Thread: Cylinder 3 misfire Tried everything I can think of

Visually, unless they are broken, you can't really see a bad one. The internals are what fail. If you are going to get used injectors or new ones, I highly recommend having an injection service done. 3M and BG are by far the best products on the market for doing these services.

Hopefully the shop got your problem nailed down and properly diagnosed. To be honest, the price for the work and diag time is pretty reasonable. Diag time at my shop starts at $89.95. Keep in mind a quality shop has some damn expensive equipment that needs to be paid for and every year that equipment costs anywhere from $500 to $1000 per year to update. We gotta pay the bills somehow....lol.

yeah well I had told them I didn't wanna stiff them on the work they did and compromised to bring them in the parts I wanted put on and give them 120 for the trouble went and filed a claim with BP about some bad gas maybe it will pan out and not cost me as much also tipped the guy who was diagnosing the problem 20 bucks for some beer money

Beer tips are always welcome....lmao

Glad you figured out what was wrong. You're lucky the diagnosis was only $60 or whatever... diagnosis with a GM Scanner is $100.

And another thing, you screwed up with what you told them. Here's how it should have went. When they told you such and such part was bad, the cost, you tell them "thank you. I will come pick the car up today and I will definitely be back to get that repaired. Make a note on the receipt of what it is and how much for my records. KTHX."

That way, they aren't all upset that you're cheaping out on them and being a big boy working on your own car. Then it's easy for you to get your car and you don't have to go through their b.s. And thus, hopefully, they treat your car well. I imagine angry mechanics losing $350 job that's really easy aren't gonna treat it like a nice new expensive car.

lol yeah agree brandon .... so three days later of them diagnosing swapping the injectors and coil.....they decided to do a fuel pressure test and low and be hold my pressure is sitting at 30 when I took it for a drive with the gauge on it would spike up to a little over thirty and than just stutter not really going any higher

so guess i'm looking at fuel pumps now

GM 550
Advance Lifetime 330
Advance 1 year 250
like I had said earlier I had seen some 355 venturi and other brands for under 100 didnt really wanna cheap out but looking for some input on what my best route would be here

Order a stock replacement from Wbodystore.com there's lasted me years and I only changed it because I had to upgrade my fuel system.

did you got with the quick change or high volume swiggle? seems like the quick change is what I should aim for but just wanted to make sure the installation is as easy as they make it seem

turns out the W body store is about an hour south of me been trying to contact them about a pickup havn't heard back yet but it seems pretty simple thinking I may go pick up car tomorrow and DIM

I'm debating on whether or not I should check the resistor/relay that switches it from low to high speed to make sure but it seems if the car was priming and idling at 30psi its gotta be the fuel pump. what I had looked showed the stock rating for primed being over 40 .

3 days without my car and 2 injector replacements before they threw the fuel pressure tester on seems a little overboard to me but maybe a bad injector had to be replaced before a fuel pressure test would be accurate....

am I allowed to be slightly upset .

Not going to bad mouth another shop but ya have to throw a fuel pressure gauge on the car to see what you got. You would have to have an extremely F'd up injector to affect fuel pressure. To be honest, I can't recall a time where A injector was required before a fuel pressure test could take place, but thats just me...lol.

Originally Posted by Tony Mendez

Not going to bad mouth another shop but ya have to throw a fuel pressure gauge on the car to see what you got. You would have to have an extremely F'd up injector to affect fuel pressure. To be honest, I can't recall a time where A injector was required before a fuel pressure test could take place, but thats just me...lol.

lol see this is what I was wondering seems like a fuel injector would have to be completely blown out and just leaking gas for it to skew a fuel pressure test

all good now though got the car home and fuel pump visible and ready for replacement comes in tomorrow morning ill letcha guys know if I'm ridin again

And so an update...replaced fuel pump and added hotwire kit...still doing the same thing
feels like the exact same problem but occurs at a little higher rpms now

seems like my fuel pump is stuck in low mode I'm going to try the bypass tomorrow and see if it helps at all

If that is not the problem I am losing fuel pressure (and a portion of sanity) but not loosing any fuel

http://media.photobucket.com/image/r...nmj/relays.jpg

this is what I am going to do if for some reason the vehicle does run fine afterwards it would be the fuel pump resistor I need to replace?

So fuel pressure is back on par priming at around 45 also checked the fuel pressure regulator by disconnecting and watching for a 10psi or so difference and it would have me believe that the fpr is good as well. Stopped at advance to have them check my electric system and make sure I wasnt getting oblong voltage and everything is good as far as alt battery and starter.

Taking it to a dealership to have a buddy there look over it kinda at my wits end here only thing left would be a leak down compression test to check my valves which will be getting done on Thursday if there is anything else I should check lemme know

the misfire is only occurring under load the car will rev fine in neutral or park but under load over 2.5k rpm it will just bog and misfire cylinder 3

You said water is dripping onto your coil oaks? Take all the coil paks off and clean the metal plate underneath. Also go ahead and change the injector 3 boring if you haven't yet. Could just be a leaky oring.

yeah the hood does but the cars been in the garage for about a week now so moisture couldnt really be the issue at this point the coil packs were also replaced and checked as well as the icm. the o-rings were replaced a little before the issues when I did the supercharger replacement.

This couldn't somehow be cause by putting a 97 supercharger on a 98 I had worked around the vac tree by plugging the hole off for it and it seems to give me boost pressure just misfires right around the time it would go to boost or over 2.5k rpm only with a load though if I have it in park and manually throttle it up it goes to 3k-4k no misfires

^^that's not impossible.

Originally Posted by SDGTP99

^^that's not impossible.

It almost seems like an intermittent vac leak that really comes out during a decent load but my idle vac is around 10psi so im not sure if I should do a manual pressure test or what

hopefully the leak down test will show something otherwise Ill go back on the vac leak search

gonna go through some other parameters on scanner if anybody could tell me what my intake manifold pressure and MAF cfm should be reading while idle and driving it would help out

right now at idle I am getting 4-5psi intake manifold pressure and my maf cfm is around 40

4-5 psi seems a little low my boost was reading at -10 to -11 but it seems like my ltft will stay on par until a misfire pop up to 10.4 and than drop back down and level out seems like thats pretty standard though

hmm ok so if I'm getting 4 to 5 psi Intake manifold pressure spiking up to about 14 at half throttle I'm keeping pressure?
my map is in cfm starts at about 40 in idle going up to 350+ at around half throttle

neither reading is froggy when the misfire occurs both seem pretty consistent and realtime to the throttle

-14 @ half throttle? No bueno. That could be a big leak.

^^^wait. Your not supercharged, correct?.Still seems wrong to me...