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low vacuum that doesn't jump up by ryan.hess
Started on: 10-29-2003 07:10 PM
Replies: 12
Last post by: ryan.hess on 10-31-2003 04:21 PM
ryan.hess
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Report this Post10-29-2003 07:10 PM Click Here to See the Profile for ryan.hessClick Here to Email ryan.hessSend a Private Message to ryan.hessDirect Link to This Post
okay... I'm getting a reading of 14" of vacuum at idle. A little low, yes. According to the books, when the throttle is blipped to wide open, and snapped closed, the vacuum should quickly drop to 0 (or nearly), and then jump up to ~3" higher than at idle, then come to rest at it's idle vacuum reading. When I do that, it drops to near zero (as it should), but then takes nearly a second to come back to 14". It never peaks over as it should... I have heard that this could be due to a restricted exhaust, which would explain why it's so quiet... What do you guys think? Oh - and I do not have any intake leaks, and compression is roughly 135 on all 6.
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Report this Post10-29-2003 07:20 PM Click Here to See the Profile for GTDudeClick Here to Email GTDudeDirect Link to This Post
Classic restricted exhaust problem. Take it loose above the cat where the two bolts are with springs. Good luck!

Phil

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87 FIERO GT 2.8 5spd
0-60 in 6.8 seconds!
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ryan.hess
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Report this Post10-29-2003 08:07 PM Click Here to See the Profile for ryan.hessClick Here to Email ryan.hessSend a Private Message to ryan.hessDirect Link to This Post
Will do. How much are exhaust systems running these days?
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ryan.hess
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Report this Post10-30-2003 10:58 AM Click Here to See the Profile for ryan.hessClick Here to Email ryan.hessSend a Private Message to ryan.hessDirect Link to This Post
Oh - and what if it turns out that removing the exhaust doesn't help the problem? What else could it be then?
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ryan.hess
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Report this Post10-30-2003 04:14 PM Click Here to See the Profile for ryan.hessClick Here to Email ryan.hessSend a Private Message to ryan.hessDirect Link to This Post
correction - 12" at idle
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ezramore
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Report this Post10-30-2003 04:21 PM Click Here to See the Profile for ezramoreSend a Private Message to ezramoreDirect Link to This Post
Just had dual exhaust with monza tips put on my 88 about 2 months ago. Cost me 200 with everything. im not running a muffler though.
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Report this Post10-30-2003 04:23 PM Click Here to See the Profile for ezramoreSend a Private Message to ezramoreDirect Link to This Post

ezramore

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oh forgot to add the cat.....I had it put on the week befor it was 125 installed by itself. so all together 325
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ryan.hess
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Report this Post10-30-2003 05:55 PM Click Here to See the Profile for ryan.hessClick Here to Email ryan.hessSend a Private Message to ryan.hessDirect Link to This Post
I took off the exhaust, and the vacuum is still low and slow Now what??
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GTDude
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Report this Post10-30-2003 06:58 PM Click Here to See the Profile for GTDudeClick Here to Email GTDudeDirect Link to This Post
ryan.....check your timing. If correct by the light, then the harmonic balancer has most likely slipped. Bump the timing up a bit and see if the the vacuum increases and the power also increases. Good luck!

Good luck!

Phil

------------------
87 FIERO GT 2.8 5spd
0-60 in 6.8 seconds!
If you found my advice helpful, please take the time to give me a positive rating. Thanks

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ryan.hess
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Report this Post10-30-2003 07:38 PM Click Here to See the Profile for ryan.hessClick Here to Email ryan.hessSend a Private Message to ryan.hessDirect Link to This Post
Sorry, forgot to mention - it's a 3.4 dohc - no distributor. Is it possible that worn cam lobes could be causing these symptoms?
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GTDude
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Report this Post10-30-2003 07:45 PM Click Here to See the Profile for GTDudeClick Here to Email GTDudeDirect Link to This Post
SILLY BOY!

Talk about leaving out pertinent info....LOL!

Let me think about it and get back to ya.

Phil

------------------
87 FIERO GT 2.8 5spd
0-60 in 6.8 seconds!
If you found my advice helpful, please take the time to give me a positive rating. Thanks

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ryan.hess
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Report this Post10-30-2003 08:09 PM Click Here to See the Profile for ryan.hessClick Here to Email ryan.hessSend a Private Message to ryan.hessDirect Link to This Post
Well, I got a response on the 60* v6 forum... apparently 135 compression is way too low. One forum member had that low of a compression with a head gasket leak... Now I'm worried.

[This message has been edited by ryan.hess (edited 10-30-2003).]

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ryan.hess
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Report this Post10-31-2003 04:21 PM Click Here to See the Profile for ryan.hessClick Here to Email ryan.hessSend a Private Message to ryan.hessDirect Link to This Post
Just an update... Oiling the cylinder only raised the compression 5-10psi, so I don't think the rings are at fault.. Cam lift is ~.360 (as best as I can measure, +-.01"), which is where it should be.. Cam timing *appears* to be correct, I'm just waiting for some responses to make sure I'm doing it right... Should cam timing be correct, I guess the only things left to suspect are worn/burnt valves and/or both headgaskets... [sigh]

[This message has been edited by ryan.hess (edited 10-31-2003).]

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