Question about 1991 Honda Accord

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When I start the car it idles high the rpms go up and down

I replaced the throtle body from a junk yard it still goes up and down at idle

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Sounds like you have a dirty EGR (Exhaust Gas Recovery) Valve. There are three things that I think of looking at when someone mentoins uneven running at idle 1) Idle speed air control valve (IAC) - this is small port that is electronically controlled that allows air passed the throttle flap at idle to maintain idle speed. You say you have swapped out your throttle body but it might be good to check that the IAC is clean as most Hondas often fall prey to the same age related faults - spray inlet port with carburettor cleaner and use a bit of old wire to hep clear out any gunk after about 20 minutes. IAC faults generally have the symptom of the car being very reluctant to start but will fire up when given lots of gas. However,as soon as any demand is made on the engine such as power steering or simply engaging the brakes to come to a halt the car will often cutout. 2) Throttle Position Sensor (TPS) tells the engine management system whether the throttle is closed or if open by how much. The symptoms are random often wildly erratic engine idle speeds. 3) The EGR valve - this system is designed to introduce a little exhaust gas back into the inlet manifold to keep the engine ignition temperature low enough to avoid the production of nitrous oxides in the exhaust. This valve looks a bit like an alien space ship about 75mm in diameter. On it top face there is a small vacuum line connector, This vacuum line is connected to the inlet manifold but it may pass through a solenoid valve on the way. This solenoid is for the Engine management system to temporarily prevent the vacuum at engine start up from reaching the EGR thus keeping it closed; the engine temperature is not nearly hot enough, when starting, to cause nitrous oxides in the exhaust. The vacuum introduced to the EGR body pulls on a diaphragm which lifts a valve, immediately beneath to open and this allows a regulated amount of exhaust to pass into the inlet manifold. Connected to the underside of the EGR valve is a metal pipe connected to the exhaust manifold. Faulty EGRs are down to either encrusted carbon deposits holding it open or a broken diaphragm keeping it closed. If closed the engine runs hot and pinks and knocks all over the place. The pipe to to the exhaust manifold can get clogged with carbon deposits and this has the same effect as having a closed valve. If open the car idles unevenly behaving as if there is a leak in the manifold, the open valve is actually just that. Locate the EGR near the throttle body, from the above description you will know it when you see it. Remove the vacuum hose, any electrical connections and undo the retaining bolts and lift clear. Clean everything to like new - the carburettor cleaning spray is again useful here . Applying some suction to the hose connection on the EGR you should see the valve opening and closing. Push a bit of flexible braided (a cut off of handbrake cable is ideal) wire, frayed at the end, to sweep the exhaust connection pipe clean of encrusted carbon. Reinstall everything and fingers crossed job done

Posted on May 01, 2010

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It might be the fast idle thermo valve which is sticking...it is located at the throttle body.....you may need to spray some solvent into it. It's cover can be opened by removing the 2 screws on top. Try to push down the valve a few times and try and error to turn the valve to the left or right until the ehgine idle is steady i.e. no longer up & down idling.

Posted on Jun 02, 2010

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When it does the up and down is your foot on the brake or does it do it at all times? i had a 91 toyota and when i was holding the brake it would rev way up and then kick back down. it was from a vaccuum leak in the brake booster...it would build up the pressure and then dump it off...

Posted on May 01, 2010

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