Ian0611

iTrader: (41)

Hey guys, I have an issue that I was hoping some of you could give me your opinnion on. My car drives fine and there doesn't appear to be any hesitation even at WOT, but it seems to misfire a little when it's sitting at idle. It's especially noticeable after I've been running the car hard such as after a tuning session or a few runs at the track.

1.) Any ideas what could be causing this?
2.) How concerned should I be?

I just threw in some new Iridium plugs and I'm running a Spoolin Up COP kit that's only a few months old, so I'm ruling those things out for now. Could it be an injector? Could it be caused by a bad lifter? I have one that's kinda noisy after cold starts but I don't usually hear it after the cars been running for a few minutes. Let me know your thoughts. Thanks!!

UPDATE Monday 8/8/11- Well I got the turbo swap done and all of the gaskets changed out but didn't really notice a difference at first. However, while I was working on retuning the boost I noticed that I had set my WGDC below 2K to 110 for some reason, so for no apparent reason I decided to set it back to 100 and afterwards the hiccups/misfires were almost completely gone.

Fast forward to today (Wed. 8/10/11)- Filled the car up at a different gas station out of town, started the car up, and right away it started idling really funny and misfiring. However, the misfiring this time was much more noticeable than it ever was before. I let it idle for a minute or two and recorded some logs of it since I happen to have my laptop with me. I noticed that the fuel trims seemed to be jumping around a lot more than normal and the idle was bouncing around too. I decided to go ahead and drive it anyway and once I started driving it seemed to drive fine. The next time I came to a stop the car idled like it did before I filled up and has been idling fine ever since.

So I have two questions:
1.) Why would the WGDC be affecting the idle when it's set above 100?
2.) What would cause the car to idle funny after filling up? I'm thinking maybe I need to check the fuel filter or one of the injectors is going bad. Thoughts?

Update 8/22/11

About a week or two ago I started smelling fuel when I would go WOT, leading me to believe I had a leaky fuel injector. I was also thinking that this might be what's causing the idle misfire so went ahead and put in some FIC 1050s this weekend that I got used from another forum memeber a while ago. When I pulled the injectors out Saturday night the plastic tip on one of them was actually broken and a piece was missing. Obviously this worried me, but at the same time I was at least happy that I thought I found my problem. Well I finally got things somewhat put back together this morning (BTW- To anyone that attempts an injector install- make sure you take off the black spacers that the fuel rail bolts run through. If they fall off, it's not fun trying to find them). Anyway, so I fired the car up this morning and the misfire and idle is now worse than before. One thing that I noticed is that it seems to run pretty smooth when the AFRs are below 13 but above that it gets progressively worse as the AFRs get leaner. I noticed the same thing before the injector swap but with the stock injectors it would idle smoothly if the AFRs were below 14. So if anyone has any input please let me know. Thanks!

Update 9/2/11

So here I am almost two weeks later basically right back where I started. Tonight I pulled out my stock fuel rail, stock FPR, and the FIC 1050s and threw in another stock rail and FPR along with some stock injectors. The end result is that I'm right back where I started. I can still hear and feel a small hiccup/msifire in the idle but it's not nearly as bad as it was with the 1050s so I'm going to stick with the stock injectors for now. After working on this issue almost every night for nearly two weeks here's what I've learned:

1. Even though one of the stock injectors had a broken tip, that was not the problem.

2. I now know how to install injectors but switching to larger injectors (FIC 1050s) made the problem worse and much more noticeable.

3. I now know how to disable and block off the EGR but that also did not fix the problem.

4. Putting in a different stock fuel rail and FPR did not fix the problem.

5. I could not find any vaccuum or boost leaks that were causing the problem.

6. Even though the idle was worse with the 1050s, in daily driving the car actually drove better with the 1050s than it did with the stock injectors. The car would go rich and nearly die when coming to a stop sometimes with the stock injectors. That problem went away after installing the 1050s. (Probably a tuning issue)

7. Tuning for larger injectors was a lot easier than I thought it would be.
I'll be sure to update the thread if and when I find a solution to the problem but at this point I'm done messing with it for at least a few days.

nightwalker

vacuum leak, ignition coil, coolant leak into combustion chamber, leaky injector, worn cams, jumped timing belt, burnt valve, carbon deposits, bad pistons rings and bad fuel.

Ian0611

iTrader: (41)

Thanks for the suggestions. Guess I have a lot of trouble shooting to do. Here's my initial thoughts:

• Vacuum leak- Always possible but I just did a BLT so I don't think so
• Ignition Coil- Shouldn't be an issue with the Spoolin Up COP
• Coolant Leak in Combustion Chamber- Possible but i hope not. What would I look for? Coolant in the oil?
• Leaky injector- Possible. Stock injectors with about 85K on them and they are a little noisy
• Worn cam- Doubtful. Car still makes decent power for my mods (330whp/320wtq) roughly. I would think the power would be way down if this were the problem.
• Jumped timing belt- Doubtful
• Burnt Valve- Hope not
• Carbon Deposits- Maybe. On what??
• Bad piston rings- Possible. Do a compression test??
• Bad Fuel- Possible. I have been filling up at a different station the last month or two but I've always used Mobil 93oct. I've noticed this problem off/on for a while but it seems like it has gotten worse as of late. I'll run this tank down low and go back to the other station I usually use. I work at an airport as a supervisor so I know how much fuel qaulity can differ from one place to the next based on their qaulity control practices.

Ian0611

iTrader: (41)

Bump for more input

JakeTheVIII

iTrader: (35)

Are those plugs supposed to be gapped? Or are they supposed to come gapped correctly? I think you would check your piston rings with a leak down test rather than a compression, or both. I doubt that's the issue though. I had a timing belt jump and caused misfire, then when the car warmed up it wouldn't start back up.

dastallion951

must be the curse of the bbys, hahah, me personally kinda in the same boat...well to rule out carbon buildup you can either seafoam your engine or get one of those fuel injection system cleaners, that you run through the vacuum lines with the car idling, as far as coolant leak into combustion chamber highly unlikely unless your oil and or coolant are contaminating each other,in which case there is a testing kit you drop in the radiator and will change color if oil is present in coolant. just because you boost leak tested it doesnt mean u vacuum tested it, vacuum leak is with vacuum lines and doesnt show bad on a boost leak test...check all your vacuum lines. As far as leaky injectors go, spray some engine start around the intake mani area, and listen for the vehicle increase rpms, if it does then you have a vacuum leak somewhere around there. Do you have a wideband on your car? If so is it spiking rich or lean at idle?? that will also help diagnosin your issue.... check what ive recommended then report back.

barneyb

You might try, before the next time you fuel up, dumping in a can of injector cleaner. This fixed a car I used to have that had a bad idle miss. Only do this once as the chemicals are harsh.

Ian0611

iTrader: (41)

Thanks guys for all the suggestions! I'll start with the cheaper solutions first and then work my way up. Tonight I filled up from a different Mobil station but unfortunately I wasn't able to get my hands on any fuel system cleaner before I did. I'll see if I notice a difference over the next week or so with just the change in gas stations. I'll try to check for vacuum leaks and I'll check the coolant and oil this weekend. If none of that works, I'll try some Seafoam or another fuel system cleaner and see what happens. Next step after that will be a leakdown and/or compression test. Thanks again guys for your input!!

alicea8541

iTrader: (32)

Mine had been doing that recently. Kept getting a P0300 random misfire CEL. My battery was going bad and I didn't know it until it had to be jumped 3 times one day. Replaced battery and now no more P0300.

Ian0611

iTrader: (41)

No CELs. I tried filling up from a different gas station this week but there doesn't seem to be much difference. My next step is going to be to dump in some fuel system cleaner the next time I fill up. It will probably be another week or so before i do that though because I only live about 10 minutes from work. I'll keep you guys posted and thanks again for the suggestions.

94AWDcoupe

iTrader: (125)

what size/brand injectors do you have? a poorly matched set of injectors is very common. injectors are usually well matched at 80% but at 2% the same well matched set can be horribly matched at idle flow.

Ian0611

iTrader: (41)

They're stock injectors with about 85K on them

dastallion951

so im curious there Ian why do you have all those mods, yet no injectors or fuel pump...???

Ian0611

iTrader: (41)

I have a Walbro 255 in the car now. I also have some FIC 1050s sitting in the basement but I'm still debating on whether or not I'm going to install them. Kinda wanna go E85 but I want to make sure I have all the bugs worked out first... I'm also trying to become the bolt-on King

Ian0611

iTrader: (41)

Well I've been driving on this tank of gas from a different station for over a week now and I haven't really noticed any changes. I'll probably fill up again in the next day or two and I have a bottle of fuel system cleaner I'm going to dump in.

Also, I forgot to mention before that I do have a leak on the gasket on my O2 housing but I've patched it two different times and it didn't seem to make a difference. One other thing perhaps worth noting is that my AFRs seem to bouce around a bit (from 14.5 to 15.2) when sitting at idle and at cruise. Not sure if that is normal or not. I have noticed though that whenever i feel the misfire/hiccup in the idle, the AFRs always jump a little bit leaner. Tonight, for example, I was sitting around 14.8-14.9 at idle and then it jumped to 15.1-15.2 whenever I'd felt the misfire/hiccup and I would feel this every 3-5 seconds. Maybe I should just take a video.. lol