Question about 1991 Chevrolet Corvette

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Car has been tuned still idles rough and at speed of 40mph is it the oxygen sensors

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Try cleaning the IAC (idle air control) sensor and check the hoses going to the MAF (mass air flow) sensor, i have found both causing me problems with erratic idle. the IAC was totally gunked up with carbon on the pintle and i had found that the screws holding it down were loose ( but only clean this with throttle body cleaner, not carb cleaner it might damage the sensor, and replace the vacuum hose to the MAF sensor, i found mine was cracked and old and brittle, a car that has been run poorly for a long period of time might also cause a problem with an oxygen sensor and this would lead to poor fuel economy also, try to clean that up or just replace it. Also have the transmission fluid serviced, i have seen this problem lead me to think i had an engine idle problem or rough perforamance when accelerating. can you rate this!

Posted on May 08, 2010

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  • steve t May 08, 2010

    also forgot to mention if your IAC is dirty then that means that the throttle body is dirty also it took me fifteen minutes and a half can of Gummout card cleaner to the varnish buildup...make sure you clean the intake plates and behind, everywhere, and TIP: after you do this let the car dry out for about an hour so it will start up easier.

  • steve t May 09, 2010

    i feel bad that i wasnt of more help...there are a couple of other things that could be causing this but i was assuming that you had replaced the plugd and wire new air filter you know normal check up stuff....try this real easy fix first $10 Go down to Autozone and purchase a can of Sea Foam and pour in only 1/2 to 1/2 tank of gas and drive the car around for 30 minutes and let this works its why through your fuel injector system...please give this a try its a real cheap easy way to see if it gets even a litte bit better then were narrowing this problem down. also i made a mistake when i mentioned MAF sensor when i Meant MAP Mass air Pressure sensor not that the other would cause this problem also. And you did service the Transmission? well if you did everything i said and really had the plugs/wires replaced in you said tune up then theres only one other thing that it could be....a bad headgasket! a very small leak not bad enought that smoke would come out but overtime you would notice a coolant loss ,...have you noticed any coolant levels slighty going down. on my camaro i found out that it doesnt come with a low coolant warning sensor but they have a provision for it but decided against it. and please do this one thing take a plug out and tell me the color of the insulator tip...does it look redish pink or anyother color besides whitish brown? to find out if you have a gasket leak is to cool down car and leave radiator cap off and start the car if within a few minutes from dead cold you start seeing bubble coming up out if the filler neck then you have a leaky head gasket or gasket plural i had this problem two weeks ago car ran rough a bad mis took 5 plugs out and they were all reddish pink looking and that was from burning water i cant get the other pplug out it seized up. so i have a slight misfire in the mornings until it gets blown clear. tell me who did the tune up and what did they replace tune ups are my specialty...98% of the time its spark plugs and wires...please let me know.

  • Tim Terzich
    Tim Terzich Jun 05, 2010

    I agree with vtaylor2 the IAC (idle air control) sensor was one of my problems plus you want to make sure the air butterfly valves are not closed all the way. Yes if the car has backfired at all most likey the MAP sensor is bad but you can test these as well

    Test The Map sensor http://www.youtube.com/results?search_qu... MAp sensor

  • Tim Terzich
    Tim Terzich Jun 05, 2010

    Test The Map sensor http://www.youtube.com/results?search_qu... MAp sensor

  • Tim Terzich
    Tim Terzich Jun 05, 2010

    Test the MAF http://www.youtube.com/results?hl=en

  • Tim Terzich
    Tim Terzich Jun 05, 2010

    Test The Map sensor http://www.youtube.com/results?search_qu... MAp sensor

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Rough idle in drive, correct rpm


Car idle is rough Inspection Service & Cost A rough idling engine can be caused by a number of issues, some of them are serious while others tend to be minor, but the symptoms remain pretty much the same. The car will feel rough and bouncy when the engine is running. The car will also idle below its regular speed, display inconsistent RPMs and may produce a shaking, skipping or slipping sound when the vehicle is running.
While a rough idling engine may seem to be a simple inconvenience it often indicates a deeper problem within the engine. The vehicle should be inspected and repaired as soon as possible because small problems have a way of turning into expensive repairs. How this system works: The idle speed of an engine is basically the rotational speed the engine runs on when it is un-coupled from the drivetrain and the throttle pedal is not being depressed. The idle speed is measured in the revolutions per minute of the crankshaft.
When an engine is running at idle speed it generates enough power to smoothly operate equipment such as the water pump, alternator, and power steering but not enough power to move the vehicle itself. A passenger car will usually idle between 600 RPMs and 1000 RPMs. A properly functioning idle should run smoothly without skipping or slipping. Common reasons for this to happen:
  • Dirty Fuel Injectors: The fuel injection system injects fuel into the cylinders, which creates a mix of air, and fuel to ignite and burn. Fuel injectors have tiny nozzles to spray the fuel into the cylinder and they can become clogged over time. clogged or failing fuel injector creates a lack of fuel in the vehicle's engine. This can cause a rough idle, it can also cause symptoms such as slow acceleration or the car not feeling as if it has enough power. If the problem is addressed early, it is possible to clean the injectors, which will restore them to full function. If this condition is not addressed in a timely manner the injectors will need to be replaced. Incorrect Idle Speed: While the average idle speed falls between 600 to 1,000 RPMs, if your vehicle is experiencing a rough idle it could be due to an incorrect idle speed setting. A trained mechanic can easily adjust the idle speed, and it should stay at the proper speed. If an adjusted idle speed becomes inconsistent or changes at random intervals there may be a bigger problem that needs to be explored. Vacuum Leak: If the vacuum system has a leak, it can seriously affect the ability of the vehicle's computer to regulate the air to fuel ratio. This can lead to a rough idle and if the problem is not addressed the car may experience slow acceleration and a lack of power. Vacuum leaks should be inspected and repaired immediately. Incorrectly Installed or Damaged Plugs: Spark plugs are responsible for creating the spark that allows the vehicle to burn fuel. If spark plugs are improperly installed or malfunctioning, the idle speed can be affected. The vehicle's engine may vibrate or there may be slipping or straining sounds coming from the engine. Defective or Clogged Fuel Pump: A rough idle can be related to fuel delivery issues. The fuel pump, which is responsible for pulling fuel from the gas tank to the fuel injectors, can become clogged or defective. If this happens the engine will not get enough fuel, which can cause a rough idle, sputtering, stalling and even slow acceleration. Clogged Fuel Filter: A clogged fuel filter can cause similar problems. The job of the fuel filter is to screen out contaminants in the fuel, over time it will become clogged and need to be replaced. A rough idle is one symptom of a clogged fuel filter. Failing Electrical Components: A problem or failure in the ignition system or various electronic components can cause a rough idle. If this is the case, the problem will usually get worse as RPMs increase. Common culprits include the ignition control module, plug wires, coils, and spark plugs. Defective Airflow Sensor: A defective airflow sensor can be responsible for a rough idle. A mass airflow sensor detects the amount of air coming into the fuel injection system and sends that information to the vehicle's computer. The computer uses that data to deliver the proper amount of fuel to the air in the vehicle. Over time these sensors can malfunction or become dirty. One of the first symptoms of a malfunctioning airflow sensor is a rough idle. The car may also accelerate slowly and even stutter or stall as the problem progresses. Dirty Oxygen Sensor: Oxygen sensors measure how rich or lean the gases are as they exit the combustion chamber. Depending on the results, the amount of fuel entering the engine is adjusted by the vehicle computer. The ultimate goal is to maintain an ideal mixture that produces the lowest emissions. A dirty or failing oxygen sensor will usually trigger the check engine light and can lead to a rough idle, lower fuel efficiency and failed emission test.

Sep 28, 2016 | AC Cars & Trucks

2 Answers

Where is oxy.sensor


Usually in the exhaust pipe near the engine.
They don't usually cause a rough idle, and the check engine light should be on if you have a faulty sensor.

Mar 21, 2016 | Cars & Trucks

4 Answers

What would cause 93 chevy c1500 rough idle smells of excess gas at exhaust


Does the truck seem fine when you first start it & then acts up when it reaches operating temp?
That would lead me to look at my oxygen sensor, a bad sensor can cause the truck to run "rich" which would explain the fuel smell in the exhaust.

Jun 28, 2014 | 1993 Chevrolet K1500

1 Answer

1997 dodge dakota running really rough


So many options...oxygen sensor, egr valve, pcv valve, premium gas.

Dec 01, 2013 | 1997 Dodge Dakota

1 Answer

Idle rough


tune-up time, also replace your air & fuel filters, check your vacumn lines , check for any trouble codes, ( @ the parts store ) . tighten all bolts @ throttle body, gaskets could be leaking, or sucking air. it could be a number of sensors causing you problems, OXYGEN sensor should always be replaced as a maintenance thing ! balls in your court BOB !

Feb 25, 2013 | 1996 Nissan Sentra

1 Answer

My car idles real rough and hesitates when i gas it


That or your intake manifold hose could have a split in it or have your mass air flow sensor checked. IT could even be as simple as a good tune up.Hope this helped please rate me! GOOD LUCK

Jan 15, 2010 | 1998 Kia Sephia

1 Answer

Bad gas milage


you may need to try to get an idle sensor and get it chgd. maybe the throttle, oxygen sensor also needs chging.

Apr 18, 2009 | 1999 Dodge Ram

1 Answer

What are the symptoms of a faulty oxygen sensor?


bad oxygen sensor will make a car run rough.also mass air flow sensor egr valve sticking open or pvc valve open.idle speed control problems.have your car scan.because there are many sensor causes it to run rough.

Apr 16, 2009 | 1999 Pontiac Grand Prix

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