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1988 Regal Fiasco Many Sensor & Electrical Problems

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Old Oct 10, 2013 | 03:14 PM
  #31  
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The instrument cluster is one of the next things I gotta get into (and/or the lighting module). All of the warning lights work, but that'* about it. I guess I need to replace every other sensor to address all remaining problems. I've been through most of the wiring harness that snakes along the engine plus the grounds. The only part I didn't eyeball was behind the A/C Comp. A lot of the wire insulation was melted together, but none to bare wire and no bad melting - just plastic coating stuck together. I separated all wires and inspected them, but they had gotten less hot behind the A/C Comp. - that'* why I didn't dig in there.

I got it inspected today, which is about a 15 mile round trip. After the car is hot I have to press the gas down a little to get it to start, then work the throttle to get it to idle on it'* own. Other than that, it runs as good as a 150,000.-ish mile engine should run. When I pulled up to a stop light I expected it to die, but it kept going. Real low idle though. Maybe turning the low idle screw up a little will help. I'm going to put the scanner on it while it'* still warm and see what'* going on now.
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Old Oct 10, 2013 | 07:11 PM
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I hooked the scanner up and still getting code 64 - low MAP signal. Still unhook the the MAF and the MAP goes up to 5 volts. I'm going to ignore this for now and see if there'* something else causing the low idle & hard start at times.

Now that I think more, when I put gas in it today there was a lot of pressure in the tank. I'm wondering if there'* too much fuel pressure causing the ECM to cut back on fuel at times, since the Canister Purge Valve isn't working right.

It looks like this is a perpetual project car. The last thing I need.
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Old Oct 11, 2013 | 07:34 AM
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your symtoms and map code sound like vacuum leak
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Old Oct 11, 2013 | 12:59 PM
  #34  
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Vacuum lines are one of the single most things I've checked. While the engine was warm yesterday, I put silicone around the vacuum lines that go into the rubber block on the throttle body. After I run some errands I'll spray carb cleaner under the body all the way to the back where the canister is and see what happens. I'll keep this in mind until I find the problem. Thanks JW.
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Old Oct 11, 2013 | 01:46 PM
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not real familiar with the older evap but if your purge valve, or whatever they used back then to limit the vapor from the canister is stuck open or leaks thats a vacuum leak. as well you could have and intake manifold leak. also any where the vacuum or map sensor plugs into the manifold. or any sensor for that matter, tps, air tube after maf, etc..
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Old Oct 11, 2013 | 02:08 PM
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That'* interesting. I figured if there was pressure in the gas tank, would mean the purge valve was stuck closed for what ever reason, but I haven't considered it as a vacuum leak source. One of the items on my list is the EGR tube. I'm thinking of bypassing/blocking that whole deal off to see what happens at some point if nothing turns up soon. I'll try harder JW.
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Old Oct 12, 2013 | 10:15 PM
  #37  
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I wasn't sure about the Gunk Carb Cleaner, but bought it anyway to
check for vacuum leaks (again). Sprayed all around LIM and Plenum,
plus all vacuum lines on the whole car (EGR & tube, EVAP system, &
vacuum resevior too). Then I tested what Gunk'* characteristics was
when shooting it into the intake duct BEFORE the air cleaner. It bogged
the engine down. I'll use something else the next time I check for vacuum
leaks. No evidence of leaks anywhere though.

I then removed the Canister Purge Valve and plugged the two vacuum lines.
I let the engine warm up and then restarted several times. I didn't need to
throttle it to get the engine running, so this is one problem I've had. Still,
the idle is too low on a warm engine. I had the engine running with my foot
on the brake and shifted through the gears and it only died one time out of several tries. It wanted to die more often, but recovered OK.

I'll have to replaced the Canister Purge Valve before I do any more work on it.

Now the cruise control quit working. Creepy.

Got an extra code today for low TPS signal, but it looks good in all of the tests I've done on the circuit and new sensor. Funny thing - I never got a code for EVAP problem even with the Purge Valve removed.
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Old Oct 13, 2013 | 12:28 AM
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Props to you JW for sticking this far!
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Old Oct 13, 2013 | 09:36 AM
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it only tests the evap so often and if the cruise module vacuum supply is with the tubes you plugged off then it wouldnt work. as far as your problem still seems the supply voltage is low if you are getting low reading back to the pcm with new sensors.
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Old Oct 13, 2013 | 01:39 PM
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The Cruise Control quit working before I disconnected the Purge Valve. I haven't found a fuse yet - still looking at schematics on that. The Cruise light on the IP comes on, but no Cruise Control.

I guess I need to back-probe the ECM to see what the voltage is on problem sensors. I can't imagine where any other grounds could be or which sensor is causing problems on the other. I noticed on the scanner the Park/Neutral switch was still in Park even when I shifted to Reverse and OD. The FSM says the ECM uses the signal from that to control IAC, VSS diagnostics, & EGR. If the 12 volt signal is grounded, the EGR wouldn't work. If the 12v is open, a dip in the idle may exist when shifted into Drive. Also the 2nd & 3rd gear switches indicates they are on, on the scanner. Only the 2nd gear switch was on previously - while in park.

I shouldn't have called this a fiasco. Sometimes you get what you think.
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