my car is blowing black smoke and is sputtering on acceleration

[midnight rider]

my car is running like crap and we cant figure out the problem. its blowing black smoke that stains asphalt and when i try to accelerate its spits and sputters (like the intercooler hose blew off) it is an intermittant problem and a real bugger to track down.
Heres what was done with the car before this started.
My k and n filter fell off on the highway after hitting a nasty pothole(montreal) and I drove the car for a few hundred miles with just a pipe and no filter. my bad. black smoke started coming out of the exhaust.

I got a complete tune up, fluids, plugs, wires, replaced broken Timing Chain,fixed oil leak at rear Main Seal. installed hi vol oil pump, and yes I replaced the k and n.

When I drove / idled the car, the exhaust was still black and now the car started sputtering on accelration. After a few days of this crap it turned out my intercooler hose clamp was broken and I thought id found the problem as the hose blew completely off while driving on the highway. It blew off 3 times before I could get to a store to buy a new clamp. i finally put on a new clamp and thought id fixed the sputtering problem and now the car would not start.
I had to have my car towed and my mechanic did the following. since he has the same car, it was easy for him to:
changed Mass Air
O2 Sensor
Cam Sensor (2)
Coil
MAP
changed Spark Plugs which were black
Checked all Fuses
no sensor reading comes out on the computer.
car can run great for 15 minutes at a time or 2 minutes without sputtering. there is no way to predict when its going to launch like a rocket or sputter. It wont stall, but there is no acceleration when it happens. it can happen during hard or soft accelration. When it works fine, the car is its usual speeding bullet.

any suggestions on where to look would be greatly appreciated.
the computer and chip are going to be switched over the weekend.

 

[buickboy]

Change the Coolant Temp Sensor (2 wire sensor mounted horizontally in the intake driver side).
Mitch

 

[2QWIK4U]

Do you have the part # on the sensor?

 

[kh440]

gm#15326386

 

[87ttypeV8]

my car was doing the same thing and turned out to be bad injectors... left soot all over the place

i put on new injectors and that really helped the bogging down and it wouldnt stall anymore!
i brought it to a shop and they couldnt figure it out forever... checked every sensor and connection first then the injectors and bingo!

good luck!

 

[midnight rider]

my injectors are a few years old and could be the problem but Im not sure at this point its them as the fuel pressure guage stays at 40 when the engine is off, but ill certainly keep that in mind.

Im going to disconnect the coolant sensor tomorrow and see if that is the problem

 

[BJM]

Don't change the coolant sensor unless its screwy. A scan tool would tell you what the ECM thinks the temperature is at. If the sensor somehow told the ECM that the coolant is below the Closed loop threshold it would go back into open loop and possibly quite rich. If its fine you will have wasted your time.

Do you have a scan tool that you can tell us something with?

 

[badboy86gn2]

Make sure he put the plug wires to the correct plugs and i think it may still be the maf sensor what kind did he put dont put to much more money in it until you get a scan master or direct scan im sure theres someone that lives close that can help you

Johnny

were do you live???

 

[midnight rider]

I live in montreal. my mechanic does have a scan tool and everything came up normal. if i remember correctly the maf does not show up in any error codes. we tapped it a few times and also replaced it with his so i think its good.
ill check the plug connections are matched as well
thanks

 

[87ttypeV8]

hmmm
when my injectors were bad it said the Fuel pressure was fine... they were just spraying irradically and causing many b ad things... lead to an extreme lean condition at one point and blew my headgasket... ARG

well good luck

 

[BJM]

I know Montreal's roads well, I appreciate how that could happen. I think your MAF might be crappy if it inhaled a lot of unfiltered crud. The stock MAFs are ancient technology compared to the new ones and not very robust. A Direct Scan file would probably answer this perfectly because the BLM matrix pops out right away. Any chance you know someone with Direct Scan? I have it but I am in Ottawa otherwise I would give you a hand.

The other thing is that maybe something happens to have clogged up an injector. You didn't mention their age or condition or type.

 

[midnight rider]

i put in some fuel injector cleanor before heading over to my friends house. when i arrived the first thing he did was to put his maf sensor in my car and that did not solve the problem. tried to raise and lower the fuel pressure, even checked the gas for water. tried to disconnect the coolant sensor. also changed the computer and chip. finally we took off my spark plug wires and put on a set of used stock gm spark plug wires. After all of this the car runs much better. the spitting is fewer and far between and now when it happens and I accelrate the car continues to go and i dont lose power. its still not running with 100% confidence but its acceptable.
Im hoping now the problem is that the plugs are fouled up and im going to replace them next weekend.
if that doesnt do it then it looks like it might be the injectors which are several years old and are 42 pounders. Ill keep using fi cleanor in the meantime.
thanks again all for your feedback

 

[BJM]

Is there a reason we trust your ignition coils and module? Abrupt engine changes are more likely ignition now that you have ruled out the MAF. On my car the ground path from module through the mounting brackets to the intake went intermittent on me. The car drove like someone had an on/off switch. If you can swap coils again but this time sand all the mechanical interfaces and use dielectric grease between the bracket and intake, the bracket and mounting plate, and the plate and the coil unit, otherwise the car could drive exactly like you describe.