I'm posting here too since we share drivetrain, hoping to maximize input. Any help would be appreciated...

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's still acting like it did with the leak. 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

 

take distributor cap off and line up timing mark on flywheel either should be pointing at #1 on the cap or a half turn from it,pointing toward intake . THe ROTOR BUTTON

 

OK, I left the battery unhooked all night. I have plugged in a new O2 sensor, no change. Tried to run codes with analog meter, DMM, and light bulb, and got nothing at all out of any of them(check engine light burned out). I am getting spark on the plugs, and FP is priming. Cam is turning dizzy, so either injectors aren't firing, or timing jumped? I'm going to have to get this thing pulled to the house to further diagnose. More ideas are welcome...

Brandon

 

....agree for here, if you want to check BEFORE you start to ripp out anything.......make sure you are on Compression on #1 and then line up mark on crank to " 0 " and this should give you an idea = IF = this indeed jumped or not........
....also, you ARE stating you DO have Spark to all cylinder/plug's, correct???.......but, NO Fuel is being fed to the cylinder's to fire???[ all plug's are dry after you try to start??? ]


mr. Charles


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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...

I changed the plugs a couple weeks ago, and they show'd that it may have been ran lean sometime during their cycle. I chalked it up to some past deal, since the truck had been running fine prior to changing them.

I haven't pulled the plugs yet. I checked for voltage off the cap on all 8 cylinders. The plugs and wires are new. pulling the plugs to check for fuel, and timing check are next. If there is no fuel, what are the possibilities, since the fuel pump can be heard priming? I know if the plugs are dry, I will pull the fuel line feeding the filter, and turn it over to ensure fuel is being fed. If so, change the filter. What then?

I really have no patience for a vehicle that leaves me stranded. The truck is lucky that my kids weren't with me when it broke down. I am already having thoughts of ripping all the crap off, and carbing it (but how to keep E40D, hmmmm), as well as the thoughts of buying a Jeep for christ's sake. Atleast you can pull the motor out of them, and have it on a stand in under 2 hours.

Brandon

 

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...

 

OK, I change the O2 sensor, and there is no change in idle/shifting. I start the truck 2 or 3 different times during this test out. So I go back home this time, turn off the truck, unplug the TPS, hit the key, and it won't start. I go plug the TPS back in, and it still won't start. This is the exact thing that happened with the O2 sensor last night, but this time it's the TPS. I had a friend turn it over while I watched the pin inside the TPS, and it is moving. It's getting spark, and there is pressure on the fuel rail. This is freakin nuts guys. Any ideas?

Brandon

 

Well, your O2 sensor won't make it idle that high. . .if you unplug it I beleive the computer just runs from some preset values until it starts to receive a signal within its range of values, same goes for most sensors. No sensor will let your engine idle that fast. Those sensors calculate fuel based on the air and it's qualities making it into the engine. With those kinda rpm I doubt a rich/lean condition is a possible cuase. Your getting more air into it at idle than it needs. . .

My best guess, is you need to check for 4 things:

-check for some major vaccum leaks around the manifold.

-check the idle-bypass solenoid. . .valve thingy (I forget its actual name). It's mounted on the throttle body, has a plug with 2 wires coming out of it. If you unplug it and your engine dies you have found your problem. If you unplug it and your engine's idle changes, then it is probably working correctly and you have a vaccum leak somewhere you haven't found yet.

-check your cruise control linkage or throttle linkage. Reason I mention this is that I had a weird high idle problem that just popped up. When I pulled into a parking lot to check it out, the plastic tubing that makes up the linkages had jammbed into each other and cuase the butterfly valves to not cloase all the way.

-there is a manual idle ajustment screw on your throttle body. Have you tried unscrewin it some to see how it effects your idle?

Anyways good places to start i think, or I could just be an idiot

EDIT: The above are for your high idle condition. . .the no start thing, well. . .I used to heave cynder blocks across the yard so I didn't lose my temper

 

very bad advice to touch the idle screw.

set at the factory and very difficult to get reset.

 

What? I had to replace the one on my '87 4.9l becuase it was cross threaded by the previous owner. . .just ran a similar screw into the boss and it was fine. . .

Unless, we are talking about two different things?

 

Quicklook2 is right.................Don't touch the idle adjustment screw.

Find the problem................it's not an adjustment.
Something is loose or intermittant.

 

Hey, I don't know if my advice will help, but check the ICM, I think it is on the distributer on the 302 (Oppps. I meant around the Coil). I remember my 89YJ having the same sort of problem, it had fuel, spark, everything, when I changed the ICM, everything worked great again. FYI, the 89YJ had a Ford Ignition, so it should be set up AROUND the same way, except it was a Carb. Check for power (I think it was the) purple wire.(Probably, not set up the same way though... ) Hope this is it.

Gig