1996 Ranger Upper Intake Swap - REALLY High Idle

[jhart92]

Had exhaust problems on my 96 4x4 Extended Cab 3.0L Manual ranger so i decided to try and bring over the upper intake manifold and exhaust manifold from a 1999 flex fuel 2wd ranger sport i had in the yard. got the exhaust manifold and upper intake to bolt up - had to get a little creative with the egr sensor placement and brought over the egr from the 99 but now the truck idles at 3500~3800rpm. checked for vac leaks, changed intake gaskets, cleaned the everything with maf cleaner, swapped icv, swapped pcv, swapped maf, and done just about everything i can think of while unplugging the battery each time. the only way i get a difference is by unplugging the maf - idle drops to about 900-1100 and runs rough. anyone have any ideas as to how this is happening would be greatly appreciated! it's my daily driver these days for various reasons and im deep enough into this project where swapping intakes again would be highly inconvenient. only difference i was able to spot was the evap system has a vac line going to it so i capped that off when i brought over the vac lines.

 

[RonD]

1999 Ranger used different fuel system and injectors(Flex), so I assume you keep 1996 fuel rail and 1996 injectors to match 1996 Computer?

IAC Valve sets idle...............if there are no air leaks
Unplug its 2 wire connector and see if idle drops down, if it does then either its stuck wide open or computer was holding it open

MAF sensor just measures "air WEIGHT" not air flow, computer already "knows" the air flow into a 3 liter engine at X,XXX RPMs, its just math
Unplugging it puts computer in to "table mode" it uses preset air/fuel tables in memory to run the engine, so doesn't calculate air/fuel mix "on the fly"
Rough running would indicate an issue with "hardware" on the engine not sensor issues

3.0l can be sensitive to Cam sensor mis-timing, when changing the intake did you move the Cam sensor?

Check your firing order on the coil pack, often mis-wired on the 5 6 4 side
3 4
2 6
1 5
front or side

3/4, 2/6, 1/5, each pair share one coil in the 3 coil pack, 1, 2, 3 is usually OK but check any way, the 5 6 4 side often gets mixed up

 

[jhart92]

checked firing order - even tried both coil packs and vacuum minus the lines (vacuum plug for the intake is different and from what i read the firing order is totally different for the 99 flex but it didnt change anything). unplugged iac and tps separately and together previously (forgot to mention) no change. did not move cam sensor. at this point the only things that were moved over were the actual upper intake, egr/tube and driver side exhaust manifold. i understand how the maf works but I dont understand what you mean by "hardware" though. it only seems to run rough when the maf is disconnected when it is connected it runs mint - albeit at damn near 4 grand haha. only code im getting is p0500 for the vss but i think its unrelated. wasn't present before though.

 

[jhart92]

i also tried/cleaned both iac valves with maf cleaner. the angle of the connector is different but i didnt see much change otherwise in design so i tried both with no change

 

[RonD]

Just upper intake swap, so you are using 1996 fuel rail and 1996 injectors?

"hardware" is anything not monitored by a sensor, because if it was monitored by a sensor and was "out of range" you would get a code
Vacuum is not monitored, fuel pressure is not monitored, at least on a Ranger, lol

RPMs are created by air, that's what the throttle plate is used for
If you add more fuel to a running engine you get a flooded engine and it will stall, not higher RPMs
If you add more air you get higher RPMs, and a lean mix which causes pinging/knocking, if no extra fuel is added

MAF sensor plugged in
Take the air tube off the front of intake, check throttle plate for looseness, its spring should hold it tightly closed
Start engine
Use your hand(with glove if you like) and put hand over air inlet of running engine and see if you can block it off enough to hear a leak, bring down RPM or stall the engine
That opening should be the only entrance for air so blocking it off completely means engine stalls