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1991 Ford Ranger rough idle, hesitation and vibration on a

Tiny
JAK182
  • MEMBER
  • 1991 FORD RANGER
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 151,000 MILES
I just had my fuel pump, fuel pressure regulator, plugs wires and fuel injection serviced. Now after all that my truck idles rough and hesitates on acceleration and then after reaching a cruising speed letting off the gas and accelerating again it vibrates. When I took it in to the shop it was just having trouble starting and had none of these issues. I suggested they might have bumped or damaged a vacuum line but they say they have checked all that. They said they are willing to run a full diagnostic to find the problem at no charge but im hoping u can offer some advice that might help.
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Monday, March 2nd, 2009 AT 7:52 PM

11 Replies

Tiny
RACEFAN966
  • MECHANIC
  • 5,029 POSTS
Ok you mentioned some parts your replace but have you checked the fuel filter and how about the spark plugs. If the spark plugs were replaced was it before or after the injection cleaning? Get back to me and we will go from there.
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Monday, March 2nd, 2009 AT 7:57 PM
Tiny
JAK182
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[quote="racefan966"]Ok you mentioned some parts your replace but have you checked the fuel filter and how about the spark plugs. If the spark plugs were replaced was it before or after the injection cleaning? Get back to me and we will go from there.[/Quote The fuel injection service and the changing of the sparkplugs were done after the the issue was discoveredwhen I got it back after the fuel pump and pressure regulator were replaced. Since they werent sure what was causing it and said that changing the plugs and doing a fuel injection service might solve the problem but since they werent sure they did the fuel injection service for free and gave me a discount on the plugs. The fuel filter was changed when the fuel pump and pressure regulator was changed.
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Tuesday, March 3rd, 2009 AT 7:27 AM
Tiny
RACEFAN966
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Ok if the injection service was done after the new plugs then I would pull the plugs and check them as the chemicals used for injection cleaning can glaze a plug and it will not fire right. I would also check the cap and rotor and ohm out the wires they should be no more then 7000 ohms per foot any more is no good. Also make sure the plugs are all gaped at.045. What plugs were used anyway? Get back to me and no need to quote me or you all I need is your response ok. Thanks.
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Tuesday, March 3rd, 2009 AT 10:22 AM
Tiny
JAK182
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The plugs and fuel injection were both done after the fuel pump and fuel pressure regulator were installed. The problem occured before the plugs and fuel injection service were done so I dont think they are the problem. The only reason I had the plugs and fuel injection service done is because the service center mentioned that could be the problem and did the fuel injection service for free and only charged me for labor on the plugs. It had been awhile since either had been done so I had it done. They are gonna take it so another shop that has equipment that they dont have to see if they can diagnose the problem. They mentioned a possible problem with the ctatlytic converter. Does this sound like it could be the problem?
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Wednesday, March 4th, 2009 AT 7:22 AM
Tiny
RACEFAN966
  • MECHANIC
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Ok no I do not think it is a cat. I think you should test the TPS (throttle possition sensor). You do this with a digital multi meter. You leave the sensor pluged in and back probe the green wire with a paper clip and hook up your multi meter and turn the key on engine off. You should have about.8 volt with throttle closed now slowly and steadly lift the throttle it should steadly increase to 4.5 or 5 volts at wide open throttle. Now if while you are lifting the throttle the voltage drops or glitches then the TPS is bad and should be replaced. Let me know what you find here.
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Wednesday, March 4th, 2009 AT 11:02 AM
Tiny
JAK182
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So would that fix the rough idling, hesitation, and vibration? How much is something like that to replace?
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Wednesday, March 4th, 2009 AT 7:54 PM
Tiny
RACEFAN966
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It will only fix the problems if it is bad. This is why I sent you the test procedure so you can test it and see if it is bad. I can not guarentee that a part will fix something when it hasn't been tested to see if it is bad. So I don't know if it will fix it without the test being done and told what is found. As for the cost it could be 20 to 40 dollars depending on which V6 engine you have.
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Thursday, March 5th, 2009 AT 10:29 AM
Tiny
JAK182
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Well im taking it in Monday ill mention that to them. Thanx for your advice I appreciate your help. Ill let u know when its fixed wht the problem was so if someone else has this problem u can hlep them out as well.
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Friday, March 6th, 2009 AT 7:15 AM
Tiny
RACEFAN966
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Ok do that. Get back to me with what they find as it may help somehow you never know. Besides I am allway's up to learning something new if it turns out that way.
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Friday, March 6th, 2009 AT 10:28 AM
Tiny
JAK182
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Just wanted to let u know what the problem was with my truck. They said it was a bad fuel injector. They said the truck was basically running on 5 cylinders. They replaced the fuel injector at no charge and now the truck runs great. One thing that doesnt make sense to me is that when they did the fuel injection service wouldnt a bad fuel injector been detected? Anyways just wanted to give u an update on what happened. Thanks again for your advice.
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Wednesday, March 11th, 2009 AT 7:15 AM
Tiny
RACEFAN966
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Ok great it is running good. We would have eventually gotten there. I will usually start at the basics and then go from there. Now as for a service detecting this. No that would not be the case. See this truck has an OBD 1 computer system so it won't detect cylinder miss fire and what cylinder it is. So the only way to do this is to do what I call a cylinder kill test which is killing one cylinder at a time and then when you find the cylinder not firing you check cap, rotor and wire and plug then the injector. So like I said we would have gotten there it just takes longer when the car isn't infront of you thats all. Again thanks for the update if you have any more questions feel free to ask.
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Wednesday, March 11th, 2009 AT 11:12 AM

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