Called FIC last Monday, Bosch III's delivered Wednesday, installed Sunday, car has new life. Had intermittent rough idle, surging, occasional stall, two injectors reading < 10 ohms, all others within spec. What a difference.

 

 

I didn't have those issues. Jon found a collapsed filter and several of the injectors were not at the same level. After cleaning and fixing the collapsed basket, all the injectors were firing at the same pattern and volume.

Moral of the story is this. Just because you can't feel the difference doesn't mean that there isn't a difference. Injectors go out gradually over time so a good test and clean is in order every couple of years. I don't believe in "cleaner in a can". I have better things to spend my money on besides snake oils. Strippers and hookers come to mind.

 

the flip side is, if you can't feel, smell, taste, or measure the difference, does it matter?

ordered my injectors Monday. I would be very surprised if I can notice any difference -simply because my 91 runs like new, best I can "feel." if mileage stays the same I will be tickled.
let's face a simple reality: we see what we want to see and expect to see.

 

That is why I prefer to rely on sensors and tests. I don't rely on how I feel about something because it is too subjective. I could not feel the difference but it can be measured. On my diesel car, the mileage did go up by 1.5 mpg after cleaning but that was after 100K of driving.

That was why I changed my wife's perfectly good ATV to one with FI. So there are sensors and you don't have to rely on how a carburetor adjustment feels. Maybe it's me. Maybe I feel more comfortable with getting readouts and asking around if I have to when it comes to making sense of it as opposed to doing something by my highly inaccurate senses.

 

Will strippers and hookers make my car run better? I'm putting my FSM for sale on ebay and taking your advice from now on.

 

It makes me run better, that is my story and I am sticking to it.

 

Your 91' may be one of the few early C4's that won't benefit, but I'd be surprised if you didn't notice a difference. The simple reality of we see what we...etc is a huge moneymaker for many consumables, but our early C4 ran like a dog and after we put the FIC injectors in, it had considerably more 'umph' to it, that's for sure! You could also hit higher RPM's than before. It'd run out at 3.8k if you were lucky and now it's pulling hard to 4,300 rpm. Yeah and we have a late C4 too, so I'm not just focusing on one vehicle and perceiving whether it's better or not.

 

for FIC and Jon

 

I mentioned somewhere that I'm being proactive, for the next owner, a grandaughter.

I don't know the previous history of the car. The three previous owners were two legged squirrels; not one note in the owner manual maint log, though lots of new parts on it.

Possibly the injectors have been replaced, but it runs same today as when I got it in '07, no start issues, no stumbles, etc. It is quiet, until you tromp it, and then you know it's a Corvette. Without question, I am not the average Corvette driver, either.

I will be objective about it, and will let you know, F22.

Thanks for the comments.
joe

 

F22: I received the injectors 6/28, Bosch III, got started on it at my slow pace that evening. Got the plenum and the stuff on the front off. I removed the coolant lines from TB, as both had been leaking at one time, maybe, wanted to change and/or shellac.

The Rochester multecs were evidently installed perhaps before 80,000mi, since previous owner had not done it, so 25,000 mi or more.

The job is time consumeing, very little tech details. But after about 15 vac lines, elec plugs, fuel lines, and all the stuff that was possibly touched in 6-8 hrs of thrashing, I actually believed the car would run fine. I did use a simple checklist, followng the Haynes, more or less, replaced seals in rail, also fuel lines (The 2 are not included in the kit.).

I had primed it for leaks, but it required about 10 secs of cranking before it fired, then ran "normal" for the 15 min warm up. I reckon I'm just lucky. Have built many engines, 'from hot tank to drag strip,' but that was carbs, 40 yrs ago!

As I said before, if it was the same as before changing, I would be happy. Have put about 20 miles on it, mostly in this small city, did get to an open stretch for a 50 to 100 test, and it was "maybe" stronger towards 5,000 rpm. Under 65 it was no discernable difference, which is great -most of my driving is below 3000.

So- my expectatins were met, and possible exceeded. Plus, I now know some recent history of the car.

regards, jc

 

Good deal and thanks for status'ng us back on what you experienced. Yeah, under 3K, you're not going to notice a lot off difference, but as you've experienced, it's 4K and above, where the new injectors really make a difference. And as we all know, pulling the plenum on an L98 ain't never a picnic!

 

Back to the subject, where do you get the strippers?

 

If I had to pull the runners again. I'd probably replace the torx bolts with allen bolts. Then get some ball end allen sockets. It's real easy to tear up the torx threads having to hit them at an angle.

 

I hear you! GM could have changed the inside 2 to cap bolts, so you can get a wrench on them. One of mine was never tightened, or had come loose, which shows that you maybe don't need it to begin with.

I pulled up the harness bundles on the valve covers, used a thin diameter extension to clear the v cover. Also careful not to over torque. All of the bolts were "loose" by specs.

jc

 

if that is to me, it was someone else who posted that. i thought it was some sort of Corvette language, or a brand name.

jc

 

Try the Accel Superram if you want a good time. It was a ROYAL PITA until you figured out that you can send the bolts from above.

 

last year i got me a set from john boschIII 24lb, and to be honest my dash gasmilage showed extra 3 or 4 miles per gallon!! but then i installed hooker long tube headers, and they had the housing for the O2 sensor on tube#7, and when i installed the wide band on the car to try to tune it myself( which is not easy as i thought) i found that once my car goes to the closed loob, it leans out all the way even when im cruising!!! and i thought that since i had 24 lb it should be rich instead of lean, so i asked a mecanic, and when he looked at the O2 sensor, he said that i need to move it to the colector of the tubes, we did that, and i end up switching to a heated O2 becuse it was kind of far of the hot spot and the car was staying on open loop, and when i posted what happened with me here, some memebers said that they have their O2 on#7 with no problems and i might have a leaky injector, my injectors were like 4 months old that time so i didnt consider that, today i hooked a gauge to check out my fuel pressure, and i saw that after i shut down the car it goes down from 46 to 40 withen 30 sec and to 30 after like after2 min!! and to 10 after like 20 min!! does that mean i have a leaky injector, and it could# 7???

 

Supposedly the Bosch III injectors have a finer spray and can cause the car to run lean. That is why I had my Bosch II injectors serviced. If I replaced them with Bosch III injectors, I'd have to retune for optimum performance.

Your other issue is that headers tend to make the exhaust more efficient and as such, it isn't as hot and the O2 sensor will go into closed loop, fall out, go back in, etc, etc. A heated O2 will help.

You could be having a weak FPR spring. Hard to say if it is leaking or not. What you want to do is find the return line and clamp it off. Pressurize it. If it falls off, then the injectors might be leaking. Slim chance but it is possible. If it holds pressure, it MIGHT be the FPR but that also is hard for me to say since I haven't had a stock FPR and mine do NOT hold pressure for any length of time. You can test the FPR by taking the vacuum hose off and running the car to simulate WOT and see what the pressure is doing.

Try putting ideas in different paragraphs since that makes it easier to read. Thanx

 

Thanks aklim for the quick response, well I just replace the dyfrum in my FPR yesterday for a new one from Autozone, and my FPR is not stock either it's bbk adjustable FPR, well I have 24 lb injectors and now that I have the O2 sensor mounted in the Colector is running rich on open loop and wot but on closed loop the O2 sensor corects it into 14 to 16:1 and the blm is like 116 so I know it's running rich because of 24 lb injectors and needs to be tuned