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1990 Skylark Idle Problems


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#1 adamcs84

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Posted 12 December 2012 - 01:12 AM

This only happens in cold weather. Hard to start the car it just wants to die. Have to pump the gas to get it to start. Once I am moving I have no problems. only when I am stopped and idling. Any thoughts on how to fix it?

#2 JohnD1956

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Posted 13 December 2012 - 01:07 AM

Which engine? Is it carburated, or fuel injected? Is the check engine light on? Have you changed the gas filter?
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#3 adamcs84

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Posted 13 December 2012 - 02:28 AM

4 cyl. Check engine light only comes on after sitting in gear idle for long time. But turns off after I move again. Fuel filter was changed last year. I need to confirm about fuel injection.

#4 JohnD1956

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Posted 13 December 2012 - 03:09 AM

If it were me, I would try to get a hold of a manual for your particular car. Now this may sound like a cop-out for an answer but consider that the difference between your car and the oldest manual I have for a computer controlled Buick is at least 9 years. So chances are there were a ton of changes in that time frame and I would hate to give you the wrong advice and have you count on it.

That being said, I would add that I would concentrate on the oxygen sensor and or the idle air control, if your car has one. I'm pretty sure your car is fuel injected, but I am not sure if it has an idle air control solenoid. That would be in the manual.

And there's one more thing I would add. The computer controls are very well explained in the GM factory manuals. When I sat down and read this section for an 89 Lesabre, not only was the function of the computer controls explained but the theoryu of how they should work was explained too. It really became clear how these things interact and work and took 75% of the fear right out of working on the car.

Edited by JohnD1956, 13 December 2012 - 03:12 AM.

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John C. De Fiore BCA # 3757

current toys
56 Super 56R: acquired September 1974. 69 GS 400: Convertible added in 2003. 72 Electra Limited added July 2014.
78 Estate Wagon added October-2008. 2013 Regal GS acquired Aug 2013.

Former toys:
69 Electra Limited 2 dr. bought 1995 or so, sold in 2007. 95 Riviera added May 1998, sold in 2006.
06 Lacrosse CXL purchased July 4th 2006, and traded in Aug 2013.

"Yes! I'd really rather drive my Buick!"
Member of the UPSTATE NY CHAPTER
check it out at : http://unybca.com


#5 adamcs84

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Posted 13 December 2012 - 01:52 PM

I have the original owners manual for the car. I can confirm it is fuel injected. i do not see where it says anything about an idle air control solenoid. however i am missing a good part of the index in the back. I will recheck my glovebox and see what I can find. I also found the original purchase invoice, that's kinda neat.... Thank you very much for your help!

Edited by adamcs84, 13 December 2012 - 02:08 PM.


#6 NCReatta

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Posted 13 December 2012 - 03:05 PM

I have the original owners manual for the car. I can confirm it is fuel injected. i do not see where it says anything about an idle air control solenoid. however i am missing a good part of the index in the back. I will recheck my glovebox and see what I can find. I also found the original purchase invoice, that's kinda neat.... Thank you very much for your help!


Your owners manual will do you little good in this situation. You need to find a Buick Field Service Manual for your car. Check eBay. For 1990, it should have a blue cover.
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#7 adamcs84

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Posted 13 December 2012 - 03:13 PM

this?

1990 Buick Skylark Service Manual | eBay

#8 NCReatta

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Posted 13 December 2012 - 03:33 PM

this?

1990 Buick Skylark Service Manual | eBay


That would be exactly what you need! Good price too. Snatch it up ASAP!
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#9 NTX5467

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Posted 14 December 2012 - 12:59 AM

With fuel injection, there is an "idle air control" motor, which keeps the idle speed to what the computer commands it to do. BUT, with time, the air passage in the throttle body can become clogged with "gunk" from the PCV system's input into the situation. When that happens, the IAC can't function as it should or completely do what the computer commands it to do, hence the "Check Engine" light.

On these newer computer-controlled vehicles, and most of the older ones too, "pumping" the gas pedal does NOTHING to help get the car to start. In the start mode, the computer is telling the injectors to fire a particular amount of fuel into the cylinders, fine-tuned by input from other engine sensors, to get the vehicle to start.

ANOTHER reason for "extended crank time" in a fuel injection system is low fuel pressure/fuel pump output, which the fuel filter change probably did not affect. If you put a fuel pressure gauge onto the pressure tap on the fuel rail, then crank the motor, you'll probably see the pressure build slowly as the engine cranks. Then, when it hits the "magic level" (usually right about 55psi!), THEN and only then will the injectors put fuel into the engine. So, that's something else to check and confirm.

A side issue is spark plugs/ignition system items. One time, along about 1990 or so, a customer's 1-ton pickup was towed into the shop. It would not start in 20 degree F temperature that morning. Our tune-up tech pulled out one spark plug and found NO center electrode above the ceramic insulator. NOTHING! Just a little too much gap, even over the .100" gap an HEI is supposed to be able to fire, for any spark to jump. A fresh set of spark plugs and it fired right up! Mileage was about 100K miles, I believe, on the factory (blue paint overspray on the plug) AC spark plugs.

Back to the throttle body and the IAC motor . . . if the air passages in the throttle body (not the big one you can see, but the smaller one in the body itself) are very clogged, you'll probably need to have the throttle body removed and disassembled for "soaking" and cleaning. On some, though, a thorough cleaning just can't be done, so replacement is necessary. Sometimes, too, the IAC motor's "internal gears" have durability issues, so that means replacement of the IAC.

As there is some history of the "Check Engine" light coming on and off, you might also see if there are any stored codes in the computer. For good measure.

I'd suggest you start with the throttle body and fuel supply/pressure issues, then work toward the output side of things (one of which might be the oxygen sensor). I suspect that once the throttle body issues are taken care of, most of the problems might disappear.

Just some thoughts,
NTX5467

#10 adamcs84

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Posted 06 March 2013 - 09:31 PM

THanks for the input, I will give this a try and see what happens. Something to add, Check engine light code reads "idle air control error" I replaced the Idle air control valve with no change. Also upon starting and while driving up until it gets warm it will lose power. I will be driving along and the check engine light will come on and speedo will stop working and i will only have about 20% power. have to push the pedal to the floor to keep it going all while its spitting and spuddering to stay along. then all the sudden it all comes back.

#11 adamcs84

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Posted 07 March 2013 - 07:40 PM

With fuel injection, there is an "idle air control" motor, which keeps the idle speed to what the computer commands it to do. BUT, with time, the air passage in the throttle body can become clogged with "gunk" from the PCV system's input into the situation. When that happens, the IAC can't function as it should or completely do what the computer commands it to do, hence the "Check Engine" light.

On these newer computer-controlled vehicles, and most of the older ones too, "pumping" the gas pedal does NOTHING to help get the car to start. In the start mode, the computer is telling the injectors to fire a particular amount of fuel into the cylinders, fine-tuned by input from other engine sensors, to get the vehicle to start.

ANOTHER reason for "extended crank time" in a fuel injection system is low fuel pressure/fuel pump output, which the fuel filter change probably did not affect. If you put a fuel pressure gauge onto the pressure tap on the fuel rail, then crank the motor, you'll probably see the pressure build slowly as the engine cranks. Then, when it hits the "magic level" (usually right about 55psi!), THEN and only then will the injectors put fuel into the engine. So, that's something else to check and confirm.

A side issue is spark plugs/ignition system items. One time, along about 1990 or so, a customer's 1-ton pickup was towed into the shop. It would not start in 20 degree F temperature that morning. Our tune-up tech pulled out one spark plug and found NO center electrode above the ceramic insulator. NOTHING! Just a little too much gap, even over the .100" gap an HEI is supposed to be able to fire, for any spark to jump. A fresh set of spark plugs and it fired right up! Mileage was about 100K miles, I believe, on the factory (blue paint overspray on the plug) AC spark plugs.

Back to the throttle body and the IAC motor . . . if the air passages in the throttle body (not the big one you can see, but the smaller one in the body itself) are very clogged, you'll probably need to have the throttle body removed and disassembled for "soaking" and cleaning. On some, though, a thorough cleaning just can't be done, so replacement is necessary. Sometimes, too, the IAC motor's "internal gears" have durability issues, so that means replacement of the IAC.

As there is some history of the "Check Engine" light coming on and off, you might also see if there are any stored codes in the computer. For good measure.

I'd suggest you start with the throttle body and fuel supply/pressure issues, then work toward the output side of things (one of which might be the oxygen sensor). I suspect that once the throttle body issues are taken care of, most of the problems might disappear.

Just some thoughts,
NTX5467



THanks for the input, I will give this a try and see what happens. Something to add, Check engine light code reads "idle air control error" I replaced the Idle air control valve with no change. Also upon starting and while driving up until it gets warm it will lose power. I will be driving along and the check engine light will come on and speedo will stop working and i will only have about 20% power. have to push the pedal to the floor to keep it going all while its spitting and spuddering to stay along. then all the sudden it all comes back.

#12 JohnD1956

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Posted 08 March 2013 - 01:45 AM

You say you lose power till the engine warms up, then suddenly it will clear up and run allright? If it were carburated I would say the choke is not opening up fast enough. This would be evidenced by thick black smoke from the tail pipe that smells of unburnt fuel. But I don't think a fuel injected car has a choke like a carburated car. Still there is some mechanism to prime the engine and it sounds like that system is in need of service.

That however would have nothing to do with losing the speedometer.
test image with cannon gateway b w 1

John C. De Fiore BCA # 3757

current toys
56 Super 56R: acquired September 1974. 69 GS 400: Convertible added in 2003. 72 Electra Limited added July 2014.
78 Estate Wagon added October-2008. 2013 Regal GS acquired Aug 2013.

Former toys:
69 Electra Limited 2 dr. bought 1995 or so, sold in 2007. 95 Riviera added May 1998, sold in 2006.
06 Lacrosse CXL purchased July 4th 2006, and traded in Aug 2013.

"Yes! I'd really rather drive my Buick!"
Member of the UPSTATE NY CHAPTER
check it out at : http://unybca.com


#13 NTX5467

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Posted 08 March 2013 - 02:31 AM

If the code relates to the Idle Air Control motor, it could well be that the passages in the throttle body for "air" (which the IAC controls) are restricted. On some newer vehicles, the passages can't be successfully cleaned out enough for things to work correctly, so a new throttle body is the only "fix".

The speedometer and odometer are run off of sensors in the transmission (an electric version of the old drive/driven gear set-up). If the speedometer "goes", the computer could well suspect the car is not moving. Hence, the "limp-in" mode you seem to be experiencing. I don't see how all of these things are really related, though . . . the IAC issues and the speedo issues. Two separate deals, to me.

In the first minues of engine operation, the powertrain computer/controller relies on historic data to make the engine run well. This is "open loop" operation. When the oxygen sensor gets hot enough to reliably control the fuel mixture, then "closed loop" operation results, with full computer control over engine spark/fuel calibrations (per the instructions on the computer "chip", the smaller one).

Remember, too, just as with carbureted engines, poor ignition can yield some of the same symptoms as fuel system issues. The main player here is the ignition module, which is under the coil pack(s). This is about the only place where engine cummulative heat might play a part in things . . . hot or cold. Everything else is computer controlled via sensors of heat and such.

ONE other thing, which might not apply with the Chevy V-6 as much as it might for the Buick 3800 (in some model years) . . . intake manifold gasket integrity. While the engine is in open loop, any additional vacuum leaks will NOT be compensated for in the fuel mixture supplied to the engine. Once the engine goes into closed loop operation, the computer will do what it can to "cover" for these intrusions of air, where they shouldn't be.

Still not sure as to why the limp-in mode is happening, though.

Just some thoughts,
NTX5467

#14 adamcs84

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Posted 08 March 2013 - 01:58 PM

If the code relates to the Idle Air Control motor, it could well be that the passages in the throttle body for "air" (which the IAC controls) are restricted. On some newer vehicles, the passages can't be successfully cleaned out enough for things to work correctly, so a new throttle body is the only "fix".

The speedometer and odometer are run off of sensors in the transmission (an electric version of the old drive/driven gear set-up). If the speedometer "goes", the computer could well suspect the car is not moving. Hence, the "limp-in" mode you seem to be experiencing. I don't see how all of these things are really related, though . . . the IAC issues and the speedo issues. Two separate deals, to me.

In the first minues of engine operation, the powertrain computer/controller relies on historic data to make the engine run well. This is "open loop" operation. When the oxygen sensor gets hot enough to reliably control the fuel mixture, then "closed loop" operation results, with full computer control over engine spark/fuel calibrations (per the instructions on the computer "chip", the smaller one).

Remember, too, just as with carbureted engines, poor ignition can yield some of the same symptoms as fuel system issues. The main player here is the ignition module, which is under the coil pack(s). This is about the only place where engine cummulative heat might play a part in things . . . hot or cold. Everything else is computer controlled via sensors of heat and such.

ONE other thing, which might not apply with the Chevy V-6 as much as it might for the Buick 3800 (in some model years) . . . intake manifold gasket integrity. While the engine is in open loop, any additional vacuum leaks will NOT be compensated for in the fuel mixture supplied to the engine. Once the engine goes into closed loop operation, the computer will do what it can to "cover" for these intrusions of air, where they shouldn't be.

Still not sure as to why the limp-in mode is happening, though.

Just some thoughts,
NTX5467


One thing i noticed is when it comes out of "limp" mode the temp light flashes quick.

#15 adamcs84

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Posted 13 March 2013 - 12:57 AM

You say you lose power till the engine warms up, then suddenly it will clear up and run allright? If it were carburated I would say the choke is not opening up fast enough. This would be evidenced by thick black smoke from the tail pipe that smells of unburnt fuel. But I don't think a fuel injected car has a choke like a carburated car. Still there is some mechanism to prime the engine and it sounds like that system is in need of service.

That however would have nothing to do with losing the speedometer.



There is black all over my garage door from the exhaust blasting it, it is also all over the ground below the exhaust pipe. However while the car is running it isnt "thick black smoke" but dark nonetheless. My car is fuel injected. So what would need to be replaced?

I just finished tearing apart my entire throttle body and cleaning it and replacing all gaskets. There was no change, actually I now have a hissing sound. I assume a created a leak somewhere.

#16 adamcs84

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Posted 17 March 2013 - 07:17 PM

Changed out the ECM (engine control module) all problems have disappeared. Thanks for all the help everyone!




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