Another one, intermittent hesitation.

Mephis · #1 08-10-2009, 06:07 PM

So now I feel like dealing with this.

I'm having a rather strange intermittent hesitation problem that only seems to occur at very low throttle. About the 1st 1/8th of the way down it seems to have no power at all then if you press it a little more it'll throw you back in the seat. It's certainly not low on power, it's caused me to almost slide off the road a few times due to wheel spin when it comes out of the hesitation.

*I had this issue before doing these things*
I have so far replaced:
Alternator.
Temp sensor.
Cleaned the MAF with MAF cleaner, properly.
Adjusted the TPS in hopes it might solve the problem, which resulted in some interesting results but the hesitation was back the next day.
Checked all my vacuum lines in hopes maybe one was busted, nope.

This issue cropped up shortly after my charging system issues and temp sensor issues. I asked subaru about it and they were clueless.

Some days I don't have it at all, some days it's so bad I'm almost scared to merge into traffic. And some times it makes maintaining speed at 45 mph almost impossible. Like I said, all the power is certainly there, there's just something funky going on at less than WOT.

The car idles smooth as glass at 600rpm steady. Transmission feels great. Gas millage is still very good. No check engine light. No strange sounds. I'm almost wondering if this is limp mode or something, but I've unhooked the battery for a good while and it seems to come right back, plus I don't think that would be intermittent?

TomsSVX · #2 08-10-2009, 07:21 PM

search the old bead crush mod... Give it a whirl

Tom

Sean486 · #3 08-11-2009, 04:30 AM

Yeah sounds like the bead crush to me too. That's what my car used to do. Do you notice it more when the car is first started and less or not at all when you have been driving a while?

Mephis · #4 08-11-2009, 05:40 AM

It can crop up out of no where. Drive all day without a problem, then it'll start doing it for no reason, or start it up and it never stops doing it.

I've seen the stuff about the bead crush mod, but I didn't know that the hesitation would just show up out of the blue one day and start being a problem. (I never had an ounce of hesitation until all of my other issues that popped up here a couple of weeks ago.)

The issue isn't just with initial acceleration, it's any time the throttle is lightly pressed.

Sean486 · #5 08-11-2009, 09:20 AM

Quote:

Originally Posted by Mephis

It can crop up out of no where. Drive all day without a problem, then it'll start doing it for no reason, or start it up and it never stops doing it.

I've seen the stuff about the bead crush mod, but I didn't know that the hesitation would just show up out of the blue one day and start being a problem. (I never had an ounce of hesitation until all of my other issues that popped up here a couple of weeks ago.)

The issue isn't just with initial acceleration, it's any time the throttle is lightly pressed.

I am no mechanic, so I can only speak to my experience. On my car out of the blue it started having hesitation around 2000-2200 rpm. Like yours under light throttle. I would push on the gas pedal and no response, then if I hit it harder it would surge forward and be normal again. On mine it only seemed to happen before the car was fully warmed up. Or if the car was warm but the engine was shut off like when you stop for gas. It would go away though, it would really only happen once maybe twice then would run fine after that.
Your problem sounds a little worse so it very likely is something different, maybe the throttle position sensor?? Hopefully someone more knowlegable will chime in because that's all I got.

SoCal LS-L · #6 08-11-2009, 12:20 PM

I agree with suspecting the TPS, they probably messed with it at the dealership while trying to diag your problem. It tells the computer when to idle, and when to advance timing as the pedal is pressed. Its supposed to give a resistance reading in harmony with the opening of the butterfly valves, but if they arent in sync, you can have more or less air flowing into the engine than the throttle reading accounts for, causing surging issues ( when you press the gas pedal, the ECU goes from idle mode to throttle advance, the air/fuel mixture volume could already be higher than light throttle, causing a surge). Since its relatively easy, I would readjust the TPS to the specifications in the service manual..... then if that doesnt work we can try to look at other possibilities.

Mephis · #7 08-11-2009, 05:22 PM

I don't have a service manual so anyone who knows how I would adjust this correctly, please chime in. (If I use a multi meter please let me know what I set it to)

I just messed with it by ear last time and it improved a tiny bit.

SoCal LS-L · #8 08-11-2009, 05:49 PM

Quote:

Originally Posted by Mephis

I don't have a service manual so anyone who knows how I would adjust this correctly, please chime in. (If I use a multi meter please let me know what I set it to)

I just messed with it by ear last time and it improved a tiny bit.

If you have signatures turned on then just look in my signature, the links right there. You can look at it online or download the entire thing in .pdf format.

Edit: Theres also a How-To in the How-To Documents/Engine/TPS section of this site. Links are up top on right.

AyeJaye · #9 08-11-2009, 08:30 PM

I have a symptom similar to this, but it only happens when I'm using my AC. Always figured it was the AC pump draining power from the engine. I've already replaced my TPS, so I'm fairly certain that's not the issue.

Mephis · #10 08-12-2009, 05:56 PM

My multimeter has everything but an 0.5volt option so I opted for playing around with the adjustment. I discovered at a certain point it kicks the fuel pump on. So I adjusted it to where you barely open the throttle before it trips the fuel pump. Unhooked the battery, let it sit, hooked it up let it run for 10 minutes, shut it off, started it back up and drove it. Lot more power and hesitation gone, and my torque converter is working like it should. Hooray.

Now the only ***** thing is my temp sensor went out again, looks like I'm buying a subaru part this time....

SoCal LS-L · #11 08-12-2009, 07:58 PM

Quote:

Originally Posted by Mephis

Now the only ***** thing is my temp sensor went out again, looks like I'm buying a subaru part this time....

How did it do that? What happened?

Mephis · #12 08-12-2009, 09:26 PM

Quote:

Originally Posted by SoCal LS-L

How did it do that? What happened?

I have no idea what's going on to be honest.

I put my multi meter on it at 20k ohm and it shows 1.0 with the engine HOT. It would bounce around a little, but it wouldn't trip the fans.

If I unhook it, fans start running like normal. The gauge seems to be worthless for keeping check on the engine temperature, doesn't raise above the halfway line.

SoCal LS-L · #13 08-12-2009, 11:23 PM

Quote:

Originally Posted by Mephis

I have no idea what's going on to be honest.

I put my multi meter on it at 20k ohm and it shows 1.0 with the engine HOT. It would bounce around a little, but it wouldn't trip the fans.

If I unhook it, fans start running like normal. The gauge seems to be worthless for keeping check on the engine temperature, doesn't raise above the halfway line.

Exchange it for another one, bad sensors arent uncommon, and its easy to do on the SVX.

Our temp gauges, since they are older now, have developed a magnetic memory for the middle spot, and it takes a much lower resistance reading to snap them out of it and show a hot temperature. The normal arc from cold to normal temp works because it is always used. Some newer cars peg the gauges to max when first started to fix this problem.

What you can do to restore normal operation is remove the sender lead and directly ground it very briefly, like a second, and repeat this a number of times. This pegs the gauge to fully hot and helps restore the gauge function above normal operating temp.

Mephis · #14 08-13-2009, 12:22 PM

Quote:

Originally Posted by SoCal LS-L

What you can do to restore normal operation is remove the sender lead and directly ground it very briefly, like a second, and repeat this a number of times. This pegs the gauge to fully hot and helps restore the gauge function above normal operating temp.

Just grounding it is how it works?

Wow brb I'm trying this.

Worked like a charm, have to wait till the next time I drive it to see if it will show when I'm overheating though.

Mephis · #15 08-16-2009, 06:29 PM

Hesitation is back now as well as some charging system issues.

With the AC on the battery will dip below 11 volts. (Brand new alternator...)

At least I have the temp sensor working now.... I'm getting tired of this. If I dropped the car off at a dealership you think they'd ever be able to figure out what on earth is going on with the car to have failures in almost everything around the clock?