1999 rough idle/hesitating at idle .drives fine i

If the exhaust smells rich,like gas the oxygen sensor could be bad,is there a check engine light on or have you scanned it for codes. A fuel filter can do this but I suspect the idle air solenoid is bad or clogged passages for the IAC.

The oxygen sensors are located under the vehicle on the exaust manafold unless you are getting a certain code wich u should be getting if they are malfuctioning then it could be something else.have you change the fuel filter? It also might need a tune up new plugs wires air filter ext

Sorry guys i was late with my feedback... So here it goes.. I have no check engine light.... Currently running the stock tune as well.. The car has no tps, pcv or egr valve.. It is all controlled by the electronic throttle body which i recently cleaned but didnt help with my problem. I ordered a new fuel pump as well, just didnt get the chance to install it yet. Cant change the fuel filter as it is builtin within the pump. However, shouldnt the fuel pump or fuel filter cause engine stalling, bucking and hesitation? I doubted the fuel pump could be causing this since the problem only occurs at idle. By the way, there is no missing on any of the cylinders.

You have an air leak around the throttle body

hello this is a fuel trim malfunction bank sensor 1 meaning O2 sensor is malfunctioning .Oxygen sensor

check plugs, wires, and coils for proper spark.

Please be fast about checking your fuel pump. It is not giving enough fuel pressure.

Cheers.

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Check for blocked/low fuel flow. ie fuel filter or failing fuel pump.

change spark plugs if still haveing probs after that change fuel filter

po301 thru po306 all misfire codes cylinder 1-6 remove plugs and replace them..... set the plug gap first
i suggest u replace the wires also if they never been replaced all these misfire codes can set the others and one is for the oxygen sensor ( 02s or HO2S) CIRCUT MALFUNCTION do u know how to check wireing systems
do the tune up plugs (set gap) .052-.056 change the fuel filter also. clear the codes hows it run
this info is for 98 E-250 4.2Litre
what engine do u have 4.2L or 4.6L i know it is a v-6 by the codes