Low RPM Hesitation

[Nihil]

I'm using my phone to post this, so please forgive me if this comes out crappy.

'92 TT from idle on up to about 2800RPMs the car hesitates pretty bad, it seems like its running rich too. Just cruising around town, its not that bad, but if you're in second gear around 2000ish RPMs and give it some gas, it hesitates pretty bad, and from a stop its pretty bad as well...once its at 3000+ RPMs it seems totally fine...

I havent had a chance to log yet, I'm looking for suggestions and what to log/look for, any and all help is much appreciated, thanks!

[blindmist]

Do you know the voltage of the Alternator?

[Nihil]

Alternator is new, probably has 30 miles on it? Im sure its within spec

[CoopKill]

Y pipe, or other vac leak would be my first spot to check.

[Nihil]

Thats what im thinkin, ive never pressure checked fully, i have a ghetto setup and it seems sketchy like somethings gonna blow up when i get to like 5psi ha i dont want to do more harm than good

[CoopKill]

If it is stalling out that bad it should be an obvious leak. Check all of your connections, check the plug on your maf. Give a look at all you can to be sure.

[Nihil]

Yeah, with as bad as the hesitation is id think with the little bit of pressure testing ive done, i would have found a leak, but nothin major, is there anything i could monitor through logging? I read that thread about about a bad knock sensor causing hesitation, but that threw a code, i dont have any codes, maybe CAS? I've got anew coils, plugs and wires, vac reduction, rebuilt TB...PTU tested fine

[CoopKill]

After thinking about it more, I was wrong. If you had a boost leak it would run ok at lower rpm out of boost and like crap in boost. My bad.

Try logging, especially the fuel trims, O2's, and timing. Post the logs and see if someone with more knowledge than I can make sense of it.

[blindmist]

I am just going to say this, if you havent replaced the caps on the ECU, you should start there, and then continue working from there if the problem persists.

[Nihil]

ECU is good as well, replaced it with known good one, I'll try gettin a log soon enough

[Nihil]

After thinking about it more, I was wrong. If you had a boost leak it would run ok at lower rpm out of boost and like crap in boost. My bad.

Try logging, especially the fuel trims, O2's, and timing. Post the logs and see if someone with more knowledge than I can make sense of it.

Should i log the lower RPMs where the problem is, or should i do a third gear pull? I've never really logged before, only use it for checking things like ISC count n what not

[blindmist]

Should i log the lower RPMs where the problem is, or should i do a third gear pull? I've never really logged before, only use it for checking things like ISC count n what not

Log everything. Post it up here, and we will take a look.

[Nihil]

Ok, I've got logs, but I can't upload an excel file...I changed the file extension, and the size exceeds the forum limits as well...

I was crusing the parkway, luggin' it in 5th gear for awhile, then dropped to 3rd to make a pass on a semi and I just held the gas on to see what would happen, it threw a CEL and when I pulled the code, it was O2 sensor and after looking at the logs, it looks like the front O2 has some low voltage readings, but I'm new to reading logs and knowing what to look for...

[blindmist]

While under a load, your o2 should be 0.93v-0.95v.

Use some file upload service.

[Nihil]

http://www.mediafire.com/?fhfa7ubsa6boj8i

http://www.mediafire.com/?byeiszyeh1uvbwf

http://www.mediafire.com/?p78amm7v240f047

http://www.mediafire.com/?u3pxo33e0g9wc50

There's the logs, Yeah, I'm sure it's the O2...

[blindmist]

TBH, I cant really tell what is wrong, but it looks like the o2's are fine from what I can tell.

There is no knock, so there is no timing retard.

[Nihil]

it threw an O2 code for a second, and looking at the logs, the front O2 drops down to .04v which seems low and I'd think the front and rear would be in the same ball park area together.

I don't know though, I'm no proffessional with reading logs

[Nihil]

thought I'd update this, just incase anyone ever has anything similar happen to them...

Yeah, the O2's looked normal, everything I logged was while driving, then, as I was checking some things in the driveway, I noticed the rear O2 sensor was stuck at .8- volts and not oscilating like it should...O2 was bad, I threw in two new ones and the car runs perfect...I should have caught that A LOT sooner...I feel retarded...

Makes sense now that I think about it, ran great in boost since under a load the O2's go open loop and it was stuck in open loop, which also makes sense as to why it'd backfire when you let off the gas...fuel cut wasn't happening on the rear bank

Anyway...thought I'd post up results, I hate topics with no ending ha

[Smithersvr4]

Thanks for the update...in currently having the exact same problem, gonna check out the O2's now