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Help me with my "stumbling" motor!!!

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mudtang89

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Discussion starter · #1 ·
Alright I know this is widely asked question on here but you guys are the best at troubleshooting.

I am experiencing a "miss" through-out the whole rpm range. It started about two weeks ago as an intermmittent problem when the car was run hard and I attributed it to a fried spark plug wire. I replaced cap and rotor two weeks ago along with the single wire that was fried. It still ocassionally missed after that! This past weekend I replaced the rest of the wires and plugs. Upon driving home about 25 miles it ran fine...The next day going to work(10 miles) it ran fine, then upon driving home it started missing. And again early this morning upon start up it started missing right in my driveway. It will occassionally run fine but that is very sparatic. Most only when cold. I do have a new TFI module however I wasn't able to get the screws out due to the small hole size...(any suggestions or do I have to buy a special FORD tool for that).

It also developed a small surge of rpms at idle only in the "stumbling" condition. TPS voltage????

What else should I be checking? I am pretty sure this is a "spark" related problem. Could I be over looking something else???

Please help!

Ryan

P.S. #7 plug had more than usual deposits. Light grey in color, with a really dark carbon coated base inside the plug. I did pull the new plug after a day of driving and it looks great now???
 
#2 ·
Check the whole operating range on the TPS. If that's not it, double check to make sure that your plug wires are all tightly plugged in.

If that's not it, I would suspect a bad hall-effect sensor. Try swapping in a spare distributor and see if that corrects it. Seems to be pretty common among the intermittant missing, not attributable to plugs and wires..

--Ed
 
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#4 ·
Crank the motor up at night time, and look under hood for blue sparks, i had same problem, turned out to broken ceramic on one of my plugs. just my 2 cents.
 
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Discussion starter · #6 ·
Because I am a lazy, cheap ass bastard that "should" go buy a code puller. Doing it with a voltmeter is a pain...

Okay 67stang, I'll go buy one, thanks for the kick in the ass... :)

What's a good one to look for... and how much?
 
#7 ·
I'm with ya man and if you're dealing with a miss run a frigging cylinder balance test with your code scanner...don't ask how, read the book.

Also, like I told someone else, hook a timing light up to each plug wire and make sure you're getting a good consistent hit out of all of them. Just because you replaced one doesn't mean you fixed the problem. This situation reeks of an ignition miss, could be a wire, could be a bad plug, could be a wire isn't tight ON a plug, could be a bad cap, etc. Let's put a moratorium on blaming the TPS or O2 sensors every damned time the car runs funny. RE CHECK THE BASICS.
 
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#8 ·
Yea what MFE said.
 
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#9 ·
i can't ever get the cylinder balance test to work with the sunpro code scanner..........i can't even do the KOER test.......i read the book and follow the instructions...i don't know whats up.... :confused:
 
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#10 ·
"Pull the codes"

What a load of crap. 87-93 Mustangs don't tell you jack crap through the computer. Sometimes, it will tell you if your TP sensor is outta wack, it can sometimes tell you if your EGR valve isn't working properly. But the TP is the only sensor I know of that will cause a "miss" feel. Everything else just affects your mixture. Not to say there isn't SOME value to looking for codes, but it just doesn't work very often on these cars. A cylinder balance test could be useful, as it will tell you if it's one cyl. all the time, or if they're all acting up. (Indicating a bad coil, or distributor part)

I've never had a bad, new spark plug, or a bad new plug wire.
Not that it's not possible, but it's not likely. If he had a cracked plug, then it would be f'd up all the time, not just when cold.

The hall effect sensor is in the distributor. It tells the engine where it's located in it's clock cycle, and tells it when to pulse the coil. It can go everywhere to working sometimes to not working at all, and I've never seen it throw a code.

When you've exhausted every other check, you've found your problem..

--Ed
 
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#11 ·
mudtang89 said:
Because I am a lazy, cheap ass bastard that "should" go buy a code puller. Doing it with a voltmeter is a pain...

Okay 67stang, I'll go buy one, thanks for the kick in the ass... :)

What's a good one to look for... and how much?
Click to expand...

Well the one I use is free...I take a paperclip from my desk, stretch it open, and stick it between the two contacts on the test harness plug. Then I run KOEO and KOER and count the codes via the check eng. light.

All the instructions are on this site in the archives.
 
#12 ·
Load of crap huh?:rolleyes: I'm the first one *****ing when someone says "there can't be anything wrong, it didn't show any codes" but that is NOT to say that some nasty things won't show up if you just take 2 minutes to do the test. It's better than chasing your tail. O2 sensors rarely throw codes on their own but if you get an O2 code you likely have a wiring problem. ACT or ECT out of range codes can save your ass. TPS out of range too. MAF voltage too high, the list goes on of things that it WILL throw at you if there IS a problem and it's better to know than to guess, is it not?

That said, I have most definitely installed spark plug wires that were bad right out of the box. Tons of parts, actually and it is frustrating as hell becuase you're treating them as "known good".

It's also super easy to THINK you have the wire seated on the plug when in fact it's not and it'll develop an intermittent or constant miss as a result. Nothing that will show up in the codes...BUT...guess what....it'll show up in the Cylinder Balance Test as a weak or non-contributing cylinder.

Now if you want to call all this a load of crap so be it. I just hate to see people throw parts at a car becuase they wouldn't take 5 minutes to check the codes or run a CBT.
 
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#13 ·
Sorry, this shouldn't have been a left field, right field thing. Let's meet in the middle, MFE... It's been a load of crap for me, but it IS another test that can save time..

I got the impression from another message here that it was the end-all-be-all test, hence my knee-jerk, opposite reaction. It could help, but for me, most of the time, I end up with unrelated or no codes what-so-ever.

Many a time I've recieved o2 sensor codes, usually caused because something else has caused the mixture to go all-to-hell, and the computer can't compensate. (Like vacuum leaks, mass-air meter screw-ups, etc. etc..)
 
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Discussion starter · #14 ·
UPDATE>>>>

#8 squirter has gone south. It is recieving signals but it doesn't squirt...

Thanks for all your help guys...


DOES ANYONE HAVE ONE 24 LB INJECTOR LAYING AROUND, PREFERABLY IN THE SOUTHERN CALI AREA.



Thanks again guys.

I let you fight on to see who would of found the problem first.... lol
 
#15 ·
mudtang89 said:
UPDATE>>>>

#8 squirter has gone south. It is recieving signals but it doesn't squirt...

Thanks for all your help guys...


DOES ANYONE HAVE ONE 24 LB INJECTOR LAYING AROUND, PREFERABLY IN THE SOUTHERN CALI AREA.



Thanks again guys.

I let you fight on to see who would of found the problem first.... lol
Click to expand...
How did your narrow it down to #8?
 
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mudtang89
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