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Old 09-17-2009, 03:35 AM   #1
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Default Injector vacuum leak?

Would it be possible for an injector isolator to leak enough to cause a vacuum leak that would cause a slightly rough idle? Ever since I rebuilt my engine, I have had a steady but kind of rough idle. Makes stuff under the dash and in the engine bay buzz and rattle. I have also been able to smell a slight hint of raw fuel. No hoses leaking or anything I can tell. Its coming from under the hood so I thought maybe somehow the injectors are leaking? I can smell it most after the engine is hot and I shut it off. I haven't had to time to pull the fuel rail and check the isolators and o-rings. I have never been able to see any fuel puddling under the manifold, so if it is a leak its slow enough for it to evaporate. Should I look into this, or do you think I should look somewhere else? I can't think of anything else that would cause my idle to be rough other than a vacuum leak. I also think I feel a bit down on power. It feels like its really bogging down at anything under 4,000rpm. Oh, both isolators and o-rings are new as of when I rebuilt it under a year ago. Pretty sure it all got torqued down correctly, so I'm not too sure how it would be leaking. Though I have had bad luck in the past getting those little bastards to seal on RX7's. Pretty much the same isolators if not exactly the same. Sorry for the noobish question, I don't have much time these days and this has been bugging the **** out of me.
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Old 09-17-2009, 11:00 AM   #2
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Vacuum leak at the injectors? Brake Cleaner is your friend. Just spray some around each injector while the car is running and see if anything happens.
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Old 09-17-2009, 12:19 PM   #3
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Fuel odor under the hood also has me thinking evap system. Check the lines to the canister (two on top and one on bottom) and the purge valve, and look over the canister for damage, cracks, etc.

A propane torch is also good for finding vacuum leaks. Obviously don't light it , just turn on the gas flow and run the tip over the areas you think might be leaking. When you're over the leak, the propane will get sucked in and your idle will change.

If you're going to spray brake cleaner around a running engine, make sure to use the non-flammable type. I think the non-chlorinated kind is highly flammable, and the chlorinated type is non-flammable. Read the can.
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Old 09-17-2009, 12:28 PM   #4
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no, use the highly-flammable stuff, im not kidding. The non-flammable stuff doesn't do anything. I've sprayed it straight into my BOV at idle and it doesn't even burp. The highly-flammable break cleaner makes the engine bog and is easier to detect with the slightest drop of it.
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Old 09-17-2009, 12:31 PM   #5
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yeah you need something that will burn, i prefer carb cleaner but anything highly flammable and aerosol propelled should do you
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Old 09-17-2009, 12:37 PM   #6
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Quote:
Originally Posted by NA6C-Guy View Post
Would it be possible for an injector isolator to leak enough to cause a vacuum leak that would cause a slightly rough idle?
Yes
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Old 09-17-2009, 01:19 PM   #7
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I had the same problem the first time I changed injectors, the brake clean works well.
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Old 09-17-2009, 01:42 PM   #8
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I will try it this weekend then. Thanks for the input. I also forgot to mention a drop in fuel economy. I probably only get an average around 20-22mpg right now. I should be getting at least upper 20's. My Evap system is modified. Canister is removed and I bypassed it with a hose or something, I forget exactly what I did, but either way its sealed and not leaking as far as I know.

PS, what about some ether, I have cans and cans of that stuff laying around. Seems like I recall its not good for the engine, but I'm sure in small quantities its OK. Heres to burning myself to death in a horrible accident when it backfires and lights me on fire!
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Old 09-17-2009, 01:47 PM   #9
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Quote:
Originally Posted by NA6C-Guy View Post
Heres to burning myself to death in a horrible accident when it backfires and lights me on fire!
Just make sure you get it all on video with a note on the camera for someone to upload the video to mt.net so we can all be entertained.
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Old 09-17-2009, 01:47 PM   #10
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i had a video on youtube of me shooting the **** into my bov and demonstrating that you wont die to haters over at m.net. too bad i removed it.
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Old 09-17-2009, 02:50 PM   #11
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Quote:
Originally Posted by NA6C-Guy View Post
PS, what about some ether, I have cans and cans of that stuff laying around. Seems like I recall its not good for the engine, but I'm sure in small quantities its OK. Heres to burning myself to death in a horrible accident when it backfires and lights me on fire!
I'd stick with brake cleaner or propane. Ether has been used as a starting fluid (might still be?) so I don't think it would cause any harm to the engine in the small amounts you'd be using.

Quote:
I have cans and cans of that stuff laying around.
Based on this wording, I would advise extreme caution. If you have a fresh can (<1 year) it's no big deal and you can handle it like any other flammable organic solvent. The problem is that in prolonged storage it eventually forms peroxides, an inevitable result of oxidation, and ether peroxides are EXPLOSIVE as opposed to merely flammable. The longer it's been sitting around, the greater the danger. Do you have any idea how old it is? If you see anything crusty or crystalline around the lids/caps that is bad ju-ju. Merely twisting open a bottle cap with peroxides gunked up in the threads can create enough friction to make it go boom. This has been a public service message from your friendly neighborhood scientist.
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Old 09-17-2009, 02:53 PM   #12
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Ues berkebile gum cutter, it works better than anything we've tried. Hell, it's what most NASCAR teams use to search for leaks as well as in a pinch prime the carbs...

Oh, and an injector that is not seated well or has a leak will cause all sorts of vacuum issues... Had this happen to me before.

Cheers,
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Old 09-17-2009, 04:46 PM   #13
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Quote:
Originally Posted by ScottFW View Post
I'd stick with brake cleaner or propane. Ether has been used as a starting fluid (might still be?) so I don't think it would cause any harm to the engine in the small amounts you'd be using.


Based on this wording, I would advise extreme caution. If you have a fresh can (<1 year) it's no big deal and you can handle it like any other flammable organic solvent. The problem is that in prolonged storage it eventually forms peroxides, an inevitable result of oxidation, and ether peroxides are EXPLOSIVE as opposed to merely flammable. The longer it's been sitting around, the greater the danger. Do you have any idea how old it is? If you see anything crusty or crystalline around the lids/caps that is bad ju-ju. Merely twisting open a bottle cap with peroxides gunked up in the threads can create enough friction to make it go boom. This has been a public service message from your friendly neighborhood scientist.
Some of it pretty old Old enough to have the can covered with rust and label barely readable. I won't use them though, they are just there because I am too lazy to dispose of them.

I'll be sure to get it on video... though nothing will happen anyway. I just laughed at the thought of a huge fireball engulfing me and me running around screaming with my arms flapping around.
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Old 09-17-2009, 05:31 PM   #14
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I would just get new injector seals. Napa part # 2-12076. You will need 4 of them as it is a multi-size kit.
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Old 09-17-2009, 10:50 PM   #15
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I have more o-rings than you can shake a stick at, and surely the isolators are still fine since they are pretty beefy.
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