86TpiTransAm

I found someone nice enough to lend me their auto xray to get some info on how my car is running. I have some info from a 30 second scan done while driving through town and also some info from a scan done while idling in drive. If someone could analyze this info and let me know what you think I'd appreciate it.

Run through town:

@1550 rpms - Idle Air 51 steps, EGR 0.0%, TPS .74v, INT 110, O2 888mv, knock counts 16, BLM 105, MAF 17gr/sec, closed loop, running rich

@3125(same run) - Idle Air 25 steps, EGR 99.4%, TPS 1.6v, INT 109, O2 924mv, knock counts 16, BLM 118, MAF 81gr/sec, closed loop, running rich

At idle in park (925 rpms)

IAC 59 steps, EGR 0.0%, TPS .70v, INT 123, O2 .941mv, knock counts 13, BLM 118, MAF 14gm/sec, closed loop, running rich

All of the above was with the fuel pressure set at 43psi with 24# injectors and the 305 computer chip (yes, I know that's why I'm running rich)

I lowered the fuel pressure to 36psi and did anothr scan at idle in park... this time it was idling at 850rpms and everything was about the same except the O2 was down to 880mv .. and still running rich.

At one point I dropped the fuel pressure from 43psi to 35psi and did an immediate scan and it showed INT at 136 and that I was running lean but when I bumped it back to 36psi (just 1 psi) it dropped the INT back to about 109 and back to rich again. So I'm assuming that the sudden drop from 43psi to 35psi confused the computer for a moment and made the INT go up so high causing a momentary lean condition.... sound about right??

I also noticed that with the car off and ignition on my TPS was at .68v and it should have been at .54v +/-.075v ... which gives a range of about .47v - .61v ... so my TPS is just a little high.



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1986 Trans AM
355 TPI
4 Wheel Disc Brakes
9 bolt Borg Warner Rear (2.77's....oh joy) :P
6" rods, approx. 9.7:1 Compression, Stock TPI (soon to be ported), 24#/hr LTI injectors (cleaned and flowmatched by Cruizin Performance), Hedman Shorty Headers, 3" exhaust with 80 series flowmaster, SBC 993 heads completely redone and modified for 1.6 RR, 1.52 RR (for now), Comp Cams XE262-14 TPI Cam, Holley AFPR, TPIS airfoil, MSD wires, MSD 6-AL Ignition, Hypertech 53,000 volt coil.

Track times to come.

Xenodrgn

I'll tell you right now (and I'm sure you noticed)... knock counts = very bad... get that fixed.

86TpiTransAm

Yes, I forgot to mention that. It's because I have a 305 knock sensor in the 355 engine. I don't think it's an actual knock problem but rather a false knock problem caused by the wrong sensor as well as having headers...which is only hurting my performance. It will be fixed in the future.



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1986 Trans AM
355 TPI
4 Wheel Disc Brakes
9 bolt Borg Warner Rear (2.77's....oh joy) :P
6" rods, approx. 9.7:1 Compression, Stock TPI (soon to be ported), 24#/hr LTI injectors (cleaned and flowmatched by Cruizin Performance), Hedman Shorty Headers, 3" exhaust with 80 series flowmaster, SBC 993 heads completely redone and modified for 1.6 RR, 1.52 RR (for now), Comp Cams XE262-14 TPI Cam, Holley AFPR, TPIS airfoil, MSD wires, MSD 6-AL Ignition, Hypertech 53,000 volt coil.

Track times to come.

ViciousZ

iTrader: (1)

About time you got a scanner!
Have you tried wrapping a few layers of teflon around the threads on the sensor? I read a thread a few weeks ago here that said it desensitized the knock sensor a little. BTW, if you're looking for a 350 knock sensor I just happen to have a spare one (brand spankin new, never installed) lying around somewhere, I'd sell it for cheap. Actually I'm not sure if they're the same for an 86 and a 91.
About your scanner data: what can I say? You're running rich. Is it rich all the time? I mean, does it fluctuate between rich and lean, or just stay rich constantly? You're computer ought to be compensating for your rich condition, 305 chip or no. It ought to shorten your injector pulses. The BLM is long term fuel trim, and it's gonna be off, especially with that chip and injectors. But the INT is short term, and if it's always that low then it looks like your computer is not compensating. You ought to cruise around with the fuel pressure lowered and let the computer relearn, then see where it's at.

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91 Z28
Come see The Vicious...

Rob P

iTrader: (1)

Remember, a misadjusted minimum air rate will cause a misadjusted TPS. As you turn the set screw, you open the throttle blades which in turn move the TPS. Just food for thought. I think you need to get the correct knock sensor first, I could be pulling timing out. My ZZ4 with 24lb injectors and a stock L98 chip reprogrammed for #24lb injectors runs rich. Your 305 chip must really be confused!

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Rob P
89RSconvtZZ4TPI Edelbrock Intake
SLP Dual Cold Air Intake 1 5/8" Headers Semi-Siamesed Runners, IROC
suspension, alum shaft. Numerous mods.
92Z28convt5spd (stock)
71Impala convt 402BB
BETTER DRIVING THRU SUPERIOR HORSEPOWER!

86TpiTransAm

Well actually I don't have a scanner yet. This guy just rode with me for about an hour today while I took some readings. I really don't even know the guy, just met him for the first time today. We talked on another message board and then got together today. I really hate to bug him again. I know I need a new knock sensor... that's for sure. Actually thanks for the offer on that one you have but they're not that expensive... I have no money or else I'd have bought the correct one. I didn't want to bother the guy too much today so we only scanned one ride down the road and a couple rides at idle in drive. It was running rich throughout the entire rpm range. I really wish I had my own scanner so I could scan more extensively. This sucks. As far as the computer compensating... the closest I saw the INT today was 123 and that was while idling in gear at 925rpms. Guess when I get another job I should hit the junk yards and see if I can find a stock 350 chip... better than the 305 until I can get money for a different chip.

Grim Reaper

Your problem is your running 24# injectors on a 305 eprom. Yes, the ECM will correct (based on the O2 sensor) in closed loop, but when you boot it, you rely on the tables and you are running too rich.

Altering fuel pressure has it's greatest effects at High Load (WOT) and least effect at low load (minimal TPS or highway cruising), so it is not going to work. I've been there, and you are finding exactly what I found. The ONLY way to correct, is by altering the Injector Constant in the eprom to let the ECM know you are running larger injectors and to shorten the pulse width.

Personally, I think 46-48 psi gives the best atomization and then adjust for this in the eprom to get the BLM/INTs 128/128.

burnoutrpm

i agree with vicios z do that and you might be ok or buy her knock sensor....cheap that'll get rid of the false detiontion..the headers dont screw with the ecm that much iknow because i had them on mine when i had a computer...but then i also started running VERY rich...but, otherwise the car ran fine i think the chip isnt helping any but, maybe the computer can partially re-learn how to operate the 350?

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89 firebird formula


360 10:1compression (350 .060 over)/fully balnced and blueprinted
comp cams xe262 cam
performer rpm intake/port matched to heads
#1405edlebrock 600
sportsman 2 heads 64cc 2.02/1.60 valves 200cc intake runner/cnc pocket ported
msd 6al/msd8.5 super condutor wires
h.e.i. proform 50,000 volt vac. advance ditributor
700r-4 with 3.08 first gear and 3.73 7 5/8 rear end.
b trans shift kit(will kill shifts...suck dong!!)
shorty heddman hedders with custom 3" pipe y-pipe back(no damn cat!) with 40 series flowmaster!
griffin daul1" core rad.cutom fabrication to fit(but no cutting )


future mods: 406 roller REALLY REALLY REALLY RADICAL!!!!!.with lots of NOS

burnoutrpm

yeah his computer is going.....huuhhhhhhhhh????



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89 firebird formula


360 10:1compression (350 .060 over)/fully balnced and blueprinted
comp cams xe262 cam
performer rpm intake/port matched to heads
#1405edlebrock 600
sportsman 2 heads 64cc 2.02/1.60 valves 200cc intake runner/cnc pocket ported
msd 6al/msd8.5 super condutor wires
h.e.i. proform 50,000 volt vac. advance ditributor
700r-4 with 3.08 first gear and 3.73 7 5/8 rear end.
b trans shift kit(will kill shifts...suck dong!!)
shorty heddman hedders with custom 3" pipe y-pipe back(no damn cat!) with 40 series flowmaster!
griffin daul1" core rad.cutom fabrication to fit(but no cutting )


future mods: 406 roller REALLY REALLY REALLY RADICAL!!!!!.with lots of NOS

86TpiTransAm

Ken, you should stick to what you know.... which definitely isn't computers and fuel injection. You work on your Caaaaarbeurator and leave the answering up to the people who KNOW what they're doing.

Glen, I'm very aware that I need a new computer chip. Problem is... no $$$$. I guess I'll just sit and suffer with the car running rich. It sucks but I can't do anything about it. At least I'm still getting 20mpg on the highway which is alot better than I was getting with the 305 before I took it out.



------------------
1986 Trans AM
355 TPI
4 Wheel Disc Brakes
9 bolt Borg Warner Rear (2.77's....oh joy) :P
6" rods, approx. 9.7:1 Compression, Stock TPI (soon to be ported), 24#/hr LTI injectors (cleaned and flowmatched by Cruizin Performance), Hedman Shorty Headers, 3" exhaust with 80 series flowmaster, SBC 993 heads completely redone and modified for 1.6 RR, 1.52 RR (for now), Comp Cams XE262-14 TPI Cam, Holley AFPR, TPIS airfoil, MSD wires, MSD 6-AL Ignition, Hypertech 53,000 volt coil.

Track times to come.

Remondi2

Don't trust your auto x-ray when monitoring an engine under load. My auto x-ray was showing up to 20` of knock retard on my '87 5.7 tpi iroc at WOT. I couldn't make it go away, differnet fuel and timming settings, so I took it to the dealer. They put a real scanner on it and couldn't get it to retard even a single degree even at WOT. In the begining of the users manual it says if your idle goes up when you monitor, that you shouldn't monitor while driveing your car around. I guess it puts you into a field service mode or something. I am not sure if it is relavent to your car or not but it is something that every auto x-ray user should know. Peace