N* Injectors?
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Dual intake valves does not necessitate dual injectors.
The ONLY engine I have ever heard of using dual injectors was the LT5, and that was done for a specific reason. They effectively shut off half of the intake valves (and injectors) for better low RPM torque and for a torque reduction function.
The LT5 doesn't even use dual injector drivers. Each injector driver runs two injectors.
Then you haven't heard of the 3.4L DOHC, it used them. I am pretty sure the N* used them also. GM's cost reduction.
What is the stock #/hr of the 96-99 N*? Jason, anything in the FSM on the injector spray pattern?
I may have to dig up my books and show pictures of it. GM seemed pretty concerned that mechanics would put the wrong injectors in the 3.4L DOHC (this was written before the N* existed in production). The injectors LOOK alike, but spray very different.
What is the stock #/hr of the 96-99 N*? Jason, anything in the FSM on the injector spray pattern?
I may have to dig up my books and show pictures of it. GM seemed pretty concerned that mechanics would put the wrong injectors in the 3.4L DOHC (this was written before the N* existed in production). The injectors LOOK alike, but spray very different.
Please do.
I've tested northstar injectors and didn't notice anything peculiar about them or their spray pattern. There are plenty of people with 3.4L DOHC's and northstars running non-stock injectors with no problems. (myself included)
As I understand it, injection events are timed to hit the back of a closed valve so that the heat helps vaporise the fuel. In fact the 3.4L DOHC was batch fire until 1994, which meant all of the injectors were activated at the same time. At best 2 intake ports were open at one time, which meant the other 4 were not.
Yes, and it appears that your supposition that they are "split spray" injectors may be correct, at least for some years, according to my '97 FSM. Regarding the fuel injectors, it states (in part):
The director plate has holes that control the fuel flow, generating a dual conical spray pattern of finely atomized fuel at the injector outlet. Fuel from the outlet is directed at both intake valves, causing it to become further vaporized before entering the combustion chamber.
It also provides a relatively poor resolution diagram of a "typical" fuel injector (no information about the spray pattern can be discerned from it).
Sorry, I missed that, ok, so 24's should be fine.
I have a few random 19's, might try to troubleshoot. But will probably get the right one, he doesn't want to replace all (my recommendation is to replace all, but this is a beater car, it is a very worn 96 Deville, not a slick daily driver)
I have a few random 19's, might try to troubleshoot. But will probably get the right one, he doesn't want to replace all (my recommendation is to replace all, but this is a beater car, it is a very worn 96 Deville, not a slick daily driver)
Right now I see the LTFT +3.9%ish on one side and -11% on the other. Looks injectorish to me. I swapped the coils around to see if the miss (only on 1 cyl, so I am not expecting a change) moves from #7 to something else. If coil, I expect to be #7 and its partner waste spark cyl.
whoa whoa whoa
first of all you need to read your O2 sensors and both upstream sensors need to range below 200mv and above 800mv if not your going to get wierd fuel trims.
Also look at short term and long term as together they sohould ad up to no more or less than 5 percent.
now you need to verifiy if you have exhaust/intake leaks sucking in air causing the banks to be out of spec.
A small air leak will give you bad problems.
why are we giving the injector a bad rap?
Also can you get to the injector plug and pull it to verify its dead.
Also if its pulling 11% fuel out that means its possibly leaking and this would be rediliy checkable if you pull the fuel rail and turn the key on and see if you have drips coming from one of the injectors.
Also if you are getting a long term what is the short term as the long term can be reset if you remove te battery terminal then redrive the car to reset the long term.
NEVER repair from long term trims. Also if it has a misfire double check the WHOLE ignition system.
shot gun aproach isnt gonna fix any car unless your rich.
If one injector is bad replace it and see what happens.
BUT the 3.9 is ok and th e -11 means its trying to pull fuel out not add more. This is indicative of a leaker and this should be very easily found, as in pull the plugs on the bank running the minus eleven long term.
BUT honestly whatch the short terms.
Trust me .
Also please try resetting the fuel trims, either with a scan tool or pull the negative battery cable with the key off.
THEN drive it and watch short terms and long terms and remeber 5% plus or minus.
Lee Abel
first of all you need to read your O2 sensors and both upstream sensors need to range below 200mv and above 800mv if not your going to get wierd fuel trims.
Also look at short term and long term as together they sohould ad up to no more or less than 5 percent.
now you need to verifiy if you have exhaust/intake leaks sucking in air causing the banks to be out of spec.
A small air leak will give you bad problems.
why are we giving the injector a bad rap?
Also can you get to the injector plug and pull it to verify its dead.
Also if its pulling 11% fuel out that means its possibly leaking and this would be rediliy checkable if you pull the fuel rail and turn the key on and see if you have drips coming from one of the injectors.
Also if you are getting a long term what is the short term as the long term can be reset if you remove te battery terminal then redrive the car to reset the long term.
NEVER repair from long term trims. Also if it has a misfire double check the WHOLE ignition system.
shot gun aproach isnt gonna fix any car unless your rich.
If one injector is bad replace it and see what happens.
BUT the 3.9 is ok and th e -11 means its trying to pull fuel out not add more. This is indicative of a leaker and this should be very easily found, as in pull the plugs on the bank running the minus eleven long term.
BUT honestly whatch the short terms.
Trust me .
Also please try resetting the fuel trims, either with a scan tool or pull the negative battery cable with the key off.
THEN drive it and watch short terms and long terms and remeber 5% plus or minus.
Lee Abel
If you have followed any of my threads, you know well I don't shotgun any troubleshooting. Component level electronic parts replacement is my job, even to TS-16949 (the new QS-9000) FAI (Failure Analysis Investigation). I want to see only one bad part on my bench when I am done. Which is why I get soooooo ticked off at these garden variety mechanics working for shops and dealerships that send you a $1000 bill for 3 bad parts. When only 1 is bad, but they use your money to troubleshoot what they don't understand. It is my soap box..... Not saying all mechanics are bad, but too many for me, so I do my own work because of it. I can't afford to throw $$ into a garbage can just for the sake of a clueless mechanic. If you put a part on that doesn't fix it, take it back off. PERIOD. You have NO right to charge the customer for it and lie about it being bad when that part didn't fix the problem. How many BILLIONS of $$ each year are wasted by customers to take their cars to shops and get multple parts replaced for 1 bad part, when they replaced lots of good ones because they didn't troubleshoot properly or take the time to do it right and pull the parts back off that weren't bad. RARELY, I MEAN RARELY do multiple parts ever go bad. Like the planets probably line up more often. I have seen it 2x on my 76 Olds, and never did get an answer, but I was able to prove it did it, but it baffled me (fuel pump went out, took out ignition module, years later, float died in carb, took out ignition module... I suspect early design and electrical surge from trying to crank it or jump it). (Getting off soap box, you don't want me going on and on...)
1. Yes, pulling #7 injector connector yields no difference in idle speed or power, it misses just the same. I have been leaning towards #7 injector for a while, but I really want to do the officially power balance test, can it be done with a 96 N* with the climate control display?
2. Swapping coil around data I should have today, but #7 is missing, #6 is not (the partner waste spark cyl). I swapped the positions of #6 and #7, no change. I didn't expect any, but simple to do.
3. If I am having a bad plug (they are new, but I didn't put them in) or wire, I would expect 2 cyls to miss, not 1 due to the nature of waste spark.
4. Looking at the BLM's, or LTFT if you call it that, (I am old school, BLM is what I use) they are split, and assuming that GM wouldn't ship them split that much, there must be a reason. GM typicallys shoots for lean over rich in the BLM range (you run the injector constant a bit over what the injector is and it runs towards the edge of lean, or positive LTFT/BLM). Being #6 and #7 are on different banks, it shows me more that it isn't an ignition problem. For giggles and grins, I moved the #6/#7 coil to the next one over and wired accordingly and still have miss, but I haven't been near the car to read the codes.
5. Reseting fuel trims won't accomplish anything, it will learn it back in seconds, or learn it right.
6. Questions I have:
1. Does this have dual cats? If one was plugged, I would get rich O2's. I can see that, but I cannot accept it would miss on #7 only. I keep fighting the owner of the car to go replace them, you can't just keep throwing money at a problem to make it go away unless you have unlimited resources.
2. I personally have never seen a leaking injector, but looking how this car was treated, I wouldn't say no, it is rough. GM did the fuel rail recently, and didn't seem to indicate anything at all, so the mech either didn't volunteer any info if he saw something wrong or there was nothing to see. Probably a R&R job and get it out the door, it took them about 1hr tops.
3. Which bank is which? Front/Back = Bank1/Bank2? I agree, time to pull the plugs back out and look. What is preferred gap? He said he set it, but again, I haven't looked at them personally. I worry when I don't do the work that is was don't right.
Fuel trims DO get balanced once you punch it (PE mode), but it doesn't take long once you get out of PE mode that they go back to -11%/3%. 11% is quite a bit in my book, I don't let my LT1 get that far out ever.
The injector ohms good, as do the wires and coils.
1. Yes, pulling #7 injector connector yields no difference in idle speed or power, it misses just the same. I have been leaning towards #7 injector for a while, but I really want to do the officially power balance test, can it be done with a 96 N* with the climate control display?
2. Swapping coil around data I should have today, but #7 is missing, #6 is not (the partner waste spark cyl). I swapped the positions of #6 and #7, no change. I didn't expect any, but simple to do.
3. If I am having a bad plug (they are new, but I didn't put them in) or wire, I would expect 2 cyls to miss, not 1 due to the nature of waste spark.
4. Looking at the BLM's, or LTFT if you call it that, (I am old school, BLM is what I use) they are split, and assuming that GM wouldn't ship them split that much, there must be a reason. GM typicallys shoots for lean over rich in the BLM range (you run the injector constant a bit over what the injector is and it runs towards the edge of lean, or positive LTFT/BLM). Being #6 and #7 are on different banks, it shows me more that it isn't an ignition problem. For giggles and grins, I moved the #6/#7 coil to the next one over and wired accordingly and still have miss, but I haven't been near the car to read the codes.
5. Reseting fuel trims won't accomplish anything, it will learn it back in seconds, or learn it right.
6. Questions I have:
1. Does this have dual cats? If one was plugged, I would get rich O2's. I can see that, but I cannot accept it would miss on #7 only. I keep fighting the owner of the car to go replace them, you can't just keep throwing money at a problem to make it go away unless you have unlimited resources.
2. I personally have never seen a leaking injector, but looking how this car was treated, I wouldn't say no, it is rough. GM did the fuel rail recently, and didn't seem to indicate anything at all, so the mech either didn't volunteer any info if he saw something wrong or there was nothing to see. Probably a R&R job and get it out the door, it took them about 1hr tops.
3. Which bank is which? Front/Back = Bank1/Bank2? I agree, time to pull the plugs back out and look. What is preferred gap? He said he set it, but again, I haven't looked at them personally. I worry when I don't do the work that is was don't right.
Fuel trims DO get balanced once you punch it (PE mode), but it doesn't take long once you get out of PE mode that they go back to -11%/3%. 11% is quite a bit in my book, I don't let my LT1 get that far out ever.
The injector ohms good, as do the wires and coils.
You need to call me.
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You say they are new plugs. What kind?
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It has just one cat
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Fuel trim at 15% is within normal running conditions. It was not when the car was new. It has to do with are FUEL.
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Both side should be within 5% max as a rule of thumb.
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If you have no driveabilty issue and they are both at 7%. You refuel and they go to -10% this would be normal.
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Bank 1 on a GM has always been the bank with #1 cylinder.
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Did the car have any other work done to it other than the spark plug?
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You are correct to look at fuel trim. That would be a more advance way to Diagnose it and I use it all the time. Some people that call me for advice ask me what does fuel trim have to do with a miss.
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I remember back in the early 90's when + or - 5 was a lot on fuel trim.
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CALL ME
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You say they are new plugs. What kind?
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It has just one cat
.
Fuel trim at 15% is within normal running conditions. It was not when the car was new. It has to do with are FUEL.
.
Both side should be within 5% max as a rule of thumb.
.
If you have no driveabilty issue and they are both at 7%. You refuel and they go to -10% this would be normal.
.
Bank 1 on a GM has always been the bank with #1 cylinder.
.
Did the car have any other work done to it other than the spark plug?
.
You are correct to look at fuel trim. That would be a more advance way to Diagnose it and I use it all the time. Some people that call me for advice ask me what does fuel trim have to do with a miss.
.
I remember back in the early 90's when + or - 5 was a lot on fuel trim.
.
CALL ME
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