byatescmco

i don't know if anyone in here can/will help but its worth a shot. I have a 95 m6, 383 bottom, advanced induction 200cc h/c, street strip a/i intake, holley 58mm, trick flow 36# injectors, running 12.2:1 cr, pacesetter long tubes, ngk 8s gapped at .040, just ran the valves (making sure everything is moving right and they were not too tight/loose), msd opti, msd coil, original icm, o2's are eliminated, maf is suppose to be (i can uplug it and the engine dies). need any more info....let me know.
The car was professionally tuned on a dynojet. it is n/a pulled 425hp 406ftlb to the wheels. it ran 12.5 @ 110 (seems weak) @ bristol, tn dragway with drag radials cutting a 1.8 60'. For the longest time the car has had trouble idling but i ended up adjusting the tb all the way open and setting my tps to .67 and it seems to be doing good. My concern now is, the engine backfires out of the intake from idle and snapping the throttle open. it also pops on lets say a 5th gear 2100 to 2300 + rpm pull every now and then. i'm afraid it isn't good on the engine and its going to eventually screw something up. i've talked to my tuner about it and he doesn't seem very concerned about it. I don't know it just doesn't add up with the whole hp/ tq #s and the et it ran and it doesn't seem very efficient. Makes me wonder if something isn't right. I have CATS tuner and i've been using a trial version of datamaster. i do not have a wideband. I'm just hoping maybe someone can shed a little light on the situation. thanks for any help at all.

byatescmco

i also had my tuner send me a tune for %tps for pe to be a little sooner to try and eliminate a lean condition but it didnt seem to help at all.

byatescmco

bump

byatescmco

bump again?.........

flame

iTrader: (13)

Check fuel pressure and see if it drops underload. Backfiring in the intake is usually a sign of it being lean.

byatescmco

will check fuel pressure tomorrow.....but the plugs are awfully dark for it to be a lean condition.

edcmat-l1

iTrader: (10)

If you have scan software, post a run log. It sounds like a lean tip in issue.

Post your tune too, if you can.

byatescmco

Checked fuel pressure today....engine idling pressure holds @ 45 - 50 psi. While driving the car (partial throttle) fuel pressure was observed being closer to 40 psi. @ WOT, pressure jumped to approximately 47-48 psi. I also pulled the fuel rail, applied pressure with the fuel prime wire near the pcm to check for leaky injectors. no drips were seen. I did not check the spray pattern of the injectors because i didn't have anyone to crank the engine but that will be next. Any other suggestions?

byatescmco

bump...

byatescmco

bump......

mvvette97

iTrader: (18)

another bump for ya. I have the same problem with my 94 LT1. Mine is a lean problem after it has went in to closed loop. I even replaced the O2s and that didn't even help. I finally tuned mine open loop and now it's fine but I would like to find the problem. It seems mine started doing this after the LT headers.

byatescmco

mine is open loop all the time. o2s deleted. givin me a fit

edcmat-l1

iTrader: (10)

Have either of you tuned your VE, or are you just tuning your MAF?

byatescmco

i know my tune still utilizes maf

pro94lt

In tuner cat look at constant tables, high coolant temp min enrich afr. I had a issue with my car randomly going lean at idle so I lowered the afr .2 and it resolved a problem I never thought could be fixed. However I've only had tunercat for about a month and am no pro at it but it fixed my problem. And my car also poped sometimes too.

koolaid_kid

iTrader: (21)

You need to get a copy of DataMaster (it is free for the first 20 uses) and an ALDL cable (it ain't free, but it is worth the cost). The 94 has a different connector from the 95. Make a couple of runs and post the data files.

JDMC5

iTrader: (3)

yeah datamaster is free for the first few times you use it. Also, the cable is only 60 bucks. You need either the 12 pin or the 16 pin connector (you'll have to look and count the number of pins).

cable

http://aldlcables.com/

software

http://www.ttspowersystems.com/DataM...ownloads2.html

BTW, there is other sofware out there that will work and is completely free.

Ed Wright

iTrader: (1)

Aftermarket Optispark?

ptrgsny

i had a similar promblem with my car with almost the same set up but i had a 350 cu in lt1. i had my best friend come and look at the car and the first thing he said after he heard the mods and the looked at the spark plugs was " why haven't you have non resistor wires and plugs pn this? he is like near 70 years old and listen to his advise as i am still learning, but i bought a wires set from Granatelli ( pricey, maybe 130-150 but WORTH IT!. and some NON RESISTOR RACING PLUGS be better. you'll get all the spark you need to prevent the fouling of your plugs. i went with autolite ar472's. give this a shot and i will bet you will be happy with the performance.

Ed Wright

iTrader: (1)

Only time the LT1 PCM uses the VE tables is if in speed density mode. Otherwise it uses the MAF.