a code for it?

 

[atlantadan]

Crank position sensor is on the front of the engine. On a 1996, the CPS does not affect the running of the engine at all. It is only there to sense misfires and report them.

You did get an LT1 OBD2 code reader, right? Anyone that owns one of these LT powered cars needs to have a good code reader. Even if you're not going to do the wrenching, it'll save you from being rooked by shady mechanics who like to load up the parts cannon and blast away. Once you get one, do the tests I mentioned earlier. The logs will really go a long way towards helping you find what's going on. Sans a reader, there are a few things you can do on your own for under $50 and some time. At the LEAST, you need a way to clear the codes to properly test. Go to Autozone and rent a vacuum gauge, and a compression tester. Since this is isolated to #4, it's probably not fuel pressure related.

Your next step needs to be getting the car home and out of that rip-off artist's shop. You can get the injectors - brand new - for $500 all day long. You can score a set of reconditioned injectors on the 'bay for $200 or less with minimal effort. Pulling the fuel rail and replacing the injectors is a 15 minute job. But you have a lot of bridges to cross before you get to 'injector replacement' time.

Getting to the opti leads on that side of the opti is a pain in the ass otherwise I'd suggest moving some leads around to see if it follows the plug lead. You can buy a cheap spark tester for $15 and make sure that cylinder is getting good spark. Good spark? Move on. Pull the plug out and look at it. Oily? Rings, valve seals, or intake manifold gasket. Good? Move on. Insert compression tester in plug hole. Pull fuse for fuel injection. Pull coil lead. Get in the car, floor it, and turn the key until the engine turns over 6-8 times. Keep the gas pedal floored - throttle blades must be open. Look at what the compression tester says. 160-200 is good. If it's low, piston rings, head gasket, valvetrain. Good? Move on. Plug everything back up and stick the spark plug back in and connect it to the lead. On the pass side of the intake, find the top vac. port and pull the rubber line off and plug the vacuum gauge to it. Go around and start the car. Watch the needle while the car idles - it should be 15# or so. If it pulses a lot, you have a vacuum leak, hole in piston, bad ring, or a collapsed lifter. Given the #4 misfire and that you never mentioned death-rattles or smoke, if you DO have a leak, its probably at the intake manifold at #4. Get some carb cleaner, start the car, and spray it all around the base of the intake - where it meets the head. If the car stumbles or the RPMs increase, its the gasket. If not - move on. (It still COULD be the inner manifold gasket. The plugs would tell you if this was the case. They'd be oily.) Another common source for a vac leak is around the injectors. Spray the carb cleaner around each injector where it goes into the manifold. If the RPM's are affected, you've found a leak.

Test the injector pulse. A noid light is the only safe way to make sure the injector harness is sending the pulse to fire that injector. Harbor Freight has a set for $40. Hook it up to #4 and start the car. Watch the light and make sure it's stable. Now you've probably done more troubleshooting than any of the mechanics you hired and the only thing you've had to actually wrench on is removing one spark plug.

A quick and easy test you can do is to pull the injector rail and swap injector #4 with injector #2, clear the codes, and see what happens. Pulling the fuel rail sounds hard, but it is stupid easy. My 10 year old daughter could do it. Pull off the home-plate, pull off the 4 bolts, disconnect the rubber line to the fuel pressure regulator, and slowly pry it up - moving around to different points on the rail as you go. Once it is free of the intake, go ahead and turn the key on to run, but do not try to start it. This will pressurize the rail. Let it sit for a few minutes with the key on. Then look at each injector for leaking. Leaks? Bad injector. Replace it. No leaks? Move on. Turn the key off. Disconnect the rubber line to the round canister at the back of the rail. Fuel coming out? Bad regulator. Replace it. No fuel? Move on. Disconnect the leads to the injectors. Get a few rags to catch the fuel that will dump out of the rail when you pull the injector. Pry off the tabs of the injector clips. Pull the injector out of the rail. Swap over to the front most spot (#2). Install is the reverse of removal. I use water on the o-rings to facilitate them sliding back into the intake. Clear the codes and start the car. If P0302 comes up, it's the injector. If P0304 comes back, it's either ignition, injector pulse, or mechanical failure of something in #4

Ideally, you would replace all of the o-rings when you take the injectors out, but for a quick test it is not necessary. If you really wanted to earn your wrenching stripes, you could service all 8 injectors yourself. The kit for this is $30 and you'd probably have an hour into the job if you were taking beer breaks. I did this over my lunchbreak in my parking garage at work. And I had to wear nice clothes to work...

Any mechanic worth their salt would have conducted every single test I mentioned here because it would have caught 99% of misfire culprits in about 2 hours. Max.

 

[Z09B4U]

There are several in car tests for fuel injectors.

Scope the voltage waveform. Scope the current waveform. If one or more injectors has a different pattern than the others find out why.

Pulse each injector and record the fuel pressure drop. If one or more injectors has a different pressure than the others find out why.

Do a balance test on the injectors. Disconnect each injector and compare the change in RPM.
Do a balance test on the ignition. Disconnect each spark plug and compare the change in RPM.

Old cars and test equipment made balance tests easier. Newer PCMs also help. I have read that Ehack has it for the OBD1.

Injector cleaning and testing is a mechanical issue. In car testing can find injector flaws that simple flow testing could miss.

 

[grandpas wagon]

Crank position sensor is on the front of the engine. On a 1996, the CPS does not affect the running of the engine at all. It is only there to sense misfires and report them.

You did get an LT1 OBD2 code reader, right? Anyone that owns one of these LT powered cars needs to have a good code reader. Even if you're not going to do the wrenching, it'll save you from being rooked by shady mechanics who like to load up the parts cannon and blast away. Once you get one, do the tests I mentioned earlier. The logs will really go a long way towards helping you find what's going on. Sans a reader, there are a few things you can do on your own for under $50 and some time. At the LEAST, you need a way to clear the codes to properly test. Go to Autozone and rent a vacuum gauge, and a compression tester. Since this is isolated to #4, it's probably not fuel pressure related.

Your next step needs to be getting the car home and out of that rip-off artist's shop. You can get the injectors - brand new - for $500 all day long. You can score a set of reconditioned injectors on the 'bay for $200 or less with minimal effort. Pulling the fuel rail and replacing the injectors is a 15 minute job. But you have a lot of bridges to cross before you get to 'injector replacement' time.

Getting to the opti leads on that side of the opti is a pain in the ass otherwise I'd suggest moving some leads around to see if it follows the plug lead. You can buy a cheap spark tester for $15 and make sure that cylinder is getting good spark. Good spark? Move on. Pull the plug out and look at it. Oily? Rings, valve seals, or intake manifold gasket. Good? Move on. Insert compression tester in plug hole. Pull fuse for fuel injection. Pull coil lead. Get in the car, floor it, and turn the key until the engine turns over 6-8 times. Keep the gas pedal floored - throttle blades must be open. Look at what the compression tester says. 160-200 is good. If it's low, piston rings, head gasket, valvetrain. Good? Move on. Plug everything back up and stick the spark plug back in and connect it to the lead. On the pass side of the intake, find the top vac. port and pull the rubber line off and plug the vacuum gauge to it. Go around and start the car. Watch the needle while the car idles - it should be 15# or so. If it pulses a lot, you have a vacuum leak, hole in piston, bad ring, or a collapsed lifter. Given the #4 misfire and that you never mentioned death-rattles or smoke, if you DO have a leak, its probably at the intake manifold at #4. Get some carb cleaner, start the car, and spray it all around the base of the intake - where it meets the head. If the car stumbles or the RPMs increase, its the gasket. If not - move on. (It still COULD be the inner manifold gasket. The plugs would tell you if this was the case. They'd be oily.) Another common source for a vac leak is around the injectors. Spray the carb cleaner around each injector where it goes into the manifold. If the RPM's are affected, you've found a leak.

Test the injector pulse. A noid light is the only safe way to make sure the injector harness is sending the pulse to fire that injector. Harbor Freight has a set for $40. Hook it up to #4 and start the car. Watch the light and make sure it's stable. Now you've probably done more troubleshooting than any of the mechanics you hired and the only thing you've had to actually wrench on is removing one spark plug.

A quick and easy test you can do is to pull the injector rail and swap injector #4 with injector #2, clear the codes, and see what happens. Pulling the fuel rail sounds hard, but it is stupid easy. My 10 year old daughter could do it. Pull off the home-plate, pull off the 4 bolts, disconnect the rubber line to the fuel pressure regulator, and slowly pry it up - moving around to different points on the rail as you go. Once it is free of the intake, go ahead and turn the key on to run, but do not try to start it. This will pressurize the rail. Let it sit for a few minutes with the key on. Then look at each injector for leaking. Leaks? Bad injector. Replace it. No leaks? Move on. Turn the key off. Disconnect the rubber line to the round canister at the back of the rail. Fuel coming out? Bad regulator. Replace it. No fuel? Move on. Disconnect the leads to the injectors. Get a few rags to catch the fuel that will dump out of the rail when you pull the injector. Pry off the tabs of the injector clips. Pull the injector out of the rail. Swap over to the front most spot (#2). Install is the reverse of removal. I use water on the o-rings to facilitate them sliding back into the intake. Clear the codes and start the car. If P0302 comes up, it's the injector. If P0304 comes back, it's either ignition, injector pulse, or mechanical failure of something in #4

Ideally, you would replace all of the o-rings when you take the injectors out, but for a quick test it is not necessary. If you really wanted to earn your wrenching stripes, you could service all 8 injectors yourself. The kit for this is $30 and you'd probably have an hour into the job if you were taking beer breaks. I did this over my lunchbreak in my parking garage at work. And I had to wear nice clothes to work...

Any mechanic worth their salt would have conducted every single test I mentioned here because it would have caught 99% of misfire culprits in about 2 hours. Max.

Ain't going to happen.

There are 2 types of people - those who do their own work and those who hire help. Nothing wrong with that......... it is what it is.

The key is knowing when to decide, and making a good decision on who does the work.

 

[_E_]

Ain't going to happen.

There are 2 types of people - those who do their own work and those who hire help. Nothing wrong with that......... it is what it is.

The key is knowing when to decide, and making a good decision on who does the work.

My bluetooth adapter is here, and my car is back from mechanic #2. He didn't charge me for the diagnosis, which is quite a blessing.

The degree to which I am able to learn as I go (with the help of this forum and YouTube) is yet to be seen. One thing's for sure: there are some in this thread who have offered a great deal of wisdom. @atlantadan really knocked it out of the park and I'm sure there will be other readers, beyond just me, who will benefit greatly from the detailed post above. My deepest appreciation goes out to the knowledgeable members in this forum. I might need more of it soon. @grandpas wagon thanks for offering what you can to the thread as well.

 

[vegas_ss]

You may want to reach out to any local Impala SS groups in the area as they may be able to lend you a hand.

 

[_E_]

I have taken sensor readings on two separate occasions. On 7/25 I drove the car up the block about 300 yards before pulling over. On 7/28 I just started up the car cold. There is a notable variance for Bank 2 LTFT between the two readings.

Does the attached table help to paint a picture in any sort of way?

 

[BALLSS]

OP

...regarding the 0300 or 0304 codes

300 means general misfire which can be just about anything. 0304 means cyl 4

Driving any car with a significant fuel smell can be DEADLY serious if raw fuel is in fact leaking somewhere on engine

Prolonged start can be a faulty fuel pressure regulator. after you shut off the car unplug the rubber vacuum elbow on the FPR. If any sign of raw fuel it is bad.

I would send the injectors to Cruzin Performance for service as previously suggested. Rich there knows his stuff

Replacing injectors is not a hard job but if you are not a wrench guy you may be forced to pay.

A service manual should give you a step by step and simple hand tools are all that is needed

You will need a fuel line disconnect tool to actually remove the fuel rail with injectors on it but you could leave the fuel lines connected and just lean over the fender swapping the injectors. For me it would be easer to remove the fuel rail with FPR and injectors and just fix that on the bench and then reinstall. The fuel lines just snap back on. No tool need to re-connect them, just to remove them

There is a Schrader valve (just like a tire air valve) on the end of fuel rail next to FPR. With a rag over it press it to purge the fuel pressure before removing injectors or fuel lines

If your plug wires are original they have to be replaced. Tedious job but doable

A OBD2 scanner. Fuel Pressure Gauge for Schrader valve attachment, IR temp gun, Factory Service or Hanyes Manual are a must at a minimum if you want to do work or self diagnose stuff

If you do have your original opti, keep it. It may need to be cleaned and a new cap & rotor but the Mitsubishi sensor is what is irreplaceable now

 

[BALLSS]

Bank 2, is where cyl 4 is and if that injector is leaking than the fuel trims will be elevated as they are on that bank

Its always much better to scan codes and engine function at full operating temp. The data you show says the car is still in open loop because its still cold

That should not affect the variance in STFT though

While its a lot of work you could swap injector #4 to another cylinder and see if the code migrates to that cyl. If you moved it to the cyl next to 4, 6, and the code came back 0306 you would know its the injector

IMHO I would just send the injectors to Cruzin for service if they have never been serviced and have over 100+k mi on them and buy a new FPR.

It takes about a week for the service as you mail the injectors to Cruzin, they service them, and mail them back. Overnight service could be done for more $ but depending on if Rich can do the service the day he gets the injectors, IDK

 

[_E_]

OP

...regarding the 0300 or 0304 codes

300 means general misfire which can be just about anything. 0304 means cyl 4

Driving any car with a significant fuel smell can be DEADLY serious if raw fuel is in fact leaking somewhere on engine

Prolonged start can be a faulty fuel pressure regulator. after you shut off the car unplug the rubber vacuum elbow on the FPR. If any sign of raw fuel it is bad.

I would send the injectors to Cruzin Performance for service as previously suggested. Rich there knows his stuff

Replacing injectors is not a hard job but if you are not a wrench guy you may be forced to pay.

A service manual should give you a step by step and simple hand tools are all that is needed

You will need a fuel line disconnect tool to actually remove the fuel rail with injectors on it but you could leave the fuel lines connected and just lean over the fender swapping the injectors. For me it would be easer to remove the fuel rail with FPR and injectors and just fix that on the bench and then reinstall. The fuel lines just snap back on. No tool need to re-connect them, just to remove them

There is a Schrader valve (just like a tire air valve) on the end of fuel rail next to FPR. With a rag over it press it to purge the fuel pressure before removing injectors or fuel lines

If your plug wires are original they have to be replaced. Tedious job but doable

A OBD2 scanner. Fuel Pressure Gauge for Schrader valve attachment, IR temp gun, Factory Service or Hanyes Manual are a must at a minimum if you want to do work or self diagnose stuff

If you do have your original opti, keep it. It may need to be cleaned and a new cap & rotor but the Mitsubishi sensor is what is irreplaceable now

I do have the "core" from my original opti. I presume this is the opti without the harness(?)

Bank 2, is where cyl 4 is and if that injector is leaking than the fuel trims will be elevated as they are on that bank

Its always much better to scan codes and engine function at full operating temp. The data you show says the car is still in open loop because its still cold

That should not affect the variance in STFT though

While its a lot of work you could swap injector #4 to another cylinder and see if the code migrates to that cyl. If you moved it to the cyl next to 4, 6, and the code came back 0306 you would know its the injector

IMHO I would just send the injectors to Cruzin for service if they have never been serviced and have over 100+k mi on them and buy a new FPR.

It takes about a week for the service as you mail the injectors to Cruzin, they service them, and mail them back. Overnight service could be done for more $ but depending on if Rich can do the service the day he gets the injectors, IDK

I have just driven the car for a few minutes before taking a reading at idle. There are some noteworthy differences in the values as compared to previous readings. Does today's reading provide any insight? The first image is just today's reading. The second is all three days'.

 

[atlantadan]

Idle/cold logs are pretty much useless here. Your third log is good, but you need to show more data. Post a log of hot idle, normal driving, and then WOT. Looking at what you posted, bank 1 looks pretty good. Bank 2 is a mess. The car is dumping fuel into bank 2 because it sees it as lean. Lean means there is more 02 in the mix than there should be. In your case, a lot more. It's maxing it out at 25%. Get a vacuum gauge as I mentioned earlier and see what you see. Your MAP readings are weird.... Is that program reading vacuum or pressure? It should be producing kpa not psi

 

[jayoldschool]

Any exhaust leaks on bank 2?

 

[BALLSS]

Any exhaust leaks on bank 2?

^^^...

 

[atlantadan]

Any exhaust leaks on bank 2?

An exhaust leak wouldn't cause a cylinder-specific miss. Looking at the MAP reading, if is is actually PsiG - its really low, which when coupled with the lean reading would indicate a vacuum leak. Its also why I suggested a log with a WOT pull. If it is an intake leak, most times they will go away under WOT because of the low vacuum associated. The trims would straighten out. But we don't really know what that MAP reading is all about, and we don't have MAP voltage to decode. The MAF looks a bit low as well. With my somewhat lopey cam, I see 8.6 g/sec at idle. He's showing 7.4 in closed loop on a stock engine. I also see 42-45 kpa on the MAP which loosely translates to 6-6.5 psi. A stocker should be seeing more than I am.

A vacuum gauge would go a long way towards erasing a vac leak as the source of the miss