1987 JEEP : TPS Question
kjlou...@earthlink.net
VIN# xJCMRxxxxHTxxxxxx with a RENIX ECU.
Where does the Throttle Position Sensor input voltage come from?
I replaced the TPS 2 years ago and calibrated the OUT divided by the IN
@ 83%, and it worked well until recently.
My current TPS readings are IN = 7.81 vdc, and OUT = 5.65 vdc.
I am suspecting my problems are centered in the origin of the voltage
being supplied too high to the TPS and not the TPS itself.
Any advice is welcomed, thanks.
L.W.(Bill) Hughes III
You forgot to tell us what you think it's doing, or not.
God Bless America, Bill O|||||||O
mailto:BillH...@billhughes.com
http://www.billhughes.com/jeep_bookmark.htm
<kjlou...@earthlink.net> wrote in message
news:BN2dnTg0BbzNAS_X...@earthlink.com...
Will Honea
The factory manual for the Renix system (same as my '88 Commanche) says that
the reference voltage should be 5.0 volts supplied by the computer but
yours may be running slightly differently. My adjustment procedure (from
the manual) is .86 volts ouput with the throttle at dead idle to 4.95 at
WOT. If it is the 5.0 reference, you'll also find that the MAP sensor
supply is high. If that's the case, good luck finding another computer!
As I recall, the Rennix system was only used in 87 and 88 - maybe a few of
early the 89's had it butthe 90's on used the MOPAR unit. That had totally
different sensors and was set up for the HO engine with different intake
manifolds and headers along with a reworked head. If the engine runs OK
beyond the idle/WOT performance, you might be able to repair the voltage
reference inside the computer but that's chancy - I've never gotten the
schematics for that beast.
--
Will Honea
bllsht
There are two splices in the sensor ground circuit that have been very
troublesome on the early (87 and early 88) 4.0L XJ/MJ. They used a
bulkhead connector on the firewall that connected the engine harness
to the injector harness. The splices are within about a foot of that
connector, one on each side. They are crimped and duct taped inside
the harness.
In the engine harness, there is a 3 into 1 splice. The single wire
goes through the bulkhead connector, then a 1 into 3 splice in the
injector harness. The circuit is brown with white tracer.
You can manipulate the harnesses in the area of the splices and watch
the TPS voltage go nuts with a scan tool. I've never seen a physical
problem with the splices (no broken wires, corrosion or high
resistance), so it appears to be the way they routed the wires in the
harness. Maybe too close to, or not protected well enough, from other
current carrying wires. Whatever it is, you can open the harnesses
and pull the splices out, isolating them from the harness and the
problem goes away.
Since the bulkhead connector can be problematic also, I'd suggest
bypassing it altogether. Just solder the 3 wires in the engine
harness to the 3 in the injector harness. The splices are close enough
to each other that it's easy to do. Tape it up and it looks good and
no more problems.
kjlou...@earthlink.net
Thank each of you for responding.
When I posted the message, I decided to jump into the jeep and go
purchase a new TPS as a last ditch effort when I considered the other
possible costs.
My initial symptoms started ALL at once, back in May this year. While
driving on the interstate, the transmission when out (save 1st gear &
some second). Low fluid. So I immediately added enough fluid to get home.
The transmission wouldn't work properly and also started having engine
idle problems (cold start kills, and also at running temperature having
very high idles).
I dropped the pan, changed the screen, cleaned the magnet (slight haze
covering it, no shavings), and the bottom of the pan was absolutely free
of debris. The fluid smelled new and clear (zero burn scent). I put on a
new screen and replaced the fluid, adding some lucas as a kicker.
I brought it into several shops and they would only tell me "oh, about
two thousand dollars", but yet I'd hit a bump and I'd have 4 gears back
up shifting and down shifting normally as if I never had a problem (but
the idle problem prevailed).
Each time the transmission would randomly go ignorant, I'd checked the
TPS. Each time it reported in @ 83ish% --until September. Once I
replaced the TPS and calibrated, the idle issue when away -- and so did
the transmission issue (save one). I did not get overdrive back. It's
been a month, and I am at another dead end on what direction I should take.
I do not know if I damaged the 4th gear/overdrive planetary when I ran
low on fluid (temperature wise) back in May, or if I have a pending
overdrive electronic issue? MT2500 didn't shed any usable clues.
Based upon each of your previous postings with advise, I am going to
break open & look into the wiring harness and also disconnect at the
bulkhead to check the contacts this weekend.
Do you think my neutral safety switch is over due at 270k miles?
--Percentage wise? Aisin Warner 30-40LE.
Any Suggestions?
Thanks,
Ken
Will Honea
At 276k on the clock, the whole power train is tired and the tranny has all
sorts of worn parts, so I pass on that. For the idle, just unplug the TPS
(both of them) and clean the plug contacts with contact cleaner.
--
Will Honea
PeterD
When you put a scan tool on it, what DTCs do you get?
Jeff Strickland
"PeterD" <pet...@hipson.net> wrote in message
news:f17he51j99fcf1273...@4ax.com...
It's an '87, not '97. There is no scan tool to pull DTCs.
kjlou...@earthlink.net
I do not own a mt2500, but I found someone who had one. We were not able
to get any specific codes from the ecu or the tcu, but all of the basic
reporting features illustrated nominal/pass results. I heard it said
that a DRB II would do nicely but no shop in the city has one. I have
the Renix ECU made by Bendix (replaced with a new one 2 years ago).
What do you think?
Ken
PeterD
>PeterD,
>I do not own a mt2500, but I found someone who had one. We were not able
>to get any specific codes from the ecu or the tcu, but all of the basic
>reporting features illustrated nominal/pass results. I heard it said
>that a DRB II would do nicely but no shop in the city has one. I have
>the Renix ECU made by Bendix (replaced with a new one 2 years ago).
>
>What do you think?
>Ken
>
Some ECU/TCUs will inhibit overdrive if there are codes, but that
doesn't seem to be the problem. I'm not sure what's up at this stage.
dave AKA vwdoc1
The Bendix Jeep Tester will get you those codes on an '87 and on my '88.
I have the manual with all of the codes.
I sent those codes to the Renix group on Yahoo after scanning them
http://autos.groups.yahoo.com/group/RENIXPower
but I don't think that they were grouped & posted in a file yet.
The Tester also allows you to see what the ECM sees, TPS position, CTS
temperature, etc.
--
later,
dave AKA vwdoc1
88 XJ 4.0 auto
"Jeff Strickland" <crwl...@yahoo.com> wrote in message
news:hca80r$rsi$1...@news.eternal-september.org...
>
> "PeterD" <pet...@hipson.net> wrote in message
snip
Jeff Strickland
the codes.
"dave AKA vwdoc1" <vwdoc1...@pleasehotmail.com> wrote in message
news:hcdjjg$1rph$1...@adenine.netfront.net...
dave AKA vwdoc1
I think the 1991-1995 "Chrysler" OBD-I might have the blinking system. ;-)
"Jeff Strickland" <crwl...@yahoo.com> wrote in message
news:hcdk38$psf$1...@news.eternal-september.org...
bllsht
will guide you through a self test (key on, key off, step on
accelerator, etc) and look for the proper response. If it doesn't see
what it expects, it'll give you a code to look up a diagnostic
procedure. Useful if you have a dead sensor, but no help if your
problem is intermittent or a sensor that's just slightly off. The most
useful thing is the serial data readout which lets you see sensor
values in real time, but only one sensor at a time.
This tool was replaced by the Jeep/Eagle adapter used with the DRBII.
Will Honea
on where to find out the specifics of the interface? I fiddled with it and
got the stream to display from a serial port connected via an optical
isolator (I don't trust anyone's implementation!) - can't recall all the
details, but it was pretty straight forward to that point. Of course, I
had no idea of what it meant but I could get a predictable stream. The
interpretation and control codes are what I'm looking for.
bllsht wrote:
--
Will Honea
kjlou...@earthlink.net
I was sure my transmission was an electrical issue, and not a mechanical
one. The TPS seemed to be a part of that premise. In the summer 0f 2010,
after driving without overdrive for a year, I pulled into a sleeply
little town in Mississippi (Pascagoula) and a home grown auto repair
shop. Ole boy said his modis scanner said my brake was depresssed. ---
Overdrive solved by replacing a burnt wire under dash near pedals. Just
saved $2,300 for what 10 authorized mechanics wanted to charge.
Well, it's winter time again and my jeep is following it's attitude as
in the past 5 winters. Cold temperature (35 to 45 degrees) it reeves
over 3500 rpms the first time starting it in the morning. I have to shut
off, and restart no less than 4 times before the reeving of the engine
subsides. Any suggestions? EGR? vacuum? relay?
Your input has been and is appreciated,
Ken
kjl.je...@gmail.com
cool weather - clod starts?
Thanks,
Ken
On 10/28/2009 1:32 PM, PeterD wrote:
> On Tue, 27 Oct 2009 09:39:55 -0600, kjlou...@earthlink.net wrote:
>
>> Bill Hughes, Will,& Bllsht,
>> break open& look into the wiring harness and also disconnect at the
Will Honea
> Since 10/2009, just wanted to follow up and update on the TPS issue.
>
> I was sure my transmission was an electrical issue, and not a mechanical
> one. The TPS seemed to be a part of that premise. In the summer 0f 2010,
> after driving without overdrive for a year, I pulled into a sleeply
> little town in Mississippi (Pascagoula) and a home grown auto repair
> shop. Ole boy said his modis scanner said my brake was depresssed. ---
> Overdrive solved by replacing a burnt wire under dash near pedals. Just
> saved $2,300 for what 10 authorized mechanics wanted to charge.
>
> Well, it's winter time again and my jeep is following it's attitude as
> in the past 5 winters. Cold temperature (35 to 45 degrees) it reeves
> over 3500 rpms the first time starting it in the morning. I have to shut
> off, and restart no less than 4 times before the reeving of the engine
> subsides. Any suggestions? EGR? vacuum? relay?
>
> Your input has been and is appreciated,
My wife showed me how to fix that on a 4.0L I6: KEEP YOUR FOOT OFF THE GAS.
More specifically, the old MJ (Renix system) does this race thing on cool
starts ("cold" around here is generally single digits, +-, and with those
the darned thing starts fine). At those intermediate temps, it will race as
you describe under two conditions: If I give it ANY gas while starting and
(oddly enough) if I pull into the drive in 2nd or 3rd then turn the engine
off without letting it idle for a second or two. The second one there acts
like a restart after stalling the engine taking off from a stop and backs
off pretty quick but I can't figure why it "remembers" a stall overnight.
Two things helped the first of the above two: 1. clean the TPS lug really
well and 2. get some contact cleaner into the TPS itself then work it back
and forth to get the corrosion off.
--
Will Honea