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phil53chevy

Engine rebuild and P1539 and P1324

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Not 15 minutes any more. Within 5. Interesting, when I sprayed flammable gas, misfires moved to cylinders ,4,5,6. I am thinking vac leak also.

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I sucked all old fuel out of tank prior to rebuild. Then 3/4 tank new premium and sea foam. Just filled up and techron after new filter but old filter was terrible.

Idle pick up with carb cleaner seems very suspect

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I should have been more clear on the orings -supposed to be replaced everytime injector replaced .

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I would be surprised if I had vac leak at manifold to head or at intake runners. However, the injectors o rings,

With 100k on them , being reused, seem suspect.

Now, what's the easy way to pull injectors ?

Kind of tight in there and then the clips are impossible!!

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Sorry to hear that another problem has cropped up. Just curious did you confirm that the plunger for the bank 2 was different than for bank1?

The old trick of spraying carb cleaner seems to indicate a vacuum leak, and there are lots of vacuum lines, boots, etc. that can leak.

Given how bad the fuel filter was I think it is a good idea to check the injectors and replace those o-rings. I am trying to remember if you can turn off an injector With the Durametric, that can help to diagnose problems with injectors.

I hope the manuals, etc. are helpful.

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If the misfires move that might be a good sign towards vac leak or something affecting both sides.

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Thanks Doug. My plunger was upside down compared to the one you sent me. Oops. The idle should NOT increase because I sprayed flammable gas on intake. Vac leak seems logical and The o rings are old and installed twice.

Can you get the injectors off easily ? Not that I have ,figured out without.....dropping engine for the third time though I'm getting faster : )

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Manuals very helpful. Not sure if plunger is different from bank 1. Did not take bank 1 variocam off.

I will replace all injectors o rings and post results

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Good idea. Bad injector orings can be an intake leak.

Bad or under sized injectors can also cause a problem.

Dont forget to lube the orings.

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Oh, sorry injectors are a PITA to replace with engine in car... (read probably darn close to impossible without dismantling the entire intake) ask me how I know....

Here's how low I had to bring mine (and a little lower would not have hurt)

IMG_4863.JPG

Oh and did I mention here's a good reason to replace old injectors (notice the crack?) BTW these were professionally cleaned with new orings... bad idea! Should have just replaced them from the beginning like I did with everything else. Cutting corners just adds time and headache and money. THis is what I found when I removed the injectors after just a few hours on the rebuild motor...

IMG_4865.JPG

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LOL mike. More like 13 year old brittle heat cycled plastic... of course the new white injectors dont have these plastic parts, they are all one piece.

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Sorry no offense -- just adding to my -- gee what would do that :-)

My 951 FI's are a pain to get them to seat properly.

Mike

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A Mighty Vac is a hand held vacum pump with vacum gauge .Really simplifies testing control valves and hoses .

Although your injectors may be suspect It's hard to believe that three would be bad on one bank only .It would seem that something else is contributing to the misfires with a time (heat ) dependency .

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It sounds like you're having mises on both banks. I never had misses with mine but I certainly had very poor running with the old blue injectors and I didn't run the engine very long at all like this. They were not sized correctly for the larger cylinders (not to mention Porsche very quickly replaced the orig blue ones with the green ones (better spray pattern) before moving to the white ones shortly thereafter). And even still a replacement came later for the white injectors...

This is a guessing game and just spending your money for you without your fuel trims, and without verifying you don't have any air intake leaks using a smoke machine but....

I would think with the right size injectors and fresh injector orings that prevent air intake leaks around the injector ports you can safely tick those off the list. Old injector orings that don't seal = an air intake leak.

I didnt take the chance with my rebuild and replaced every single seal and oring on the engine. Didn't skip any of those, including with my old injectors when I had installed them, they even got new orings. Of course, even though they were sealed well, they were still not sized correctly and the injector time was higher than it should be as I verified with Durametric.

Air intake leak or too small fuel injectors or both they are both going to show up as the DME adding more fuel and the engine is going to run like crap when it is running LEAN.

Edited by logray

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I have two sets of ~350 cc/min injectors from Carrera S 3.8L if that is any help. They don't have the plastic green portion. I bought them to diagnose a misfire but didn't need them.

Edited by 987_RDC

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I missed the fact that the miss moved to the other bank when sprayed with flamable stuff .A good candidate would be the pipe from the throttle body to the AOS .It can be tricky to seat properly and not too hard to crack .If it were an injeftor or even an intake manifold leak I don't think it would affect the other bank .In what area were you spraying when it moved to Bank 2 ?

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Why not bring it to a shop that has a smoke machine to check for leaks? That way, you address all the leaks in one shot if there are more than one.

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I'm hoping you put in new plugs too?

I would guess random misfires on both banks could be due to manifold leak or injectors or fuel delivery problem or all three.

Sure other stuff is possible but it sounds like you sorted most of the mechanical stuff out already, and have new rings, new pistons & cylinders, and the timing is good.

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yes, everything new, plugs, coils,

I have two sets of ~350 cc/min injectors from Carrera S 3.8L if that is any help. They don't have the plastic green portion. I bought them to diagnose a misfire but didn't need them.

thanks 987-RDC- can anyone tell me if they will fit my 996 engine. If so, I'd like to try them...after I pull the engine for the third time. Really not worth the time and effort to fish around on your back with the mirror/ mag light approach to install almost anything that is not on the top of the engine. Doesnt work as its just too tight to see in there. Yes, new everyrthing, plugs,coils, etc..EXCEPT injectors and o rings. Also, I am starting to think I don't have the injectors "clipped on" properly or seated as number 1 cyl., which I can see, was not all the way down in the receiving "hole" and I installed all of them the same.

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I missed the fact that the miss moved to the other bank when sprayed with flamable stuff .A good candidate would be the pipe from the throttle body to the AOS .It can be tricky to seat properly and not too hard to crack .If it were an injeftor or even an intake manifold leak I don't think it would affect the other bank .In what area were you spraying when it moved to Bank 2 ?

I cleard ecu after the flam gas spray. I sprayed at the base of the intake around the injectors on 1-3 and then 4-6. all bank one misfire and then cyl 4. another reason I think the injectors are not seated. They should should "suck" on the intake side ( read vac leak) and "push" on the fuel rail side. I could also see a portion of the yellow o ring "guide " taht is after the o-ring on cyl one, whic I pushed in and reinstalled the clip. can't get to the others obviousley without dropping engine.

Any one have a pic of a properly installed injector and clip? thanks.

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Why not bring it to a shop that has a smoke machine to check for leaks? That way, you address all the leaks in one shot if there are more than one.

yep. gonna try the new injectors, which from what i am reading are too small, and new o-rings. If I still get misfires then the smoke machine seems the best approcah.

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Just to be sure might not be a bad idea to check the fuel pressure .Based on Lograys experience the injectors are probably a good idea .Did you replace the AOS as part of the rebuild ?

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+1 to checking fuel pressure and for quantity. The harbor freight A/C manifold kit works perfectly for both functions and is cheap.

When you say you got misses when spraying around the FI area, did you install new orings and gaskets for the intake riser and manifold? Did you use the correct torque and new micro encapsulated bolts on the manifold and risers?

+1 to dropping the engine to do the injectors. The problem with doing it from the top and removing all the intake is you risk introducing more intake leaks! (been there done that when I did an AOS, not fun).

thanks 987-RDC- can anyone tell me if they will fit my 996 engine. If so, I'd like to try them...

I believe any of the M96/97 injectors are backwards compatible. I think I remember reading the newest ones available on engines up until they switched to DFI will work, however I can't recall my sources. I also remember rt.org member 1999porsche911 who used injectors that were not porsche specified (read HIGH flow), and his car ran fine, although I think he was also running a few pounds of boost. ;) FWIW, I'm running one generation below the latest (they are white colored) and they work perfectly. I think the only difference between those and the 3.8L ones are flow rate. The white ones are the injectors designated for the 3.6L and my TRA are quite steady around 0.97 for both banks.

Any one have a pic of a properly installed injector and clip? thanks.

The new design is slightly different than the original. The 996 MK1 clips will not line up to the new style injectors without modification to them. When I installed mine I thought that it was important to retain the clip to "hold them in place", however I later saw an engine where this wasn't done and they were just "floating" for lack of better term (but they were all installed at the same depth). Well they actually would not float if they are seated. What I believe is important is that they are all installed the same way (either all the way down or all the way up, and they are fully seated), dont forget to lube the orings, I used tire sealant IIRC. Mine are all the way 'up' and clipped in as you see in the pic below, and I've seen them installed all the way down with the clip just used as a "spacer" without any modifications. Both engines perform flawlessly.

As you can see I dremeled small slots above the existing slots so that they would fit around the injector and the flange on the rail. Edit: and forgot to mention the new injectors don't have those fiddly plastic guides to worry about.

IMG_4866.JPG

Edited by logray

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