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Old 01-04-2013, 05:05 AM   #1 (permalink)
Bex
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Default Limp home

Interesting new video from Duane:
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Old 01-04-2013, 08:14 AM   #2 (permalink)
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i see you get the same emails i get.
great
he checked for bad fuses but not missing... this was the first error.
the op guide on all car shows each fuse and it's function.(so do all 3 online FSM)
non opted functions,may not have fuses.

FYI: (how to find limp home, notice many hard fails on old neglected cars)
typical:
14 mins into VID,see the fuel trim is dead, but 02 sensors working
the means he ECU is in LIMP. (mpg horrible) A FORD deal
all can be done with out OBD2 or that high end tool.

notice the fallacy: (stated this forum , over and over (not 1.6L)
no timing adjustments! Duane mentions it as a dig. (good)
sure, but that don;t mean you don't LOOK! duh?
the jogging timing would have been clear, the mechanical, failures! timing jitter.

In the video. the owner abandoned it, with it's many faults, ....

btw , if you get the motor running perfect at"stoich", ive seen many 02 wake
back up form AF poisoning.
Limphome keeps them dead and full of carbon, once repaired right
they get real hot and can bake out good.
FYI hints.... for DYI (hope happens if lucky)

in retrospect.
the video
all techs,check fuses first, pros use a meter, as fuses can look good
and be bad (hair line cracks) (once burned ,twice shy)

also the heaters all love to fail. in the 02 , it's there thing.. and
so, do wires on them melting on the exh, pipe. (missing clamps ,typical)
so ,02 fuses blows. (PO got quoted, $200 each for new 02 , my guess)

on Suzuki (96+) the ecu reports this , i guess FORD dont. DTC P0135 never lies!
he would have seen the 02 sensors wake up way too late. and not at all at idle.
or keep dropping out
most wake up 10 seconds. key on. (in the Bosch spec, no secret.and is EPA spec'd)


keep mind this video is for 96+ cars only and fords, are odd beasts.
how would this play out on say a 95 MPI KICK.

1; car runs rich and has 18mpg fuel usage. crying towel?
tech, time.
motor tests good, and as the video shows, the cat is under 1psi under load of tranny.
spec is <2psi 2500rpm (suz)
vacuum steady.
spark hot, and static time working, and spark does not advance off the scale at 3000 RPM./ ops, Evidence failure #1.
he has a scan tool and sees no CLOSED loop hot idle.
or
using manual O2 monitors. (other tools)
uses a scope or GMM ,DSO or high end DMM to see if the 02 swings. DSO rules roost


some cars, swing in limp home, but the Closed loop is not happening. Like in Vid.
on Suzuki it usually swings and is proof NONE limphome, (fails safe is suz,name)
as my 0bd2 page shows, i always check 3 things (applies to all EFI cars)
1: 02 fast wake up. 10seconds,
2 CL now. at idle. holding and at steady cruise. say 2500 rpm,
3:LTFT and STFT working. not dead.

the ECU may drop closed loop with the DRIVE tests,(in VID) due to low fuel pressure.
sure can. (ecu cant get the 02 to cross, 0.5v due to gross lean running.)

with no scan tool ,you can only see, 02 signals.
(you can not communicate with the ECU. with no scan tool, so the tech must work hard for evidence.... very hard. )

Keep in mind, that there are vast numbers of ECU. on many cars. and years
and some may drop closed loop, CL, for other ECU reasons , many have other inputs
to said ECU that can cause that. That is why you need a FSM
to understand what those logic rules are. (not all ECU's work the same,)

Limphome happens for 5 reasons: (at least)
1: Gross DTC fails on major sensors. (the FSM lists them) MAP/MAP, TPS, ECT....etc.
2 one or more sensors, so far off ,it can not PULL the 02 across the .5v transition
3: each for UNKNOWN reasons (it's not a diety) can not find the 02 transition .
4: some other reason , listed in the FSM. (how about, zero 02 heater current?)
5: all the above can be ok.? but the fuel pressure drops , under real engine loads
that is, in Drive , say the pressure dropped to 15PSI. the 02 sensors go lean.
the ECU is flummoxed and CL, ends.

Keep in mind the VIDEO is for FORDs, a whole different system.

i use my ammeter clamp on all cars with no OBD live current monitor ( pre 96s)
it reads 1amp, about
if zero ANPS I check voltage, to heater,then it check, ohms. the Bosch data sheet shows
all these specs, are published .
if the heater is dead, MPG will suffer,at idle and low speed. (way bad city MPG)

too bad no CL lamp on the dash of car but and AFR meter,will be a good substitute.
DYI $20
just that 1 lamp can save you from wasting fuel too. drive in such a way to keep
the lamp on. as much as possible.... or the gauge at stoich.






keys: Limp in, limp home, fail safe.
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Old 01-04-2013, 08:32 AM   #3 (permalink)
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Makes me wonder about the trouble code explanation...About how one needs to drive around in order for the trouble codes to come back? Maybe an attempt by Ford to get problem children out of the shop for a while? That sucks for the customer

Do the 16 valve trackers go into speed density mode when there is a fault?
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Old 01-04-2013, 10:00 AM   #4 (permalink)
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all OBD2 monitors (great questions)
need to run out.
Read up on obd2, tech.
for example
the egr
the vss
the EVAP can tAKEs, 30 mins to run out. 97+ has that.as does that ford.
cat efficiency. p0420s
fuel trim , Railed.
to name at least 5 , of the 11 in 1996 , more later. all EPA edicts

some DTCs are instant "Called comprehensive monitor sets)
like, bad TPS, stock at 5v.
ECT wires fell off, IAT fell same.etc,

see?
prior to OBD2 uSA std. there were only a few monitors
like
code 13
51.


here are some.

http://www.fixkick.comECU/AuthorityA....html#monitors


why does this suck?, what parts suck?, the running kids or how OBD2 works.?

great questions, (all these facts in my links to wiki OBD2, endless there)

what is limhome? well for your example, that is easy.
loss of MAF you say.

as you know many 95s don't have one signal map sensors!


so, cant really switch to speed density. no MAP.
i think racing ECU call this ALPHA mode. (go to megasquirt on line its there)

answer 1:
in one line
it uses all other sensor inputs to emulate a MAF.! its in the FSM.
eg:
RPM , TPS ANGLE, engine heat. , air temp.
it will go to retarded timing. a big clue and takes 3 min to see.
and restricted, RPM. (rev cut governor)

in a word : CRUDE ! FUELING WILL BE RICH and exhaust BLACK.

that is why its called limphome , in stand of walk home.

which begs the question.?
does a 96+use the EGR map with a dead MAF. i dont know.?
so, easy pull the maf and then the EGR map, and see what she does.
i was going to that the once, but my GF, distracted me. (nice.....)

i can guess? what your next question might be...?.. i get it all the time
why , does it take so long for monitors to run out.
ill pick one. at random, each has its own little story
----------------------------------------------------------------------------------------
EGR. P0400
the EGR needs to be tested moving ,
because its dead , not moving, (VSS guarantees that)
if the eCU were to open the EGR, at idle it would stall.
the time rule is for Fuel trim. completions see link.

so your moving, and there are 2 tests to be done.
and nether test must be done such that it interferes with the driver
(or get nailed like toyota for $1billion bucks) huh?
they must do 2 testd(dead (stuckclosed) or stuck open) very simple tests.

they do one test coast from high speed, then one for coasting. so a not to causes
power issues. it's in cut fuel mode too, coasting.
they use the EGR map and check vacuum (baro) very carefully,
baro means barometric sensor ,that is what an eGr map is.

the other test, cruise testi is....
this explains the complex FSM steps for this test.

http://www.fixkick.com/sensors/EGR/P0400-NG.html

as you can see this test is very tricky and only runs
on a hot engine and only under very limited, conditions.
------------------------------------------------------------------
the evap 2 system 1997+ can take up to 30 mins to walk out,
in fact will suspend until the tank if 1/4 empty from full.. 3/4.
why
with no air space , tests are impossible.
this is why they(epa stations) to allow 1 monitor to be incomplete.
reason ,tank is full.

ask more questions....???
btw , motormag.com has back issues, covering all obd2 from the
beginning for the first one, to now. old issues are free.to read.

even covers the EPA rules, and how manufactures, complied.
ive read most 10 times, over the years. in fact all in my library.

Last edited by xxx; 01-04-2013 at 10:48 AM.
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Old 01-04-2013, 10:24 AM   #5 (permalink)
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I think the problem child thing didn't translate too well sorry... Problem child is a vehicle that a mechanic is unable to troubleshoot. Typically they just BS the customer until the customer gets fed up. My comment was the trouble codes don't appear right away so the mechanic clears the codes and returns the vehicle to the customer. Shady work...how could an average customer know? That's why I say it sucks for the customer.

I didn't know there was not a MAP sensor so it makes sense.
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Old 01-04-2013, 11:56 AM   #6 (permalink)
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clear now.
yes, most customers think it's all magic. (let them)
the mech there is a master, see sleeve? he's no hack.
and the customer , gave the car away because the repair costs exceeded car value.
dead engine cars have very little street value, for sure any ford.
new head gasket $1000?
new 3 more things,, taking, 3 to 4 more shop hours, $500 more.
so customer throws in the towel.. i'd do that on any ford, that old, POS.

yes, he clears the codes, not for that, clear and send is impossible here....

he said, the car came in dead,and said the prev. mech fiddled every part of car.
so all codes will be false, sure write them down. only and idiot clears them and no log.
but he's and ASE master. and knows too well only the here and now counts
an all new head gaskets, and that the AF usually wrecks the front 02
so you clear codes and drive, it fast to get the full set of codes ! but.... but..

but has no power, so can't (cant get out of its own way ,)
so, he works the codes in hand and a full set of tests, basics.
i wonder what that cam sync costs, another $300?
his only fail was not checking for missing fuse..... a gotcha....

that ford has rear crappy limphome.. must be bad ecu code.
at least 1/2 power should be on tap in limphome. with this failure.... sad...
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Old 01-04-2013, 12:09 PM   #7 (permalink)
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I agree the instructor in the video is really good at what he does and his videos are really cool to watch. The video was educational for sure and I'm sure he right away started with the advanced diagnostics to show why it was doing what it was doing.

IMO the students that were working on the vehicle should have known to check the fuses....but they are there to learn and I bet learn they did!


One thing also speaking of good and bad mechanics.... The certifications doesn't guarantee a good mechanic.. I know a lot of book smart people in my field (non automotive) that can pass certification exams and get good grades in classes but when it comes to actually troubleshooting all they end up doing is throw part after part after part to try to fix the issue...
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Old 01-04-2013, 02:10 PM   #8 (permalink)
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Quote:
Originally Posted by xxx View Post
i see you get the same emails i get.
great
he checked for bad fuses but not missing... this was the first error.
the op guide on all car shows each fuse and it's function..
Yes, I really like his videos, although, of course, with me being OBD1, I can't duplicate a lot of his scan info and testing. I suppose if he had checked for the bad fuse at first - there would be no video!! (Actually, while I was watching this, I actually thought that perhaps he had taken the fuse out on purpose to throw the car into limphome, just for the lesson - after all, putting the car into drive, and suddenly going into limphome would direct you toward engine load from the tranny).
And the info on Identifix was pretty nice too.
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'97 Suzuki Vitara 8v, 1.6L 5 sp, 4wd, 2dr, tintop, horribly purple
'61 NSU Quickly - 150mpg
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Old 01-04-2013, 03:18 PM   #9 (permalink)
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you understand , duane well , he does just that.
once you have 100s videos
to cover a new topic, you must break something, or wait forever.

i suspect that here.

all of his pages, everyone, where they show tool x, you can use other tools
he does not say that because he has the good tools.
and he don't see to many old cars, the labor rate, is more that the car.
so in Duanes world OBD1 us deadsville.

the scope can, do most the tests. voltage prop and current probe,
he just forgets to say that, to keep the video short'
one thing you can not do, is see the CL bit. closed loop (no scan tool)
so we must so other tests to discover that. (a nice tap dance)
the killer is not seeing LTFT. (note: he finds it DOA)

LTFT tells me , if the o2 is working and in fact the ecu can do the corrections.
or it all fails.
no scan tool ,, a long row to hoe.

no tools at all is just wild guessing. one poster didnt like my 60 fails for idle.
he even thought i was saying replace all 60 parts.
i use physics to do everything, no rote.

the ECU can and will hunt, if it can not correct the idle
pull the DP hose and watch.
it tries hard to drop idle, to 800 and is impossible
so closes the valve, and it does , goes dang, resets and repeats.
try it ( on a good car,)

it will also hunt a gross lean engine. (backwards,)
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