Idle all over the place with hesiatation during acceleration

Asked by Feb 24, 2017 at 12:54 AM about the 1994 Ford Explorer 2 Dr Eddie Bauer 4WD SUV

Question type: Maintenance & Repair

All part have been replaced within a year or less:
fuel pump, fuel filter, mass air flow sensor, all 6
plugs and wires, and coil pack. Trans was checked
✔ cats and muffler was checked ✔ with all those
parts replaced and components being checked
and cleared I am at a loss. Hesiatation only
happens in overdrive not drive. Truck has 188000
miles I have owned it for almost 5 years. Change
the oil every 4 months trans get serviced every 6
months battery and alternator is good. I'm totally
lost. HELP! Please any thoughts or suggested
would be greatly appreciated.

7 Answers


You could have a vacuum leak. Check with carburetor cleaner at an idle, spraying along the intake gasket, throttle body gasket, and vacuum lines. RPM will pick up if there is a leak.

1 of 1 people found this helpful.

So i do have a vacuum leak at the intake gasket that will get fixed asap but I also noticed an oil leak at the valve cover right by the intake. Could there be a lot of engine oil in my intake now and what problems am i looking at if this is happening?


No problems with oil going into the intake. There is no accumulation of oil to worry about. Just have the valve cover gaskets replaced at the same time as doing the intake manifold gasket.

Ok. Took my truck to a shop yesterday and had the intake gasket checked, no leaks. They did a vacuum pressure test with a gauge and pressure was consistant at 20. Tested pcm and got 3 codes; 411, 538, and 566. Test the crankshaft sensor and it is mildly out of range so I am replacing that today but still having idle issues. The idle rises on it's own and drops on it's own. Kind of all over the place. It will go as high as 1500rpm and as low as 400rpm and feels as tho it is going to stall unless I rev the engine then all is fine. Totally lost at this point. Help! Please. Any suggestions on what to check next would be really helpful. A little back history, within the last year, mass air flow sensor, spark plugs, plug wires, coil pack, fuel pump, and fuel filter all have been replaced. Cleaned the throttle body and no crud build up present. Totally lost on where to look now.


P0411 FORD - Secondary Air Injection System Downstream Flow...Possible causes; Faulty Vacuum hoses damaged, Faulty Air Pump inoperative, Air bypass solenoid harness is open or shorted, Air bypass solenoid circuit poor electrical connection, Air bypass solenoid leaking/blocked or stuck open/closed, Air diverter valve leaking/blocked or stuck open/closed......Possible symptoms: Engine Light ON (or Service Engine Soon Warning Light); Engine hesitation... P0411 FORD Description; An air pump is used on the vehicle to lower tail pipe emissions on start-up. The Powertrain Control Module (PCM) grounds the Air pump relay control circuit which energizes the Air pump. The PCM also grounds the Air combination valve vacuum control solenoid circuit, which energizes the Air vacuum control solenoid. Vacuum is then applied to both Air combination valve diaphragms which opens the shut off valves. The PCM enables both circuits simultaneously when Air system operations id desired. When the AIR system is active, then Air pump forces fresh air into the exhaust stream in order to accelerate catalyst operation. The AIR combination valves replace the conventional check valves. When the AIR system is inactive the shut off valves prevent air flow in either direction......P0538 FORD - A/C Evaporator Temperature Circuit High Input...Possible causes; Faulty A/C Evaporator Temperature Sensor A/C Evaporator, Temperature Sensor harness is open or shorted, A/C Evaporator Temperature Sensor circuit poor electrical connection.......P0566 - Cruise Control Off Signal Malfunction...Possible causes; Faulty Cruise Control Switch, Cruise Control Switch harness is open or shorted, Cruise Control Switch circuit poor electrical connection.

Thank you for all of that. I didn't get that info when I looked up the codes myself so this definitely very helpful. When i return the truck to the shop I will show them this post. Thank you again for all your suggestions.


Your welcome. Its the po411 code that is giving you grief.

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