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| ISC not working; possible problem with relay | |
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| Tweet Topic Started: Jan 27 2015, 01:02 PM (5,931 Views) | |
| TripleThreat | Feb 5 2015, 06:06 AM Post #76 |
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THANKS GMF!
Edited by TripleThreat, Mar 14 2015, 11:08 PM.
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| Woodie | Feb 5 2015, 07:41 AM Post #77 |
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Edited by Woodie, Feb 5 2015, 07:42 AM.
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| freegeo | Feb 5 2015, 10:31 AM Post #78 |
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Haven't messed with my 96 at all and it has ran really well the last 2 years i have had it. Wait a minute there is one thing I need to check on.
Edited by freegeo, Feb 5 2015, 10:32 AM.
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| freegeo | Feb 5 2015, 01:15 PM Post #79 |
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Started my 96 up and drove it around work fine. Don't know what happened but it seems ok. Adjusted the TPS on the 97 some, .01 volt at a time. After each adjusment the surge was at a lower rpm. Each time it still surged until I got it to 1.02 volts. Didn't surge anymore at idle but it idles higher than 850. Idles at 1100 rpm. One thing I did notice that each time I put the feeler gauges back in I would get a little different reading. Not much maybe .02 volts. But that is quite a bit since the factory spec is .98 to 1.02. I started adjusting the tps and then taking the feeler gauges out and checking what the reading was at with the throttle on the stop. Wrote down what the readings were. Going to check what kind of reading I get on my 96 and compare it. I have had the battery disconnected some also so I'm not sure if the computer has to re-learn some things. Will drive it some and see if it makes a difference. |
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| Hanuman | Feb 5 2015, 02:19 PM Post #80 |
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"The Almighty Grounds Cleaner"
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i think your throttle stop screw is off. i have a theory that the throttle stop screw may vibrate in some over the years.....i have seen this now enough times to suggest it as "my theory" try this, back your throttle stop screw out 1/4-1/2 turn.....and see if that cures your idle surging. note how much you turned the screw so you can put it back exactly......if need be. |
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| TripleThreat | Feb 5 2015, 02:41 PM Post #81 |
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THANKS GMF!
Edited by TripleThreat, Mar 14 2015, 11:08 PM.
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| freegeo | Feb 6 2015, 02:23 AM Post #82 |
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I don't think it is the throttle stop. While it was at a raised rpm the ISC had the throttle open. |
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| Hanuman | Feb 6 2015, 05:58 AM Post #83 |
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"The Almighty Grounds Cleaner"
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there are 2 types of idle conditions. from now on lets call them pulsing idle and surging idle.....(unless we find better names, then we can change them again to further confuse the lurkers using google search. )now, regarding what the isc is doing......the 2 types of pulsing idle. pulsing: is the plunger pushing on the throttle, then backing off.....usualy its a gentle surge and in a rythem. surging: if the tps is way off or there is a big vacuum leak.....it revs up, ecm cuts fuel....rpm drops suddenly, fuel turns on, idle stabilizes.....a short pause as the vacuum levels change, engine revs up suddenly, and the cycle goes on and on.......this is a more violent surging and isnt in perfect rythem......it varies based on how long it takes for vacuum leaks to "open up" or how long it takes for the air mas to get moving again. see when the engine revs up fast the intake has a huge mass of fast moving air, then the engine suddenly drops to idle .....that air smashes into the intake valves and eather stops dead or bounces backwards.....but the engine still wants air, so there is a pause as the air stops, bounces backwards stops, and begins accelerating forward again. all this takes time. this same process happens when you attempt to drive with a tps thats way off. its interesting listening to the differences in the idle. the pulsing idle....isc pushing it up and down is .........often a grounding problem or tps slightly off. usualy only after engine is hot. pulsing idle while car is rolling in nuetral is usualy on the positive side ....but may still be a grounding issue. enginehot or cold. surging idle (fuel cut) is tps way off, or a vacum leak. pulsing idle is the sensor readings being off slightly and the computer is trying to find correct idle. surging idle is the computer shutting down fuel because idle speed is racing out of the computers control. its the computers responce to a bigger problem. if idle only pulses when head lights/heater fan is on or off......check the positive side. if idle races to fast when cold, or races while coasting in nuetral......you have a corroded connection some where on the positive side. these symptoms are based on knowing how the system responds to varies conditions based on my experiences. this is not including some things listed in my thread "idle problems''' in my signature. ............................................. when the tps is set right, and the gas peddle is at the idle position.......the ecm uses a map for idle. at idle the goal is to be smooth first, emisions second, fuel consumption third. airfuel ratio is slightly richer, and open loop. less timing advance is used. idle speed high enough to be smooth, spin alternator fast enough to charge, idle fast enough to heat up the cat. idle not to fast to reduce fuel consumption. thats the goal. the metro ecm isnt looking for a certain idle speed......its looking for a certain manifold vacuum level. it bases the idle speed on the manifold vacuum. if the relation ship between vacuum/tps/and how much the isc is pushing on the throttle dont line up, the computer will begin increasing and decreasing idle speed as it searches for the correct vacuum/throttle position. if something is out of adjustment, or a vacuum leak is present, or the voltages are wrong because of a grounding issue......the computer willcontinue pulsing the idle up and down while never finding what it wants to see. if a big vacuum leak occurs raising idle speed to high, or the TPS is way off and you attempt to drive......the computer will go into de-acceleration fuel cut mode......it turns off the fuel injector untill idle speed is reached. however, if the geo is moving, the computer is recieving a signal from the vss......now the rules change, idle speed is raised while the car is rolling to make gear changes easier, anf fuel cut is disables below a certain speed...i cant remember it right now. ......................................................... at full throttle another contact closes in the tps. now the computer uses a special map for full throttle. at full throttle airfuel ratio changes to full rich.....around 12/1. max timing is pulled. the goal: federal law states that all gas engines must run at 14.7 to 1. however federal law allows automakers to program ecm to provide max power for acceleration while at full throttle because the driver may be flooring it to avoid a accident. so the goal is max power. fuel consumption and emisions arent a concern. ...................................................... in between idle and full throttle contacts the computer is looking for "rate of change" it wants to know when and how much the throttle angle changes. the map sensor and intake air temp sensors are the sensors the computer uses for fuel trim. the coolant sensor doesnt have a direct effect on fuel mapping.......it does directly effect ignition timing. cool coolant temps tell the computer to use its warm up maps....they are richer. as the coolant warms up the computer switches to leaner and leaner maps. members on the forum with scan guages have reported cts pulls harder on timing. the iat directly effects the air fuel ratio. the warmer the air, the leaner the a/f ratio. it even over rides the o2 sensor in closed loop. both members with scan guages and myself have confirmed this. with the iat modded it runs much leaner even on the highway when the ecm is definately in closed loop. the car has much less power with the iat mod...you can feel it....my vacuum guage reads much lower due to the increased throttle. this is evident on the highway. what ever the mapping is, the iat will make it richer or leaner based on temp. the max the ecm can account for IIRC is 147 degrees. rate of change: when the throttle is snapped oen or closed, it tkes time for the air to accelerate through the intake tract. the engine will swallow alarge amount of air before the manifold vacuum has a chance to change...meaning the map sensor wont read the change yet. it the computer knows the rate of change, it knows how extra air the engine will swallow, and adds the correct amount of fuel to prevent a lean acceleration stumble......it serves the function of the accelerator pump in the old days. most of what i said applies to most 1990 era cars...some is unique to the metro. systems change...this is not how newer cars work.......the 89-91 metros there is no rate of change because they had a 2 position throttle switch verses a throttleposition sensor. drive ability only improves with time. my 97 is far better than my 92 was for engine responce..... icould go on for a long time discusing how theecm and sensors respond...but its bed time. |
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| freegeo | Feb 6 2015, 10:01 AM Post #84 |
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This is what mine does. PULSING the pulsing idle....isc pushing it up and down is .........often a grounding problem or tps slightly off. usualy only after engine is hot. Mine only does it once it's warmed up. All my vacuum lines are new. Replaced them when I put the engine back in. the metro ecm isnt looking for a certain idle speed......its looking for a certain manifold vacuum level. What does the ECM use to check manifold vacuum? Edited by freegeo, Feb 6 2015, 10:33 AM.
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| freegeo | Feb 6 2015, 01:33 PM Post #85 |
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I checked the TPS signal on my 96 (the one that runs right) when it is on the throttle stop. It measured .63 volts. I adjusted the TPS to the same reading on my 97. Let it warm up and it ran fine. No pulsing. reved it up a couple of times and it did not pulse. The idle is a little high. Was at 1100 rpm. I checked to see if the ISC had it off the throttle stop and it wasn't. So I carefully adjusted the idle down to 950 rpm. It doesn't run smooth at idle as I had hoped, since I balanced the rods. I'm going to leave it were it is at for now and start checking to make sure the throttle body gasket and intake gasket is not leaking somewhere. That could be adding to my problem. Would trying to disconnect a vacuum line off the intake and plugging the vacuum port help verify there is not a problem with that vacuum line and system. |
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| TripleThreat | Feb 6 2015, 02:46 PM Post #86 |
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THANKS GMF!
Edited by TripleThreat, Mar 14 2015, 11:08 PM.
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| freegeo | Feb 6 2015, 07:11 PM Post #87 |
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I'll test it and see what happens. i think i have an extra. |
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| truckjohn | Feb 6 2015, 09:16 PM Post #88 |
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Sounds like it's all hosed up... You don't adjust the idle with the butterfly stop screw.... That screw is only there to prevent the butterfly from sticking shut. It's not an idle adjustment. What you do with that screw is to screw it out till nothing touches. Gently flap the throttle a couple times to make sure nothing's touching... Screw the screw in till it touches the throttle butterfly - then turn it like 1/8 to 1/4 turn "in" and that's it.... If your ISC lets the throttle go all the way to this stop - the engine shuts off... That's how it's supposed to work. Now.. When the ISC retracts so it's not touching the throttle..... Unplug it from the computer. NOW test the voltage on the TPS - and adjust it till it's the same as your '96 when the '96 is in the same position.... It takes my '94 a week or 2 to properly "Re-learn" the TPS... While it's doing this - it generally goes through a period when the throttle returns very slowly to idle..... Don't fool with it during this period.... now - if the throttle doesn't return to idle right after 2 or 3 solid weeks of driving - then adjust it slightly... Thanks |
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| TripleThreat | Feb 6 2015, 11:29 PM Post #89 |
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THANKS GMF!
Edited by TripleThreat, Mar 14 2015, 11:08 PM.
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| freegeo | Feb 7 2015, 02:04 AM Post #90 |
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Yes I can get back to were it was. I barely moved it. I have been writing done what adjustments I have been making. I'm not sure a 94 is the same as a 97. One is a obdi and the other a obdii. Quite a bit of difference in how they work. I'm not giving up until I get it running right. Only way to learn is to try and learn how it works. Edited by freegeo, Feb 7 2015, 02:08 AM.
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