Question about 1999 Chevrolet Tahoe

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Does not start when cold and back fires in the motor

It has a hard time starting when it below 40 and when it gets hot run temp and driving it losts power. runs at idle nothing more and back fires in the motor not the exhust and I check the upper intake for cracks. But when I turn it off and restart it it gets its power back but still acts up

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I would check the tune up on it they have lots of problems with the distributor cars also has the fuel filter been changed at all ?

Posted on Jan 07, 2009

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The vehicle is 2004 buick century. sometimes the temp guage rises and comes back down. during this time, clod air blows. sometimes the temp guage is 1/2 way and cold air blows. thermostat has been changed....


is your electric fans running constantly. and most times then not you`ll need a water temp sensor or water temp relay. usually the temp sensor on that model comes usually next to the thermostat with a little wired plug on top. or on the radiator. either way pull the plug while the motor is cold. unscrew the sensor and screw the new one in and replace the electric plug back on top of the sensor. 2 things: Cold motor, have every thing set up and ready because when you take out the sensor the coolant will start to come out. you will not loose much if you work quick. keep rags or paper towels below the sensor to keep coolant off the motor and smelling when it gets hot. you have also pour or hose off coolant after your done installing the new coolant temp sensor.

Feb 10, 2014 | 2004 Buick Century

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At times it justs starts to sputter and run rough and then die


hello Dennis. (no miles stated)
what engine, 4.0L I6 2.5L? I4
ever tuned it up? all spark and filters, the 60k mile, ever?
this post is random engine stalls?
so does it stall hot or cold or both
does it stall moving, right foot planted, cruisng
or only parked, or only as you come to a stop
do dash lamps/gauges or? go out before the stall? (look)
CEL off running.. ok, no DTCs stored if USA car. is it?

my guess is this stall can happen hot or cold engine.
location not in klondike (location not stated, so wild guess.)
hot stalls, ?
1 lets say coming to a stop. is very common EGR sticking open
2 never tuned up, ever or even the last decade?
3: ISC/iIAC sticking closed, jeeps love to do that any I4 , its a big issue. the idle stepper motor cone gets gummed up, clean it.
i clean both my jeeps, I4 ISC like 100 times since 1988.
4: bad TPS. but usually it throws DTC'S for this. if driven hard)

some I6' have no EGR valve. PCM has no EGR pins.!
you can monitor DC power at the CIG lighter, to see if power drops
at stall, easy, 13.3v to 15v is normal or ALT system is dead..

make sure the Automatic shut down relay is not being shut down
by PCM (DB/YL wire) goes to 12v is shut down, 0v is not.
the PCM can cut the ASDR for may reasons, oil pressure or battery overheat,? many, best it to find out of this RELAY is dropping EFI
off LINE. IT can .

lets do stalls.
i see tachometer drop below 800 RPM hot .
i try to save the stall, ISC stuck closed, and my right foot
opens throttle instictively and i save the stall.
easy, that is loss of air. see why?
on mine the stupid, ISC/.IAC works like this
the PCM remembers to ISC positions (stepper)
one cold start and one hot start (a secret i learned)
it then looks at water temps and guess (math) at a best start position.
if it used hot ISC for a COLD start the engine will want to flood due
to valve mostly closed, from last hot shut down,.
so floods, use right foot 10% ,

so i cant comment on what it might be until you state (displacement)
the engine temps. at fail
the operational mode, parked, stopping or between 5speed mt shifts.
or what?
if it fails parked in drive way.
or only moving or only coasting.
stalls on the fly?

im online at alldata.com and there are 16pages for PCM only.

this car the PCM controls the Alternator, (a software reg)

now another tack.
the car in usa, as OBD2, i connect my scan tool
and log, i drive and log. car stalls
i drive home ,play back my logs, and bingo
i see what happens at the stall, all sitting at my desk.
warm and dry.
lost comms,?. is DC power lost.
Pending DTCS
real live DTCS
some DTCS auto clear, at die.
some PCMs will reset the CKP or CMP sensor or spark failures.
so can only be seen live. (watching, 1 more secret)

now Bar stool answsers (any EFI car)
ever tune it up, ever do the 60K>? if not why not now?
lost spark, see if spark is being lost at stall, (at all plugs)
bad fueling, (too high or low fuel pressure at stall)
loss of air (ISC/IAC failed)
EGR (if there) stuck wide open,


if the engine runs perfect at most times, its probably ok
so is bad spark or fuel
spark is first. but not if never tuned up.
fueling is last to check , as PCM cuts fuel with spark failure sensed.
bad fueling can be bad injection or total loss of air supple , at idle.








Dec 14, 2013 | 1999 Jeep Cherokee

1 Answer

Does the 2002 regal have a cold motor sensor Car hard to start when cold motor (in the morning )


Your vehicle uses the coolant temp sensor and the intake air temp sensor to determine the engines temperature on a cold start. If one of them is dramatically different than the other it will flag a code.

Is the check engine light on?

When was the last time you had a tune-up? if recently what brand of plugs where used?

Have you noticed any hard start issues after a hot soak? A hot soak would be driving the car until fully warmed up, shutting of the engine for approximately 15 to 20 minutes, and then starting the engine again.

Oct 27, 2010 | 2002 Buick Regal

2 Answers

It runs fine in the summer when temps are warm, but when it turns cold,especially when you first crank it up, it spits and sputters and will not run. It like its not get gas


PUT A SCANNER ON IT AND CHECK THE TEMP READING FOR THE COMPUTER IT IS MORE THAN LIKLY BAD LIKE IF ITS 40 OUTSIDE THE SENSOR IS READING 90 SO IT DOESNT GIVE IT THE EXTRA FUEL IT WOULD NEED WHEN COLD

Oct 15, 2010 | 2002 GMC Yukon XL

1 Answer

Starts and runs good when cold , shut engine off after motor gets hot , will not start back. After I let the engine cool down it will start back. When weather is cooler starting back is not a problem ,...


Sounds like the coil has gone bad. This is usually the syptoms of this. When it is in the non crand status cool the coil down quickly with ice and see if it doesnt crank.

May 19, 2010 | 1994 Jeep Grand Cherokee

1 Answer

1998 Sebring Conv 2.5 L JX Starts but dies immediately when cold


sounds like a possiable coolant temp reading -40 degrees have it checked

Apr 25, 2009 | 1998 Chrysler Sebring

1 Answer

1995 ford windstar overheat after replacing the thermostat


Let your engine warm up with the rad. cap off and see if the coolant level drops. and make sure your overflow is full. It blows cold air because there is no water getting to the heater core. And it shows a normal(ish) temp because the water needs to be touching the temp. sensor. I really do think there is air in the system and there is not enough coolant but hard to tell from here. Also as with overheating any time make sure to check your oil and look for any coolant as the head gasket seldomly holds together if the motor overheats.

Dec 22, 2008 | 1998 Ford Windstar

1 Answer

Block heater


Naaaa.Old wives tales.I grew up in northern NY and back in the day,30 years ago,the climate was much more severe than today.I have seen -40 below up there.Block heaters back then were necessary for especially diesel trucks,as they do NOT like to start in those temps.Gasoline engines with today's fuel injection and computerized engine controls have no need for a block heater as they will fire at the hit of the switch immediately in those temps.Old carbureted cars from 30 years ago normally would NOT fire right up at -40 below WITHOUT a block heater.The only reason i can think to install a block heater is that you will have instant heat when you get in the car.If you are worried about accelerated engine wear because of extreme temps,then by all means install one,or just have a remote start installed,fire the car in the morning and let it warm up 10 minutes at idle before you drive it off.I have a certain relative in N.C. that does this in the summer time.Start the car out in the driveway from inside the house via the remote start,let it run for 10 minutes with the A/C on high to COOL it DOWN,lol.

Jul 08, 2008 | 2007 Mitsubishi Outlander XLS

2 Answers

Astro starting problems


your battery is about to die....

May 20, 2008 | 1996 Chevrolet Astro

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