I have a 91 honda accord that stalls out when driving. I've replaced fuel lines and maf sensor. I replaced the maf sensor because it was throwing the codes for it. I've read other forum posts that say it might be a ignition switch.

So my question is, if the ignition switch isn't working properly will that prevent the fuel pump from turning on? And how can I diagnose it to be the ignition switch.

 

Did the code go away after replacing the map sensor? Did you get any other codes. Was any work done on the car before you had the stalling problem? Any chance you filled up the gas tank before this happened?

A faulty ignition switch can prevent the fuel pump from turning on. A faulty ignition switch can also cause the car to stall, but keep powering the fuel pump. It depends on how the ignition switch failed.

For testing:

1. Caveman test. Shake the key when the engine is running. If the engine stalls, then you confirmed the ignition switch isn't making good contact. If the car doesn't stall, it does not rule out the ignition switch.

2. Test light(s). The input to the ignition switch is the white wire. The switch sends that power out through 3 different wires. wht/blk, blk/yel, and yel. You would need to back-probe at the ignition switch connector under the steering column on each wire. Hook a test light from each wire to ground. See if the light turns off when the engine stalls.

 

Do you mean the MAP (manifold absolute pressure) sensor?The 91 Accord doesn't come with a MAP sensor. I know because mine (91 Accord LX) doesn't. It's OBD1.So I don't know how you replaced it being that it's not supposed to be there. Nor does it have a (Mass Air Flow) MAF sensor. Was there a engine switch? However, the on board computer will give you that reading if the engine is not grounded properly. I found this out when my Accord was throwing the code for the MAP sensor which it doesn't have. I attached a ground wire between the back of the engine and the firewall.
The issue is most likely related to the fuel relay which is above the steering colum under the dashboard.

 

I'm pretty sure the 1991 accord has a map sensor. Later accords had the mass air flow (maf) sensor starting (I think) with the 03 accords.

 

Pretty sure? No offense but I have to disagree. Mine was throwing a Map sensor code so I went looking for it and couldn't find it. They're usually on the air intake and there was another possible position on the bottom of the transmission Which didn't make much sense to me. Then I researched it for a month. Come to find out the 91 didn't include it. However since it does throw the code I guess it can be added on but it wasn't standard as I understand it.

 

So the oem accord parts site shows a map sensor for the 91 and the oem shop manual has a map sensor code listed, so I'm 100% sure the 91 accord has a map sensor. It has to, so the ECU can control the air/fuel mixture on a fuel injected engine.

The map sensor is listed as #32 on the parts diagram.