ready to pull my hair out

[Nathan N]

I have a few problems than I have been tracking down that has going nuts.

1. I have this radom stumble/cut out when crusing on interstate. It onlys hapens 1 or 2 a week(500-700mi) apart. but it will spazz for 2-3 mins then go away till next week hapens at between 2000-3000 rpm 5th gear under light pedal. If you steep on it it will pause for a sec. then pull hard like it is loading up on fuel. smells like it is running a little rich to resantly too. have to get the wide band from work to check base idle is good, checked everything else I can think of.

2. So today after to has a spazz on the way home from work I stoped at Oreilly's to use there code reader wont go in to test mode I know there tester works well and even tryed ther backup one. I run codes on the SVO once a week there, some weeks more

car is a 86 svo
it has
motorcraft cap and rotor 6mo old 10Kmi
MSD wires 6mo old 10Kmi
motorcraft plugs 2kmi
crane AFPR 3mo old
255 pump 1mo
HG set with all new vac lines 2mo
TC intercooler with NAPA conectors
mitsubishi 1G BPV
stock injectors with one of the large bottles of lucis injector cleaner ran thru it over many tanks of gas
MBC set at 17psi
BP 93 pump gas
K&N air filter
timing 10*
cam timing dead on
EGR is working

[Raven855]

Definetly get the code issue fixed and the codes dumped. Check the plugs, are they the correct heat range? Are you burning any oil and do the plug porcelains look consistent. Double check that your fuel pressure is good and be sure to check it under boost. For an intermittent issue like this, check your tfi for the proper amount and grade of grease to make sure it has not gone south and been overheated. Did you retorque the head gasket?

[thebigt]

My car used to do this when the vam spring was out of adjustment.

[86svo9l]

My car did this randomly sometimes too. Ended up being a short in my grounding system that I had to trace...

[Nathan N]

Ok it got worse. so i sterted fixing things. new ect sensor and pigtail, new cap and rotor, switched out the distubter with a know good one, added a 4 gauge ground wire from batt. to block, and a new 4 gauge alt. to batt wire. checked charging system, reseset base idle, cleaned and tested injectors, checked wirring, checked for vac leaks, checked and cleaned and regaped plugs to .32 (they have less than 2k on them), changed out vam, replaced ignition switch, pressure checked IC, and setup a oil catch can after pvc.


so tonight after I got everything back to gether and timed we went for a 50mi test ride. It is still there slightly in 3rd 4th 5th under 2500 rpm sometimes. thinking about picking up a set of wires to see if my MSDs have gone to crap other that that what have I not replaced that could cause this The other thing that has me confussed is I can only pull 12" of vac at idle with no vac leaks. I pressure tested the whole intake trying to track this one down.

[Alex L]

holy overkill batman! you went to town on this sucker over the weekend didnt ya?

can you pull codes yet? if you cant pull codes, all the rest of the testing is moot as the ECU becomes suspect.

did the plugs look good when you regapped them? fuel pressure checks out?

'under 2500rpm sometimes' under light load? heavy load? steady or transient pedal?

id sweep test the TPS next. dead spots/ false values in the TPS can cause all sorts of weird stuff to happen.

put a voltmeter on the HEGO, confirm that its cycling when the engine is at running time. if that went south, ECU could be tossing all sorts of LTFT at it causing it to run rich; then when the computer recals, it goes super rich and stumbles out.

[Nathan N]

plugs looked good , fuel pressure checked out good.
It starts acting up as you try to pick up speed or go up a hill. I can back off and it will stop till you give it a little more to will get worse till about 3000 rpm then hit boost and take off fine. totaly random intervols between spazes.
I have tested the tps serval times, even switched it out for my spare a few weeks ago thinking that might be the problem. Still test out good.
Now as for codes I got it to pull codes last time the next day. 11 system pass But to night I tried to pull codes on the way home and it is not working agen Is the 1 pin plug on the test conector supost to have 12v key on power? because when checking things to see what is wrong I found it to be dead(no power or ground)
what and where is the HEGO? and what are LTFT? sorry I just may have a brain fart but it is not comeing to me thanks for the help And yes I did go to town on it this weekend, it pissed me off

[svono50]

Nathan, what does your tach do when you get the stumble/cut? Does it drop straight to "0" then snap back to the right rpm or does it just drop slightly and flutter up around the correct rpm? You may need to pay attention to this next drive if you haven't looked for it.

If it drops straight to "0" your ignition is cutting out, which could be caused by a bad PIP, TFI or ignition switch. If it is a PIP or TFI it is more likely that your engine would die and not come back to life until the engine cools off for a while, as they will start to die as the engine warms up and the interal traces pull apart and cause failure. I had a PIP do this to me years ago.

BTW, I would check your MSD wires by opening the hood when it is completly dark out and blipping the throttle a few times to see if you have any 'glowing' going on around the wires. If so, that will confirm that they have broken down internally and need replacement. Stick with the Motorcraft wires and replace on a yearly basis or step up to a set of Magnecore units if you want to spend the $$.

[Nathan N]

Nathan, what does your tach do when you get the stumble/cut? Does it drop straight to "0" then snap back to the right rpm or does it just drop slightly and flutter up around the correct rpm? You may need to pay attention to this next drive if you haven't looked for it.

If it drops straight to "0" your ignition is cutting out, which could be caused by a bad PIP, TFI or ignition switch. If it is a PIP or TFI it is more likely that your engine would die and not come back to life until the engine cools off for a while, as they will start to die as the engine warms up and the interal traces pull apart and cause failure. I had a PIP do this to me years ago.

BTW, I would check your MSD wires by opening the hood when it is completly dark out and blipping the throttle a few times to see if you have any 'glowing' going on around the wires. If so, that will confirm that they have broken down internally and need replacement. Stick with the Motorcraft wires and replace on a yearly basis or step up to a set of Magnecore units if you want to spend the $$.

tack bounces 500-1000 rpm insync with stumble. I was puting my distubiter back together after replaceing PIP and droped the gear and chipped it. cussed..... thru something.... then when and barowed the one from the motor waiting for the vert. till i can fix the other. It has a know good motorcraft PIP and TFI. The MSD wires and coil were 2 weeks old when I bought the car 6mo ago. so I think they are still good but I will go out and check for any glow. The stumble feels like you are to low in the gear but i know i am not

[Alex L]

ted ++

<hijack>
HEGO = O2 sensor
LTFT = long term fuel trim.

sorry bout using internal EEC terms, ive had my head up my LA3 trying to get closed loop working correctly. (the datalog, it LIES!!! dumps STFT to LTFT @ 93 ~ 97, never hits unity...)
</hijack>

[Horsewidower]

(the datalog, it LIES!!! dumps STFT to LTFT @ 93 ~ 97, never hits unity...)
</hijack>

Sounds like the Borg.

[roberto2000]

I was puting my distubiter back together after replaceing PIP and droped the gear and chipped it. cussed..... thru something.... then when and barowed the one from the motor waiting for the vert.

Nathan swaping distributors is not a good idea
your original distributor and aux. shaft are worn together
so are the units from the vert. A mis-matched pair can cause lots of problems
check the distruibutor for signs of failing teeth and the aux. shaft

[NavySVO]

ive had my head up my LA3 trying to get closed loop working correctly.

You can get a good look at a T-bone by sticking your head up a bull's.......

[Nathan N]

Nathan swaping distributors is not a good idea
your original distributor and aux. shaft are worn together
so are the units from the vert. A mis-matched pair can cause lots of problems
check the distruibutor for signs of failing teeth and the aux. shaft

O2 checked out good
So when I get a new gear for mine I need to get a new aux. shaft two?
The car is back to normal driving just fine. It acted up on the test ride and a little the next morring then nothing since. I hope it stays that way for a wile so I have a chance to put on some of the new upgrades waiting to go on. picked up a set of fox koni yellows, BBK CC plates, SSM uppers and lowers and a 8.8 with richmond 3.73s. Ordered today a centerfoce DF clutch kit thru work. still need to find a quad, GT cable and make the bracket that lets you use the GT cable on a 4cyl bellhouse agen as I did not save the last one of the 89 vert..

[Alex L]

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