OK guys, I am asking this question for a neighbor. He has a 93 F150 with the 4.9L inline 6. The other day his starter died and he today he changed it. The truck has sat for a couple weeks and today after the starte change the truck is hard to start(turns over normal) and when it does start you have to keep your foot on the gas. We pulled a few codes and changed the MAP, plug and plug wires. The truck acts like it has a very bad miss with the exhaust popping every once and awhile. It also acts like a vaccum leak. We inspected a few lines and changed a few. I also noticed the converter started glowing red when the truck was running. Is it possible the truck is running to lean or the converter is clogged. What could be the possible problems?

Thanks,
Brian

 

If you suspect the converter, and it is possible, unhook the exhaust at the manifolds and try starting it, if it is plugged exhaust than it will run normally ( but noisy ) with it unhooked. If you pulled codes, was there any O2 codes as the O2 can make a vehicle run lean...

 

I was thinking it's running rich since the converter is overheating. Inspect all of the vacuum lines, sensors and wiring to make sure some animal hasn't gnawed through anything important. What were the codes you got?

 

I agree that the motor is probably running too rich rather than lean. It might indicate an excess fuel supply caused by a gummed up/leaking injector after sitting for a few weeks. Run the codes again and post them so that we can see what's happening. You might also want to check the fuel pressure regulator to make sure that it isn't pumping too much pressure into the fuel rail.

Keep us posted!

Cheers!

Mike

 

Guys thanks for the help. We are going to pull codes again today and disconnect the exhaust at the cat to see. We didnt get a o2 sensor code yesterday but that doesnt mean I didnt miss the flash. I will keep you guys posted.

Thanks,
Brian

 

OK guys we didnt get very far today but we did the codes a again and this what we got with the ignition on, engine off.

22
26 or 28 (he was watching)first thought 27
32
42
52

We did all this by jumping the two terminal. He is trying to find a scan tool to try. The fuel filter didn't come off so he has to get the special tool.

Brian

 

I wouldn't bother with a scan tool. It won't tell you anything more than what you know already. How sure are you of the codes? My dad's 92 4.9 uses 3 digit codes instead of the 2 digit ones. The reason I ask is because 52 is for power steering pressure switch, which should only appear on 5.0 trucks with a manual transmission.

 

I am certain about 52. His truck is the 4.9 with a manual trans. I don't think is to worried about that code. He just wants to get it running again. All the codes we got were 2 digits. We did it twice yesterday to make sure we didn't miss something. Any other ideas of what we could check?

Brian

 

I'd check the wiring to the MAP sensor. You said you replaced it already, so I don't think the sensor itself is the problem. If that is causing the rich condition, that could also trigger the O2 sensor code from the computer not being able to adjust the mixture enough to overcome running too rich.

 

I checked the wiring to make sure we are getting the proper volts and ohmed the sensor out. The old sensor didnt meet spec so we replaced it. We checked the idle control sensor also and it was good. We removed the 2 screws and cleaned it but it was already pretty clean. Any other ideas? I cant help him today because of work but I can have him check the wires again and pass along any other ideas.

 

You can't really "ohm" a MAP sensor, you'll ruin it. They use a frequency based output, so measuring voltage out or internal resistance won't really tell you anything useful. Another thing to test is the fuel pressure regulator, although I'd try to take care of what is causing the codes first.

 

How do I check the fuel pressure regulator? At idle I removed the vaccum line to see if that changed anything but it did not.

 

Bump, fuel pressure reg check?

 

You can check the fuel pressure with a fuel pressure gauge. If you didn't get any fuel out of the vacuum line with the engine running, the diaphragm should be fine.