1995 grand am chugs/loosing power

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Texan4Life

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1995 grand am with 3.1L V6 and about 70,000 miles.

It chugs and looses power if you want to try and go past about 1/2 to 3/4 throttle. and is getting crappy gas mileage.

It is not throwing any codes.

So far we have replaced the fuel filter and fuel pressure regulator with no improvements.

any other ideas?
 
Could be alot of things , possibly a clogged catalitc converter, bad Mass airflow sensor, (which would usually leave a code) also I would check the fuel pressure and O/2 sensors for issues, and possibly have the ECM checked ..
and also check to make sure your SES light is still working ..
(not burned out)
 
this is actually my brothers car and sunday he is coming so I can change his oil. I will test fuel pressure and use scan tool to test ses light and report back with my findings.
 
Brother came by so I could change his oil.. turned out to be 17,000 miles on that oil change!!! chewed on him for that one. Also put in a new air filter.

and he said the ses light goes on and off. so I hook up scan tool and got one code.

history code 35
Idle air control problem
cant set idle speed.

and the old oil smelled like gas.. probably from running rich all the time?

It was dark so i didnt get a chance to test fuel pressure.
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Holy shi..... 17K on an oil change!
uhh, I would think a bit more than a simple chew out would be in order for that one ....

anyway the IAC code could have something to do with it but if the oil smelled of gas it could have taken out an O/2 sensor if its getting out the pipe in the exhaust ..
I think I would do a simple computer reset and relearn (just disconnect the batt - cable for 15 min, then start and let run without touching the throttle) for about 5 min
and see what returns for codes if anything ...
 
disconnected the ground for 15 min then let it idle for 10. no codes as of yet. he will drive it home and report if the check engine light comes on.

was just going through the view data on the scan tool and one thing that stood out was the listing of quad drivers.

quad driver 1 - bad
quad driver 2 - ok
quad driver 3 - ok
quad driver 4 - bad

does that mean anything?
 
the Idle air control problem code come one again.

talked to a mechanic at GM dealership he thinks its the ECM. Gonna put in a new ECM next week.

And for what its worth the engine oil already smells like gas again.

9 time out of 10 the ECM isn't the problem. but hopefully it will fix it.
 
Put in a new ECM, my bro says it is a little better. mechanic also said it has a vacuum leak (explains alot). but we had looked it over before thinking vacuum leak and couldnt find anything cracked, broken, or missing.

Maybe the intake gasket?

any other ideas?
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got it tested for vacuum leaks.... the verdict is Intake gasket and injector o-rings leaking.
 
The quad drivers are the part of the computer that drives the injectors so if they are bad you won't get fuel from that pair of injectors ..
replacing the ECM should take care of that (if the wireing is all good)
also the intake leaks are a common issues..and if you had both problems it definately would make for an interesting diagnosis..
 
Got done putting in a new intake manifold gasket, injector orings (injector to intake), intake plenum gasket, new bosch platinum plugs (yes we gapped them). found a broken plastic vacuum line and ordered new assembly from GM and put it on, changed the oil. While we were down there we put in a new Tstat cuz it was super easy and would be a PITA to do it later.

and we are still having problems.

new oil smells of gas again with all the same symptoms.

Said check engine light came on the went off. Checked for codes but scanner said everything was A-ok (no codes).

When we replaced the spark plugs, 4 were clean looking while 2 were sooty and black.

Maybe some dribbling injectors?? poor spray pattern? So we put in some injector cleaner in the gas to see if that helps.

That or there is a huge vacuum leak still.
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FOUND IT!!

the two dirty spark plugs were from cylinders 1 and 4.

1 and 4 share an ignition coil.

new coil = runs FANTASIC

It NEVER set a misfire code. what a POS. just glad to have it running right. Changed the oil again and this time it should stay gas free.
 
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