Diagram of vacuum hoses placement on 1988 mercury grand marquis LS 302 v-8 5.0 liter

Question edited for clarity.
Question moved to model category.

Very strange. I just answered this question. Did you post twice? It was about the factory recall? I suggested calling the dealership and telling that the module has failed and you need to be fast tracked for a fast replacement.

Here is the wiring diagram

https://www.google.com/search?q=2004+mercury+grand+marquis+ls+headlight+wiring+diagram

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Question edited for a lot of clarity.
Question moved from MISC to correct category.

https://www.google.com/search?q=1991+Mercury+Grand+Marquis+GS+5.0.+Vacuum+hose+diagram&rlz=1C1QJDB_enCA643CA644&sxsrf=ALiCzsbNrlH1W5VV0OAK4h8jTsQrUJYYeQ:1662518015156&source=lnms&tbm=isch&sa=X&ved=2ahUKEwjzjued0oH6AhWShYkEHWqvAisQ_AUoAXoECAEQAw&biw=1920&bih=937&dpr=1

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Look at 1993 mercury grand marquis fuse box diagram Google Search

Fig. Fig. 191: Calibration 7-21C-R5-8-302 Mustang 1988 California

Fig. Fig. 192: Calibration 7-21C-R5-8-302 Mustang 1988

i have a 1991 grand marquis ls and the speedometer is not working but the temperature gauge and gas gauge works what could the problem be thank you

It sounds like your Idle Air Control Valve (IAC) is sticking.

No. The car has a bad headgasket. I have a 1987 Colony park, 302.

1993 Mercury Grand Marquis 4.6 liter SOHC V-8 VIN "W" (click for zoom)



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1995 Mercury Grand Marquis 4.6 liter V-8 SOHC VIN "W"



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what is the issue?

Check the vacuum harness on the back of the heater control head to see if it's leaking or not tight.