Question about 1988 Toyota 4Runner
Your EGR valve is not closing correctly because of carbon built-up.
vacuum leaks on intake manifold,
the air tube between the air filter.
intake manifold vacuum hose.
clean throttle plate with Berryman carburator cleaner
SEE sample picture HERE
Also remove carbon built up behind the EGR valve and the EGR passage tube.
Vacuum leak WILL offset the intended 14.7 to 1 air fuel ratio.
More un-metered air (leaks) will lean out the fuel mixture.
Use small amount of Berryman carb clearer at potential air leak area will help you identify trouble spot.
At idle,just spray and listen for the RPM surge.
The in-rush of carb clearer will increase the RPM on the motor.
Record the problem spot(s) and address it later.
EGR carbon built up require 2+ hours to clean from start to finish.
You will need a new EGR base gasket before your start.
Locate and remove the EGR valve after the vehicle is cool down.
Carefully record the connector and vacuum line (for older vehicle) location by drawing an easily to follow diagram.
Remove the EGR valve.
Inspect the location of the carbon built-up inside the valve and the EGR passage tube.
SOAK these areas with WD-40 spary.
You will need a small screwdriver,cloth hanger and lot of newspaper and time to get this cleaning done right.
RE-SOAK the carbon and let it sit for over-night will also help.
One the last round,pass a shop vacuum of the EGR valve and the passage pipe.
Install the new EGR gasket and connectors.
Allow the vehicle to warm up outdoor to burn up any remaining WD-40.
Take it for a test drive.
Please rate my answer if it's useful to you.
Posted on Dec 19, 2009
You have a leak on your EGR system disconnected the vacuum hose going to the EGR valve and plug it up that will stop the EGR valve from opening and leaking air in to the intake manifold. or you can locate the leak and fixed but in a old truck the EGR sistem wont make mush difrence. keep on mind the EGR system is just for emission control and do nothing to the engine performace. your truck will work fine whit out it.
NOTE: this will not work in newer vehicles bacase will cose the MIL light to come out and fail inspections.
Posted on Jun 18, 2009
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Posted on Jan 02, 2017
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