Mechanics

RUNNING RICH

1999 Ford Ranger • 190,877 miles

Starts up idles high then comes down like its supose to idles good throttle about half let off it dies hard to get started, idles rough about 1 minute smoothes out idles good, throttle again let off real slow idles rough 1 minute smoothes out idles good. Clean plugs they get black again. Changed maf sensor, tps, fuel pressure regulator fuel filter, iac. Fuel pressure 65lbs.
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Cb8061
September 17, 2013.



Have you checked for a vacuum leak any where pass the MAF sensor? A lean condition will cause the computer to enrichen the air fuel mixture. Vacuum leaks are common on these especaily on the intake tube and intake gaskets. Let me know what you find. TY

Ty Anderson
Sep 17, 2013.
Yes I have checked for vacuum leaks, no leaks.

Tiny
Cb8061
Sep 17, 2013.
Do you access to a scan tool that can read datastream (what the computer sees from the input sensors)?

Ty Anderson
Sep 17, 2013.
Yes a snapon scanner. Forgot to tell you no cil, no codes, scanner shows every thing fine, it doesn't even show rich mixture.

Tiny
Cb8061
Sep 17, 2013.
A few things to check. What are the short term fuel trims and long term fuel trim at idle and 1500RPM?
What is the throttle positioning sensor read at idle and 1500RPM.
At idle can you kill the engine just by cranking the steering wheel (vehicle not in motion)?
What happens when you turn on the a/c does the engine RPMs increase or does it cause the engine to stall.
I forgot to ask if the engine stalls when driving or at idle? Does the engine stall more frequently when it is cold or at operating temperature? Answer these questions and get back to me, TY

Ty Anderson
Sep 18, 2013.
I'll have to get the scanner back from my brother. I forgot to tell you, I changed the temp sending unit. I'll get back to you.

Tiny
Cb8061
Sep 18, 2013.
Ok let me know

Ty Anderson
Sep 24, 2013.
Finally getting back to you. Fuel pump stopped working put new pump, pressure regulator and guage in, didn; t fix it. Ac doesn't effect idle, idles ok. Turning steering wheel doesn't effect idle. Sft fuel trim at idle 6 to 12 lft 0to 3 1500 rpm sft 0to11 lft 3to11. Tps v idle.77 1500.92 engine shakes at 1500, short plugs out, can't find one not firing. Unplug one coil pack, runs the same unplug other, runs same unplug maf senser runs same. Mechanic for 40 years never seen anything like this.

Tiny
Cb8061
Sep 30, 2013.
Have you checked the throttle body for build up around the throttle plate. Build-up can cause a air restriction when the throttle plate closes causing the engine to stall. Clean the throttle body with a rag and appropriate intake clean designed for throttle bodies (the throttle plates are coated so brake clean for example will strip that coating off). Try this and get back to me.

Ty Anderson
Oct 7, 2013.