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Is intake manifold can affect timing?

Tiny
POKALAY
  • MEMBER
  • 1989 TOYOTA COROLLA
  • 100,000 MILES
Idling is to rough. I tried to adjust timing but the timing is to far from 10deg almost 20deg I think. I tried to adjust idle mixture screw but it wont help. I changed sparkplug, cleaned the carburetor and distributor's contacts but the idling still moving up and down. Already checked vacuum cables.
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Tuesday, September 13th, 2011 AT 10:01 AM

6 Replies

Tiny
MHPAUTOS
  • MECHANIC
  • 31,937 POSTS
These do have a habit of sucking in the inlet manifold, spray a little starter fluid around the manifold, if the revs pick up there is a leak, check this first.
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Tuesday, September 13th, 2011 AT 11:46 AM
Tiny
KHLOW2008
  • MECHANIC
  • 41,814 POSTS
Improper valve adjustment is another possible cause. So would a bad PCV valve and unequal engine compression pressure.
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Tuesday, September 13th, 2011 AT 12:11 PM
Tiny
POKALAY
  • MEMBER
  • 9 POSTS
My engine is 5af shim type and no need to adjust valve clearance. I tried to replaced gasket on intake manifold hope this will end up my trouble. Thanks for the quick reply.
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Thursday, September 15th, 2011 AT 5:34 AM
Tiny
KHLOW2008
  • MECHANIC
  • 41,814 POSTS
Shim type does not mean valve adjustment is not necessary.
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Thursday, September 15th, 2011 AT 12:48 PM
Tiny
MMPRINCE4000
  • MECHANIC
  • 8,548 POSTS
Shims are adjustable, they do wear. Clearence should be.010 on intake and.008 on exhaust (cold engine). You simply put a new shim in.

But the intake gasket can leak and if large enough will cause significant loss of power.
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Thursday, September 15th, 2011 AT 1:26 PM
Tiny
POKALAY
  • MEMBER
  • 9 POSTS
Idling is now good and the engine is fine but I cant set the timing
to 10deg. I plugged 2 vacuum from distributor advance diaphram. 15deg is the lowest degree I can set. I already changed and checked the timing belt and set all timing marks, set the pulley at 0" TDC at the compression stroke and rotor at the spark#1. My current timing is 15degree. How can I reach 10 degree? Is my distributor faulty or my engine need to be top overhauled? My engine is toyota 89 model 4af carb with egr system.
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Wednesday, October 5th, 2011 AT 8:42 AM

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