93 Bronco, 302, auto.
OK, long story on how this all got started, but here's the just of it. I had a hole in the exhaust right next to the O2. Basically the O2 sensor was exposed on one side. The truck wants to idle at 2500+ RPM's, won't shift into OD, etc. There was no problems at all before this, so I thought for sure it was due to false readings from the O2. I park the truck for a week. I got the exhaust fixed up tonight, and start the truck. It idles up to about 1600 RPM, so I decide to go for a spin to see if it just needs to re-tune itself. I get a couple miles down the road, and it still isn't acting right. I put it in park, and it idles up to 2,600 RPM. I figure I'll try unhooking the O2, and see what it does, figuring the thing just went bad from being exposed/maxing it's reading. I shut the truck off because I don't want to crawl under it with it running like that. I unhook the O2, jump back in the truck, and it will crank, but won't start. Weird, I think. I have had cars run without O2's before. Oh well, I'll just get a new one tomorrow. I jump out hook it back up, hit the key, and the truck still won't start. I'm stumped now. Fuel pump is priming when I turn the key on. All fuses associated with ignition, engine management, coil, etc. are good. I had just replaced plugs/wires a week before, and truck ran perfect until the exhaust leak.

I can only come up with 2 possibilities...
#1) I turned the truck off at 2,600 RPM, and somehow that caused the timing chain to break without me hearing anything.
#2) Something is now causing the truck to not get spark. The plug on the O2 is in a small harness with the starter wiring, but starter is turning over fine. I inspected surrounding area, and nothing seems out of the ordinary.

Nothing else was touched after I turned the truck off. All I did was unhook the O2 sensor. Any help, or ideas would be much appreciated.

Brandon

 

Pull Codes

www.fordfuelinjection.com has instructions. reinstall the o2 sensor disconnect the battery over night and go back the next day reconnect and see if it will start. the only way for the ecu to relearn after something like this is to have the memory cleared (no battery power).

you might need to replace the o2 all together, if so buy from ford do not use anything else.

 

I forgot to mention...
After hooking the O2 back up, still not getting it to start, and checking all the fuses, I disconnected the battery for approx 2 minutes, and hooked it back up. Still no change. I figure I will need to replace the O2, but the truck should still start atleast, should it not? I will go disconnect it now, and let it sit til morning.
Brandon

Add: I just went down there to unhook the battery. I figured what the hell, and hit the key. There was a definate hick-up when I first hit it, so I think it is getting spark. I have been searching/reading, and have thought of something else. Before all this started, and truck was running good, it did have a weird habit. When I cold started it, it would idle up to about 1,500 rpm, come down to 800, back up, back down, etc. One tap of the gas pedal, and it would idle just fine. I got in the habit of tapping it as soon as it started, and it only did it when cold, so it hasn't really bothered me. Now I am reading about the TPS. Should the truck run with the TPS unhooked? If so, I will try that. I can't do the paperclip thing because the check engine bulb is burnt out, or was disabled by a previous owner. Other than the cold idle thing, the truck ran perfect, and gets 14 mpg average, so I never thought to run codes before now, and I don't have a scanner.
Brandon

 

you dont need a scanner, that site has directions to use a voltmeter if need be. the truck needs the tps,iac,o2 sensor and various other sensors to function properly. the idle you mentioned is some what normal at start up for efi motors. when you turn the key on do you hear the fuel pumps come on? when was your last tune up? have you replaced the fuel filter?

 

Cool, I'll try the voltmeter deal tomorrow. I know it needs the TPS to run properly. I was just wondering if it would start at all without it, my thinking being this...
If faulty TPS is causing it not to start, but truck will run (even badly) without it, it would be a good troubleshooting method to determine if it is the cause. Fuel pump is priming with key. Plugs and wires were done a week before exhaust leak occured. I haven't changed the fuel filter, but truck was running until I turned the key off to unhook the O2. I am leaning much more toward something broke, something electrically was disturbed when I unhooked O2, or some sensor was going bad, and is now shot completely although I don't know which ones have the ability to make the truck not run at all.
Brandon

 

get the codes and we can go from there

 

Tried test with digital meter, analog meter, and light bulb. All result in absolutely nothing...

 

then perhaps your ecu (computer) is bad. the battery was connected when you did all this correct?

 

Getting voltage to plugs. Plugged in new O2 sensor, no change. Fuel pump IS priming. Either timing chain, or injectors aren't firing.

Well, timing chain can't be broken because cam is turning the dizzy. Maybe jumped time due to being turned off at 2,600 RPM's??? Is that even possible?

Brandon

 

Every time I grounded the input, the fuel pump would prime, relays click, etc. I just got nothing off of the output.

 

Quick check for timing chain...pop the distributor cap. Ask someone to try to start it while you see if the rotor turns.

 

What the truck was doing before (idling at 2,600 rpm, not wanting to shift, etc.). Could that be caused by a lack of fuel? I assumed that it was running rich, but the consumption on this tank so far doesn't show that. If anything, it may have been getting a tad better mileage through 1/2 a tank...

 

you can check fuel pressure at the rail. with key on it should be 35-39psi. while engine is running it should be the same. if you pull the vacum line off the fuel pressure regulator and fuel comes out that part is bad. also check your oil for any pressence of fuel. if so then the fpr is bad or an injector is stuck open but that would show up on the plug as well.

 

Well, I got it home. I started pulling the plug on sensors, and trying to start it. I got to the sensor that has one line coming from the egr, and other one feeding the TB right up front, pulled the plug on it, and the truck fired right off. Don't ask me why. It is still trying to idle at 2,500 rpm's and all, so I will go ahead and swap the O2 sensor, and try to find a replacement for this one, and see what happens. Has anyone deleted the EGR all together? I deleted the smog off my 95 Mustang GT, and would like to do so to this one if it can be done without causing idle problems...

 

was the sensor you disconnected look like a silver canister next to the throttlebody?