Fix one problem, causes another

[JenkinsBS]

So, my car was having issues with a hanging idle @ 2k - It would happen when shifting mainly, going from 1st to 2nd, the RPMs would not drop, same from 2nd to 3rd, so i just dealt with it, wasnt too big of a deal.

The main issue i was having a problem with was when I would go WOT, pedal to the floor, the car would buck and sputter hard, no backfiring though (running around 16* timing running premium).

So i figured i would double check my idle and retard my timing a bit, see if it would change any thing, and it did -

Firstly, warmed the engine up, then when adjusting the idle, I removed the IAC, and started backing out the idle adjust screw... but the idle would not drop, so started tightening it, and the idle increased, backed it back out again, and it wont drop lower than about 500 - 600 RPMs, but i set it to about 700, put the IAC back in.

Secondly, with the Spout removed, checked timing, it was still at about 16*, so I backed it down to about 12*, plugged spout back in.

- RESULTS -

The hanging idle problem is now gone, the car idles around 900 RPM, when i shift from 1st to 2nd, the RPMs drop quick when depressing the clutch, as it should, same with the rest of the gears.

The problem is now the car starts to buck and stutter at about 3/4 throttle instead of WOT, before i could push it up to redline and it wouldnt stutter or buck, as long as I diddnt floor it, NOW it will start to buck as soon as it gets to around 4K, not even giving alot of gas.

Any Ideas?

RECENT CHANGES

Just changed out spark plugs, there was a bit of oil around the threads, but not a whole lot, color of the diode spark thing was a toasty marshmallowy color

Cleaned out MAF, removed from housing, used rubbing alchohol with q tips to gently clean the wires.

BUT KEEP IN MIND - the hanging idle only went away after i redid my idle and retarted the timing

 

[Mustang5L5]

Around 4000 rpm is a critical area where a lot of sensors get ignored and the car relys on data in the computer.

Any codes? 1986 mustangs don't have a check engine light, so you have to take it upon yourself to check codes.

Off top of my head, EGR and o2 sensors would be suspect, but there would be codes for these.

 

[JenkinsBS]

O2s are brand new, but ill check the connectors and grounds to make sure its all proper, Ill just go buy a new EGR to replace that, no too hard.

But what gets me is the bucking was virtually non existant until i floored it to WOT@ the higher timng. Even running above 4k RPM, i could 3/4 throttle it into it until redline and it would be fine.

Now that the timing is lower, even easing it up to the 4K causes the bucking. Could this still be EGR?

 

[jrichker]

Did you get an EGR code? If so what was it? The EGR valve is expensive, so you would be better of doing some troubleshooting to find out if it is causing problems.

You did not set the mechanical base idle speed correctly.
See http://www.stangnet.com/mustang-forums/698148-help-me-create-surging-idle-checklist.html#post6855020 for the best way to set the mechanical base idle and cleaning procedure for the IAC/IAB.

 

[JenkinsBS]

Thanks for that link about the idle richker, ill be doing that tomorrow, due to the fact that the alternator took a crap tonight.

I dont have any updated codes yet, ill have to do that after the alternator.

Without having them codes, i can only think that when i go WOT im just dumping too much fuel into the chambers to be ignited, so it bucks and jerks, or maybe its just too much burt fuel exhaust for the stock intake to expel?

 

[Mustang5L5]

Without seeing the codes, we're really guessing here.

Not trying to be a PITA, but we don't want to see you waste time and $$$ that you don't need to spend. EGR valves are expensive. If there's no code, no need to buy one just yet. A simple cleaning might be all you need.

It really is worth the time checking the codes, or investing in a $25 code reader to make this job easy.

 

[JenkinsBS]

Should be posting codes today - we shall see what comes up.

I know Richkter has a tutorial on doing this, but from memory, all i need to make sure of is that the car is at temp, in neutrall, ebrake on, and all accesories off... and make sure not pressing on the clutch?

 

[jrichker]

With a 5 speed trans, you must press the clutch in. If you don't you'll get a code 67 and will not be able to dump engine running codes.

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.

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.

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.

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.

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.

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) – It has a 3 digit LCD display so that you don’t have to count flashes or beeps.. Cost is $30.
Or for a nicer scanner see http://www.midwayautosupply.com/p-7208-equus-digital-ford-code-reader-3145.aspx– It has a 3 digit LCD display so that you don’t have to count flashes or beeps.. Cost is $30.

 

[Mustang5L5]

Highly recpmmend this code reader

Amazon.com: Equus 3145 Ford Digital Code Reader: Automotive

Its cheap and easy to use. Makes reading codes a 5 minute thing so you can do it om a regular basis