Hesitation, but not hesitation? help

[NewGenSTi]

ok here it is. when driving my car 1995 ls I notice that it feels like it pulls for a second and then the power flattens out then it pulls again then flattens out again. very smooth like not a jerking or like its starving for fuel. but more like its running good and then almost like advancing the timing a tad then going back to where it should be. The only CEL I have gotten so far was a bad cat and I took the cats out and replaced them with a high flow and although it runs better it still had that problem where it flattens out.
I have New spark plugs, fresh oil, new air filter, recently pulled the injectors and cleaned them up a little and then put injector cleaner through the fuel system. The car runs and idles great just has this flat spot every second or so. could this possibly be #1 a failing 02 sensor maybe giving mixed reading causing hte system to compensate to mixed readings? a failing knock sensor pulling timing? This happens at a steady throttle like if I hold the pedal at around 50%.. One other thing that I think it may be is the Auto Transmission. its been starting to shift a little funny. if its cold it will not shift out of 3rd, and it seems like when it shifts into the next gear at any time it really slams into gear and doesnt like to downshift going up hills. so maybe its a trans problem


BUT.... if I sit at Idle and I punch the pedal right to the floor and hold it it will pull then cut completly over and over again no matter how long i hold the pedal it wont stop doing that untill I let go.

maybe the trans is in a high gear and wont downshift to compensate. this is only from a dead stop or rolling at like 1-2 mph. anything over that it will take off fine

I didnt check the tranny fluid yet, or change it, and I didnt do anything with the fuel filter yet. I am going to replace the fuel filter today. maybe I will pick up a trans filter and fluid for hte hell of it too

[NewGenSTi]

Here is an ilustration to help explain what its doing.
https://sl-i.net/FORUM/images/imported/2006/01/powergraph-1.jpg

note: the power numbers are irrelavent to anything they are just there to give an idea or how it flattens out and then pulls again

[shazapple]

My car does flatten out right around 3500 rpm.

Try doing the grounding mod. That may get rid of a bit of hesitation. Also, when cold the auto tranny is designed to stay in 3rd. It helps warm everything up a bit faster.

I find that sometimes Ill go to punch it and the car just wont go. Thats more a problem with the AT not being in the right gear (theres a bit of a dead spot right at the bottom of 2nd) It is an AT afterall, so you cant expect it to read your mind!

[NewGenSTi]

My car does flatten out right around 3500 rpm.

Try doing the grounding mod. That may get rid of a bit of hesitation. Also, when cold the auto tranny is designed to stay in 3rd. It helps warm everything up a bit faster.

I find that sometimes Ill go to punch it and the car just wont go. Thats more a problem with the AT not being in the right gear (theres a bit of a dead spot right at the bottom of 2nd) It is an AT afterall, so you cant expect it to read your mind!

right. but if im at a dead stop and I floor it, it will pull for a second the n cutout, then pull another second, then cut out. that almost feels like what fuel cut on my STi when overboosting felt like but at a slower pace. I dont know. I am running to get a fuel filter in a few and then I guess I will see what happens. I coubt its the filter though, because the car seems to be running a bit rich anyways and if it was starved for fuel I would expecti t to lean right out. Cant wait to get rid of this auto tranny. its the first I have owned in my life and its driving me nuts. the price was right on the car though. it is in near mint condition very well kept and I only paid $2400. so I cant really complain too much.

[Huffer]

Try replacing the MAF.

[Tokio]

is this a manual or automatic?

[Huffer]

One other thing that I think it may be is the Auto Transmission. its been starting to shift a little funny. if its cold it will not shift out of 3rd, and it seems like when it shifts into the next gear at any time it really slams into gear and doesnt like to downshift going up hills. so maybe its a trans problem

It (the surging/hesitation problem) won't be directly related to the transmission - because the older the cars get, the more likely they are to act this way.

Not shifting from 3rd when cold is a fail-safe/rev limit mechanism.

Changing fluid and adding Lubegard ATF Protectant will help in this instance.

[NewGenSTi]

Yeah it is an automatic. but I really dont want to put any money int o a filter and fluid and additives for the simple fact that i have a 5mt in my parts car that I am swapping over and I would rather put that money towards a new clutch for it :)

Took my SAFC and leaned her out a bit. seems to be running about 90% better. not as noticable now and has much more power and smoother power at that. I changed the plugs. old ones were black so for some reason I think the ecu thinks it should be dumping fuel inside. maybe maf, but I doubt it because the readings I see on the SAFC look about right on that. But either way after leaning it out about 10% and running it the new plugs are about a nice tanish brown which to my eyes and years of riding dirtbikes and atvs looks about damn perfect. Wish I had a wideband 02 to confirm this. Oh well have a spare everything. lol so I guess I can start switching sensors over.
:roll:

this rich condition seems like it could be the problem though. I mean if its running that rich and I punch the gas it will basicly flood out and cause it to bog like it does from a dead stop...

[shazapple]

Usually its the O2 sensors which cause it to run rich. They dont always have to throw a code to be 'bad'.

[Huffer]

How in the heck are you tuning it with an S-AFC without using a wideband O2???

That's madness, no wonder your plugs are fouled up, you can't tune accurately without proper O2 monitoring.

This is a case of giving us all the information right from the beginning.

I bet if you replaced the plugs, reset the ECU, and removed the SAFC, your car would run just fine once it relearned.

[NewGenSTi]

Not new to this gig man. The SAFC is there because I also have a turbo kit built I am just saving up for some gauges for proper tuning. I had the safc let alone at stock setting and only adjusted after noticeing the rich conditions. the car has been doing this since I bought it when it was 100% stock. I believe its running rich, because the stock cats went on it and when I inspected them they were blued and multi colored showing they had seen much heat. usually when the car is rich and the unburned fuel builds up in the cats it was actually burn in the cats causing this problem. so I replaced them and it still seems sluggish. Could very well be an o2 sensor has just about seen its day. I will pull them out of my parts car and try it out again on stock settings. but as of right now the car runs great. and its going to be boosted shorty anyways so Im not too overly concerned right now. I mean the o2 sensor is going to be throwing codes left and right when it sees all that exhaust coming staight down the downpipe and out the rear end. . Picked up a few resistors and capacitors and I plan on fooling the ecu to fix that.

You do not need a wideband o2 to tune the safc either. the plugs give a very accurate reading if you know how to check them and what your looking for. and an EGT gauge will also give tons of information.

[NewGenSTi]

also I find it difficult to believe that leaning it out will foul a plug.. maybe in the sence of burning one up from heat, but my plugs were black and saturated in gas. so leaning it out afterwords is only going to help things because apparently all of the fuel wasnt igniting and was just screwing everything up

[Wiscon_Mark]

also I find it difficult to believe that leaning it out will foul a plug.. maybe in the sence of burning one up from heat, but my plugs were black and saturated in gas. so leaning it out afterwords is only going to help things because apparently all of the fuel wasnt igniting and was just screwing everything up

usually running rich fouls the plugs.

[Huffer]

Well, I don't know anyone who has successfully tuned a car using an SAFC and no wideband.

Fact is, the stock O2 gives such pitifully wide results (ie. inaccurate) because it's based on a fuel/air map that is designed on purpose for the maximum compromise between power, economy and longevity.

Tuning with a stock O2 is senseless, unless you have software that is actually altering the ECU tables, not just intercepting a signal.

[NewGenSTi]

I agree that the stock o2 is useless for tuning, but I am not using it for tuning. the stock o2 signals fluctuate back and forthfrom like .45v to 1.5 volts or somthing like that the entire time your driving. The ECU pulls signals from this and many other sensors to decide what to do. I hadent adjusted anything with the safc.. it was left at stock position. and once I realized that the car was edf running richI leaned it up a bit. Not saying this is exactly where it should be. but it seems to be pretty close. So to clear things up a little the caqr fouled the plugs stock. now I replaced them tuned slightly with the safc, and it isnt fouling the plugs anymore. and its running much better.

[Huffer]

Seems like a good workaround, now that I understand the situation.

Has this contributed to, or alleviated the hesitation issue you are having?

Do you know why the car was running rich to begin with?
Maybe your O2 sensors are on the way out - are they factory originals?

[NewGenSTi]

Think this may have alot to do with it because it is running much smoother now. they are the stock sensors, and they have about 130k on them so they have probably just about seen their day. I have a couple of spares on my parts car I will pull and try out.

No other ideas really why the car is running soo rich. I was thinking maybe the knock sensor is going or somthing so maybe its pulling timing slightly and throwing in extra fuel. could be a combination of things I guess.. Im not all that worried anymore, because I have my eye on a jdm ej20tt here that I may pick up and swap out and just sell the turbo kit I built. Not sure yet