arioch

So the GF's car does fine at WOT but at about 30-50% throttle has a nasty hesitation. Its in multiple gears.

The car has been seafoamed but thats about it. Any ideas?

Oh and its throwing no codes at all

lt1pwr1

iTrader: (1)

Yes, probably the MAF or possibly o2's but sounds more like a bad MAF. You can try cleaning it but I've personally never had that work. Many guys on this forum have so you might give that a shot first.

LS6427

iTrader: (2)

If you're fine at WOT its not the MAF.

Low rpm range hesitation is usually a dirty fuel filter, and no codes. Could also be a failing 02 sensor(s). You'll need to hook it up to a OBDII scanner to see how the 02 sensors are switching.

.

Chrismikeb

iTrader: (2)

i had a very similar problem...turned out one of my spark plug wires seperated at the boot to the spark plug, i just berely touched it and it came apart. Might want to check the wires

LS6427

iTrader: (2)

^^^ yes, also make sure none of your spark plug wires are touching any metal exhaust manifold piping, that causes misfires.

.

rabbit320

iTrader: (11)

id check or replace o2's... same problem for me i chased it for a year, then ta-da! found new o2's...

98boxer

iTrader: (7)

2 days ago i noticed my car started to stumble between 40 and 50 mph, let me know any new updates, i plan to check my plugs and wires and change fuel filter. Now that some here post about 02's maybe i change those too, 149k miles and still have the original 02' sensors.

01ssreda4

iTrader: (96)

Seafoam is the devil. Do a plug and wire swap and ir should clear it right up.

LS6427

iTrader: (2)

They can last a long time.....but hell they're only $45.00 each for Densos...get some new ones, you'll have better overall performance.

www.rockauto.com Densos #2344087 I believe.

amazon.com also........

.

LS6427

iTrader: (2)

I think its gonna take a few more years until people start realizing that. lol

.

O2Form

Well cruising you are using the 02s and WOT you are not so it could be 02s but it could be other things like dirty injectors, tune up,vacuum leak, loose intake bolts etc. I had a hesitation at about 25% throttle and it turned out to be rusted fuel lines. All the injectors had rust in them from the fuel lines. It ran great WOT. If you pull the Accumulator-pulsator on the fuel rail you can take a quick look inside the fuel rail and see its condition. Mine was full of rust.

SH1ZN1T

iTrader: (16)

I'm having the same problem with part throttle acceleration in 2nd, 3rd, 4th gears. I bought some 13444 Bosch O2 sensors last night and will be installing them Monday or Tuesday this week. I will post up and let you guys know if that fixes the problem.

SH1ZN1T

iTrader: (16)

I installed the new Bosch 13444 O2 sensors today...
results were 100% successful! No more hesitation/stumble between 2200-2500rpm at part throttle and my mpg's went up from 12mpg lol..

DarkJuggalo

iTrader: (6)

i had a hesitation/stumble and it was a bad 02, didnt throw a code at all.

SH1ZN1T

iTrader: (16)

mine didn't throw a code either.

LS6427

iTrader: (2)

Thats right.......our PCM's are still just like the 1970's idiot lights.

Mine doesn't throw a code for bad MAF, bad TPS, bad 02's, or TCS issues. I got an SES light and a code when an 02 sensor went bad and finally would hardly let the engine run...then I got a light. Good thing it came on 1 mile from my friends place who threw the new ones in for me.

.

SH1ZN1T

iTrader: (16)

I was wrong guys. The hesitation is back and a little worse. Anything part throttle under 2500rpm it hesitates bad. I already did the rear O2s, fuel filter is good. It's also pinging above 5k..

65panel5.3

id maybe have a look at fuel pressure and see what its doing, pump on the way out would seem like a bad fuel filter and the pinging at high rpm would seem like a lean condition, fuel pressure at idle should be around 48 i believe, you can pull the fuel pressure regulator vacuum hose off and see if the pressure jumps when you do. it should jump to around 56 pounds or so if the pump is good. just throwing out another suggestion.

SH1ZN1T

iTrader: (16)

fuel pressure is at about 58psi at idle.

mike171562

iTrader: (4)

The rear o2's wont affect it, change your fronts, sounds like my car when my passenger side o2 was dead.