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91 mustang 2.3L 4cyl. bucking and power loss! need help!

1774 Views 11 Replies 7 Participants Last post by  davido30093
hi, need help! i cant find a solution on the internet to the problem my mustang is having! when i turn the car on my batter level gauge drops to almost the red line, and my temp gauge goes straight to the top when i start to drive, then when i get to about 1500-2300Rpm's the car starts to buck violently and lose power, my lights dim, my radio turns off, it is impossible to drive with the heater on because i guess it uses too much power? not really sure what the problem is. ive tried unplugging my temp. sensing unit to see if that fixes it, with no avail. the only thing that worked (for a short while and no longer) was unplugging my negative battery terminal and then plugging it back in after 3 or 4 minutes.
once i manage to work the rpms up enough to actually shift through the bucking, they seem to get less intense, when in 5th gear all i see and hear is a click and and everything dims for a split second and then turns back on. someone please help!
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Welcome to the site!! I moved your thread to the 2.3 Tech section for a better response.
there could be a lot or a little going on here.
first things first, pull codes. if you dont know how just check the thread i did, it gives easy instructions. post the codes you get, what order you get them in, and whether they came from the engine off test or the engine running test. i highly suspect that your problem is electrical but it is good to cover bases and the codes should give us a direction to start with.
after having several test done, including one today by the auto parts store, the car pretty much checks out perfectly except for a 564 power steering code. ive replaced the coils, wires, and plugs, and the EGR valve, checked my fuses, and had my voltage regulator and alternator checked and they were fine. when sitting at an idle the car seems to do fine, but when i turn the lights on or the heater, my rpms drop by about 400. when driving, the car does fine when im over 2500 rpms but if i drop below that it causes the car to buck over and over, and im pretty sure it effects my fuel pump because i can hear the car firing but there is no fuel. ive checked that i have fuel pressure and i dont have a vacuum leak. could this be a fuel injector problem? or maybe a ground issue?
oh and at the parts store they couldn't do a KOER test so i had to settle for a KOEO test.
Something doesn't sound right.

I also have a 91 2.3, and I may be wrong, but I have never received a 3-digit engine code from my car. Always a 2-digit. I have worked on other fords that spit out 3-digit codes.Additionally, code 564 pertains to the A/C Fan Circuit for vehicles that produce a 3-digit code. More accurately: Fan Control (FC) circuit failure – A/C and Fan Circuits.

You should perform the scan yourself. This link: Ford OBD Trouble Codes – will provide all the information you need to scan for codes.

The only tools you need are a paper clip, a pen/pencil, and a piece of paper.

Report back what you find.
Weird. I was just wondering. Since seems like a voltage problem. Could the a bad ignition switch cause this. I had read of problems in that area. Maurice
oh and at the parts store they couldn't do a KOER test so i had to settle for a KOEO test.
Did they say why they couldn't do the KOER?
they said that they didn't have the proper scanner for a koer test. and every test that i have done including the one myself has been a 3 digit code. and that those are the codes in my chilton manuel as well. one morning about a week ago it turned on and everything was fine! pissed me off more than anything! and then it ran for a week perfectly fine! and just tonight i turned it on and everything was great and i went to drive away and my voltage dropped again and the bucking and everything was reoccurring.
The KOER test uses the same scanner, not sure what their taking about. But anyway, I'm not sure whats up with the Chilton's either. All research on code 564 points to the fan circuits which makes me think along with your gauge and engine problems might point toward a faulty ECU.
I might suggest a few things here before you get too far into this. If you have access to a volt meter, it would be good to know what kind of voltage you are seeing especially when the car starts acting up. Since the issue seems to be worse when the heater fan is on (read higher electrical load) it kind of points to an issue with low current or low voltage.

I would examine electrical connections. Look for burned or corroded wires at the following points; starter solenoid, battery cables, Alternator, Ignition switch, ECU connector plug. Have the alternator and battery checked as well.
I agree with OHC 230.

If you are SURE that the alternator is OK, then you need to get a good wiring diagram and check ALL, that is ALL, ground points. There are many.

If your alternator, battery, and wiring connections are good, you almost certainly have a grounding problem somewhere.
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