1999 Grand Marquis Starting Problem - Ford Forums - Mustang Forum, Ford Trucks, Ford Focus and Ford Cars

danodemano · 02-15-2010, 04:47

So this has been happening for a couple of weeks now but it seems to be getting worse. The car has been running great since my last incident back in August (1999 Grand Marquis P1405 Code) and I just passed 160k miles. However, I'm now seeing a new problem. When it's cold out (below 30 mainly) I have trouble starting it. It will crank and fire up in 2-3 cranks but then the RPMs drop off and the engine dies. The only way I have managed to overcome this is that as soon as the engine fires up I get on the gas for a second or two then let off and the engine will stabilize and the car will stay running. This morning it was especially bad since I didn't drive it for 3 days and it sat outside in 20 degree weather. I had to keep the RPMs up until the engine warmed up them it was just fine. I can experience this problem though after it's been sitting for just 5 or so hours in the cold. This seems strangely reminiscent of a problem I had on my '92 Crown Vic 4 or 5 years ago where a vacuum leak would cause the engine to die at low RPMs. The difference though is that the Crown Vic would start fine but as soon as I would pull up to a stop light and the RPMs would drop, the car would stall. I'm not seeing that on the Grand Marquis. It's fine once you get it to stay running. I've thought possible something in the EGR system but haven't a clue where to even start to diagnose this problem. The computer has not thrown any error codes, I hooked up my OBDII scanner just to be sure. Any help would be greatly appreciated, thanks!!!!

**Bert** · 02-15-2010, 08:13

Several things can cause that. Try cleaning the IAC and MAF. The ECT engine coolant temp sensor (Cyl. head temp sensor), IAT sensor and throttle switch. They won't set a code if they're reading what they're supposed to and getting the wrong reading for the temp or position.

danodemano · 02-15-2010, 08:17

I can handle that I think, can you please point me in the right direction as to where I can find each of them on the 4.6? I think I have a repair manual somewhere but in general is seems to be less than helpful. Also, how would I go about cleaning them? Thanks!

**Bert** · 02-15-2010, 10:00

The MAF is in the cover of the air cleaner box. There's a special cleaner for them. The IAC is on the throttle body. I'd start with them and see how that does. There could also be a vacuum leak, so you could look around the hoses and see if any are loose or cracked.

danodemano · 02-15-2010, 10:31

I'll stop on my way home and get some cleaner. Vacuum leak was the first thing that came to mind when it started happening. I did a vacuum check on it last summer when I had trouble but seeing as how I drive 30k+ miles a year it could have easily been compromised since then. I actually have a vacuum gauge so I will go through and check it again. I will post back in a day or two after I get things cleaned and checked and let you know. Thanks for you help!

EDIT: Due to bad weather (7 inches of snow and it taking me 2.5+ hours to go 40 miles) I wasn't able to get to this today. I will try to stop tomorrow and get what I need to clean it then let you know what I come up with.

danodemano · 02-18-2010, 07:57

You rock!!!! I picked up some throttle body cleaner and MAF cleaner on my way home Tuesday. When I got home I took the MAF off and took it inside and cleaned it. The IAC was a problem, the two screws holding it on were stripped out so I did what I could to clean the throttle body and IAC. Let it all dry then put it back together. Yesterday morning it didn't want to fire up right away (it cranked 10 or 12 times) but I think there must have still be some of the throttle body cleaner gumming up the works. This morning when I fired it up it started without a problem, I didn't have to touch the gas pedal. It's idling real smoothly and seems to be back to normal. Thanks for your help!!!!

**Bert** · 02-18-2010, 08:37

Glad you got it fixed. Thanks for letting us know.