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ISC not working; possible problem with relay
Topic Started: Jan 27 2015, 01:02 PM (5,929 Views)
freegeo
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TripleThreat
Feb 23 2015, 12:27 PM
Where's your ignition timing at with engine fully warmed up and diag connector under hood jumpered?

Glad to hear you are seeing improvement!
9 to 10 BTDC.
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Hanuman
"The Almighty Grounds Cleaner"

freegeo
Feb 23 2015, 12:10 PM
The car has been running pretty good. Has only died once since I last posted. One thing I have noticed is that when it is in decel (the trans still in gear and slowing down) is when the engine seem to stumble. What part of the engine control system needs checked out to se if I can correct this?
define 'stumble" more clearly......during decel fuel cut off the fuel is cut off......the engine is essentially not running, but is still spinning because its in gear. you have spark, but no fuel.

describe exactly how it stumbles, and when exactly it happens.
(i think i may know what your talking about, but i want to be sure. and im still working on a new idle issue with my car that may be what your now experiencing)
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freegeo
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Hanuman
Feb 23 2015, 02:18 PM
freegeo
Feb 23 2015, 12:10 PM
The car has been running pretty good. Has only died once since I last posted. One thing I have noticed is that when it is in decel (the trans still in gear and slowing down) is when the engine seem to stumble. What part of the engine control system needs checked out to se if I can correct this?
define 'stumble" more clearly......during decel fuel cut off the fuel is cut off......the engine is essentially not running, but is still spinning because its in gear. you have spark, but no fuel.

describe exactly how it stumbles, and when exactly it happens.
(i think i may know what your talking about, but i want to be sure. and im still working on a new idle issue with my car that may be what your now experiencing)
Let me drive it a little more, it will be a couple of days. My wife needs to drive it to the doctors office. I'll try and get a better understanding of what it is doing so I can describe it better.
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freegeo
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I got to do it today. Once the car is fully warmed up and driving down the street. Say if I'm in 3rd gear and the rpm's is around 3000. When I let off the gas the engine goes to open loop and starts decel (fuel shuts off). When I push in the clutch the engine rpm's will drop below the 850 idle and stall out. It does not do it all the time only once in a while.
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TripleThreat


THANKS GMF!
Edited by TripleThreat, Mar 14 2015, 11:10 PM.
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Hanuman
"The Almighty Grounds Cleaner"

TripleThreat
Feb 28 2015, 12:51 AM
That almost sounds like fuel pressure regulator, have you ever replace it on this car? I someone on here recently posted something about how to easily test it. I wanna say it was a resident Almighty Grounds Cleaner. Let me see if I can find it...
nope, not the fuel pressure.
lack of proper fuel psi or over psi would present itself as a problem while engine is under load...aka...driving the car.
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Hanuman
"The Almighty Grounds Cleaner"

freegeo
Feb 28 2015, 12:45 AM
I got to do it today. Once the car is fully warmed up and driving down the street. Say if I'm in 3rd gear and the rpm's is around 3000. When I let off the gas the engine goes to open loop and starts decel (fuel shuts off). When I push in the clutch the engine rpm's will drop below the 850 idle and stall out. It does not do it all the time only once in a while.
there are several possibilities floating in my head.....let me sleep on it.
ill get back here in the afternoon sometime.
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freegeo
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ok. I agree it would not be a fuel pressure problem.

Like I said it doesn't always do it. Like it doesn't have a smooth transition from open loop to closed loop after decel.
Edited by freegeo, Feb 28 2015, 03:41 PM.
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Hanuman
"The Almighty Grounds Cleaner"

i recently corrected three issues with mine.

problem #1 increased idle speed from normal while coasting in neutral...and pulsing. no problem with car stopped

problem #2 increased warm up idle speed, rough transition from decel fuel cut off to normal. slow bucking while in first gear just off idle. (fuel while just off idle)

problem #3 loping idle while warm and car stopped. no headlights on. often higher than normal warmed up idle speed.

....................................



problem #1 started after i had accidentally blown the ignition 50 amp fuse. i had just twisted the ends together inside the fuse as a temporary fix....this change in operation started the next morning. there was a very light layer of green on the copper ends i had twisted together. replaced fuse solved problem

problem #2 i noticed corrosion on the positive battery cable post, cleaned.....inspected my grounds, they were still visibly shiny. no change after cleaning the battery post.....so i dug a little deeper, where the main positive cables are pinched into the battery cable clamp i found corrosion.....cleaned the wire ends, cleaned out the pinch connection on the battery clamp. this clamp does need replacement. untill then, removing this corrosion has solved the problem.

problem #3 turned out to be the negative battery post needed cleaning. cleaned battery post solved problem.

try having a look at these three areas.... (and by look...i mean open them up...and while there open, clean them up just because)
bottom line is the signal to idle up or to leave decel fuel cut off.... isnt reaching the computer.
it could be the signal is just weak.

get back with us again in.....
Edited by Hanuman, Mar 1 2015, 05:23 PM.
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freegeo
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Hanuman
Mar 1 2015, 05:17 PM
i recently corrected three issues with mine.

problem #1 increased idle speed from normal while coasting in neutral...and pulsing. no problem with car stopped

problem #2 increased warm up idle speed, rough transition from decel fuel cut off to normal. slow bucking while in first gear just off idle. (fuel while just off idle)

problem #3 loping idle while warm and car stopped. no headlights on. often higher than normal warmed up idle speed.

....................................



problem #1 started after i had accidentally blown the ignition 50 amp fuse. i had just twisted the ends together inside the fuse as a temporary fix....this change in operation started the next morning. there was a very light layer of green on the copper ends i had twisted together. replaced fuse solved problem

problem #2 i noticed corrosion on the positive battery cable post, cleaned.....inspected my grounds, they were still visibly shiny. no change after cleaning the battery post.....so i dug a little deeper, where the main positive cables are pinched into the battery cable clamp i found corrosion.....cleaned the wire ends, cleaned out the pinch connection on the battery clamp. this clamp does need replacement. untill then, removing this corrosion has solved the problem.

problem #3 turned out to be the negative battery post needed cleaning. cleaned battery post solved problem.

try having a look at these three areas.... (and by look...i mean open them up...and while there open, clean them up just because)
bottom line is the signal to idle up or to leave decel fuel cut off.... isnt reaching the computer.
it could be the signal is just weak.

get back with us again in.....
Problem # 2, rough transition from decel fuel cut off to normal. That is a good description of what mine does.

Here is a picture of my battery post and clamps.

Posted Image

Posted Image

I replaced the original ones when I put the engine back in.

I have even added a extra ground (green wire) from the radiator core support to the back of the intake.

One thing I did notice today while driving it around was if the rpm's is around 3000 rpm's and let off the gas pedal it goes into open loop and starts to decel. At around 1700 rpm's the engine goes back to closed loop. Like I said before if I push in the clutch before the the engine goes back to closed loop it will sometimes stumble trying to go back to closed loop. Sometimes it catches itself and the rpm's go back up and sometimes it dies.

I have a autotap program that i can run and record input and output data. I'm not sure what input and outputs i can view yet.

Any recomendation as to what to try and watch to see what differences between when it dies and when it runs normal?

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freegeo
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I think I may have figured out what is going on with my engine. I got a PO400 code pending today right after it stumbled. Looks like it might not be closing off in time. Time to dig the FSM and start testing again.
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Hanuman
"The Almighty Grounds Cleaner"

if its open...aka not closing fully and the higher vacuum during decel fuel cut is pulling in some egr...this may cause a stumple or stall.

check first to see if the egr is plugged.....pull up on the under side of the diaphram while car is at idle.....it should stall or idle very rough. if not, the egr is plugged and thats the source of your code.
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Hanuman
"The Almighty Grounds Cleaner"

Hanuman
Mar 4 2015, 03:17 AM
if its open...aka not closing fully and the higher vacuum during decel fuel cut is pulling in some egr...this may cause a stumple or stall.

check first to see if the egr is plugged.....pull up on the under side of the diaphram while car is at idle.....it should stall or idle very rough. if not, the egr is plugged and thats the source of your code.
also......if its leaking egr.....a small amount at idle would effect the relation ship between the map sensor reading, TPS value.......in other words...this whole 8 page thread on idle problems...... :D
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freegeo
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Hanuman
Mar 4 2015, 03:17 AM
if its open...aka not closing fully and the higher vacuum during decel fuel cut is pulling in some egr...this may cause a stumple or stall.

check first to see if the egr is plugged.....pull up on the under side of the diaphram while car is at idle.....it should stall or idle very rough. if not, the egr is plugged and thats the source of your code.
My idle has not been very smooth since I put the engine back in. The egr valve was cleaned very well before I put it on the engine.
It could be it's not seating fully closed. The passage ways are all clean and open. I remember using my finger and opening the egr valve manually at idle and it died almost instantly.
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freegeo
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Hanuman
Mar 4 2015, 03:22 AM
Hanuman
Mar 4 2015, 03:17 AM
if its open...aka not closing fully and the higher vacuum during decel fuel cut is pulling in some egr...this may cause a stumple or stall.

check first to see if the egr is plugged.....pull up on the under side of the diaphram while car is at idle.....it should stall or idle very rough. if not, the egr is plugged and thats the source of your code.
also......if its leaking egr.....a small amount at idle would effect the relation ship between the map sensor reading, TPS value.......in other words...this whole 8 page thread on idle problems...... :D
Yea you maybe right. This may just come down to every possibly idle problem you can have all rolled into one.
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