My 1988 ford bronco 2 rpm’s is using high at 1500 sometimes and in the morning she screams at 2000-2500 and drops back down to 1500 when the engine gets warm. I noticed going highway speeds at around 65 the Rpm’s was going crazy and fluctuating up to 4000-5000 rpm’s and coming right back down to around 3000-3500 which is normally doesn’t go past but it starts at 1500 and works it way up to 3500 rpm by the time I’m going 50 and up. I was riding on my way home and suddenly I couldn’t accelerate at all no sounds at all but it just seemed like it was bogging down whenever I put my foot down on the gas. I just put a new idle air control valve in it, tfi module, fuels pumps, fuel filter, and spark plugs and wires
I had also replaced the map sensor it’s only a couple weeks old and it didn’t sound like it was a fuel problem I was able to pull over shut off engine and turn it back on and it ran fine. The fuel injectors are the original ones I do believe.
I actually replaced the maf sensor like 2-3 weeks ago anywho I ended up replacing tps and boom problem fixed thanks everyone for your input I appreciate it. Now on to the next problem 😂😂 don’t you just love old fords
Check the MAP sensor and its vacuum line
the map sensor is brand new just put a new one on a couple weeks ago
@samuel_50 this sounds like an air/fuel issue to me
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If it were a bad fuel injector it would be difficult to explain how you could "pull over shut off engine and turn it back on and it ran fine"
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This sounds more like the computer is using the fuel mixture it's calculating from the MAP sensor voltage input, and then seeing the rpms are running away (because of what it's seeing from the TPS sensor), and cutting back on the injector pulses, and then repeating the exercise over and over
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This doesn't seem like a spark or timing issue at all
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What's left?
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Air/Fuel
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But why would turning the engine off and restarting the engine make the problem go away?
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I suggested "checking your MAP Sensor" but that short answer was too vague and that's my bad
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The reason I suggested that is because the 5 volt reference and the computer's Ground are shared with the MAP Sensor and the TPS (sensor)
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That symptom where you "couldn’t accelerate at all sure sounds like a MAP Sensor or TPS (sensor)
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So to properly "check the MAP Sensor" you need to grab a multimeter and when the Bronco is acting up, check the Power and Ground at the MAP Sensor electrical connector
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Let's look at how this thing is wired,
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Here's a close up of the MAP Sensor (and TPS ((sensor))
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You're dealing with a 35 year old vehicle with 35 year old wiring and connectors so you can't just replace sensors, you have to check them
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In your case (referring to the wiring diagram) you have a 5 Volt reference signal (ORG/WHT wire) being provided by the computer which is shared by the MAP Sensor and the TPS Sensor
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You should check it at the MAP Sensor and the TPS Sensor
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Also, the Computer Provided Ground (BLK/WHT wire) is also shared by both sensors
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If you refer to the diagram, there's either a splice or a connector that branches Ground off to both sensors which could be a problem area
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You can also check the signal back to the computer (DK BLU/LT GRN wire) if you have a multimeter which can display Hertz (Hz)
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You can just check that signal wire for continuity between the MAP Sensor and the Computer if you don't have a multimeter that can read Hz (because you have a brand new MAP Sensor)
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Do the same tests for the TPS (sensor)
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If this is an intermittent issue you'll have to perform these tests when the Bronco is acting up
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Also the ECT sensor shares that Ground so a problem with that sensor or its wiring shouldn't be ignored
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I didn't find a link for testing the voltages on the sensor for your 2.9L but here's a link for testing it on larger Fords which should be helpful
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https://troubleshootmyvehicle.com/ford/4.9L-5.0L-5.8L/how-to-test-the-map-sensor-1
Okay so it recently stopped running out of no where it just simply wouldn’t go when this happened I pulled into some ones drive way and waited it cut off slowly coming into the driveway as I pressed on the breaks and the breaks and steering wheel locked up and cut off I tried starting it after like 5-8 min and it wouldn’t start up so I waited another 10 minutes, put it in neutral and it started back up it’s been starting normal again now like it doesn’t have the problem so I got to my buddies house and unplugged the tps and it ran weird for a second and then ran like it was plugged in so that might be the issue? I’ve got the brand new map sensor on there and the connections look good and the wire looks good as well.
How old are the fuel injectors?
Have you cleaned the MAF sensor?
a MAF sensor in a 1988 vehicle... that would be a sight to see!
😂
So I got a old 1988 ford bronco 2 xlt 4wd back in October of 2021 and I have replaced the following: tps, maf sensor, 2 fuel pumps, fuel filter, spark plugs, wires, idle air controls valve, battery, and oil filter. I just recently replaced the throttle position sensor because it was running like crap 5 minutes down the road and would cut out on me. But my problem now is my idle rpm is around 2500 for like 30-40 second first start up of the morning and comes down to about 1800-2000 rpm’s and stays there when I’m driving she’s shoots up and then comes back down when I’m cruising at high rpm’s like around 2500 now when I go past 55 she goes to 3000 and then at like 60-70 she’s at 3500-4000. I noticed that the rpm gauge will fluctuate going 65-70 and up it will go as far up to like 5000 rpm’s but quickly come back down to like 3000 again and then again and again and just fluctuate. I don’t notice no like weird revving noise or performance when it does this either. But when I go up to around 25-35 depending on how hard I press on the gas it will like buck and feels like it doesn’t wanna go into the next gear but all the other shifts are decently smooth. I also don’t know if this is a problem but it will also buck real bad when I put her in drive. I had put bars transmission fix crap in there like 1-2 months ago. So with all that said tell me what you think. This website hasn’t been wrong yet😂