slow acceleration = good. fast acceleration = bad
 

1999 blazer ls 4x4 with 4.3L (W)

when im driving around town or even on highway everything is pretty much fine
i have a tiny little miss when im idling about every 10 secs or so.
the fuel economy is below avg

the main problem is when i floor the gas pedal when im going from 10mph to 50mph
it dont switch to a lower gear to increase my mph and also rpm dont go up.
it does not kill the motor either or any negative effects
it only slowly goes faster (rpm and mph)

now if i only go from 20% throttle to say 60% throttle it acts as it should.

i dont have a fuel pressure guage to check fuel system and i dont have a laser gun to check the heat before and after the catalytic converter.

i should be getting one of those cheap obd ii things today or tomorrow.

any suggestions?

i have searched the forums and google and there is just a ton of stuff (and i have read alot of it) but im not either wording my search correct or the way im describing it.

any suggestions / tips would be great

just wanted to add that if im in park i can rev it up and down all day long with my foot (off and on etc...)
working as it should

it only happens when im driving

fuel issues is most common with these. If you don have a fuel pressure gauge,go to autozone and get a free one (loan tool program) you just have to leave the retail deposit incase you dont return it. pressure needs to nail 60 psi or more at key on. and then hold above 55 for 10 minutes. If that passes cool,onto the next.

Could be the tps. There are ways of checking it with a multimeter,i just dont know the specs on it on these 2nd gens. Also,pickup a bottle of maf cleaner and clean your maf air flow sensor. They get dirty and can cause this kind of issue. Dont cheap out and buy brake cleaner to do this job,as that can destroy it. thats why they make maf cleaner.

dont have enough even for the deposit for the fuel gage until after the 1st so thats a bummer.

i do have a multimeter to check the TPS but if the engine is on and tranny in Park and i have the hood open i can manually move the throttle and it revs just fine it seems

only when im casually driving and then floor does it not do what it is supposed to do
if i give gas like a normal person and not floor it (it seems like it pretty much behaves like it is supposed to)

if im going 55 and am in 4th and i step on it then it dont kick into a passing gear....the RPM`s dont go up and my speed stays the same for quite a long time until it gradually increases

when i do step on it i think the throttle plate does open as i do hear a change in sound when i floor it but rpm and mph just change very slowly

the MAF or the MAP sensor i did clean with carb cleaner a while back and i was carefull not to get it on anything except that wire in the screen

was that the map or the maf ?
it is in between the throttle body and the air breather.

i did check my tracking number for that obd ii device and it says its out for delivery for today
i dont get mail for about 5 more hours

the maf,you need to reclean with maf cleaner. carb cleaner leaves a white residue which will basically make your maf go nuts. and yes the one between your tb and air breather.


also,for the obd 2 thing. you know you could have autozone or advance etc check codes for free right?

got this Super Mini ELM327 V1 5 OBDII OBD2 Interface Bluetooth Auto Diagnostic Scanner | eBay and it seems to work with ignition in "On" position but not in "Run" position

it works fine on my 1997 dodge caravan in "On" and in "Run"

anyone know why?


i was going to use the info from that device to give info in this thread like fuel pressure.

crap...gonna go searching.

got the obd ii device working

Regular Sensor Data at idle, 1000, 2000 and 3000 rpm's.

there is also an emission screen and i could not complete alot of those tests (later on) when i was on the road.

Sensor Data - Imgur


these are Wide Open Throttle tests 1 second after i slammed pedal to the floor from cruising at speeds of 20MPH and 56MPH

pictures should show that also

WOT Sensor Data - Imgur

Fuel Pressure is not showing.

today the car ran pretty crappy to begin with (not so much at idle but when driving down the road less then 45mph) even after the car was warmed up
couple stutters here and there and when i floored it i even got a back fire after it reached high rpm (or when i let off...cant remember)

maybe someone can make sense of the data i was able to get

just wanted to add something else i forgot to mention
after i let the car warm up (just by letting it idle for 15mins or so) is when i started to collect data for the 1000, 2000 and 3000 rpm pictures
when i would move the gas pedal from idle to 1000 rpm it did not want to stay stable right away. i really had to fidget with the gas pedal (it was not linear when i moved the gas pedal to get to 1000, 2000 or 3000 rpm)
i mean it would either be to much or to less and it took a couple mins each time to get it stable at 1000, 2000 and 3000 rpm