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Surging/Thrusting Problem Under Acceleration

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Old 01-02-2013, 09:15 PM   #1
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Surging/Thrusting Problem Under Acceleration

Alright guys, I'm quite literally at my wits end trying to figure out what the hell is wrong with my truck. It feels very similar to a misfire, but without the sound a misfire normally makes and it's not consistent. Its more of a thrusting/surging feeling as if it is accelerating normally, and is if i for a second lifted off the accelerator pedal, and then mashed on the pedal again, and then repeats several times like a rocking chair. Only happens under moderate acceleration and is much more noticeable going uphill. At WOT sometimes it feels normal, sometimes the truck feels like a 4 banger instead of a supercharged v6. And coming back from the valley the other day up rather steep mountain grade, supercharger was boosting full balls at 10 psi and it felt like I was driving a ford escort. At one point I could almost swear to hearing a ping and lifted immediately and just limped home. This leads me to believe the problem is either with fuel delivery or spark.

I have absolutely no check engine fault codes or any previous stored codes.
I've inspected the coil boots thoroughly and they look absolutely fine.
I changed both the fuel filter and fuel pump when I did the URD 7th injector kit for the supercharger less than 20k miles ago. Fuel pump is actually a larger 190 lph pump.
On the same hunch, I changed the fuel filter again last week with no change in the symptoms.
Plugs are also brand new as of last week. Old plugs looked like normal wear, greyish/brownish color. If anything there's a minor amount of carbon soot deposits and minimal electrode wear.
As far as cleaning goes, I seafoamed, cleaned the MAF, and cleaned the throttle body.
I've inspected and measured according to the FSM (resistance, voltage, etc):
1) Plug wires
2) Coils
3) Camshaft position sensor
4) Crankshaft position sensor
5) Air/Fuel sensor (Pre-cat O2 sensor)
6) Post-cat O2 sensor
7) Mass air flow sensor
8) Throttle position sensor
9) Throttle control motor (both motor and clutch resistance)
10) Pedal position sensor

I've also completely disabled the URD 7th injector kit to try to eliminate possibilities. And today, i pulled the supercharger off completely and went back to the factory intake manifold and bought factory NGK plugs. While far less noticeable, the damn problem is still there.

I have 3 or 4 injectors from the old engine. I suppose the next step I could swap half the injectors at a time to see if that's the issue? I have no idea how to test the fuel pressure regulator short of buying a new one, and at $140, that's a semi-expensive guess. So at this point...I'm looking to TW to see if anyone's got some more ideas.

The good news is, I found my pliers I lost a year and a half ago when I swapped the supercharger on this engine

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Old 01-02-2013, 09:28 PM   #2
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Sorry cant help you. But I did follow your link from the other thread and cant help but laugh at the pliers...
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Old 01-02-2013, 09:28 PM   #3
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Fuel pump have good pressure? sounds like the problem is in fuel delivery. what parts you looking for off a v6?
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Old 01-02-2013, 09:32 PM   #4
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Sounds like dip on valve timing switch... Hondas do it on VTEC actuation, there is a dip at cam switchover as it switches from fuel saver lobes to power mode, making it fall flat, lose some hp, then a surge like a shift kick almost. The VVTi on the 1.8l celica GT-S did it bad too. Just a thought, and it would never show up anywhere on a fault code scan as it is normal operation.
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Old 01-02-2013, 09:34 PM   #5
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Originally Posted by nfs257 View Post
Sorry cant help you. But I did follow your link from the other thread and cant help but laugh at the pliers...
Yeah, despite how damn annoyed I am with the taco right now, admittedly I LOL'd when I saw them.

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Originally Posted by blake5995 View Post
Fuel pump have good pressure? sounds like the problem is in fuel delivery. what parts you looking for off a v6?
I'm inclined to agree, but it just seems weird. Fuel pump is less than 2 years old. I'm not sure how I can really test fuel pressure short of going out and buying one of those in-line pressure gauge thingys.

I still have my old fuel pump, so worst comes to worst I can burn thru the gas I have in my tank and drop the damn thing again and swap in the old pump. This would be the 3rd time dropping the tank.

As for parts, I just want to start swapping shit to see if anything fixes the problems. Parts high on my list are fuel pressure regulator, MAF, and coils.
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Old 01-02-2013, 09:36 PM   #6
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Quote:
Originally Posted by Shaggs View Post
Sounds like dip on valve timing switch... Hondas do it on VTEC actuation, there is a dip at cam switchover as it switches from fuel saver lobes to power mode, making it fall flat, lose some hp, then a surge like a shift kick almost. The VVTi on the 1.8l celica GT-S did it bad too. Just a thought, and it would never show up anywhere on a fault code scan as it is normal operation.
I had a vtec integra in a previous life. It's not like that.
Think of it more as if you were in a rocking chair while driving.
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Old 01-02-2013, 09:37 PM   #7
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Originally Posted by jberry813 View Post
I had a vtec integra in a previous life. It's not like that.
Think of it more as if you were in a rocking chair while driving.
maybe the timing is off?
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Old 01-02-2013, 09:40 PM   #8
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Quote:
Originally Posted by blake5995 View Post
maybe the timing is off?
I thought that too, but that doesn't really explain why the truck drives fine otherwise and no CEL.
I mean honesty the truck drives completely normal around town, just a really specific acceleration situation where it becomes an issue. And the supercharger just exacerbates the problem probably 10 fold.
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Old 01-02-2013, 09:41 PM   #9
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Quote:
Originally Posted by jberry813 View Post
I thought that too, but that doesn't really explain why the truck drives fine otherwise and no CEL.
I mean honesty the truck drives completely normal around town, just a really specific acceleration situation where it becomes an issue. And the supercharger just exacerbates the problem probably 10 fold.
those damn superchargers making problems worse yea if the timing was off you would have loss of power all the time. Maybe get the injectors cleaned?
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Old 01-02-2013, 09:43 PM   #10
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Sounds like you've covered everything but the injectors. I'd go ahead and swap some since you have them on hand and have the truck apart. It'd be nice if it would throw a code so you could have some idea as to where to start.

Cleaning the TB was a common response when I was researching for my misfire. While it may not cure your problem, it can't hurt.

I just got done fixing a mysterious misfire on mine so I know your pain. Luckily/shamefully mine was just an injector I didn't plug back in from when I redid my valve cover gaskets

Best of luck to ya, I hope you can get it figured out.
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Old 01-02-2013, 09:43 PM   #11
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To start, I honestly have no idea, but I'm gonna throw out some ideas that you may or may not have already had.
Could there be more driveline resistance from when you remade your rear axle?
Although now that I think about it, removing the supercharger should make that worse, not better, so that idea's probably out.
Could it be bad gas? Have you filled up since you've had this problem?
Could there be a blockage anywhere? A kink in a hose? Collections of ice?
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Old 01-02-2013, 09:45 PM   #12
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You clean the throttle body yet? Check for carbon buildup? Also is the idle off? What rpm are you at and what is tps reading id you have live monitor or scangauge2
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Old 01-02-2013, 09:48 PM   #13
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I was also thinking something with the accelerator. Could something be messed up between the pedal and the engine?
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Old 01-02-2013, 09:48 PM   #14
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Quote:
Originally Posted by blake5995 View Post
those damn superchargers making problems worse yea if the timing was off you would have loss of power all the time. Maybe get the injectors cleaned?
Quote:
Originally Posted by Gear Head View Post
Sounds like you've covered everything but the injectors. I'd go ahead and swap some since you have them on hand and have the truck apart. It'd be nice if it would throw a code so you could have some idea as to where to start.

Cleaning the TB was a common response when I was researching for my misfire. While it may not cure your problem, it can't hurt.

I just got done fixing a mysterious misfire on mine so I know your pain. Luckily/shamefully mine was just an injector I didn't plug back in from when I redid my valve cover gaskets

Best of luck to ya, I hope you can get it figured out.
Yeah I think I'm gonna swap 3 injectors at a time.
I just looked in my drawer-o-taco-shit and I still have 4 of my old injectors. Figured I can do half the injectors at a time and hope i get lucky.

I forgot to mention in the OP as far as cleaning goes, I seafoamed, cleaned the MAF, and cleaned the TB before anything else.


Quote:
Originally Posted by 92shawman View Post
To start, I honestly have no idea, but I'm gonna throw out some ideas that you may or may not have already had.
Could there be more driveline resistance from when you remade your rear axle?
Although now that I think about it, removing the supercharger should make that worse, not better, so that idea's probably out.
Could it be bad gas? Have you filled up since you've had this problem?
Could there be a blockage anywhere? A kink in a hose? Collections of ice?
I thought about the rear axle as well. Since this issue started, I've had the rear driveshaft shortened to fit my new needs as well as balanced. The same problem has been exhibited as well with two different 3rd members too (one with the detroit, one with the ARB).

As far as gas goes, I'm well into 5+ tanks of gas since the problem started. I always fill up with premium (for the s/c).

Ice definitely not the problem. I was back in the bay area for 3 days and had the problem there too.
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Old 01-02-2013, 09:54 PM   #15
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What about an exhaust leak?
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Old 01-02-2013, 09:54 PM   #16
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Quote:
Originally Posted by Shaggs View Post
You clean the throttle body yet? Check for carbon buildup? Also is the idle off? What rpm are you at and what is tps reading id you have live monitor or scangauge2
OP updated. TB was cleaned before i started doing anything invasive.
Engine idle is dead nuts what FSM says it should be at. Right around 700 rpm.

I don't have a live monitor/scangauge/ug. I did just borrow an OBDII thingy that uses bluetooth to sync to my computer, but haven't done anything with it other than check for faults.

Quote:
Originally Posted by 92shawman View Post
I was also thinking something with the accelerator. Could something be messed up between the pedal and the engine?
My TB is a DBW throttle body (ETCS-i). It has a single cable from the pedal to the TB, but the TB itself is all electronic.


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Originally Posted by m3bassman View Post
could it be the pliers?
No. They have plastidip on them so there's no way that could be the problem.
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Old 01-02-2013, 10:02 PM   #17
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Quote:
Originally Posted by blake5995 View Post
Fuel pump have good pressure? sounds like the problem is in fuel delivery. what parts you looking for off a v6?
You mentioned it was larger than the previous pump. I might look at that to eliminate it-could you replace it? Another possibility could be you have a vacuum leak.
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Old 01-02-2013, 10:04 PM   #18
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Originally Posted by ian408 View Post
You mentioned it was larger than the previous pump. I might look at that to eliminate it-could you replace it? Another possibility could be you have a vacuum leak.
he said he has the stock one but there are only 20,000 miles on the new aftermarket one and would be much easier testing pressure than dropping tank and replacing
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Old 01-02-2013, 10:07 PM   #19
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FWIW Jason, even if you have the correct resistance for a particular sensor doesn't mean that it's functioning properly. You about need a lab scope or a "known good part". Double check all your grounds for the hell of it as well.

Also, when I got my air filter wet, it was doing what I imagine to be the exact same surge you have under agressive throttle input. I'd really look into that MAF.
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Old 01-02-2013, 10:11 PM   #20
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Quote:
Originally Posted by Nightstr View Post
What about an exhaust leak?
Doubtful. I've dealt with my fair share of exhaust leaks with previous vehicles and I've got a pretty keen ear for them. The rest of the symptoms don't seem to line up with it either.

Quote:
Originally Posted by ian408 View Post
You mentioned it was larger than the previous pump. I might look at that to eliminate it-could you replace it? Another possibility could be you have a vacuum leak.
Replacing the fuel pump with my old one is on the whiteboard at the moment.

I hate vacuum leaks. They are just effing impossible to figure out. That said, when I pulled the s/c today and replaced it with the factory manifold I eyed all the lines and replaced a couple and removed the t-fittings for the boost gauge and URD calibrator.

Quote:
Originally Posted by blake5995 View Post
he said he has the stock one but there are only 20,000 miles on the new aftermarket one and would be much easier testing pressure than dropping tank and replacing
You happen to have a good link or instructions on how to do a fuel pressure test? I mean, my google-fu skills have been pretty good lately, just wondering if you had something on-hand.

Quote:
Originally Posted by maxamillion2345 View Post
FWIW Jason, even if you have the correct resistance for a particular sensor doesn't mean that it's functioning properly. You about need a lab scope or a "known good part". Double check all your grounds for the hell of it as well.

Also, when I got my air filter wet, it was doing what I imagine to be the exact same surge you have under agressive throttle input. I'd really look into that MAF.
10-4.
That's one reason I'm hoping someone can swing by my house to do play parts switcharoo (cough cough Eric cough). MAF was honestly the very first thing I thought of when all this started.
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