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Topic: Engine Stalling Intermittently on Deceleration (Read 3710 times) previous topic - next topic

Engine Stalling Intermittently on Deceleration

1984 Cougar
3.8L
Throttle Body

Car is stalling intermittently (not every time) when stopping.
Able to restart immediately after stall.

Replaced distributor rotor and cap.
EGR value OK (tested per shop manual instructions).
OBD-I codes show OK.
TFI replaced at 19000 miles (now 150000 on TFI). 
Have noticed wiring (harness wires) seems to be brittle in places and some cracking.

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Questions:

1.  Any chance removing and regreasing TFI will help?
2.  Any simple solution to repair cracking without cutting wires and using heat shrink tubing?
3.  Best place to get a new harness if cracking can't be resolved?
4.  Any place to get the old multi_point ignition rotor -- can't find here in Arizona -- always had better luck with them than T type.
4.  Other tests to perform to solve stall problem?

Thanks
David

Re: Engine Stalling Intermittently on Deceleration

Reply #1 –
Most likely this problem would be the fault of the Idle control motor assy forward of the CFI on driver side.

With a cold engine, does the plunger shoot out and eventually retract as the engine runs for about one minute?

If it does not,, try to adjust it forward and see if the motor starts to respond.

Check the 4 wire connector for bad wires or connection.

with the engine off and key forward, check the tps green wire for less than a volt dc.  Look for 4.5vdc or better at wide open throttle.

I would also be checking the Pick up module down in the dizzy.  It might be going out on you.  There is a magnet on it so see if there are shavings or debris on it. You will have to remove the metal round thing with two screws but mark it to the dizzy prior to removal. if there is  on it,, just insert a stronger magnet down to it and it will suck off any metal shavings.  finish it off with carb cleaner.  there is no drain hole in this area which really  me off.  the dizzy will hold water and the actual drain hole in way way in the wrong area.  I drilled a hole where i thought it should be.  You might wanna replace this part anyway cause these give you little warning when they go.

Next id hook up a fuel pres tester to the Shrader valve on the top of the CFI and drive the car with the guage duct taped to the windshield.  Watch the presure as you drive and cycle through gears.  If it drops extreeeeemly low like below 20psi,, you might wanna invest in a new pump.  I purchsed the 3.8L supercharge pump fore 40 some odd dollars (just the pump) and installed it into my old pump housing assy/rubber bushing.  Now when i drive, the presure gets no lower than 35 between all gears or trottle range.

My next experienced guess for stalling and bucking issues would be to remove the cfi and egr base plate.  Lay a flat edge along the surface of each and check for warpage.  Beltsand down the warpage and install a new gasket kit.  This is a major common problem i have noticed that people tend to ignor.  Ignoring the thin paper gasket on the intake to egr plate could be a problem that leads to chasing phantom problems down the line.

Next up would be to remove the injectors and just toss the injector screens for new ones or leave them out,, i have and it works fine.

Next id check to see about a vac issue. Does your PVC valve suck your finger right up,,? if not,, Remove the vac line from the driver rear side of the CFI (gold fitting).  slide a wire up inside the metal tube to bust up any carbon.  Run some carb cleaner up in that hole while the engine is running and womp on the trottle a little to help clean out.  If your situation improves,, then you need to remove the cfi and chip away all the carbon build up in the area of the gold fitting as well as anywhere else.



EEC not dumping any codes is a good thing...... Do you end up with CODE 11?

as for the brittle wires and such,, someone else here has the same problem.  Theres no reason to leave these wire on the car.  change them out as far back as you can.  I have not replaced this section (injector/TFI harness) so i have no idea if it dead ends along the fire wall.  It should even if you have to to the Pin extaction thing incase the harness splits up between a couple different connections.  That burnt wire thing is not good and needs fixed first.

as for the TFI regrease,, it might but no reason why you cant replace those scews with more reasonable types like allen or self tapper phillups.


BTW,, good job on your description of the problem,, who,what,when, where and why all adressed. :bowdown:

i have a few other suggestions but let us know what you find out.

Re: Engine Stalling Intermittently on Deceleration

Reply #2 –
jcassity

Thanks for response.  Give me this weekend to check out your suggestions and will repost this thread.

Have noticed wire insulation looks bad on yellow wire where it enters TFI connector.  Any suggestions for repair at this location or do you know of a source where I can get a new harness/partial harness with the TFI connector?

Thanks
David

Re: Engine Stalling Intermittently on Deceleration

Reply #3 –
that should the yellow/light green.  Its probably the sprout connector wiring.  If its bad then the eec isnt seeing the shorting plug and your running in "open loop" mode.  If your running in open loop mode,, i dont think the eec will even provide you with any codes.

someone verify this for me please...


did you get a code 11?  if you did not,, then your eec is not communicating with you at all.

dont unplug and replug this plug while the engine is running,, bad.  one easy way to check to see if your running in open loop is to put a timing light on the car.  If your timing is flashing on or about 10*btdc,,, then the eec is hybernating waiting for someone to fix something.  If the timing is way off,, most likely your not running open loop and the eec is doing its job by advancing the timing according to current engine running conditions.

You probably have a problem if your timing shows up at 10 or so degrees.

do this test with the shorting plug in,, dont unplug it.

Re: Engine Stalling Intermittently on Deceleration

Reply #4 –
did you get a code 11? if you did not,, then your eec is not communicating with you at all.

YES - Code 11 for both constant and continuous test

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BTW Prior to post had checked idle control motor and worked OK --
as this was #1 on your checklist.

Re: Engine Stalling Intermittently on Deceleration

Reply #5 –
To fix deteriorated wire insulation I use a product called Liquid Electrical Tape. It's made by "Star brite" and comes in a yellow can with a applicator brush cap. The brush is too big and clumsy for car wiring but you can use something smaller and it works pretty good.

The insulation goes bad where the wires enter sensors and connectors.

Check where electrical supplies are sold. Mine is black but I think it also comes in red.

Re: Engine Stalling Intermittently on Deceleration

Reply #6 –
'The idle speed control motor connector has four wires. Two wires run the motor. The other two wires are for the idle tracking switch. When the throttle linkage presses on the ISC plunger tip (you took your foot off the gas) it makes the idle tracking switch. This tells the EEC that it is in control of the engine  speed.
If this switch fails the EEC will not operate the ISC.

Re: Engine Stalling Intermittently on Deceleration

Reply #7 –
Idle control motor (ISC adn idle tracking switch check) 3.8 and some 5.0 engines


ISC motor>>>
yellow/black{eec pin21}ISC+
white/light blue{eec pin 41}ISC-
add power and ground to either of the above wires to extand and retract motor plunger
isc motor + to - resistance is to be about 5 ohms
motor should extend greater than 2'' from mounting braket
motor should retract less than 1.75'' from mounting braket and off the face of throttle linkage
 

ITS (idle tracking switch)
retract motor plunger and mesure resistance from the following
light green/white {eec pin 28}ITS
black/white {eec pin 46}(also at self test conn)SIG RTN
resistance should be less than 5 ohms.

Re: Engine Stalling Intermittently on Deceleration

Reply #8 –
Another way to check the ISC motor:

Remove the air cleaner so you can see the ISC motor.
Turn key on but don't start.
Install the self test jumper like you do to run the KOEO tests.
The ISC motor will retract the plunger.
The gap between the ISC motor tip and the throttle linkage should be 7/32". Use a 7/32" drill bit for a feeler gauge.

Turn key off and remove jumper.

Start the car. The ISC will extend.

Re: Engine Stalling Intermittently on Deceleration

Reply #9 –
Quote from: softtouch
The gap between the ISC motor tip and the throttle linkage should be 7/32". Use a 7/32" drill bit for a feeler gauge.

It should be 9/32" (.281"), not 7/32".

Re: Engine Stalling Intermittently on Deceleration

Reply #10 –
oh , and by the way..........
another thread made me think of an idea for them as well as you.

after your car is warm,,,,
remove the serpintine belt and reach down to the smog pump plully.
if its hard to turn or does not free spin,,,,,
you just found your problem.  smog pump is putting your engine in a bind while on decell situations.  it happend to me exaclty like your situation.

Re: Engine Stalling Intermittently on Deceleration

Reply #11 –
Quote from: JeremyB
It should be 9/32" (.281"), not 7/32".


The '84 shop manual says 9/32" but the manual was corrected by technical service bulletin 84-10-13.

The adjustment is 7/32" with an acceptable range of 3/16" to 1/4".

Re: Engine Stalling Intermittently on Deceleration

Reply #12 –
I'm just going by Probst.

Re: Engine Stalling Intermittently on Deceleration

Reply #13 –
My '84 T-Bird had a multipoint rotor as original equipment. The replacements have been the blade type.
Looking into this I found a service bulletin for all Ford/Merc/Linc cars 1983-86 replacing the multipoint with the blade type. They also replace the non-vented distributor cap with a vented one.

The reason they give is, the sparks in the cap cause the formation of ozone and nitrogen oxides that react to form nitric acid which deteriorates the cap and other components.

The blade type rotor generates less ozone and the vent allows the gas to escape.

They also remind you to put dieletric compound on the rotor blade tip.
The '84 shop manual says don't put dieletric on the multipoints.

I don't know if I have a vented cap or not. Something I'll have to check.

Re: Engine Stalling Intermittently on Deceleration

Reply #14 –
Thanks for all the responses guyes.  Will be busy this weekend.

1.  Fixed the electrical (plastic coming off wiring from connectors to about 1/2 back from connectors).  Used a product called "plastic dip".  Marketed under a number of different names including "liquid tape".  Breaks down under UV, but under hood hoping this won't be an issue.  Temperature range is -32 to +200F.
In talking with manufacturer indicates a number of people have used for for automotive so will see what happens.

Repaired TFI, coolant temperature sensor and manifold charge temperature sensor wiring.

2.  Pulled the TFI and regreased.  Ran car this pm and still intermittent failure.  Get about 10 miles, and after several stops in between, engine quits on next stop.  Then go about another 5 miles and OK, then if stop again, quits.

3.  Will go back and double check idle speed control motor.

4.  Just put a new smog pump on about 3 months ago but will doublecheck.

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JCassity, where did you get a fuel pressure tester with a hose 24-36 inches long.  Longest I've seen is about 14 hose which won't reach windshield?

David