MDTAHOE

If it was a intake vac leak it would have to be on cylinder #3 only. The propane would have reacted over that cylinder. The injector could still make noise but not spray correctly. Any fuel treatment that you can buy in the store is not really strong enough to do much of anything. If you want to try fuel treatment you would need to buy something commercial strength like what a shop would use. Go to www.bgfindashop to locate a shop in your area the uses BG products. You would want to buy 44K. However if this is an injector problem you are beyond dumping any cleaner in the tank for a repair. If it is an injector problem then your best shot of fixing it is having a professional fuel injection service done. A high strength cleaner will be used. It will be hooked up at the fuel rail, the cars fuel pump will be disabled and the truck will be run directly off the cleaner. It is not mixed with gas and not passed through any kind of fuel filter/screen. I recommend you use the above web site to find a shop that can do a BG carbon depletion. The can of 44k comes with the service and is put in after the service. Sometimes injectors can not be "fixed" with any cleaner and must be replaced.

MDTAHOE

You need to check compression on cylinder #3. Timing can not cause a SINGLE cylinder misfire. Timing can not be reset by anyone. If ignition timing was out truck would have to have a bad cam or crank sensor, failed computer or incorrect valve timing (jumped t-chain). All of which can be fixed by anyone who could diagnose the problem. Cam and crank correlation can be set by any Snap-On scan tool or equivalent (not a code reader). Timing IS NOT what is wrong with your truck.

coppola7

If it helps, I tried fuel injector cleaner (not commercial strength), it didn't do anything. Not sure how the pepboys service would work.
I was tempted to replace the injector to cyl 3 but decided to stop here. So I'm biting the bullet, made an appt with a mechanic for tuesday. I will post what he tells me.

starcraft1

Hey coppola I hope he finds your problem. Did you listen to the #3 injector to see if its at least clicking? You can do this either by getting a paper towel tube or a stethoscope and listening to the injector while the truck is running. It should make a constant "click, click, click" noise that increases with rpm. The injector could still be clogged but at least you know its not completely shot. Also did you test for a vacuum leak?

I am going to be doing a compression test as soon as get my tester in the mail. If everything checks out on that front I am going to buy a fuel pressure guage and test if I have proper pressure there. If that tests out ok, I think I am going to go get a BG44K service from a local service station (they shut off the fuel pump and run the truck off of the cleaner only, which will clean out the injectors much better then just running the stuff through the gas tank)

Hey MDTAHOE, since there is only a misfire on #3, can the problem be with fuel pressure? My next step is to do a compression test like you said, but if that checks out ok, I want to know if it is worth while to check the fuel pressure. Seems like if there was a fuel pressure problem the misfire would show up on multiple cylinders. I have been reading that this could be the problem but I wanted your expert opinion. Thanks a lot for the help.

MDTAHOE

Fuel pressure will not cause a single cylinder misfire. You need to look at things like ignition (plugs, wires, coils), compression, vac leak over effected cylinder or fuel injector problems.

coppola7

So MDTahoe is right. In my case, all plugs, wires, filters, cap and rotor were replaced. I checked the vac with a gauge. there were no vac leaks. So I bailed at this point and brought it in to a mechanic (one that I trust). Diagnosis:There are 2 bad injectors, one is not firing at all, the other is leaking fuel into the cylender even when the motor is not running. The leaking injector caused a drop in fuel pressure to all the injectors. the excess fuel also overheated the cat and burnt both left O2 sensors (bank1). So all injectors and the 2 sensors need to be replaced. On the 4.3 L the injectors are inside the intake manifold. Manifold needs to be removed to get to them. Hope that helps.

starcraft1

Glad to hear you found your problem cappola, although it sounds pricey. I hope it wasn't too bad.

I have an update on my situation. I did a compression test this evening and I came up with the following numbers .... #1, 160 / #3, 165 / #5, 165 / #7, 152. I only did the drivers side bank because I ran out of light outside. Regardless, I guess this shows that it's not an internal engine problem causing my p0303 code. MDTAHOE, what should be my next move. I checked out the bgfindashop.com like you said and found a close shop willing to do the treatment for $115 (that's the cheapest I could find). Is this what I am supposed to do or is there something I should check first. As a reminder I've done the following:
1) checked the spark plugs, ignition wires, and coils (bought a in line spark plug light just to make sure everything was ok
2) checked for an intake manifold gasket leak
3) cleaned the MAF and throttle body
4) listened with a stethascope to make sure the injectors were firing properly
5) checked the compression

Let me know what you think. Thanks so much for the help

MDTAHOE

$115 seems to cheap you need to ask what chemicals they are using. Ask them how they do it? At work we charge around $200 parts and labor. You may want to have a shop take a look at it. It is possible the injector needs to be replaced. Get a estimate on the injector make sure it is for a oe injector not cheap aftermarket junk. That $115 could be used to towards injector

starcraft1

Well if you think that's the best way out then I can make an appointment with my mechanic. Would I be able to replace the fuel injector on my own though? Doesn't look to be too bad .... I don't believe you have to remove the intake manifold to get to them but I could be wrong. It looks like you can just remove the fuel rail and pull them out. Is there any special tools or special tasks required to do this? I am an avid DIYfer but I'd rather not go screwing something up if you think it should be left to a professional.

If I can do it myself, where would be the best place to buy an injector from?

Ohh and throughout this I have been using the truck as little as possible to prevent anything else from breaking. If it is a random misfire though, and is not running rough or anything, am I causing any damage by driving it around? I kinda need it for work.

Thanks again.

coppola7

My fix is very pricey. About a grand just for parts (all oe), each injector is about $115 . I was told I should replace all the injectors which makes sense if you put the time in to take it apart, it also depends on the miles on the injectors. You need a gasket set for the intake manifold if your set up is the same (injectors inside the intake manifold)plus the injector(s). You could get away with replacing only the bad one and save a bundle, but you could be looking at repeating the procedure in a few months.
Not sure about the chemical injector service though.