2008 Chevy Impala 3.5 Hard Starting When Cold

nickb2

Wrench. Diagnostic Tech.
Joined
Nov 22, 2008
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Location
St-Hyacinthe, Quebec, Canada
I can actually GOVE you a tool, just pay shipping to get it of my hands. It is free. A sps auto boss v30, with mercedez and europe bells and whistles
 

NickD

wrench
Joined
Aug 28, 2007
Messages
4,988
Points
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This kid has been working on vehicles for over 70 years, earliest was a 1908 Buick well before electronics and code.

If you get a code, either the sensor is not reading the expected information or that sensor is defective, you simply don't know the difference, throw parts at it.

Simple tests such as compression, vacuum, and even oil pressure quickly give valuable information on the mechanical condition of the engine, and this was been true since day one.

Ha, was told by a mechanic in 1985 my bumper is not falling off, he ain't getting a code, like there is a code for a bumper falling off. What you really need is common automotive sense.

If an intake or exhaust valve is not closing will read 0 psi on that cylinder, may start and will run very rough, compression test shows this instantly. Scanners do not.
 

NickD

wrench
Joined
Aug 28, 2007
Messages
4,988
Points
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A sensor is a device that converts some physical parameter into some type of electrical or electronic signal that a computer program can recognize. And as such, some physical parameter/s are inputted a precise rates to obtain a corresponding precise electrical/electronic output.

Back in the 80's automotive companies started hiring attorneys because of liability laws, if you didn't know this a good portion of the cost of an automobile goes toward attorneys paychecks and insurance. Was so bad, I could not even talk to another head engineer at another department unless an attorney was present.

Another thing attorneys did was to prevent the vehicle manual department from listing testing specifications of all these sensors. What parametric inputs with corresponding outputs numerical values as would be subject to warranty replacement. Engineering department would provide all these specifications.

So what does a manual tell you since then? Replace with a know good sensor, essentially from an identical donor vehicle that seems to run okay. True is, you don't know if that sensors is good or bad or whether the information its receiving is the culprit.

Talk about the blind leading the blind! Was involved in designing distributor less ignition system, EPA requirement so a user could not screw it up. Just had to remove the timing marks on the harmonic balancer.

Not one of mine, but a sensor was mounted under the harmonic balancer on a bracket that was bend. Had to mark my own timing marks to properly adjust it. PITA!!!

This is telling it the way it is.
 

billr

wrench
Staff member
Joined
Mar 12, 2007
Messages
6,748
Points
48
OP, can you elaborate on this statement?

"...the ECT jumped up to 82 and then 85. It would fluctuate up and down..."

The ECT rising that you described recently sounds fairly normal, but a significant "fluctuation" would not be.

I urge you (and others) to quit blaming this all on the ethanol bogeyman, that is only detracting from finding the real problem here.
 

montego_gto

Full Member
Joined
Jan 12, 2009
Messages
87
Points
6
OP, can you elaborate on this statement?

"...the ECT jumped up to 82 and then 85. It would fluctuate up and down..."

The ECT rising that you described recently sounds fairly normal, but a significant "fluctuation" would not be.

When I pulled up the live data, the ECT was more erratic.
the next time I started cold and took readings every minute, it progressively went higher compared to the IAT.
just got home from work and IAT was 48 and ECT was 52.
MAP started out at 29 and dropped to 11 until it started and it stayed there.
now after running for about 3 minutes, ECT is 113 and IAT is 52.
Nick
 
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