Could engine rev after slamming car hood??

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  #1  
Old 10-14-14, 01:08 PM
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Could engine rev after slamming car hood??

Hi, I have a 92' Ford Ranger XLT with 2.9 V6. I have been having this problem for several years now.

1.The truck will have a loss of power with check engine light illuminating. Almost as if it is stuck in a lower gear.

2. The engine will cut off while idling in park.

3. The engine might surge slightly while stopped at a traffic light with brake depressed.

4. On the rare occasion it may 'miss a beat' or misfire


All these symptoms do not occur often. I would say very infrequently. And if the engine cuts off, I am always able to restart.

But it did something today I have never experienced before. I was closing the hood after checking my oil. When the hood slammed down, I could have sworn the engine revved as if I was pressing the gas pedal!

Is there enough information here to narrow it down?
 
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Old 10-14-14, 01:24 PM
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I suppose anything is possible. I would start by wiggling every wire, connector and electrical component relating to the engine checking for an intermittent connection that could be affected by vibration.
 
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Old 10-14-14, 01:26 PM
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If the check engine light is on, you ought to be able to pull a code out of the computer.
 
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Old 10-14-14, 03:17 PM
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The only thing that would make the engine rev up would be to open the throttle plate.
If you can discern how the hood hinge is connected to the throttle cable then you have found the fault.
 
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Old 10-15-14, 07:16 AM
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I know it doesn't make sense with the rpm increase when the hood shut. I have a cheap code scanner at home. It's not the easiest thing to use and then one may have to interpret the code. I'll see what I can come up with and respond no later than Monday. I already touched electrical connectors and wires and didn't come up with anything.
 
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Old 10-15-14, 09:38 AM
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Just pull into an auto parts store. Most will read your codes for free.
 
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Old 10-15-14, 10:14 AM
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In regard to the "engine rpm increase while shutting the hood":

In addition to the above I'd follow "2granddaughters" advice of checking the throttle cable and how it's routed and secured. Make sure that it's not coming in contact with the hood and the hood hinges. Causes for this are usually due to the cable coming loose from its guides (also look for broken or missing guides).

Another thing to check would the vacuum line condition and routing (look for cracked and/or miss-routed vac lines and broken/missing vac line guides).
 
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Old 10-15-14, 10:20 AM
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Sometimes the oddest things can cause issues. Buddy back in the late 70's had a Ford Courier? (Small 4 cyl pick-up truck) that would run rough as he11 when accelerating. Revved fine at a stop, was ok with very gentle acceleration, and ran fine once it reached speed. This was a simple vehicle and we were pretty much motor heads with all the common test tools and could never find the issue.

I went back to my Navy duty station and talked to him a few weeks later. He had the hood off for some body work (that's another story) and while accelerating the first time and it ran fine, noticed a spray of water on the windshield. Turns out there was a pinhole leak in a hose that only flexed and opened up under acceleration. With the hood on it was splashing/dripping on to the ignition. Of course it was all evaporated if we opened the hood after driving and revving while parked didn't torque the motor over like under load.

Like I said...can sometimes be the oddest things.
 
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Old 10-15-14, 09:23 PM
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Interesting 'domino effect' story from Vic.

I checked the vacuum lines several times, and replaced a couple cracked sections many months ago. Within the last couple days, I also cleaned the throttle butterfly plate, linkage, and idle air control valve intake holes with air intake cleaner.

I just checked the routing of the throttle cable. Although it does trail close to the hood hinges, I don't see it as an issue. I almost wish I didn't bring up the engine rev I heard. I can hardly believe it myself.

I also gently wiggled electrical connections again, and nothing happened. Interesting note................I wiggled the connection at the ignition module 2 years ago and the engine cut off immediately. Had it repaired with a pigtail connector.

I used the code scanner tonight. I have the budget type that requires the user to write down beeps or blinking lights. Not an easy system for me to use. My truck uses the EEC-IV system with OBD-1 codes. If I was reading the series correctly, these are the two trouble codes I got:

72................Insufficient manifold vacuum change detected during dynamic response portion of engine run self test...OR....problem with message center control assembly-failure in data communications link.


73...............Insufficient throttle position change detected during dynamic response portion of engine run self test.

I drove the truck over 300 miles during Columbus day weekend through high altitude mountainous terrain and it ran flawlessly

Does any of this help to narrow it down?
 
  #10  
Old 10-21-14, 07:30 AM
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It definitely happened again when I slammed the hood shut this morning in my garage. But it wasn't the engine revving like I previously thought. The engine starts to cut off, and then increases rpm to recover and establish a normal idle.
With this occurrence and the trouble codes I listed below, does this narrow it down?
 
  #11  
Old 11-03-14, 12:10 AM
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I suggest whacking the throttle Position Sensor, and seeing if the behavior occurs then.
 
  #12  
Old 11-09-14, 10:51 AM
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Yes,

I tried tapping the throttle position sensor, other parts, and electrical connections several times. Nothing happens.
 
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