Misfire. Please help me get to the bottom of this.

[mmvic]

Ever since around the time I reinstalled the stock injectors Ive had a misfire. I'd think the logical thing to do is remove the injectors and get them flow tested. But why am I not getting any check engine lights from the faulty injector?
I see on the forum the most common reason for a miss is spark related (plugs,wires,cap). But if I checked all the plugs and they all look the same, would'nt that tell me everything is ok? I brought it to a mechanic and he told me it was the middle cylinder on the passenger side. And he also told me that it had nothing to do with the plugs or wires. And I'm not sure about his reasoning. He also checked the compression and said that was fine. He said its either the injector or something in the head. I don't want to believe its in the head, especially after reading Tookys write up on installing vortecs. Too many hours for me!
After all this I am back to my original question, Why no codes for faulty injectors? I just pulled the injectors out and started second guessing my reasoning for starting this project b/c of not having any codes. The injectors are out now so I might as well get them tested, and since I have some room in my engine bay should I replace my plugs, wires, and cap? Even thou the mechanic told me they were ok. I just need some confirmation on my logic and what to do. So let me have it, all opinions, questions, comments, and constructive critsizms are welcome.

 

[dalwine250]

Re: Misfire. Please help me get to the bottom of this.

more info. when does it miss ?all the time?mods ?i would start with a complete ignition tune-up including the module.i dont think a bad inj will throw a code unless the o2 reads too lean or rich,i could be wrong.i chased a miss for 2 years,ended up being a lower intake gasket.ya never know .
dave

 

[NecroWolf]

Re: Misfire. Please help me get to the bottom of this.

do a leak down and check for a burnt valve?

 

[mmvic]

Re: Misfire. Please help me get to the bottom of this.

It misses all the time. The only time I dont feel it is at WOT. The truck is stock, once I can fix this and find out why I loose coolant I'd like to modify. Speeking of me loosing coolant, could I have a leak in my head gasket next to where the cylinder isnt firing?

 

[dalwine250]

Re: Misfire. Please help me get to the bottom of this.

try spraying carb cleaner along the intake to head gasket,with the engine running.if it falls on its face......intake gasket.dont think its the head gasket,that would preasureize the cooling system

 

[mmvic]

Re: Misfire. Please help me get to the bottom of this.

cool, will do when back together. Do you think its the injector?

 

[dalwine250]

Re: Misfire. Please help me get to the bottom of this.

well,its just a quick & ez test to see if the intake gasket has failed.mine was bad around an intake port and coolant passage.i'm not sure this is your problem but it will tell you if it is.
dave

 

[Don W.]

Re: Misfire. Please help me get to the bottom of this.

I had exactly those symptoms. And it was the middle cyl on the pas side. After much head scratching and throwing parts at the thing I pulled the lower intake and the gasket was bad. Take another look at that middle plug, comparing it to its mates on that side. I'll bet it's a bit different. My gasket was bad on the bottom so spraying carb cleaner had no effect. Good idea though. I you really think it's an inj just swap that one with another.

One other idea is to take it to a good well equipped shop and just pay them to put a scope on it.

 

[mmvic]

Re: Misfire. Please help me get to the bottom of this.

Ok heres the history of my truck leading up to this point. Hopefully all this will help with an answer.
The first shop I brought it to did a compression test for me. They also used a scope to look at the cylinders. They told me everything was ok. At the time my truck was running fine, I just wanted a professional to look at it because I had a kboom chip in it and 40lb injectors. It was running really rich b/c of that setup. So the shop gave me the same advice you guys all did which was put it back to stock and see how it runs.
So after I got it back I went to work(let me add this was my first ever mechanical project I ever attempted, but it seamed to go smoothly). Put the stock chip and injectors in.(The injectors have been sitting in a bag for years that the previous owner gave me, didnt read up enough to know that I should have done a flow test first). After I was back together I ran some top end cleaner throu it to clean up all the carbon build up caused from the kb setup that ran extremly rich. I replaced the plugs and changed the oil after that.
When I first drove the truck it seemed to run fine until.... It started Not turning off. So once that happened I didnt know what to do, I had a thread about it but I couldnt figure it out. Didnt drive it for about 2 months. Went to a mechanic I knew and told him my problem so he told me to bring it to him the next day. Drove it over and went to show him how it wouldnt turn off and it turned right off. he didnt know what to do or what it was. So I started driving it again. Thats when I noticed the miss. I brought it back to him and hes the one that told me it was the middle passange cylinder, also told me it probably the injector or head. He just said that not know THIS much about the truck.
DAVEP6999 you mentioned intake leak. Should I have replaced the gasket when I pulled the upper manifold? Is that a possibality? I'll check the spark plugs next. And I think the compression is still ok, dont know thou. Thats for the advice keep it comming.
And DON W how much more work is it to remove the lower intake so I can check it out. Can a novice tackle that? Thanks for all the replys everyone Im going to get back in the garage asap.

 

[Don W.]

Re: Misfire. Please help me get to the bottom of this.

If you've had the upper intake and injs out then the lower is not much more work. I would see if you can get that mech you know to help (buy his dinner or something) because the reassembly can be tricky for a first timer. Requires radiator drain, proper application of the correct silicone (to prevent oil leaks) and dist removal which, of course, requires re-timing.

If you haven't done the injs yet then I'd try that first. You might have a stuck one or something.

Here's the link on when I did mine.

Just don't drop anything...

http://www.syty.net/forums/showthread.php?t=50844&highlight=intake

 

[mmvic]

Re: Misfire. Please help me get to the bottom of this.

Today I checked the three spark plugs on the passanger side and they all looked the same. I mean the color is really close even the middle one which was the suspected bad one. The only difference in the plugs is the gap. I gapped all the plugs at .35, and now the two outer plugs gaps are at .40? I'm sure I gapped them all the same. I havent checked the driver side plugs yet, hopefully I can get to it tomorrow.

Does this happen for a reason ? or did I just miss gauge them, and would this have anything to do with my misfire?

 

[2fast4u]

Re: Misfire. Please help me get to the bottom of this.

Today I checked the three spark plugs on the passanger side and they all looked the same. I mean the color is really close even the middle one which was the suspected bad one. The only difference in the plugs is the gap. I gapped all the plugs at .35, and now the two outer plugs gaps are at .40? I'm sure I gapped them all the same. I havent checked the driver side plugs yet, hopefully I can get to it tomorrow.

Does this happen for a reason ? or did I just miss gauge them, and would this have anything to do with my misfire?

Thats eerie, I had 2 plugs do the same exact thing... Wow :roll:

 

[mmvic]

Re: Misfire. Please help me get to the bottom of this.

did you have a misfire?

 

[supersports10]

Re: Misfire. Please help me get to the bottom of this.

check the plug wires for restistance with an ohm meter.

im willing to bet you have a bad wire on that one...reason.......

outer 2 plugs are "worn" from being used.

center plug isn't worn nearly as much because it isn't being used, or fired as often.

replace at least that plug and wire.

best bet would be to go full tune-up and CHECK THE NEW PLUG WIRES WITH AN OHM METER!

get taylors from hood (sytyguy) cheap like 39.99
also get a set of ngk's while your at it.

EDIT: do not i repeat not buy msd plug wires... they melt way to quickly, and HATE heat.

they will self destruct on the turbo side within 1000 miles.:tdown:

 

[mmvic]

Re: Misfire. Please help me get to the bottom of this.

thanks dude. will do

 

[2fast4u]

Re: Misfire. Please help me get to the bottom of this.

did you have a misfire?

Actually, i do have a misfire... im going to replace wires first...then the distributor, if no change. But here's the funny thing.. Sometimes it runs like a swiss watch. My Typhoon is like a woman...i swear!! :rant:

 

[mmvic]

: Misfire ---Update--

: Misfire ---Update--

Finally got around to taking off the lower intake and found the problem. Just like suggested by dalwine250 the gasket right over the middle intake was blown out. This weekend im working on removing the gasket completely and reinstalling the lower intake, install my new msd ready to run distributer and taylor wires.

In the past couple months I've been working slowly on alot(for me). Installed a walbro 225 hi flow(after some broken cladding,I think its good), sent out a set of 50lb injectors to get flowed and cleaned, sent my turbo and chip to waller performance, building an A2A kit thanks to epixs thread, deleting my abs and relocating a new battery to that location. hopefully when I'm done Everything works right and get some good numbers. I am also going to be a first time datamaster user thanks to Tookys website. Thanks for all the help guys! I will try to get some before and after pics when complete.

 

[Tooky]

Re: Misfire. Please help me get to the bottom of this.

LOL! Get this, I was just searching this thread minutes earlier to solve my own misfire problem, and it hadn't been updated since 2007. I clicked New Posts and suddenly you JUST made a new post, AND mentioned my name - is that weird or what???

Glad to hear you found the source of your problem!

Anyhow, if your lower intake has the crappy stock black overspray, consider cleaning and/or painting it while you have it out!! It will look SOOOo much better - one of the best things I ever did to clean up my truck!

PS: Glad you like the site.