thunderstruck507

iTrader: (18)

Ok, so the engine is a 98. Odd thing is occasionally it acts like its in limp mode or something...like it feels gutless, upshifts softly and as soon as possible, and won't downshift. This has happened 4 times now. It lasts for a few minutes then it just goes away.

I don't get any codes and can't see anything wrong while monitoring engine stats with a snap on 2500 diagnostic tool.

Also right after it goes away the engine generally picks up like crazy. Not like "oh hey i installed this thing and I can kinda feel it pull harder", more like "HOLY CRAP WTF WAS THAT?" Shifts are extended to the full 6200 I asked for in the tune instead of the "normal" 5800. Then shortly after goes back to normal (everything seems normal, and pulls "good" but nowhere near as intense, shifts earlier)

I can only get 91 octane so that's what I've been running. A datalog shows me getting 24 degrees advance at WOT, but the scanner says 29 which I find odd.

Yesterday I put 5 gallons of 94 octane in the car, ran around with the exhaust cutouts open (felt slower than normal by a large margin with them off). Put them back on and drove to a movie. Came out and it felt like crap...tried restarting and still the same. Then all of a sudden on one try at WOT it went back to normal but again much much more intense.

I'm at my wits end. Is it possible to have a faulty knock sensor with no code or it showing in the scanner its pulling timing? Most timing I've seen it pull is 2 degree.

LS1MCSS

iTrader: (18)

I have heard that the 98 knock sensors would sometimes pull timing when there was really no reason. Some people have updated theirs to later models. If you decide you want to try that, pm me. I have a set of later model sensors that you can have, for the cost of shipping.

thunderstruck507

iTrader: (18)

I've heard that as well which is why that's where my finger is pointing.

I was also thinking maybe for some reason the converter might be trying to stay locked, but that wouldn't explain the way the car just comes alive sometimes even compared to when I know the converter is working properly.

LS1MCSS

iTrader: (18)

If the convertor was staying locked, the motor would die when the car stopped.

thunderstruck507

iTrader: (18)

I just can't think of anything else to check.

It's so random that it's hard to reproduce. Like I said its happened less than half a dozen times since October.

I'm just afraid it might be a symptom of a serious issue and also I want the extra power that seems to randomly show up. I'm willing to bet that's the power I'm missing from my low number dyno pulls.

I am willing to bet when this happens the car picks up in the area of 20hp or more. It's enough to shock me even now that I'm used to how the car feels at WOT.

thunderstruck507

iTrader: (18)

does anyone have any ideas at all?

could it be the solenoids in the transmission just not allowing downshifts? or maybe trash in the tranny oil temp blocking a passage leading to low pressures? wouldn't explain the appearance of power but might explain the sudden lack of *****/downshifting/sloppy shifting

poolshark021

iTrader: (8)

Do you still have seperate low and high octane tables in your tune? If so try and copy the values from the high octane table into the low one. That way there is really only 1 base timing table. See if that changes anything.

LS1MCSS: I am interested in your knock sensors if thunderstruck doesn't want them. I have a 98 that has been hampered by a false knock problem for a while now.

thunderstruck507

iTrader: (18)

what else would I need to change to update the sensors?

I might be putting an ls6 intake on soon anyway

DONAIMIAN

iTrader: (18)

Do you have any way to monitor the 02 sensors?

thunderstruck507

iTrader: (18)

my scanner does yes

they are both working fine from what I can tell

thunderstruck507

iTrader: (18)

might be unrelated but my fuel mileage seems to have dropped off a good bit in town...might be from extra romping trying to duplicate my problem but just thinking about it I'm thinking I've still been burning more than I should be

good news is I'm getting a big tax refund so as soon as I get a job and feel safe spending some I can get a tune