poor idle high rpm sputter what next

[dstubbs]

Hi guys,
I have a 1999 ford ranger with a 3.0 v6 and manual tranny. The engine is new only 1k miles on the long block. My problem is high rpm cut out and poor idle. When I first start the truck in the morning it runs great good idle nice power and good rpm pull. within 5 min of running I start to get sputtering at higher rpms almost like fuel is cutting out. as the truck get warmmer the problem becomes more apperant and the idel becomes choppy. I've got new motorcraft injectors and fuel filter as well as new wires and plugs (all motorcraft). I'm a little strapped for cash and wanted some opinions on what to try next. from what I've reading looking at fuel pump and/or regulator and possibly coil pack. Any other ideas or suggestion on what to try fisrt.

Thanks , Dave

 

[Earl43P]

So it runs fine cold (open loop) and badly when warmed up (closed loop).

That indicates an Emissions system problem.
It could be anything from an IAT, ECT, O2, MAF, TPS, etc.

Most of those sensors can be tested quite easily with a multimeter.
A scanner that shows live data (like a ScangageII or similar) would let you see what each sensor is reading.

Nothing about your symptom makes me think fuel pump or fuel pressure regulator (yours is in the tank by the way, that thing on the fuel rail is just a damper). It's easy enough to test the coil, just connect a spare spark plug to each wire, one at a time and start it up with that plug's body touching a ground (the intake works). If all the wires deliver a bright blue spark, the coil is good.

If all this started with the engine replacement, take a good look at your wiring around the transmission. You wouldn't be the first guy to pinch the O2 sensor wires between the block and the transmsission, or have them melted by the manifold.

 

[dstubbs]

Thanks Earl,
I don't have an SES light on so I didn't think to check emission system. It had the problem before the engine swap but not as bad. is their a part of the emission system that if bad will not put up a code?

 

[Earl43P]

Might be simpler if you list which emissions parts you reused from the original engine.

 

[dstubbs]

Used All of them. You are definetly correct about the emissions. I just pulled the plug off the MAF and the truck runs like a champ. I cant say its the MAF or just the fact it is running in "open loop". it was remarkably better though more power better idle and top end is back.

 

[Earl43P]

http://easyautodiagnostics.com/ford_maf/maf_sensor_ford_1.php


Another easy way to get it into open loop without disconnecting the MAF, is floor the gas pedal. It does sound like a bad MAF though.

 

[dstubbs]

Feel silly, turns out my throttle wasn't even close to going full throttle not sure why it sputtered but once I did the zip tie fix going to 5K no problem with more power of course.