high idle after headgasket install

dee242

New Member
Oct 20, 2014
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vancouver canada
Hey did a hg on the 7mgte and it starts right up but idles at 3k rpm or higher. Now I haven't messed with the idle screw or tps and it idle fine before the hg. I noticed that if i take the silicon hose off the turbo the car will idle correctly and smooth but will run pig rich well of course because of boost leak can some one help me.
 
Oct 11, 2005
3,815
13
38
Thousand Oaks, CA
You need to find the leak downstream of the throttle valve. The upstream leak at the TB coupler would not cause a high idle problem. I'd start by making sure the throttle plate closes fully.
 

jetjock

creepy-ass cracka
Jul 11, 2005
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Redacted per Title 18 USC Section 798
For those of you that have properly running engines try this: pull the brake booster hose off. Let us know if the idle increases. If you think the resulting stumble is because the leak is too big try modulating it with your finger. Again, observe what the idle does...
 

dee242

New Member
Oct 20, 2014
53
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0
vancouver canada
The throttel plate was clean and fully closed but i could get it to idle lower to where the car cuts off if I pushed on the linkeage really hard.
 

jetjock

creepy-ass cracka
Jul 11, 2005
9,439
0
0
Redacted per Title 18 USC Section 798
dee242;2028081 said:
booster made no diffrence there was 3 bolts missing off the lower half of the manifold tho

It won't. That was my point. On L Type EFI systems pirate air will not increase idle speed. The only things that will are bypass air (air around the throttle plate), timing, or fuel.

Assuming the last two are good it has to be the first. That means the ISC, throttle plate, or PCV systems. If the throttle plate is closed, the ISC hose is pinched off, and the PCV system blocked, the engine can't run.
 

super51fan

New Member
Jul 28, 2010
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Indianapolis
Well maybe it has a map sensor.


Naa I guess not.

Are you positive that the throttle plate is setting against the stop screw? See page FI 102. So did you take a pair of needle nose visegrips and squeeze closed the hose to ISC. I cant' see that much air from PCV port however you should clamp that off close to throttle body also. Have you looked at page FI 18 in the repair manual.