Recently I addressed a hard start/stall issue with my 95 F150, apparently successfully. No stalling now, just hesitation when I engage the throttle. Seems the RPM may drop slightly, but after about a second it accelerates. I replaced the MAP sensor, idle control valve, fuel filter, starter, alternator. Tested the throttle position sensor with a multimeter, looked good.

After the work, I'm not getting a check engine light on anymore, so no codes. Any suggestions?

Thanks!

 

How old is the oxygen sensor?

Had the same problem and the original O2 sensor with 200k miles was the culprit.

 

Did you find any active or stored fault codes in the KOEO self test? Is that what lead you to replacing the MAP sensor? Have those codes been fixed? When retesting for faults have any of them returned/ do you have new codes? The check engine light does not need to be on for there to be codes.

Have you put a gauge on the fuel pressure test port? If so, with the engine running what is the pressure with vacuum hose on and then disconnected? Did you use a digital or analog meter to watch the voltage sweep on the TPS? It can be difficult to see a dead spot with a digital meter.

 

I will rescan shortly, I thought lack of CEL meant no codes. I have the 3145 scanner. Prior to replacing parts I read these codes over several scans: 116, 118, 172, 332, 538, 636. I will buy a gauge and try to test the fuel pressure, hopefully there's a procedure somewhere for me to follow. I did test with a digital meter, will look for a analog tester.

Also, I replaced a burnt fuse, related to the O2 heater, IIRC.

Thanks!

Add: don't recall what lead me to replace the sensor, it was about a month ago, it must have been suggested in this or another forum for similar problems.

 

Just listing the codes does not mean much. Since you are using the 3145 scanner you know that some codes can be active (KOEO), engine running codes or stored in memory. You should have also read in the owners manual (page 32) that “The KOEO Self Test must be performed first, and a “pass code” ( code 11 or 111) must be obtained before performing the KOER Self Test; otherwise, results of the KOER Self Test may be invalid.” It is impossible for us to know what they are. The truck needs to be up to operating temperature before performing the KOEO or KOER. If not that could explain the 116 & 118 codes unless they are stored codes. Did you quickly press the gas pedal to the floor and release it during the KOER test? If not then that is why the 538 code was set. I’d also say that the 636 code is from the transmission not being up to temp.

A procedure for testing the fuel pressure? The correct way is to disconnect or trip the inertia switch and run the engine until it stalls. The schrader valve is on the fuel rail. Connect the gauge the reset the switch. Start the engine. You need to not only get that reading but also disconnect the vacuum hose (keep your finger over the end of the hose to prevent a vacuum leak) and there should now be a higher pressure.

 

Thanks, yes, you've reminded me of the warm up condition being required when I obtained those codes last month. I will follow the manual closely to read the codes shortly. BTW, also replaced ignition coil.

 

I just read the codes and they are 111, 10, 332. I know what the first two are, 332 is insufficient EGR flow detected. Perhaps I should look for vacuum leaks. Strangely, the hesitation I saw yesterday was absent today. Still, would like to address the code. Should mention, last month I replaced my thoroughly rusted vacuum cannister by supergluing the top connector section to an empty pineapple juice can. Seemed quite air tight.

Edit: gorilla glue gun, not superglue.

 

I would clear the codes, drive it for a while and then check to see if it comes back.

 

OK, will do, thanks.

 

Jim, complete novice here but my mechanic found the throttle/carb body sensor/adjuster plastic thingy on top of the bit where the activation lever is on top of the body had worn & was slipping.
Hopefully someone can translate my garbled info & fading memory!

 

Thank you for the suggestion. I have ordered an analog voltmeter to check the throttle position sensor over it's range.

 

How was the results??