Please help! Merkur Scorpio Plenum swap

[coach_87]

Dvdswan,
Not sure I know what your mean. The only vacuum not hooked up right now is my carbon can(which I'll put a breather on the can and call it a day) and my cruise control(because I haven't found the right cable yet).

I've ran the truck three times now with better results each time. Idling at 950rpm and coming back down to idle quicker from any open throttle. I'll go for a test drive around the block before I mess with timing.

 

[alwaysFlOoReD]

Slow to come down to idle is a oem strategy for less emissions. But I'm not sure exactly how long the hang should last...
It seems to last forever to my senses, but I was raised on carburetors.

 

[coach_87]

Alright so happy to report back after first test drive, I went 30km one way and back to my preferred junkyard. Truck runs great, except it does a high idle when first getting to my destination but I blipped throttle and came down to 950-1100rpm. I think its still learning a bit.

I tested other ford map sensors while there, my current map sensor holds vacuum better than anything there. Also looking for a cruise control cable that I wouldn't have to modify to make work, no luck.

I think the truck is running a bit rich but not sure if from the recent changes or the months old gas.

I'd say the truck is not faster at all lol but it does feel like a bit more torque in the lowers gears in the 2-4000rpm range.

Side note, scored a 98 console with cup holders to go around my shifter, even has the inserts. Super excited, been looking for that forever! No more hill Billy cardboard cup holders!

 

[dvdswan]

My apologies I've done most of trouble shooting on Nissans which use a MAF not MAP sensor.

How much vacuum do you have at idle?

 

[coach_87]

Dvdswan, not sure what I have for vacuum now that it's idling closer. I'm inside for supper right now, I can pull back inside the garage and test it after when I pull out timing light. Everything is close at this point I feel. But I'm a fairly beginner backyard mechanic with only basic problem solving skills.

How much vacuum should my map sensor be seeing? I could not find the answer anywhere.

I think an adjustable fuel regulator may be in my near future.

Also everything I googled merkur scorpio vacuum diagrams I came up with these pictures from UK, do I need those extra parts to make my truck run right?

 

[dvdswan]

I found this page below and believe it may have some good information for you. I'm learning as well as you are.

Manifold Absolute Pressure MAP Sensors (aa1car.com)

 

[coach_87]

That's a good read. So by the sounds of that article my map sensor is bad because it doesn't hold vacuum. Which makes sense with my still slightly high idle and rich condition. But 3 of 7 at junkyard tested the same as mine so.... I dunno.

I wonder what difference it would make if I ran map sensor vacuum off the same T as the fuel regulator at the back of the intake? Probably not a good one but nothing to lose my trying it.

 

[dvdswan]

So, 3 of 7 measure the same as yours, what did the other 4 read. Maybe they're good. How much does the j/y want for a sensor? If its 10 bucks I'd try just to see if there's a difference.

 

[coach_87]

I didn't ask how much they wanted. The other 4 did a worse job of holding vacuum, 2 didn't hold vacuum at all. Only 2 of the 7 were from 2.9l's and they were bad, the other 5 were just what I could find similar in ford's. Sorry if that doesn't make sense, but long story short I figured I had the best condition map sensor so left them.

But new at local store $120 or order from rockauto for $50-60.

I do see your point though so maybe I'll travel around the junkyards this week after work hours and see what I come up with. A slightly differently calibrated map sensor could be my key too.

By the way dvdswan and everyone else responding thank you for all the helpful responses.

 

[coach_87]

Reporting back for anyone following this.

Truck was running a bit rough at first but I came to figure I hadn't driven the truck much lately so maybe I should spin the tires a few times and see how it goes. Running and driving amazing after very slight adjustments, switched which vacuum off the throttle body went to vacuum(the more forward one), set the tps at 0.715 and not sure if it did anything but dropped a degree of timing to 9(from factory 10). It does the cold start high idle much longer than it used to but probably not excessively long. According to my timing light it idles just under 900rpm when warm and I cant figure how to get it lower at this point, it's fine there though. Throttle response is way better as well.

Overall I'm happy with the results. Still gotta get a cruise control cable.