Skip to main content ↑ ↓
Topic: pin pointing intermittant problem (Read 1301 times) previous topic - next topic

pin pointing intermittant problem

90 ford bronco 5.8L 5 speed

*converted from e4od to 5speed
*smog tubing on rear of heads plugged off
*egr is removed and evp not connected
*recently replaced fuel pump relay due to contacts failing (relay would stay on after engine cut off)


problem
one Intermittant violent jerk/ buck.
feels like the engine dies but recovers less than a second later.
vehicles does a single buck when it fails
the buck feels very violent.
this buck or jerk has no observable pattern that i can share since it started earlier this year.
Feels like vehicle looses electrical power but all lighting/cluster systems are not effected.

-------------------

Has anyone had any luck pinpointing an intermittant problem?  I was thinking about a way to put a few dash mounted bulbs in the dash and break into critical circuits on the power plant and try to observe which light flickered when this happens such as the fuel pump , certain relays or the green wire on the tps ect.  I just hate hacking into the virgin wiring to do this.
I guess i could shot gun the problem and start with the TPS but that darn TPS is sooooooooooooo crazy hard to to get to on the 5.8 trottle body.

I can pull the codes but i know the system is probably polluted with egr codes since im running without one.

pin pointing intermittant problem

Reply #1 –
I would suspect ignition. Pull the codes anyway. We
can weed out the EGR codes.

pin pointing intermittant problem

Reply #2 –
check all your grounds. look for a fuse holder looking ground wire around your battery. it is all black. take it apart and clean the contacts inside it.
louie  :birdsmily:
[SIGPIC][/SIGPIC]       
My famous last words:
It seemed like a good idea at the time.        88TC R.I.P.      88 Sport build in progress

pin pointing intermittant problem

Reply #3 –
The only intermitent I remember curing was on my old 78 Nova.
It would seem to "cut out" at certain throttle settings, as if the engine had just been turned off. More gas okay, less gas okay, in the middle; sputtersputtersputter. Had lots of air, had lots of gas, had lots of spark??? Hmmm.... tuned the radio to a "dead" spot between stations on the AM band so I could hear the sparkyspark static while it was running. Sure enough, the noise stopped when the engine "cut out". Traced it to a wire from the distributor pickup coil. Mid-throttle made lots of vacuum, the advance pulled the pickup around, the wire flexed and broke the circuit. More or less throttle made less vacuum, so the wire unflexed and reconnected.

A not-so intermittent was a 62 Pontiac Stratochief, bucked like crazy going up steep hills, fixed by replacing a defective (though brand-new) plug #8.
Death awaits you all with nasty, big, pointy teeth.

1988 5.0 Bird, mostly stock, partly not, now gone to T-Bird heaven.
1990 Volvo 740GL. 114 tire-shredding horsies, baby!

pin pointing intermittant problem

Reply #4 –
i forgot about doing the radio thing,, ill have the codes in a min or two.
my freaking buzzer stopped working that i got out of an old microwave so im back to using a visual aid.  Wish the bronco had a buzzer instead of a dinger,,

brb

--------------------------------

ok,, im back
Please read the first post cause i added some info / history
*= ommit cause these codes make sense due to my mods

Codes (first group)
56-VAF high
*31-EVP signal (no egr)
91-sys running lean
92-sys running rich
93-trottle linkage binding / bad ISC / HO2S not reading
*94-air sys inop
99-ISC needs to learn

Codes (second group)
22-MAP sig out of range
*67-Park/Neutral fault
*59-AXOD fault
*69-AXOD fault

I would guess the following is wrong,,,,,,,

MAP- replace it or check the vac lines
ISC- CHeck for carbon which i have or it is just bad.  I dont think i have any info on how ot check readings on that type isc that bolts directly to the trottle body.  Ill have to check and see cause it should be the same process as for the 86 and up 5.0L.  Ill muddle through my shop manual and see.

pin pointing intermittant problem

Reply #5 –
Back to your original desire to monitor various circuits. The shop manual always calls for the "breakout box" to be installed in the EEC cable when checking anything that goes to or from the EEC.

This one for sale on E-Bay is the same part number the manual calls for.

http://cgi.ebay.com/ebaymotors/Ford-Rotunda-EEC-IV-Breakout-Box-T83L-50-EEC-IV_W0QQitemZ230130204081QQcmdZViewItem

pin pointing intermittant problem

Reply #6 –
Intermittents should show up as memory codes. Not clear if any fall in that catagory.
Did it have a Borg Warner 97LE automatic transmission? If so that could be some of your codes.

Here is a list of Bronco codes:

http://zenseeker.net/4x4/eec_iv_2_digit_codes.htm#top10
 

pin pointing intermittant problem

Reply #7 –
yeah,, thats what i thought they always meant by a "breakout box".  I used breakout boxs all the time on aircraft parts in the navy.  It would be nice to have that tool as it should be pretty interchangeable with different vehicles.

The trany use to be an E4OD but was locking up when on the highway according to my brother in law.  He said it was dangerous so instead of fixing the e4od,,, i found this Mazda TK 5 speed ford put in a lot of thier med-light duty trucks. 

aside from the egr/emissions codes and the tranny codes,, it appears i need to look at that ISC and MAP a little closer. 

The sudden jerk or buck i feel happens often enough that im really curious as to what it is.  Im contemplating hooking up the fuel pres tester up during a drive and see if the fuel pump isint the problem. 

I gotta go to savanna ga all this week so ill get to it this weekend.  The bronco runs so its all good.