car still running bad, got some sensor value ?s

[tpivette89]

long story short, my car is still running badly even after i troubleshooted and replaced a few items. it hesitates and pops at idle, cruise, or under acceleration. i replaced the fuel pump, and one of the plug wires that had cracked cause it was touching the downpipe.

so this afternoon i took it for a test drive around my neighborhood with a scan tool attached so i could see what my sensors were reading. i recorded seven values: MAF, O2, knock, BLM, coolant temp, IAC, and TPS. heres what i got when driving around the block a few times

1st trip:
MAF - (idle) 9, (cruising at 1300rpms) 16, (part throttle) 51
O2 - switching anywhere from .120 to .870
KNOCK - no counts
BLM - 128
COOLANT - started at 20 and got to around 45 at end of 1st lap
IAC - anywhere from 75 - 130 depending on throttle application
TPS - .44 at idle and went to around 1.8 at part throttle


2nd trip:
MAF - same as above
O2 - same as above
KNOCK - same as above
BLM - 105
COOLANT - got up to 76 and stayed there
IAC - same as above
TPS - same as above

anything look out of place? i know my BLMs were off during the second trip around the neighborhood, but when i gave it gas and got into about 4-5 lbs of boost, the reading jumped from 105 to 128. also, the IAC went down to 0 when i stopped the car and put it into park. is that right?

any help would be greatly appreciated. im getting tired of searching for this mystery problem... i just want to start driving and enjoying this car already

 

[boostmaster]

We need to have @ idle values.

 

[tpivette89]

ok... values at idle, with car warmed up:

MAF - 9
O2 - switching (.120 - .870)
KNOCK - no counts
BLM - 105
COOLANT - 76 (assuming this is C and not F)
IAC - 0
TPS - .44

 

[turbot2496]

When and what were the circumstances when the problem started. Did it just start running bad out of the blue or was it after you changed something etc.? Fuel pressure?

 

[boostmaster]

Running rich : BLM 105- too much fuel, computer is trying to lean it out. More than likely caused by a bad maf sensor 9gps @ idle is way high should be between 4-7 if idle speed is 850 rpm's or less. Also iac 0 , way low should be between 10-30 counts @ idle need to follow the iac reset procedure on www.gnttype.org

 

[tpivette89]

When and what were the circumstances when the problem started. Did it just start running bad out of the blue or was it after you changed something etc.? Fuel pressure?

car was running great, then i decided to top off the tank. drove to the gas station, put about 4 - 5 gallons in, started the car up, and suddenly it ran like crap

i checked FP, and found it to be a bit on the low side, so i swapped out the fuel pump... no change. then i was just BSing under the hood, tightening grounds and stuff, and found a burnt plug wire (had been touching the downpipe). replaced that and tied it out of the way... no change

 

[tpivette89]

Running rich : BLM 105- too much fuel, computer is trying to lean it out. More than likely caused by a bad maf sensor 9gps @ idle is way high should be between 4-7 if idle speed is 850 rpm's or less. Also iac 0 , way low should be between 10-30 counts @ idle need to follow the iac reset procedure on www.gnttype.org

i disconnected the MAF to see if it would run any better in "limp home mode" (i had tried this on my 89' Vette when it started running like crap, and it ran much better with the sensor disconnected. i replaced the MAF on that car and problem solved) and saw no change. maybe this test doesnt work the same on turbo Buicks as it did on my TPI Vette?

 

[boostmaster]

This is a long shot, but there may be a possibilty of a leaky fuel injector also causing rich mixture. To check it do a leak down test, turn the ignition on let the fuel pressure come up and then turn the switch off. Watch the gauge and see if it holds pressure for at least 15-20 min. Pressure should not drop anymore than 10 psi. As for the maf the easiest way to check it is with a known good one.

 

[cool 84]

Make sure the coolant is reading in celsius. If not, a bad coolant temp sensor could make it run like it's running.

 

[turbot2496]

Did you change the fuel filter also when you did the pump?

 

[my85grandnation]

Check and make sure your inlet hose is tight where it mounts to the throttle body also if there are any holes in it. If its lose or has a hole in it the vehicle will get more air coming in then the MAF senses and it will try to compensate and throw everything out of wack. This happened on my car, the inlet tube came lose and caused the same things your describing. Also you may check the rest of your plug wires with a meter to see if there is any that show any signs of mre resistance than the rest.

 

[HOTSIX]

Vac

How 'bout vac leaks ?

If the car had even a small vac leak it will run like crap. Any amount of unmetered air getting in - no good.

 

[boostmaster]

Cool84 is on to something if the coolant temp is 76* farenheit that will make the car run like crap, but assuming 76* is celsius that's about 160 something degrees which is pretty good.

 

[tpivette89]

This is a long shot, but there may be a possibilty of a leaky fuel injector also causing rich mixture. To check it do a leak down test, turn the ignition on let the fuel pressure come up and then turn the switch off. Watch the gauge and see if it holds pressure for at least 15-20 min. Pressure should not drop anymore than 10 psi. As for the maf the easiest way to check it is with a known good one.

fuel injectors are new, only about 125 - 150 miles on them. is it possible for an injector to suddenly fail? my problem wasnt a slow gradual occurance... just BAM running like crap

 

[tpivette89]

Did you change the fuel filter also when you did the pump?

while i didnt change the filter when i did the pump, i did replace it when i rebuilt the top end of the motor. that was about 125 miles prior to this problem

 

[tpivette89]

How 'bout vac leaks ?

If the car had even a small vac leak it will run like crap. Any amount of unmetered air getting in - no good.

all vaccum hoses were replaced when i did the rebuild. i did double check them though, and all is well

 

[tpivette89]

Cool84 is on to something if the coolant temp is 76* farenheit that will make the car run like crap, but assuming 76* is celsius that's about 160 something degrees which is pretty good.

that would make sense, since i installed a 160* stat to compliment my rebuild. wonder how i go about confirming the scan tool is reading in C and not F?

 

[HOTSIX]

That a simple one. Just feel the hoses when the car is warmed up to temp....if they are hot to the touch - bingo its 160 deg - if not so much...gotta be F. Compare it to a 76 deg day....u know how warm (not hot) that is. My guess is that it cant be F - if so - give us your secret and we will all run that cool !!

As posted by Boostmaster:
This is a long shot, but there may be a possibilty of a leaky fuel injector also causing rich mixture. To check it do a leak down test, turn the ignition on let the fuel pressure come up and then turn the switch off. Watch the gauge and see if it holds pressure for at least 15-20 min. Pressure should not drop anymore than 10 psi.

Did you try this ?

What about the MAF - u stated earlier that you disconnected it and it ran better right ? Its possible that if u swaped it with a known good one - it was not. Try another swap maybe.

Also - id be curious of the gas - maybe try and drain the tank with the green wire to POS (on the harness close to the coilpack) and try some fresh stuff. If for not other reason - to eliminate that.

Other things to consider - coilpack / module - have them tested to ensure they are good. Bad plug(s) - possible but less likely.....

 

[tpivette89]

That a simple one. Just feel the hoses when the car is warmed up to temp....if they are hot to the touch - bingo its 160 deg - if not so much...gotta be F. Compare it to a 76 deg day....u know how warm (not hot) that is. My guess is that it cant be F - if so - give us your secret and we will all run that cool !!

As posted by Boostmaster:
This is a long shot, but there may be a possibilty of a leaky fuel injector also causing rich mixture. To check it do a leak down test, turn the ignition on let the fuel pressure come up and then turn the switch off. Watch the gauge and see if it holds pressure for at least 15-20 min. Pressure should not drop anymore than 10 psi.

Did you try this ?

What about the MAF - u stated earlier that you disconnected it and it ran better right ? Its possible that if u swaped it with a known good one - it was not. Try another swap maybe.

Also - id be curious of the gas - maybe try and drain the tank with the green wire to POS (on the harness close to the coilpack) and try some fresh stuff. If for not other reason - to eliminate that.

Other things to consider - coilpack / module - have them tested to ensure they are good. Bad plug(s) - possible but less likely.....

my injectors only have about 150 miles on them MAX. they should be good. however, i will do the pressure test to see if they are leaking

i disconnected my MAF, and the problem didnt go away (in fact the car actually stalled out). the only way i can truely test it is if i order another sensor, and thats kinda pricey. id like to troubleshoot some more and narrow things down abit before i drop that kinda money on a sensor that may or may not be the problem

i did drain the tank and refilled it and got no improvement

im also thinking possible coilpack/module... but there just as pricey as the MAF deal, so i want to test a few more things before i spend that kind of $$ on a guess

thanks for the help/suggestions guys. ill keep you updated if i make any progress

 

[turbot2496]

Well if I had to gamble I say its a bad Maf. See if you have someone close who can help you to swap test a 'confirmed' good one.