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Rough & High Idle After Intake Manifold Swap

reansor

Well-Known Member
Joined
May 21, 2013
Messages
131
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4
City, State
Baltimore, MD
Year, Model & Trim Level
2003 Mercury Mountaineer
2003 Mountaineer 4.6. I've posted a few items about assorted issues on this truck in the last month. The truck was running fine, but I recently changed my intake manifold because it was cracked and slightly leaking coolant into cyl. 5 spark plug well. I was a PITA, but I got it done and fired it up and it ran terribly. It was idling very rough and then smoothed out as the idle speed jumped up to about 3000 rpm all by itself for a little while. I scanned it and got 2 codes back for a bad coil pack and 2 fuel injector open circuits. I replaced the coil pack and put a dab of dielectric grease on the injector connectors. This cleared the codes, but it's still running like sh*t--like it was previously, but now "only" idling at 2000 rpm. After a few minutes the idle will taper down and it stalls.

Someone please help! I used to be a very good mechanic back in the day, but my skills and knowledge are a little dated. I mean stuff I could have narrowed down to 2 or 3 possible problems 20 years ago could now be one of 50 on newer vehicles.
 






Your idling way too high. Have you adjust your butterfly to lower idle. Doubt that will fix the problem but it's worth a shot. Ideally you would want it to idle at about 600 and no more than 1200 on startup. Your idling in dangerous rpms for a cold engine impo. Did you swap out spark plugs and re gap them. Have you checked fuel pressure? Tested the fuel rail sensor. I would take those injecorts that had codes and put them into an empty water bottle and see if they are spraying when you turn engine on. Did you ever locate and hookup that connector? Post some bigger pictures of as many shots of engine as possible. Pm me if you don't know how to post them. I'd also suggest getting a code reader compatible with forscan so you can see what's really going on. The cheap eBay ones typically won't work with forscan at least the 3 I have tried.
 






Your idling way too high. Have you adjust your butterfly to lower idle. Doubt that will fix the problem but it's worth a shot. Ideally you would want it to idle at about 600 and no more than 1200 on startup. Your idling in dangerous rpms for a cold engine impo. Did you swap out spark plugs and re gap them. Have you checked fuel pressure? Tested the fuel rail sensor. I would take those injecorts that had codes and put them into an empty water bottle and see if they are spraying when you turn engine on. Did you ever locate and hookup that connector? Post some bigger pictures of as many shots of engine as possible. Pm me if you don't know how to post them. I'd also suggest getting a code reader compatible with forscan so you can see what's really going on. The cheap eBay ones typically won't work with forscan at least the 3 I have tried.

Yes, it's definitely idling way too high. As I said, it was idling and pretty much running fine before I dismantled it. Tomorrow I'm going to go through the vacuum lines and over everything with a stethoscope to see what I can find. The two injectors that came up with code readings were for "open circuit." I noted this was truly an injector flaw and simply a bad connection and disconnecting them and putting a dab of Dielectric grease on them corrected the the code. The code reader I have is an Actron entry level one, but I'm told it's pretty reliable. Again, at this point I'm thinking vacuum leak or misconnected vacuum line, but I'll keep you posted. Thanks for your advice.
 






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