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Engine runs rough when warm. Have added premium gas and injector cleaner, also new air cleaner. Roughness is at low speeds. 94 lexus ls400, 130k miles.
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1. Error Code 24. Intake Air Temperature Sensor.
Solution: Check the following:
- IAT Connector and wiring.
- Intake Air Temperature Sensor.
- Engine Coolant Temperature Sensor.
- ECM. 2. Rough Idling when the engine is hot. The following are the reasons due to which the engine can perform bad when it is hot.
- Fuel pump control circuit.
- Fuel pump pressure.
- Fuel injectors.
- Non Return Valve clogged, located on the lower side of car chassis above the fuel tank.
- Engine compression, valve clearance, spark plugs.
Dirty air filter, dirty throttle body...try 2 bottles of gas line fuel injector cleaner...has your car been parked for awhile? Heet gas additive will work on any low gas tank sludge that you may have. Hope this helps.
Could be a number of engine related problems, but rough idle on an old car is most often from dirty injectors. Go to autozone, for less than $5, get a bottle of injector cleaner and mix with a tank of premium gas. Let it cycle through and that should help the rough idle.
p 0300 is random misfires and 0302 is no 2 cylinder misfire
most misfires are from dirty injectors rather than plugs
run a quality injector cleaner and see if there is improvement
seeing how the truck is an 88 there could be a few solutions that will not cost alot of money. I would try to add fuel injectior cleaner to your next full tank of gas as well has using a higher octane fuel or octane booster. Also try some heet. this takes some of the extra moisture out of the gas and should be added in a full tank as well. Some of the Lucas brand injector cleaner will remove moisture. If there is any knocking in the motor, on your next oil change put in a bottle of Lucas oil treatment or something I use called Hyper-Lube. They both are only 1 quart bottles so you will short the amout of oil put in the engine by 1 quart. When the truck is sitting overnight or for a few hours especially in a cool environment the oil will get thick, when the truck warms up the oil thins and you notice problems like what you described. I live in Indiana and the winter here can be a bit rough on a car/truck. If additives don't solve the problem then you will have to look into the possibility that there is a mechanical/electrical component that is bad. They can be:
throttle position sensor
dead fuel injector
lose of compression in a cylinder
dirty fuel filter
dirty air filter
spark plugs
engine timing off
faulty spark plug wire/ wire being on the wrong plug causing firing order being wrong
since it runs fine at driving speed I would check into the fuel injector cleaner 1st. The injector or the throttle position sensor.
I have a family member who has the same truck and for a smaller truck it's pretty tough. Definately a keeper
I had a similar problem in a 1994 Taurus, and after spending nearly 300$ on ignition parts, it turns out the problem was a bad spark plug wire that cost me 8.88$ to replace.
You will not see any vacuum from the egr solenoid until the engine has reached normal operating temperature and certain other driving conditions have been reached (like throttle position and road speed).
If the engine runs rough when warmed up, check the CTS (coolant Temp sensor) when hot and cold and if no fault shows there, start checking input sensors for engine and cam position, engine timing, RPM etc.
If the EGR valve was leaking, it is only adding air to the exhaust stream and usually, manually opening the valve and blowing out the seat with compressed air should fix the issue.
This can also be an issue with clogged injectors. When the engine is cold, fuel enrichment supplies more then normal fuel amounts to encourage even running. When the engine warms up (normal operating temperature), fuel enrichment mode is turned off. If your injectors are clogged (even if only slightly) fuel starvation will cause rough running. Fuel enrichment overcomes the starvation of clogged injectors. Try adding a propriety injector cleaner to your fuel tank and watch for an improvement. If you do see an improvement, have your injectors cleaned and tested professionally. If you locate any other issues with engine sensors, replace them and ensure the new components are adjusted correctly if required..
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