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HDGENE
HDGENE, ASE Certified Technician
Category: Mercury
Satisfied Customers: 4784
Experience:  25 years experience Ford Senior Master Technician/Diesel certified ASE Master Technician
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1990 MERCURY GRAND MARQUIS. WHWN IN STEP ON THE GAS HARD THE

Customer Question

1990 MERCURY GRAND MARQUIS. WHWN IN STEP ON THE GAS HARD THE ENGINE SURGES. CAN HARDLY SLOW DOWN THE CAR,BUT WHEN I DO I PUT IT IN NEUTAL AND THE ENGINE IS STILL RACING. BUT, WHEN I PUT BACK INTO GEAR THE ENGINE GOES TO NORMAL IDLE. ONLY HAPPEN WHEN I PUSH DOWN HARD ON THE GAS. IF I BABY IT,EVERYTHING IS FINE
Submitted: 6 months ago.
Category: Mercury
Expert:  HDGENE replied 6 months ago.

Hello, so the car has normal power just races when you accelerate? High Idle in park or neutral on start up? Is the check engine light and have you had it checked for codes with a scan tool?

Customer: replied 6 months ago.
NO CHECK ENGINE LIGHT. ONLY SURGES WHEN I AM DRIVING AND I PUSH HARD ON THE ACELORATOR AND THE ENGINE SURGES AND HARD TO SLOW DOWN. I WILL PUT INTO PARK, ENGINE IS SURGING VERY FAST,REAR WHEELS ARE FISH TAILING. BUT, WHEN I PUT BACK INTO GEAR THEN IT GOES BACK INTO NORMAL IDLE. THIS DOES NOT HAPPEN EVERY SINGLE TIME,IT IS INTERMITTENT.
Expert:  HDGENE replied 6 months ago.

Is the accelerator pedal hard to push like it is sticking? Have you checked the engine for any vacuum leaks back by the throttle body area. There is a vacuum tee on both sides of the throttle body that likes to collapse and suck in air.

Customer: replied 6 months ago.
NO HAVE NOT CHECKED VACUUM LINES YET. THE GAS PEDAL DOES NOT STICK. HOWEVER I HAD A NEW THROTTLE POSITION SENSOR PUT IN 2 YEARS AGO AND A IDLE CONTROL SELONOID PUT IN AT THE SAME TIME. CAN THEY BE GETTING GUMMED UP? UNDER NORMAL CONDITIONS THE CAR IDLES NORMALLY, NO HESITATION OR STALLING OR ROUGH IDLE. SO, I DO NOT THINK IT IS VACUUM LINES. JUST THIS PERIODIC ENGINE SURGE
Expert:  HDGENE replied 6 months ago.

Ok, double check the two vacuum tees at both sides of the throttle body for being collapsed, this is a common issue for a high idle as it pulls in unmetered air. The Idle air control valve controls the idle speed so it may be sticking at times. Usually they cause crank/no start issues when they have problems but is a possibility. Make sure the throttle plate is free from any carbon buildup. If it is sitting patrially open when it should be closed it will also cause a higher idle.Remove the air inlet tube to it and use carburertor cleaner and a small toothbrush and clean out any carbon buildup around the throttle plate. Start the car up it will crank longer until it burns out the carb cleaner. Then recheck. If it is still having a n issue, a diagnostic check for trouble codes would need to be done. Being an EEC IV system, if you dont have a scan tool, you can jump the self test connector under the hood and count the check engine light flashes. 11 or 111 is pass.

Expert:  HDGENE replied 6 months ago.

Do you need more help with this concern?

Expert:  HDGENE replied 6 months ago.

Hello, do you need more help or information?

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