I just grabbed some Bosch injectors off a Lincoln from the yard... No problem really, but something caught my interest... The tips that go into the engine have this little seemingly plastic cover/shield on them. Now uhh...maybe I'm behind the lighthouse on plastic technology...but PLASTIC....in the combustion chamber? :eek: How does it not melt? lol

The plastic is not in the combustion chamber, it's in intake, or the head ports on some cars. Plus with the incoming air cooling it, it's not like it's going to melt!
The intake manifolds on the 95-up Northstars are plastic! No problems with those melting! :)

Yeah... spark plugs go in combustion chamber, injectors go in intake manifold... stay in a realitivly cool area....

The Bosch injectors are a nice upgrade :).

The Bosch injectors are a nice upgrade :).

Are they? I bought a set for my 4.9 but haven't put them in yet. Does it run smoother or get better mileage?

Oh ok...I just thought the fuel had to have a clear enough path to the chamber that the heat would get to it.

Too early for me to say about the injectors. Little amusing story with mine though... Finished installing them, and took it for a spin...started off great, but once it shifted it was like a 4 banger and wouldn't go up to 70 mpg when off the throttle... Drove it back with many foul words racing through my mind, as changing injectors is not hard, but it's not something I like doing twice when I just paid 50 bucks and have to work tonight lol. Anyway, turned out I forgot to hook the TV cable back up--PHEW!

I'm hoping that I will no longer have the classic gas gauge discrepancy (mine's 1.5 gallons off)...and thus better mileage... Time will tell.

I'm hoping that I will no longer have the classic gas gauge discrepancy (mine's 1.5 gallons off)...and thus better mileage... Time will tell.

My gas discrepency is more like 3 gallons or more at fill up! :eek: But the car runs great with 130k on it, so I don't know what's up with it! :bigroll: So hopefully the new injectors will take care of the leakage I assume mine have.

Are they? I bought a set for my 4.9 but haven't put them in yet. Does it run smoother or get better mileage?

The greatly helped the rough idle issue of the 4.9.

It idles more smooth.

Seems more peppy.

mileage... is *supposed* to go up, but my car has been quirky with milage the last 2 years... its driving me crazy... then tonight I got 26mpg on an extended highway cruise... exactly what I have been trying to target... I just don't get it.

The Bosch also have a better spary pattern then the stock Nependenso. The stockers were 18lbs, these Bosch, on the Ford were 19.4lbs, but Ford runs their fuel system around 38psi, GM is 42 IIRC... either way, the Bosch injectors in our engines come out to be 22lbs/hr.... nice upgrade.

I think to take full advantage of the upgraded injectors tho, you'll need to work on the intake and exahust. For the intake, either a cold air induction kit, or maybe something like i did... drop in K&N panel air filter and drilled holes in the air box. For exhaust, the stock system is very well designed, but 2 areas of improvement, the cat. conv. If you can get rid of it, go for it... if not, maybe a high-flow cat... really though, it isn't that big of a deal... from what I have been reading though, swapping to an aftermarket high-flow muffler greatly helps power and even mileage.... That is next on my list, the Edelbrock muffler... I think then, I'll finally be able to see the results of alot of the stuff I have been doing, as I think the stock, origanal muffler is holding it back some....

Oh ok...I just thought the fuel had to have a clear enough path to the chamber that the heat would get to it.

Too early for me to say about the injectors. Little amusing story with mine though... Finished installing them, and took it for a spin...started off great, but once it shifted it was like a 4 banger and wouldn't go up to 70 mpg when off the throttle... Drove it back with many foul words racing through my mind, as changing injectors is not hard, but it's not something I like doing twice when I just paid 50 bucks and have to work tonight lol. Anyway, turned out I forgot to hook the TV cable back up--PHEW!

I'm hoping that I will no longer have the classic gas gauge discrepancy (mine's 1.5 gallons off)...and thus better mileage... Time will tell.

The fuel is sprayed out and atomized with air before it even reaches the cylinder..... if you think the fuel has to travel a long time with a modern PFI system... I dunno what you'd think about carbs :).

TV cable eh? Yeah, that would do it.... 4.9 has the electronically shift-controlled tranny.... since I have both, I can honestly say the 4T60E is a better shifting trans... it knows exactly when to shift and to what gear... its great.

When we did my injectors, while they are a direct replacement, they didn't fit perfect... there was a very slight gap on a few.... the fuel rail had to be slightly bent at the boss for a snug fit... I know we used 1/2 of the o-rings from the old injectors, don't remember if it was top or bottom... but one of them wasn't fitting very good with the Ford o-rings, once they were switched it was nice and snug.

Remember once its done to spray some carb cleaner in the little dip where ech injector sits, let it stay there for a few minutes and if it drains down, you know that injector isn't making it a good seal, it can't leak at all... once you did that, spray the injectors again and start the engine, make sure you don't see any little air bubbles come up thru the injector seat... then you know the o-ring is making a good seal and you are good to go.

Remember once its done to spray some carb cleaner in the little dip where ech injector sits, let it stay there for a few minutes and if it drains down, you know that injector isn't making it a good seal, it can't leak at all... once you did that, spray the injectors again and start the engine, make sure you don't see any little air bubbles come up thru the injector seat... then you know the o-ring is making a good seal and you are good to go.

That's a good idea. Mine seemed to fit fine, but I suppose I wouldn't know. But I did a fuel pressure test afterwards, and it seemed to act very similar to the previous injectors...wait, maybe that's bad LOL. I just used the O-rings that were on the Ford injectors. I cleaned them off best I could with isopropyl alcohol, then used petroleum grease on the O-rings. I was afraid to take the bottom O-ring off the Ford anyway because of the aforementioned plastic doohickey. A couple I took out at the yard were cracked, and even if it isn't significant, I didn't want to crack that...(Thus, my injectors actually came like 5 off a Town Car and 3 off a Crown Vic lol).

My mileage has been "quirky" as well, and is also driving me mad...

Before I test it out though, I must fix a gushing power steering leak at my return line... I think I need 2 O-rings that have come up missing...seems to be 3/8"...and of course, Advance Auto has 1/4" and 1/2" :rant2:. That's right, my car is immobile because of a lack of O-rings...

the fuel pressure SHOUDLN'T change.... that is controlled by the fuel pressure regulator and the rest of the fuel system.

But GM runs their fuel system at a higher pressure then Ford.

So the Bosch injectors, when ran to GM spec on pressure, are actually going to flow more then what they did on the Ford, and it comes out to be 22lbs/hr.

The pressure doesn't change when it's running...just bleeds off slowly when I turn the ignition to "ON" and after I turn the car off... It goes noticably slower after I turn the car off, but does eventually bleed down. I still think that's shady...but I don't know what to do. The injectors done, NOT ONE THING in the entire fuel system is original lol.

well....

when the key is turned on, the fuel pump gets primed, and runs to pressurize the fuel system, you can hear it....

then it shuts off, now the only pressure in the fuel system is what is in the lines, the pump isn't feeding it anymore...

so naturally, the pressue will bleed down, but still maintain quite a bit... the fuel pressure when the pump isn't on dosn't matter... I mean, thats like asking what the oil pressure of your engine is when it is off.... it dosn't make a difference.

If the pressure checks out fine when it is running, then you are good to go.

I replaced my fuel pressure regulator today... would have been easy, except to get at the damn bolt that holds the FPR on, the whole fuel rail had to come out....grrr.... well, got to see those orange Bosch injectors quite a bit today....

I replaced my fuel pressure regulator today... would have been easy, except to get at the damn bolt that holds the FPR on, the whole fuel rail had to come out....grrr.... well, got to see those orange Bosch injectors quite a bit today....

No it doesn't...all you need is that GM Tool J-xxxxx...or so my manual says. Has anyone actually seen some of these GM wonder tools? Bastards lol.

so naturally, the pressue will bleed down, but still maintain quite a bit... the fuel pressure when the pump isn't on dosn't matter... I mean, thats like asking what the oil pressure of your engine is when it is off.... it dosn't make a difference.

If the pressure checks out fine when it is running, then you are good to go.


Hmm, well I was just wondering where it goes... How do I know the fuel is bleeding back into the tank or something, and not through the injectors?

Its a Torx T-27 bolt.

There is very limited room under the FPR, I wasn't able to get it any other way.

LOL yes I know...I did the same thing a few days ago. I was being somewhat sarcastic...and wish GM would SHARE some of these miraculous tools they have... These things are done so stupidly... I'm surprised the tools don't have tools...:bigroll: I'd better be quiet...

Well one strike against the injector-fuel gauge theory. I can't say for certain because these aren't new injectors, but I just filled up with "1.5 gallons used," and it took 1.8...didn't take long to start offsetting :bigroll:. Quite sure I will eventually go mad looking for the reason for this...yep...yep I will.

lol, the fuel used is not totally accurate, mine isn't nad bever has been... I didn't change injectors for my fuel used readings to be accurate...

Well that wasn't the ONLY reason lol...but I was hoping it would at least make a difference... Also, I figured it was inaccurate because it's loosing fuel somewhere that the system doesn't acknowledge. I'd heard on here that the discrepancy is usually either FPR or injectors...and it doesn't seem so on mine. I like better and smoother performance, which is hard to tell because right now I have an exhaust leak #*$ER! :-P...but yeah anyway...I just don't want to pay for fuel these days if it's finding ways to make itself scarce in my car.

Ahem...correction, the Bosch injectors seem to have slightly WORSENED my fuel gauge discrepancy! :rant2: The fuel pressure hardly changed though when I tested it....

And...I would not care if the fuel data center were reporting some absurdly high mileage and the actual was normal...but I just filled it... It took 6.8 gallons and I had gone 102 miles...which comes out to 15 mpg.... That's mixed driving, some town, some highway, and I allow the car to warm up... Also, my "in town" is not hustle and bustle city...there are as many places to coast as there are to stop and go. Obviously, this is unacceptable lol.

I'm completely lost as to why though... I've cleaned the engine with GM TEC, oil is fresh and not using any. Cooling is fine...The fuel tank and sender unit were replaced less than a year ago. Fuel filter is good, plugs, wires, cap, rotor, and ignition coil all have been replaced...(perhaps the cleaning fouled the plugs and I should check that?) I cheaped out on Xact plug wires...because the AC Delco ones are IMPOSSIBLE to get off lol...could that have that much of an effect? I'm under the impression that the fuel pump is part of the sender unit, so has also been replaced... Can't see any fuel leakage... I know I've posted this problem before, but it's driving me absolutely insane lol...that, and it might be useful info that it's either not the injectors, or I just happen to get injectors that cause roughly the same problem...:rolleyes:

Does anyone know EXACTLY what the fuel data center uses to calculate the fuel used?

1) fuel pressure is NOT going to change based on different injectors. The flow of the injectors may change, but the pressure in the rail is control by the fuel pressure regulator, so unless you change that with a different spec then factory, or adjustable, the pressure is the same.

2) no need to let the car "warm up" THAT is killing gas mileage....

3) Xact spark plug wires are fine, and would not cause bad gas mileage.

4) My mileage hasn't been great either, I am waiting on 2-3 tankfuls to see how the new FPR is doing... so far it seems to be better... 125 miles on the trip odo and 10 gallons of gas remaining... so I need to see, its the same driving as I was doing before and I used to have to fill up between 190-210... tho I never run it totally empty. Back a couple years ago I would routinely get 260+ miles form a tank... non-steady highway driving... so I gotta see.

From what I understand, the computer calculates mileage by injector pulse width, which is *supposed* to be increidbly accurate system to measure MPG.... I have never seen one close, and I'd say if its off as much as 1 gallon (says you used 8 gallons but it takes 9 to fill) then you are fine....

another thing with the FDC.... when you fill up at the gas station, stop at the first "click" of the pump, don't keep going and going until it spills out... supposedly if you stop at the first click, it should be very accurate... still though, that fuel needs to go thru the injectors, but I dunno, its just what I heard. I know how much its off and it dosn't bother me, none of the computerized systems are correct.

Sorry, when I was talking about the fuel pressure, I didn't mean the pressure while running or what it charges up to with the pump or anything. I meant the bleed-down after the car is shut off, or after the pump primes it. It does bleed down...not fast, but fast enough that I can see the needle moving...in both cases.

The FPR has been replaced as well, did that just before the injectors. If I use a full tank, the discrepancy is closer to 2 gallons than it is to one....and I saw Caddydaddy mentioned his was 3 :bigroll:. My 85 was always within .1 or .2, so I know these things are capable of being accurate. The fact that it's inaccurate alone doesn't bother me.... But the fact that the actual mileage is not what it's supposed to be does :tisk:.

When I fill up, I always stop at the first click...and then there is a delay...and then it overflows and spills a bit onto the ground lol... If that means something...?

I can see how warming the car up would hurt the mileage overall, just sitting there, but I know it improves it when driving. My friend was getting crap mileage, and it turned out to be because of the thermostat sticking open, keeping the engine too cold. Either way, it doesn't explain the computer's confusion over what it has and has not sent...

If it's calculated by injector pulse width...then it would stand to reason that they are spraying more than they should... Maybe injectors, Bosch or otherwise, just won't last at peak efficiency that long? I'd be glad to experiment with that once I feel like I can part with the cash, among other expenditures...

Maybe I wasn't thorough enough in my inspection for a leak...but I can't easily swallow that a leak I missed is doing away with that much fuel. Is there anyway that the ECM could be screwing up and sending more fuel than it thinks? I know this crap goes through the BCM, but not much more. Ah well. I'll live with shady fuel economy if I have to, but a mystery will not do! :annoyed: