Good Lord I'm Down To One Last Thing...but I Need Help

mysd455

New Member
Dec 1, 2014
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Well after fixing the power mirrors, power door locks, fog lamps, headlight switch the four warning lights, ( Its a 1988 GT) two little dome lights, power gas cap release, power steering pump noise ( just needed new fluid )A/C (one can on real R12)...I'm down to one last thing. If I rev the car to say 2000 rpms then floor it to go to 3000 rpms let go of the gas then as the rpms come down to 2000 and again floor it the engine pops from the air cleaner. The timing is set ( Maybe to much advanced 12 degrees?) fuel pressure issue? I was doing this reving of the motor since I thought it was reving slower then I remember these engines from years ago Maybe the factory "cats" with 140k miles are starting to plug up? Does get to 5000 with no strain Thanks in advance for any ideas. BTW all these issues cost in total no more then $100 dollars and many fun filled hours with a test light. So I end up with a almost new looking car for the price of a pretty good HDTV. The last owner just gave up on it...go figure.
 
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Sorry I'm old school. It has a factory intake but the air cleaner is a round open element K@N type. Other then that the car is 100 percent stock. As far as the "popping noise" its just one pop as I quickly floor the gas then release it (going from 2000 to 3000 rpms.
 
Dump the codes: Codes may be present even if the Check Engine Light (CEL) isn't on.

Dumping the computer diagnostic codes on 86-95 Mustangs

Revised 26-July-2011. Added need to make sure the clutch is pressed when dumping codes.

Codes may be present even if the check engine light hasn’t come on, so be sure to check for them.

Here's the way to dump the computer codes with only a jumper wire or paper clip and the check engine light, or test light or voltmeter. I’ve used it for years, and it works great. You watch the flashing test lamp or Check Engine Light and count the flashes.

Post the codes you get and I will post 86-93 model 5.0 Mustang specific code definitions and fixes. I do not have a complete listing for 94-95 model 5.0 Mustangs at this time.

Be sure to turn off the A/C, and put the transmission in neutral when dumping the codes. On a manual transmission car, be sure to press the clutch to the floor.
Fail to do this and you will generate a code 67 and not be able to dump the Engine Running codes.

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If your car is an 86-88 stang, you'll have to use the test lamp or voltmeter method. There is no functional check engine light on the 86-88's except possibly the Cali Mass Air cars.

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The STI has a gray connector shell and a white/red wire. It comes from the same bundle of wires as the self test connector.

89 through 95 cars have a working Check Engine light. Watch it instead of using a test lamp.

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The STI has a gray connector shell and a white/red wire. It comes from the same bundle of wires as the self test connector.


WARNING!!! There is a single dark brown connector with a black/orange wire. It is the 12 volt power to the under the hood light. Do not jumper it to the computer test connector. If you do, you will damage the computer.

What to expect:
You should get a code 11 (two single flashes in succession). This says that the computer's internal workings are OK, and that the wiring to put the computer into diagnostic mode is good. No code 11 and you have some wiring problems. This is crucial: the same wire that provides the ground to dump the codes provides signal ground for the TPS, EGR, ACT and Map/Baro sensors. If it fails, you will have poor performance, economy and driveablity problems

Some codes have different answers if the engine is running from the answers that it has when the engine isn't running. It helps a lot to know if you had the engine running when you ran the test.

Dumping the Engine Running codes: The procedure is the same, you start the engine with the test jumper in place. Be sure the A/C is off, and clutch (if present) is pressed to the floor, and the transmission is in neutral. You'll get an 11, then a 4 and the engine will speed up to do the EGR test. After the engine speed decreases back to idle, it will dump the engine running codes.

Trouble codes are either 2 digit or 3 digit, there are no cars that use both 2 digit codes and 3 digit codes.

Your 86-88 5.0 won't have a working Check Engine Light, so you'll need a test light.
See AutoZone Part Number: 25886 , $10
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Alternate methods:
For those who are intimidated by all the wires & connections, see Actron® for what a typical hand scanner looks like. Normal retail price is about $30 or so at AutoZone or Wal-Mart.

Or for a nicer scanner see Equus Digital Ford Code Reader (3145) Equus - Digital Ford Code Reader (3145It has a 3 digit LCD display so that you don’t have to count flashes or beeps.. Cost is $22-$36.
 
Old school hot rod logic tells me that getting a pop thru the intake side after a rev sounds like a worn timing chain with waaay too much slack in it, allowing the cam to be where it isn't supposed to be. Worn timing chains do bad things.
 
Well the pop is gone, needed a new MAP sensor 100 percent sure that and wires solved the problem The only thing left to fix now is a rough running engine (Can feel it in the steering wheel) at about 1500 rpms.Idles rock solid at 800...take it to 14/1500 hundred not so good. Almost like a bad plug (all new) at 18/19 hundred it smooths out. Can't hurt to but in new 02 sensors. Thanks for the help ( A lot of smart people on this forum)
 
Maybe this info could help someone else out. It seems I've gotten this 1400 rpm rough running issue fixed by emptying a can of carb cleaner via an easy spray into the air cleaner (Open K @N round type) By easy I mean not enough to stall the engine by just enough to bring the rpms down to 500 range. After that I thought I see what if any effect it had and was pretty surprised to see after bringing the revs to 14/1500 a smooth running engine.
 
If the car sat unused for a long time, the injectors can get gummed up and not seat making them leak or even get totally clogged in extreme cases . That can cause false responses from O2 sensors. Not necessarily false though, as the O2 sends the signals of the condition to the ECU which tries to correct the condition by adjusting pulse rate. Until you correct the mechanical problem with the injectors, the ECU will remain confused.
 
I was hopeful that between injector cleaner (Seaform) and what I did it will stay fixed. I only got the car a few months back but have not had time so far to registered it, I have a few cars in my small collection that I do drive ,Mostly Maserati's from the 60s Yep ,the car wasn't used much. The PO.. after I paid for it said 'By the way I only drove it a few hundred miles within the past few years" I didn't know that at the time I was looking at it because it had plates on it. I used a friends dealer plate to drive it the 40 miles home......but it makes sense he didn't drive it because the headlights didn't work....any pretty much everything else. Which it all fixed. I had fun fixing it