Help me diagnose two problems
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Junior User
Joined: Mar 2004
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Help me diagnose two problems
The first is after I have been driving my Bronco for a while ,say from work to home, and then I shut it down and park then go back say with in the hour that is when the problem occurs. The thing doesn't want to idle. It fires up fine but then idles for a few seconds then shuts down. It usually takes a few times before it will idle and even then I usually have to goose the gas pedal. My buddy thinks that the low idle is set to low, but if that was the case wouldn't it do that all the time and not after it has been run for a awhile then shut off, then turned back on after a few minutes. What is the problem and how do I fix it?
Then second problem is that now I am burning through the gas. I have new tires, good alignment, clean gas and air filter, not speeding, not revivng the engine, etc. This same buddy has told me that the fuel mixture is too rich. How do I know if I am running too rich or too lean and how do I fix the situation?
On another note just wanted to thank everyone for the help I have gotten here. I am new to Broncos and this forum has been VERY helpful. I don't post a lot, but I read A LOT in these forums. Thanks again.
Then second problem is that now I am burning through the gas. I have new tires, good alignment, clean gas and air filter, not speeding, not revivng the engine, etc. This same buddy has told me that the fuel mixture is too rich. How do I know if I am running too rich or too lean and how do I fix the situation?
On another note just wanted to thank everyone for the help I have gotten here. I am new to Broncos and this forum has been VERY helpful. I don't post a lot, but I read A LOT in these forums. Thanks again.
Senior User
Joined: Mar 2004
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From: South Texas, right on the border
For the FIRST PROBLEM: i too have the same thing goin on with my 90 bronco with 302 except that it also happens in the morning. I have asked around in here and most of the guys tend to think its the TPS (a.k.a. Throttle Position Sensor). If it goes bad it may cause spikes in your RPMs and/or the idle may vary and then shut off until you 'play' with the gas pedel a bit. I still havent replaced it on mine because of LACK of 'funding' but i checked at autozone and it was about $35 bucks
For the SECOND PROBLEM: Is this a recent thing or has your bronco always had this mileage (what is your MPG and engine)? Like FordPerf300 said, try replacing the O2 sensor. Also, the fuel your using may be low in octane, pick up a 97cent bottle of octane boost from Wal Mart and see what that does. Maybe there is mineral build up in parts of the engine, you may try to run a bottle of engine cleaner in your gas. And it may just be that you need a good tuneup (new distributor cap, rotor, plugs, plug wires, O2 sensor).
PS: My bronco is getting about 11.5 MPG in town (a little better on highway) and from reading others posts this is pretty good. Hope i could help.
For the SECOND PROBLEM: Is this a recent thing or has your bronco always had this mileage (what is your MPG and engine)? Like FordPerf300 said, try replacing the O2 sensor. Also, the fuel your using may be low in octane, pick up a 97cent bottle of octane boost from Wal Mart and see what that does. Maybe there is mineral build up in parts of the engine, you may try to run a bottle of engine cleaner in your gas. And it may just be that you need a good tuneup (new distributor cap, rotor, plugs, plug wires, O2 sensor).
PS: My bronco is getting about 11.5 MPG in town (a little better on highway) and from reading others posts this is pretty good. Hope i could help.
Lead Driver
Joined: Jul 2003
Posts: 7,406
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From: Wheatland, Mo
Another thing you can do is get a can of BG44K. You can find it at your local parts store, but it costs about $16. DO NOT use it more than once a year. This stuff will clean out your fuel system real good. May help and it an easy solution.
Posting Guru
Joined: Apr 2004
Posts: 1,399
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From: Corinth, TX
TPS and/or O2 sensor going bad can cause a rich or lean condition, which will affect MPG and idle. It should also cause a couple of codes to register in the computer. Is your Check Engine light on? Might pull the codes just to be sure. These things work together to decide how much fuel is needed, and if somethingis wrong... well you get the idea. I'd start with the codes, then test the TPS. If that's ok, and no codes... something strange is going on. The O2 sensor could be to blame, but that should definitely throw a code.
-Josh
-Josh
Posting Guru
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From: Still under the hood in O
Yes, the FPR can indeed cause both his problems.
It will run rich which in turn fouls the O2 sensor. Then when it sits, it can allow gas to creep into the intake and puddle (causing the restart condition).
Usually if it is running rich though, it will spit out black soot from the tailpipe when you rev it. Have someone hold their hand behind the tailpipe while you rev it a couple of times to verify.
It will run rich which in turn fouls the O2 sensor. Then when it sits, it can allow gas to creep into the intake and puddle (causing the restart condition).
Usually if it is running rich though, it will spit out black soot from the tailpipe when you rev it. Have someone hold their hand behind the tailpipe while you rev it a couple of times to verify.
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Elder User
Joined: Apr 2002
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From: NJ
sounds like a bad fuel preesur regulator to me. how drastic has your milage changed?when the regulator goes bad it will run rich and foul the o2 sensors. you must fix this condition or you will ruin the cats because they wont be able to burn the excess unburned fuel in the exhaust. did you check to make sure that the vacumn hose on the FPR has not come off or cracked and you now have no vacumn to the regulator.
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Junior User
Joined: Mar 2004
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Well, I have checked my mileage the last two weeks and I am got 12.56 mpg and 12.39 mpg. I guess I thought it was worse than I thought. With regards to changing the sensors mentioned; I guess it probably couldn't hurt anyways, right? Can you all give me an idea of where the TPS, the o2 sensor, and the fuel pressure regulator is at?
Posting Guru
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From: Still under the hood in O
I would start with the FPR and O2 sensor.
The FPR is mounted on the fuel rail at the back on the drivers side mounted with 3 allen screws. Just unbolt and lift it off, you don't need to unhook the fuel line.
The O2 is screwed into the pass side exhaust pipe. This would be bad if the FPR was dumping too much fuel in, so changing it wouldn't hurt.
The FPR is mounted on the fuel rail at the back on the drivers side mounted with 3 allen screws. Just unbolt and lift it off, you don't need to unhook the fuel line.
The O2 is screwed into the pass side exhaust pipe. This would be bad if the FPR was dumping too much fuel in, so changing it wouldn't hurt.
Senior User
Joined: Feb 2002
Posts: 167
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From: Orlando, FL
No idle on warm restarts, my vote is for a bad sensor either TPS or IAC but pull codes first (its the cheapest choice 
), clean w/carb cleaner, then replace if need be. Had the same problem with my 5.0 mustang. It was very annoying.
), clean w/carb cleaner, then replace if need be. Had the same problem with my 5.0 mustang. It was very annoying.