Answer: Your problem may be an IAC (idle air control) valve. Also, check for a faulty EGR valve (exhaust gas recycling) that is sticking open.

Question: 1989 GMC 1500. I've read that the GMC are sort of prone to getting carbon build-up in the intake manifold. Is there any kind of carbon cleaner or cleaners that you could recommend that I could use to spray into the throttle body to clean it out, without harming the other components? I'm kind of new to having a fuel-injected truck. I've always had a carburetor in my cars. When I wanted to clean out the crud, I would just spray carburetor cleaner down the throttle bore and that would take care of all the build up. But, with an injected vehicle, I feel a little lost. The problem that I've been having is that I keep getting carbon pieces flaking off and getting trapped in the EGR valve.

Answer: The intake manifold should be removed to properly clean the carbon buildup from the inside of the manifold. On engines with high mileage that are starting to use oil, the oil causes a carbon buildup to occur at an accelerated rate.

Question: 2003 Acura RL3.5  mileage: 63,000. Re: Check Engine Light - Dealer stated computer indicated a blocked line to the EGR valve. Inspection revealed no blockage and dealer stated it has to be blocked or has carbon build-up in intake manifold and would require cleaning and replacing all the intake manifold gaskets. Instead, dealer reset computer and added fuel line cleaner. Check engine light came back on after two weeks. Should I let the dealer perform the cleaning of the intake manifold or is there anything I can do to clean the carbon such as gas additives etc?

Answer: If carbon is building up in the intake manifold and is blocking the EGR valve, the only way we know to clean this is by removing the manifold and mechanically scraping the carbon out. We know of no gasoline additives that will cure your problem for you.

Question: 1988 Chevrolet Cavalier 4 cylinder mileage: 66,271. Is it normal that the EGR valve has to be replaced with what I consider low mileage - 66, 271 miles?

Answer: 66,000 miles sounds a little early for an EGR valve. But on a five year old car, it is not unexpected.

Question: 1999 Ford-Taurus mileage: 60,000. I own a Taurus, and for the past several weeks, the engine service light has come on and off. I took it to the local mechanic where I bought the car and they said even with the light not on they got a code for the EGR valve. They changed the valve for $90.00 and a $100.00 labor. I have two questions: 1. Can they determine what's wrong even if the service light is out? 2. Would I have noticed any poor performance as a result of a malfunctioning EGR valve?

Answer: To answer your first question, yes, the problem can be determined even if the service light is out. When the engine service light comes on, it is because a fault code is being stored in the computer. This information is held in the computer until it is scanned and cleared. You may or may not have noticed any poor performance as a result of a malfunctioning EGR valve. It would depend on the degree of failure.

I blew into the controlled pressure inlet to the PFE valve, and that was open. I also pushed a wire through it. Then I tried to blow into the intake manifold, and that seemed to be blocked. I forced a heater hose into the EGR opening in the intake manifold, and tried to blow into it again, without success. I connected the hose to an air compressor, and tried to force compressed air into the intake manifold, but was again unsuccessful. Then I tried to push a wire into the intake manifold, but could only push it a short distance, where it was always stopped by some obstruction. I removed the intake air hose, and opened the throttle plate, and looked into the intake manifold. It seems to be carboned-up. But is it possible that there could be so much carbon in the manifold, that the EGR is completely blocked? Or am I looking in the wrong place, and for some other reason, the intake manifold is not open at this point? I would appreciate any help that I can get from somebody here, before I remove the intake manifold.

Answer: Sounds like the EGR port in the intake manifold is plugged.

Question: 1989 Ford f-150 mileage: 96,000.  My truck has been experiencing many problem caused by carbon deposits in the EGR Valve.  We have replaced the valve and cleaned out the valve many times, including, most recently, three days ago.   However, the truck stalled again and when we checked the EGR valve, more carbon deposits had built up and had to be removed.  I understand that the GM Vortec engine has a history of carbon build up problems.  Is there anywhere else we should check for carbon buildup that's already in the system, or anything we can do to prevent the carbon buildup from occurring so frequently?  Thank you.

Answer: The carbon buildup in the EGR passages is probably the result of excessive oil coming down the valve stems.  We've found similar problems with other cars usually at 60,000 or more miles.  Replacing valve stem seals reduces oil use.  The stems are made out of rubber and over time become hard and brittle and will no longer seal.

Question: 2002 Dodge Dakota Sport mileage: 39,000.  You have touched on the subject, but I wonder if you might help me. I have low rpm spark plug knock in my 99 Dakota 4x4.  The dealer says I need higher-octane fuel.  In your FAQ archive, I noticed that you told another Dakota owner to check the EGR valve.  Is 96 octane high enough, or do I need an additive (102 boost, etc)?  This pinging is making me crazy.  Thanks!

Answer: The EGR valve can cause the pinging but also check the knock sensor.  If the knock sensor is functioning properly, it detects the pinging and retards the timing.

Question: 1999 Chevrolet Lumina, miles: 89,000  My Lumina (as I was told) needs a new EGR valve, what is it and what does it do?  The symptoms my car seems to experience are, it is very hard to start if it is cold or especially hard when it is wet out.  When this happens the car needs at least 10 minutes to warm up before it will move or else it stalls.  Does the EGR valve problem sound correct or could it be something else?

Answer: If a major tune-up has not been done recently, this could be the cause of your problem.  Replace the spark plugs, plug wires, fuel filter and air filters, etc.   Also, replace the oxygen sensor.  In addition, service the fuel injection system.  Clean the carbon deposits from the throttle bore and idle passages.

Question: 1995 Chevrolet Monte Carlo 3.1 V6 _mileage: 100,200.  What does the EGR valve in my car do and does it affect performance?

Answer:    EGR stands for exhaust gas recycling valve.  During cruising speeds, the valve opens allowing exhaust into the intake manifold.  The purpose of this is to cool the temperature of the combustion inside the cylinder as the spark plug fires.  This in turn, lowers emissions.

Question: 1995 Mercury Grand Marquis 4.6 mileage: 75,000.  Check engine light code 332? The EGR valve not opening.  Had this problem on another Mercury Marquis and dealer cleaned EGR with spray without removing and changed vacuum regulator.  How can I tell if it is the vacuum regulator or carbon blocking the EGR valve?

Answer:   The EGR valve is controlled by the vacuum control motor.  It has been the “weak link” in this system.  Check the EGR valve to see if it is plugged by manually raising the EGR valve with the engine idling.  If it is not plugged, raising the valve should almost kill the engine.

Question: 1983 Ford Bronco 302 mileage: 160K.  I’m not sure if my EGR is bad.  Current problems are rough idle, bad mileage, engine missing at high speed when climbing a hill & temperature.  Fluctuates while driving.  At idle its fine.   When cold I hear a high-pitched noise (almost like a air leak) until it warms up.  All vacuum hoses are fine.  What other symptoms would EGR give?

Answer:   Your car may be ready for a major tune-up including spark plugs, plug wires, distributor cap, rotor, fuel filter and air filter.  Also, perform a fuel pump pressure test.  Clean fuel injection system including throttle bore, idle speed control motor and passages.  If problem still exists, scan computer for trouble codes.

Question: 1984 Subaru GL Hatchback 4WD 1800 mileage: 178,000.  After it warms up there is a flat spot when accelerating from idle to 2200 rpm.  I have rebuilt carburetor, and installed new coil, cap, rotor, plugs, plug wires.  All vacuum lines OK.  Float level good.  Choke setting good.  EGR valve good.   Thermal vacuum valve good.  Vacuum control valve good.  What is the problem?  Please!  P.S. It has the Hitachi carburetor.  Would appreciate any help you could offer.

Answer:  The return spring in the EGR valve could be weak allowing the valve to open to quickly.  Try temporarily disconnecting it and test drive.

Question: 1995 Saturn mileage: 39,000.  I recently had to have my EGR valve and map sensory replaced on my car.  When I bought the parts the man at the parts store told me that there was a government regulation that required an EGR valve to be guaranteed for 5 years or 50,000.  Do you know if this is true, and if so where can I find this type of information?

Answer:  The owner's manual for your car should have the information you need or check with your local Saturn dealer.

Question:   1994 Nissan/Quest 6 cyl mileage: 96,000.  How do I check to see if the EGR Solenoid is bad?  I have a handle on checking the EGR valve but not the solenoid.

Answer:  Apply voltage to solenoid to manually open.

Question:   1985 Dodge Ramcharger 318. This vehicle does not have California emissions on it. The EGR system failed the California smog test, and my husband was informed that the EGR passages needed to be cleaned. Is this a job I could handle (I do have some mechanical experience) and if so, where can I get information on how to do it?

Answer:   Cleaning the EGR system is not too difficult. Two bolts secure the valve. Removing the valve will expose the EGR passages. A stiff wire should work to open the passages. With the EGR valve off, apply vacuum to check that the valve opens and closes.

Look up your EGR valve question in our Car Repair forum section.

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