Almost every other 99 Mits w/ an erratic or rough idle that ever rolled in was a vacuum leak due to cracked intake hose w/ a new MAP sensor or just a new/ map sensor (not properly diagnosed) .It's a vac leak or idle solenoid. ( I found common on 98-99 Mits
Check for a vacuum leak. Use a spray carburetor . Spray vacuum lines. Sudden drop in RPMs you found the leak.
SOURCE: 4.9 liter will idle but wont accelerate have to start with ether
yes checked fuel pressure and replaced the fuel filter, checked the mapp sensor,tested throttle position sensor, has strong spark, 50psi fuel pressure, fresh tune up, runs real rich and rough idle but wont rev up like fuel injectors arent speeding up, also checked exhaust. thanks julius
SOURCE: Rough idle until warm
HMM, ya ont get a code unless ya figure out how to read the morse code values the OB1's use. Hmm sputters, and rough idle can be from poor air circulation, as well fuel delivery.
first air.......inspect and clean your vacuum hoses, cracks and leaks will most notably ruin your day. as well as the performance of your ride. check the seal for your intake hose around the throttle body, then clean the ports in and around your throttle body as well. Bad air supply, poor idle.. follow me..
second is fuel delivery. Your getting your gas, thats evident, but are you getting the required amount. hard to guage unless you disconnect a line and test its pressure. so lets USE the KISS method.. KEEPING IT SIMPLE STUPID
first, check and or replace your fuel pressure regulator...
second, inspect condition of your fuel filter.
thrid, and certianly the last thing, your fuel pump. go in that order. or your gonna seriously annoy yourself when a 5 dollar fix turns into a 3-400 dollar fix.
CHECK THE IDLE SPEED SENSOR, UNPLUG IT AND SEE IF THE VEHICLE REVS UP A BIT. IF IT DOES, THEN REPLACE IT. ALSO CHECK THE FUEL PUMP RELAY IN THE FUSEBOX. HOPE THIS HELPS. .LET ME KNOW. GOOD LUCK
SOURCE: 4.3 cpi rough idle ,pops on acceleration to
Chk theTPS Throttlrposiyion sensor Good luck, Ned
SOURCE: 3 symptoms in random! one Car ! 2000 Impala 3800
First thing I'd check is fuel pressure. 55psi
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