Hesitation Problem on Cultass Cierra 3.3L

Hesistation problem – car hesitates on acceleration at lower speeds (0-30mph). Does not hesitate on acceleration at higher speeds.

Took car in to the shop a few weeks ago. Checked fuel pressure and TPS, both OK. Found bad injector, replaced. Still had problem.

Found that with the MAF sensor disconnected the car does not hesitate. Swapped out the MAF with a different one from the junk yard. Still had problem.

Took injectors off of car and sent them in for cleaning. They all flow tested OK before and after, but the pattern was pretty bad before and much improved after. Put the injectors back on and still have the problem.

So, here's where I'm at...
-Cleaned injectors
-New fuel filter
-new oxygen sensor
-new plugs and wires
-changed out the MAF
-TPS was checked
-Fuel pressure was checked

I haven't touched the EGR vale or the PCV valve (I can't find them)

Any ideas???

Do this.
1. Locate your IAC (Idle Air Control solenoid). It is located on the throttle body and just

above the TPS (Throttle Position Sensor).

2. Remove the IAC, spray it with throttle body cleaner to get rid of any carbon build up and use

a brush. Clean also the spot where you remove the IAC from and clean it good.

3. Put back the IAC (dry) and test the vehicle.

4. You may have to replace the IAC as they go bad over time.

5. Location for the PCV valve? http://www.automotiveforums.com/vbulletin/showthread.php?t=234985
Search the web for "PCV Catch Can", to help your intake protect against from unwanted oil that the PCV introduces. I recommend to just put air/oil separator that is normally used for the Air Compressor. Your intake hoses, intake manifold, IAC, Throttle Plate will be free off oil that could cause it to gunked up.

Thanks for the reply. I did this, but to no avail. Lots of carbon on the IAC and in the passageway, and I cleaned it all up, but it still hesitates.

Any way to tell if the IAC valve is good or bad?

Thanks!

I read through my Chilton's for the car and found that I could verify the IAC valve as working by doing the paper clip thing in the diagnostic terminal. The IAC vavle is working fine.

Any other suggestions?

I recently had the same problem with the addition of running rough. I went through most of the things you did (I also changed the PCV valve, you might want to give that a try since it is only a couple bucks) and finally took it to the shop. There they replaced the coil and my rough running was gone, but my hesitation was not. I was on my way back to the shop when the hesitation went away on its own.

The only thing that I can think of is that the bad coil caused the computer to make some sort of adjustments and when the coil was replaced it took the computer a while to readjust itself.

Got it. Broke down and took it back into a different shop today. They scanned it and scoped a few signals, found nothing. Then they checked the fuel pressure. 28psi. The other shop I had it at a month ago checked the pressure too, but they said it looked fine -- and it very well could have.

They wanted $380 for parts and labor to do the pump. In addition to the $90 for diagnostics. I did it tonight in an hour and a half and $100 in parts. I did break down and get a fuel pressure gauge so I could verify what they said, and check out my before and after. 28psi before, just like they said and 45psi after. Now she runs like a champ.