Fuel Imbalance (Left and Right Bank)
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HT4100 4.1, 4.5, 4.9 Discussion, Fuel Imbalance (Left and Right Bank) in Cadillac Engine Technical Discussion; I'm getting a code 046 on my 1990 Cadillac Eldorado with a 4.5 engine. The check engine light came one ...
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    Fuel Imbalance (Left and Right Bank)

    I'm getting a code 046 on my 1990 Cadillac Eldorado with a 4.5 engine. The check engine light came one several days ago and then it went off the next time I drove the car. I reset the codes at that time. The check engine light was intermittent for several days and now it stays on all of the time. I check the codes and it's 046 again.

    Just a few months ago I replaced the entire fuel system including all 8 injectors, fuel pressure regulator, fuel filter and fuel pump. I don't even have 3000 miles on the car since then.
    I have been noticing a huge drop in fuel mileage according to the computer but since I don't usually drive very far very often I haven't really been able to notice a bigger use in fuel just yet. I filled up yesterday and reset the odometer so that I could check it the next time that I fill up.

    I have a few questions about this code. Which bank is which? I get that the side of the engine closer to the front of the car is one and the one closer to the firewall is the other but which is considered left and which is right?

    Another question is that when I replaced the injectors I did so with some Bosch injectors because I was told the OEM injectors didn't last long because the windings fall apart and they weren't very durable.
    Now that I have Bosch injectors would the resistance (ohms) still be the same (between 11.6 and 12.4) as the OEM injectors or would it be different number of ohms?

    Could this be a sensor problem? If so where is the sensor located and how do I check it? Any more ideas of what could be causing this would be greatly appreciated.

    Thanks for any help.

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    Re: Fuel Imbalance (Left and Right Bank)

    Left bank is the one facing you when you open the hood.

    Assuming that the injectors are ok, I would say either spark plugs misfiring(although it would have to be a seriously heavy misfire problem to cause the difference) or a bad or sluggish O2 sensor(yes there are o2 sensor codes but they dont always get set).

    The first thing I would do is go into diagnostics and look at the B/L(block learn) to see which bank is richer and which one is leaner then switch the oxygen sensors from left to right bank and see if the rich/lean banks switch sides on the B/L. A high B/L represents a lean mixture, low B/L is rich. The range is 59 to 255 and ideal value is 128.

    If the banks stay the same after this test then its probably a bad injector on one bank. A stuck-open/leaking injector will drive the B/L down and a stuck-closed/non-functional injector will drive it higher.

    The ideal ohms range for injectors is 12 to 17 so yours are on the low side but probably not a big deal. You should check them when the engine is hot(via the injector harness connector) They will almost always show lower resistance when hot.

    So, the most likely causes of a fuel imbalance are: (in descending order)

    1. Injectors
    2. O2 sensor
    3. heavy misfire

    OH!! I forgot about vacuum leaks! A leak on one bank will tell the O2 sensor that the bank is running lean and as a result the ECM will drive the mixture rich (lowering the B/L)

    There are only 2 places where a vacuum leak could cause a problem on only one side of the engine: Injector port holes, and intake gaskets. A leak anywhere else will affect both banks the same.

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    Re: Fuel Imbalance (Left and Right Bank)

    For the record, ALL GM OBD1 mp fuel injection runs with a B/L scale of 108-160. I think the scale that Sevillian posted is for the regular integrator.

    It's a '90...meaning it includes an A.I.R. system. I've diagnosed this code on a few '90's now and more often than not the problem is in the AIR system, specifically the diverter valve. If the second chamber in the diverter valve leaks (due to getting fried from leaking exhaust check valves), it will direct fresh air into the front exhaust manifold even though it's being commanded to dump to the CAT like it's supposed to. Along with tripping this code, the fresh air in the exhaust manifold plays tricks on the O2 sensor and causes some drivability issues since it makes for a rich running bank.

    the above is likely if you have high B/L numbers on the left bank.

    All of Sevillians suggestions are possibilities as well.

    Anyway, before getting into that, figure out what each bank is doing first. Report back with those Block Learn values and we can move on from there.

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    Re: Fuel Imbalance (Left and Right Bank)

    Yup, I had the B/L ranged mixed up with the integrator range (not that it matters much because you are looking for a difference) and now that I think about it, it may be easier to use the integrator (engine warm at idle in P) in your tests to see what each bank is doing since you wont have to wait for the B/L to adjust values after making a change such as swapping the o2 sensors from left to right. B/L and INT are closely related (do some googling) INT reacts much more quickly to changes than the B/L does. In fact, I believe that the 'idle learn' process includes the B/L self adjusting which takes around 15 minutes or so.

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    Re: Fuel Imbalance (Left and Right Bank)

    Quote Originally Posted by Sevillian273 View Post
    Yup, I had the B/L ranged mixed up with the integrator range (not that it matters much because you are looking for a difference) and now that I think about it, it may be easier to use the integrator (engine warm at idle in P) in your tests to see what each bank is doing since you wont have to wait for the B/L to adjust values after making a change such as swapping the o2 sensors from left to right. B/L and INT are closely related (do some googling) INT reacts much more quickly to changes than the B/L does. In fact, I believe that the 'idle learn' process includes the B/L self adjusting which takes around 15 minutes or so.
    Not necessarily. I respectfully disagree. If the computer is able to do it's job, calculating the B/L properly (which really only takes a minute or two for each cell...the idle learn is 15 minutes long to account for multiple cells using different idle conditions. you can test this by making a change yourself while the engine is running; the B/L will begin to respond within seconds.), the integrator will not be depended on very heavily and should remain near 128 at all times on a properly running engine. The point of the block learn is to get a somewhat accurate estimate as to what the fuel trim should be at a specific load/rpm.

    The integrator is adjusted using O2 signals. The object is to create cross counts across 0.45 volts, cycling between rich and lean constantly. When the INT varies from a 128 average, the B/L is adjusted (therefore B/L adjustment is based on the integrator itself!). That's the goal, to keep the INT at a 128 average. If the computer gets the block learn close enough, the integrator should vary by little. If the integrator needs time to adjust at every cell, it's probably because the B/L is at either limit (108 or 160) and therefore the B/L can't get close enough to optimal trim.

    Using my cars as examples, my '95 has a B/L of around 130-132 for each cell and no matter what I do, the integrator hovers between 126-128 at all times. On my '90, the B/L stays around 122-128 for every cell and the integrator hovers around the same 126-128. The low variance in the integrator means that the computer is doing a good job of calculating the Block Learn and little further "fine tuning" adjustment is needed.

    If the computer needs time to adjust the fuel trim using the integrator and the integrator varies greatly from 128, that means that something is prohibiting the computer from calculating an accurate B/L.

    That said, in the OP's case, if the computer is correctly adjusting for a bank difference with the B/L, the integrator will probably still remain around the correct 128 average on both banks. That is, unless the difference is so bad that it's beyond the B/L's range bounds.

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    Re: Fuel Imbalance (Left and Right Bank)

    Ah, and this reminds me Sevillian, I thought about you a few months ago when working on my '90.

    I had a similar problem as you with a/f mixture problems. I had driveability symptoms with a strangely acting integrator...it continuously dialed back no matter what I did. I soon realized that it was because the B/L was near it's lower limit all the time.

    I also had the DIC mpg and fuel used variances you did. The car thought it was using far less fuel than it did.

    So, somehow the car needed to remove ridiculous amounts of fuel. I thought long and hard and came to the conclusion that a lot of this started when I began playing with injectors (I installed a rebuilt set of 19#'rs). So, on a whim, I pulled out the originals that I still had. I looked up the part number on Delphi's website and found that the '90 4.5 came with 16# injectors...not the 19# that this board assumed. 16# vs 19#..that's a HUGE difference.

    The poundage difference was large enough that the computer had a hard time compensating for all of the extra fuel. The integrator and B/L (and therefore the injector pulse width) were dialed back so much that the car thought it was getting ridiculous mileage/low fuel consumption.

    I ordered an injector rebuilt kit from Mr. Injector, cleaned my injectors by soaking them overnight in a bucket of injector cleaner and blasting them with 60# of air while activating them with a 9V battery.

    When I reinstalled them everything went back to normal and the car runs like a friggin swiss watch. All my power is back like new, the DIC readouts are all correct and the integrator is nearly always at 128.

    So, an FYI for all on the 4.X boards, the 4.5 uses 16# injectors!!!!

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    Re: Fuel Imbalance (Left and Right Bank)

    Holy crap are you kidding me? I searched far and wide for the 4.5's stock flow rate and found nothing. Do you have a link? I did all kinds of testing to find the closest match to oem but was afraid to go with too small of an injector in fear of leaning out at WOT. All the results I came up with are in the DIY injector test bench thread. I have a set of perfect BMW injectors that I believe are around 16# at 43.5psi. (dont have time to get into it now...) If I can get proof that the 4.5 uses such small injectors, I wont hesitate to swap them in!

    LOL, the OP is gonna come back and reads this thread and say f**k it! Getting information off the internet is like taking a drink from a fire hydrant!

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    Re: Fuel Imbalance (Left and Right Bank)

    Quote Originally Posted by Sevillian273 View Post
    Holy crap are you kidding me? I searched far and wide for the 4.5's stock flow rate and found nothing. Do you have a link? I did all kinds of testing to find the closest match to oem but was afraid to go with too small of an injector in fear of leaning out at WOT. All the results I came up with are in the DIY injector test bench thread. I have a set of perfect BMW injectors that I believe are around 16# at 43.5psi. (dont have time to get into it now...) If I can get proof that the 4.5 uses such small injectors, I wont hesitate to swap them in!

    LOL, the OP is gonna come back and reads this thread and say f**k it! Getting information off the internet is like taking a drink from a fire hydrant!
    No problem man. Here you go. This is for the stock injector on a 1990 Eldorado 4.5

    http://go.delphi.com/CS/DPSS/CATALOG...Number=FJ10007

    The part number has been changed multiple times over the years. You can cross-reference to the original if you want. The actual part number stamped on the '90 Multecs for a 4.5 is 5235274. If you want an actual picture, I can snap one. The newest part number for it is the one in the link.

    Otherwise, for further proof, you can go here and search by vehicle and find the injector that way. http://go.delphi.com/cs/welcome.aspx

    EDIT: I felt ambitious and actually somewhat excited that you are still interested in getting that thing to run right. Here's a picture of the part number of the freshened original Multecs back on the car:

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    Re: Fuel Imbalance (Left and Right Bank)

    Outstanding! I cant believe I couldn't find that... Here is the data from the testing I did in April:

    Some things I found out:
    -Not all stock Ford injectors are 19#. That includes the Bosch III's. Some of my sets that are out of ford 5.0 liter engines are actually 18.25lb/hr.

    -This is very handy for looking up the flow rate: http://users.erols.com/srweiss/tableifc.htm

    -Several calculators for determining injector size, etc: http://www.gtsparkplugs.com/InjectorSizeCalc.html

    -Not all injectors are rated using the same pressure. This can really screw with the advertised flow rate. For example, I bought 9 BMW injectors that were advertised at 18#/hr. What I didnt know was that the 18# is at 50.7 psi not the usual 43.5psi(3 bar) so the BMW injectors are actually 16.6lb/hr at 43.5 psi. According to the above calculators they can still support up to 212 hp so I should be safe.

    -I cannot find ANY flow rate data for the original injectors on the 4.5 or 4.9. I cant measure flow rates on this machine like the pros do because for one, I cant get a steady 43.5 psi and two, I didnt want to spring for 8 glass graduated cylinders. But what I can do is compare other injectors to the oem's flow rate.

    -I found that the 19lb and 18.25 lb bosch and denso injectors flow MORE than both the Allante and 4.5L injectors.
    -The Allante injectors flow just a tiny bit more than the regular 4.5L injectors.
    -The BMW injectors(M50, 325i, 525i) flow less than the Allante and 4.5L injectors.
    -So the flow rate for the stock 4.5L injectors is somewhere between 16.7 and 18.24 lb/hr @ 43.5psi
    Looks like the true flow rate roughly coincides with what I found in my testing. That is excellent! With the 19lb bosch III's that I've been running ever since, the B/L is almost always at 108. It looks like the system is at the bleeding edge of its correction limits which would explain why my mileage is 16mpg tops. That's just the best it can do with such large injectors.

    To the OP: Sorry for the thread jack! I'll start my own on the subject when I get a chance.

    Anyways, here is the 'goodwrench approved' way to diagnose E046:




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    Re: Fuel Imbalance (Left and Right Bank)

    Well, you should be able to determine pretty accurately if those BMW injectors flow like the original multecs by using the stock pcm tuning, right? If the B/L stays around 128, they flow just like the multecs. Either way, as long as you know everything else is in order, deviation from 128 to correct for slightly different flow should be fine as long as it's not at the 108 or 160 limit as yours is now.

    When the everything is working correctly and your pcm can finally adjust the block learn accurately, you shouldn't have the wandering integrator anymore. Rather it should sit at 128 nearly all the time.

    I'm glad I was able to help and I'm glad your interest is renewed. Good luck, be sure to let me know how it goes.

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    Re: Fuel Imbalance (Left and Right Bank)

    Well its only a difference of .7lb at 43.5 psi so I will expect to see the B/L go down just a tad but that's fine by me! Back when I made the machine I wasnt working much and had lots of time to tinker and do research. Now all I've got is the weekends to mess around. Anything I do to the car must fit between friday evening and 5am monday morning... Post #6 gave me a eureka moment! It now makes sense why the calculated and displayed mileage differ so much. I never knew that the BL range was so narrow so It never even crossed my mind that the system was maxed out. i always thought the BL could go as low as 59 like the integrator. I pretty much said the hell with it and attributed the poor mileage to my heavy foot. It will be great if I can save some fuel and get her running close to original again.

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    Re: Fuel Imbalance (Left and Right Bank)

    Quote Originally Posted by Sevillian273 View Post
    I never knew that the BL range was so narrow so It never even crossed my mind that the system was maxed out. i always thought the BL could go as low as 59 like the integrator. .
    Yeah sorry...for some reason I always assumed you knew that. I wish I brought that up when you were trying to diagnose. You could have had this solved long ago.

    Anyway, keep that B/L range in mind if you do work on any GM fuel injection...they used the same parameters on everything.

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    Re: Fuel Imbalance (Left and Right Bank)

    Just an update to this, while I was on a roll relaying my discovery, I decided to let the Fuel Injector Connection (where I bought the incorrect 19# injectors) know about the problem. They offered thanks and the opportunity to test out a set of 16lb Bosch injectors in my car before they make a permanent switch.

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    Re: Fuel Imbalance (Left and Right Bank)

    Hey that's awesome. I guess the Delphi site isnt proof enough.. Did you refer this thread to them? The problem for our 90's is that the 4.x PFI interest is dominated by 4.9s. Its funny that for an increase of 27 cubic inches GM added 3lbs/hr to the flow rate. Even the allante 4.5 uses 19lb injectors. Im glad this is finally sorted out because the common assumption for the flow rate of all PFI 4.x engines has been at 18lbs for years. Maybe after you run the 16#'ers you can get a thread sticky'd at the top of the forum to set the records straight once and for all. Im sure there are at least a handfull of 4.5 owners running aftermarket 19# injectors. quins90lac comes to mind - I pretty sure he bought a set from FIC. Whats funny about them is that the car runs pretty good on the 19#ers but just uses a ton of fuel. I bet there are a lot of 'satisfied' 4.5 customers since the 'upgrade' is usually installed after a period of bad driveability problems and on top of that it makes the avg mpg display a high number. Mine currently says 21.6 - far from the truth.

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    Re: Fuel Imbalance (Left and Right Bank)

    Quote Originally Posted by Sevillian273 View Post
    Hey that's awesome. I guess the Delphi site isnt proof enough.. Did you refer this thread to them? The problem for our 90's is that the 4.x PFI interest is dominated by 4.9s. Its funny that for an increase of 27 cubic inches GM added 3lbs/hr to the flow rate. Even the allante 4.5 uses 19lb injectors. Im glad this is finally sorted out because the common assumption for the flow rate of all PFI 4.x engines has been at 18lbs for years. Maybe after you run the 16#'ers you can get a thread sticky'd at the top of the forum to set the records straight once and for all. Im sure there are at least a handfull of 4.5 owners running aftermarket 19# injectors. quins90lac comes to mind - I pretty sure he bought a set from FIC. Whats funny about them is that the car runs pretty good on the 19#ers but just uses a ton of fuel. I bet there are a lot of 'satisfied' 4.5 customers since the 'upgrade' is usually installed after a period of bad driveability problems and on top of that it makes the avg mpg display a high number. Mine currently says 21.6 - far from the truth.
    Yeah, I linked them to this thread. They said they'll send out some 16#'ers free of charge. That's pretty sweet.

    Honestly, mine ran pretty *ok* on the 19# injectors as well. Most of the quirks they caused I'm not sure many people would notice. I noticed because I cared enough I guess. I DID notice some lack of top end power but it ran pretty smooth . The only real driveability problem I had was a strange stutter on throttle tip-in. Just after touching the gas, say after taking off from a stop, the car would stutter for a split second and then take off like normal. When diagnosing I found that the computer had the hardest time compensating for those injectors at idle...that's when the B/L was pinned at 108 and it would take the integrator 1 minute or so to dial back far enough to get the mixture correct.

    Anyway, now that I have 16# injectors in, a world of difference is there and only now that it's right am I realizing how poor it was actually running. And it's not placebo. Idle is so smooth it's like glass and the power is really there like it should be. I forgot how well this car flies for it's low horsepower ratings. This little 4.5 Eldorado feels far faster than any 4.9 powered car I've driven or owned.

    Once I put the Bosch 16# in, maybe we can collaborate by making a thread about how GM fuel injection works, taking some DIC onboard diagnostics pictures and doing a step-by-step explanation...what the parameters are, how the PCM calculates fuel trim, how the parameters are used, what's acceptable and whats not, and finally how to properly use them as a diagnostics tool.

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