sputtering from 2400-2800 rpms

[mjoekingz28]

On my Saturn I've been having this hesitation/bucking/shaking/sputtering from this rpm range and only in this range. All other areas of the powerband are very smooth and cause me no grief. Its pretty bad and while it still has enough power to accelerate it is much reduced. I can watch my speedometer and see that it accelerates faster below and above this range, but I know its down on power because its a 4cyl and it seems to have the same power in this range as it does below 1500rpms

Anyways, i've replaced the EGR valve with a used very clean unit from eBay. Oh yeah, I blocked off the EGR with a couple of quarters and the sputtering was much reduced and bearable but still there. New wires, plugs, air filter. Now Im thinking the TPS maybe the cause because it acts differently depending on the level of throttle applied. Like if I hold it just right (almost floored) I hardly notice.

 

[HangerHarley]

Originally Posted By: mjoekingz28
On my Saturn I've been having this hesitation/bucking/shaking/sputtering from this rpm range and only in this range. All other areas of the powerband are very smooth and cause me no grief. Its pretty bad and while it still has enough power to accelerate it is much reduced. I can watch my speedometer and see that it accelerates faster below and above this range, but I know its down on power because its a 4cyl and it seems to have the same power in this range as it does below 1500rpms

Anyways, i've replaced the EGR valve with a used very clean unit from eBay. Oh yeah, I blocked off the EGR with a couple of quarters and the sputtering was much reduced and bearable but still there. New wires, plugs, air filter. Now Im thinking the TPS maybe the cause because it acts differently depending on the level of throttle applied. Like if I hold it just right (almost floored) I hardly notice.


Do the RPMs "Go Down" when you have Steady Throttle applied?

Could be Vacuum, or a Fueling issue as well.

 

[mjoekingz28]

thanks for your reply

If I hold a certain rpm in that range nothing is wrong, it is fine. Only while accelerating. When accelerating you can see the tach bounce around. Its not bad enough to 'lose' rpms on level ground but you can really feel it when the AC is on and going up hills.

 

[Boomer]

Get the codes pulled!! Then repost, please.

 

[mjoekingz28]

no codes Boomer.

Only code I've ever had was when I bypassed the EGR.

 

[Mr_Incredible]

The last time this happened to me it was bad plug wires. I thought they were still in great shape but one of them was definitely not up to par. I would recheck each of them for some internal mis-manufaturing or breakage.

I tried changing out and working on about ten different things until I checked the sparkplug wires ("It's too soon, it can't be them.") REAL bad carbon tracking on the #3 plug wire at the spark plug. The plug connector had disassociated itself from the core wire.

 

[Nick R]

Let me know how it turns out, I have this same thing on my cavalier. Mine seems to be less RPM dependent. I have the same basic thing going on though. I hope it's not plug wires because those are a PITA to get to on this thing (on the back of the engine against the firewall- on the bottom)

 

[mechanicx]

This car has a manual transmission? Try unplugging the MAP sensor and see what happens.

 

[mjoekingz28]

Oh I forgot to add, that it has good power and pulls very smooth the first few minutes of the morning. Its not exact, but when it gets halfway to operating temp. it decides to start misbehaving.

Will test and try the MAP sensor. Thanks for suggesting, watchig the RichPin video right now.

MrIncred, it did it before changing the plug wires and afterwards so I ruled that out already.

 

[mechanicx]

You have a tough one with no codes. Now I wonder if it only acts up when in closed loop. Sometimes 02 sensors cause the symptoms you have. It would be good if you have a scanner to watch sensor values and maybe a freeze frame when it acts up.

 

[Nick R]

Originally Posted By: mechanicx
You have a tough one with no codes. Now I wonder if it only acts up when in closed loop. Sometimes 02 sensors cause the symptoms you have. It would be good if you have a scanner to watch sensor values and maybe a freeze frame when it acts up.


Wait, O2 sensors can cause this too? Hmm.... Well, I have a code for catalyst efficiency, these two combined.... I don't wonder if the after-cat O2 sensor is gone, instead of the cat like I suspected before....

 

[NateDN10]

The after-cat O2 sensor isn't used for closed loop; it's mainly there to know whether the cat is working. It shouldn't affect the way the engine runs.

 

[Nick R]

Originally Posted By: NateDN10
The after-cat O2 sensor isn't used for closed loop; it's mainly there to know whether the cat is working. It shouldn't affect the way the engine runs.


Would the pre-cat O2 throw that code too? Sorry to get off topic =P

 

[mechanicx]

As Nate said the post-CAT O2 sensor wouldn't affect engine performance. A pre-cat sensor problem won't set a CAT sensor code.

 

[mjoekingz28]

Swapped the TPS and MAP sensor out with another and no change. I'm going to try one last thing: another EGR valve. The one on my car didnt work well and the one I got from Ebay still feels the same. I figure I cant get three duds in a row, but who knows.

I'll post back if that fixes it this weekend.

Its bad because I already have limited power with a 1.9l. It has as much or MORE power down below 2k rpms that it does from 2.4-2.8k. Its not really a linear build of power. Right now how it sits, it builds slowly from off idle to 2400, the spits and sputters til 2800 where it begins to have a surplus of power (I can climb any hill around here with little throttle above 2800 rpm, below that I have to floor it and it still loses speed), then at 4k it feels like vtec kicks in then tapers off at 6k to its 6.5k redline.

mechaincx, unplugging the MAP made the car very unstable, especially at lower rpms when starting from a stop. It feels just like that, only to a lesser severity.

 

[meep]

does this engine use variable valve timing? or variable length intake?

You swapped TPS, you swapped MAF, you've swapped plug wires, what's left? timing? restrictions in exhaust? flakey injector?

 

[mjoekingz28]

ok, update

I blocked off the EGR valve with a couple of quarters and it will run excellent until the SES light comes on. I got it narrowed down, the light will come on when I let the engine do some braking, but other than that it will stay off for very long periods of time. It runs so good now-pulls strong and clean.

I will try yet another EGR valve from the junkyard, which will make 3 (original, ebay, JY unit), but I don't think this will cure the problem for some reason. I'll just have to keep a code reader in the back seat and shift to neutral when approaching stoplights.

Whenever teh SES comes on, I just reach behind the seat and plug it in and erase the code. Also, my mpg went up 2-3 points, but is too soon to say for sure yet.