I have a 2000 firebird with the 3800II v6 engine and 5 speed manual transmission. It has the 'drive by wire' throttle body. I like to do a lot of coasting down hills instead of keeping it in gear. When the engine is warm and coasting in neutral, the engine will drop the idle to normal, then shortly after drop real low, almost until it stalls, rev itself up and then do it again. This happens repeatedly until i come to a complete stop, or i play with the clutch pedal. When this happens, the engine looses oil pressure for a seccond. It still happens after i cleaned out the throttle body with cleaner and bypassed the clutch start switch. It doesn't happen when the car is stopped or cold. Can someone please help me?
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Re: idles rough when coasting
Have you checked all the vacuum pipes around the top of the engine.? It`s not losing oil pressure, it`s just about to stall when the oil light comes on. Listen for a hissing noise under the hood. Vacuum leaks can cause real problems with the inlet manifold pressures. Good luck.
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First try cleaning the engine throttle body and the idle speed control valve, it may have a slow idle due to these parts being full of sludge. Use a can of spray throttle valve cleaner. After cleaning disconnect the battery negative post for 5 minutes and then drive it about 5 miles, if the idle shake continues the next step is to install new engine and transmission mounts,.
Not having an IAC would only affect idle speed. A rough idle could be a weak coil, or injector among other things. It takes more spark and fuel to fire a cylinder when the engine is cold.
Are you getting a trouble code for any one cylinder ?
Apr 12, 2013 - Uploaded by MapleBoarder78
Part one of installing a new clutch on my 2000 Trans Am. Part 2 will include installation ... How to Master Cylinder Install and Drill Mod (LS1 F-Body) - Duration: ... 6:28. Removal and Servicing ofClutch Master Cylinder to Slave Cylinder ... LS1 98-02 Chevy Camaro Z28 SS Pontiac Firebird Trans Am F-Body ...
It's been almost 2 years since you posted the question so it's likely you will not see my answer to your question.
First, do NOT make any adjustments to your throttle body idle setting. The screw most likely never budged since 2006 so you should not touch it since this is not the root cause. But yes it is wise to check all vacuum lines as "craig" suggested.
I have a 2007 Corolla CE, 1.8 liter VVT engine, 5 speed manual transmission which I bought new from the dealer. Currently has about 108k miles on it. After about 4 or 5 years in cool to cold weather it started doing the same thing. I researched it online then asked my local Advance Auto Parts person who confirmed my hunch. It is known as "idle hunting" when the engine is cold, in colder outside temperatures the idle rpm's will increase up to roughly 2000 rpm then drop to idle, then back to 2000 rpm, then repeats multiple times. Then after driving a short distance, stopping and running at idle, the idle speed may drop to 600 or 500 or as low as 400 rpm, running quite roughly but still keeps running. My Corolla normally idles smoothly and steadily at 800 rpm when warm or hot. The idle hunting or low idle rpm will typically correct itself when the engine warms up enough.
The problem: the intake manifold gasket has aged and shrunk a bit, allowing engine compartment air to get pulled directly past the gasket and into the cylinder head intake port. This causes an imbalance between the reduced air filter airflow sensed by the Mass AirFlow (MAF) sensor versus the actual air/fuel ratio versus the engine rpm versus the oxygen level in the exhaust stream. The gasket will shrink more as the temperature under the hood drops, allowing more air to flow past the gasket. The Engine Control Unit (ECU) is simply trying to do its job as programmed by increasing fuel delivery to compensate for the overall imbalance, then when rpm's get too high it will reduce fuel delivery.
The solution: purchase a new intake manifold gasket for roughly $10 to replace the stock gasket. Mine is a thin orange polymer gasket with round cross-section which seals around all 4 intake ports. You can search for instructional video of how to install it on YouTube.
I purchased one but did not install it yet. I am sure this will resolve the problem since all other suggested fixes I found on the internet did nothing but unnecessarily frustrate the owners.
It could also be a vacumme leak. A quick way to check for that is to starting fluid around hoses and gasket areas. If the engine picks up speed when you spray around the engine and not directly in the throttle body, you have found your leak. I also believe these cars have an idol air control valve or IAC that might need to be cleaned or replaced. Check your spark/coil wires while you are checking around.
There are usually return springs but it could just be that your car coast a long time when in high gear before it starts to slow down. My Jeep is the same way, if I'm running at 55 I can coast for a few miles before I slow down very much.
Your idle air control valve may be dirty or the wire harness may be damaged. First try cleaning the throttle body with throttle body cleaner and make sure you use all the can up and try to get the idle air control valve cleaned. A faulty or dirty idle air control valve will cause engine to stall when put in to gear from idle. Good luck and hope this helps. Keep me posted, be glad to help you get your car running 100% soon.
Sounds like it's your IAC (idel air control sensor). The IAC is a computer-controlled air bypass valve located in the throttle body. It helps control idle speeds by allowing air to bypass the throttle plates as to increase the idle speed. If the IAC isn't working properly the car will stall when you are not pressing the gas pedal. It is located on your throttle body and is relatively cheap and a simple change since it is normally held in my two screws. Let me know if you have any other questions. Thanks for an honest ranking and for using FixYa!