Hesitation Problem, Anyone Had This?

[sct12]

I have been chasing a problem on my car for some time. After I put a 2.7 pulley and tune, my car will fall on its face inbetween shifts, and when you go wide open throttle to redline then let the rpms bring you down, then stab it again around 4grand it hesitates for at least 1.5 sec then goes. This is very obvious when driving but not so much when a passenger. I have removed my pprv and had my tunner get most of it out but it is still there. I am just wondering if others have seen this and if so what causes it?

Its very obvious if you just leave it in second gear and just keep jumping on it without ever putting in the clutch. Anyone with any ideas?

 

[Snakebite2k3]

I would check for spark plug blow out. I’m ditching the TR6’s and moving up to a colder plug this summer.

post up your mod list.

 

[sct12]

Yea thats the thing I dont have that many, but here they are. 2.76 pulley, jlt ram air, tr6s, lightning force HE and tank, head cooling mod, pprv delete. Thats about it for engine. You can hear the throttle open and the supercharger whine but no exhaust noise. I have data logged this and saw fuel pressure to go very low at wide open, and my tuner says that he sees it too but he cant seem to get rid of this hesitation. Racing season is coming up and I really want to get rid of this before.

 

[AaronK]

I have been chasing a problem on my car for some time. After I put a 2.7 pulley and tune, my car will fall on its face inbetween shifts, and when you go wide open throttle to redline then let the rpms bring you down, then stab it again around 4grand it hesitates for at least 1.5 sec then goes. This is very obvious when driving but not so much when a passenger. I have removed my pprv and had my tunner get most of it out but it is still there. I am just wondering if others have seen this and if so what causes it?

Its very obvious if you just leave it in second gear and just keep jumping on it without ever putting in the clutch. Anyone with any ideas?

I have the exact same problem and so does my friend in his 03... I've heard something about the stock fuel system being non-returnable or something but I honestly have no idea what it's from... I can't stand it when it happens though :bash:

Even when my car was STOCK this happened

 

[sct12]

Ah thank you, have you asked your tuner about it? I have my car tuned by Amazon and Rick is really trying to get rid of it. He has gotten it down to only doing it when left in gear and not inbetween shifts. A friend with the same mods, his car dosent do this.
Does your car do this all the time Aaronk?

 

[AaronK]

Ah thank you, have you asked your tuner about it? I have my car tuned by Amazon and Rick is really trying to get rid of it. He has gotten it down to only doing it when left in gear and not inbetween shifts. A friend with the same mods, his car dosent do this.
Does your car do this all the time Aaronk?

It does it probably 75% of the time. I've heard from a couple people that it's a fuel issue... I talked to my tuner over the phone about it and discribed the problem and he said without looking at it he is guessing (don't quote me on this, something to do with...) a non-returnable fuel system... but I didn't understand because it did it while it was stock also...

My friend has an 03 with over 500rwhp and has the same problem... It's very irritating when you stomp the gas and it doesn't go anywhere for a second. :fm:

 

[04cobra13]

i had the same problem, and also have the same set up as you. Get the pprv valve deleted, then bye bye hesitation!

 

[sct12]

Yea that is the same thing that I have on my car. Its odd though I dont remember it doing it when it just had a 3.0 pulley. Hmmm. Well Rick at amazon is really helping me out with it, but it is wearing me down and I am about to say f-it. Just wanted to know if anyone else has seen it? Do you still have the pprv?

 

[AaronK]

Yea that is the same thing that I have on my car. Its odd though I dont remember it doing it when it just had a 3.0 pulley. Hmmm. Well Rick at amazon is really helping me out with it, but it is wearing me down and I am about to say f-it. Just wanted to know if anyone else has seen it? Do you still have the pprv?

Yes, I do have the pprv... I just found this online though as a discription on the delete kit...

"This kit will allow you to install Aftermarket Pumps, upgrade the lines to 3/8", and remove the PPRV which causes the infamous hesitation."

Sounds like the solution to the problem... Even if it's not, it couldn't hurt :shrug:

 

[sct12]

Didnt change a thing on mine.

 

[Snakebite2k3]

Didnt change a thing on mine.

That’s weird because once I did the pprv delete the hesitation was gone


good luck with the fix

 

[AaronK]

Didnt change a thing on mine.

Well then, there goes that idea :bored: I hope someone else chimes in on this!

 

[04cobra13]

im pretty sure its the pprv...l

 

[sct12]

Yes but I removed mine and no change.

 

[rich5150]

Double/triple check the PPRV. I had the exact same issue on my GT when I went with the dual-cobra pumps/cobra tank. You can spend all day adding fuel pressure, changing voltage tables... but that's not the culprit.

When you datalogged a pull where it hesitated, did you log Fuel Pressure drop? I'd be curious to see where your fuel pressure was at during those shifts.... I'm guessing that your car DOESNT hesititate if you aren't at WOT.... when you shift..

Basically see if you can go up the RPM band but not @ WOT.... do it at like 75% throttle or something... if you don't have any hesitation..etc and its smooth as glass.. its not belt slip, ignition..or any of that stuff. More than likely you just don't have fuel to burn for a split second.


POST A DATALOG

 

[sct12]

Ok I have a data log that I can post somewhere. I did record the pressure drop and it goes away after wot. I didnt shift in my data log I just went on and off wot at high rpm. Is this hurting my motor, I mean going lean for a split second? I will post that datalog in a few minutes.

 

[sct12]

I meant to say the pressure goes very low right after you stab the pedal. If the pprv is gone what is causing this?

 

[rich5150]

I meant to say the pressure goes very low right after you stab the pedal. If the pprv is gone what is causing this?

How LOW? Does the pressure drop below 30PSI once you STAB the gas hard? As soon as the computer senses load, your tune's voltage tables should start sending more and more voltage to your pumps to increase pressure...

You also may want to DATALOG Fuel Pump Duty Cycle. You very well may have a bad fuel pump or something else going on. Perhaps a faulty wire going to one of the pumps...

If the pressure drop across the injectors is great enough, your injectors won't squirt enough(or any at all) fuel into the cylinders...it'll be mostly air(could be lean at this point I'd say).

 

[sct12]

It drops very low like 17 or lower right after I stab it. Then goes way up after about 1.5sec to at least 45 or higher so I didnt think it was a mechanical issue. I will post up my datalog tommorrow, not sure how, but I will figure it out. I have dynoed the car looking for the cause and the duty cycle was ok on the fuel pump. I couldnt recreate it on the dyno because couldnt release power and then back on.