billyhoss

iTrader: (1)

hi i have a 91 z with a 305 tpi auto and it started running really rich on me, iam thinking it maybe my o2 but i just wanted to see if anyone knew what the voltage for the map should be at idle in park, i have hooked up ecm 852 and it shows 1.5 at idle, does that sound right?or does it sound like a gasket leak, i have checked the gaskets and vacuum lines and they seam fine, thanx for the help

Vader

How does that compare to your idle vacuum reading:

billyhoss

iTrader: (1)

thanx for the chart vader, looks like i will have to find a vac gauge and fine out what its pulling, or is there a place in ecm 852 that will some me that, i do not remember seeing vac there tough

billyhoss

iTrader: (1)

vader
i was looking more into the results i got with ecm 852 and i noticed that the o2 vm were over 800 at idle and when i rev up to 2500 they drop to 200-400 and my cell is at 4 and blm at 108 at idle, i was wondering if a leak at the header collector just below the o2 sensor would give a false lean condition(800 i think is lean) and tell the ecm to max out the fuel hense getting 108 blm, i have listened and iam sure theres a leak coming from that collector (can hear a thud thud iam sure)but it has been rain way to much to get under it and check it out, wish i had a garage, just wondering if this makes any sense into why iam running rich?

billyhoss

iTrader: (1)

vader got a vac tester today and it turned out to be 16-17 but the map reads 1.5 volts or so? and its still running pig rich, should i try to replace that map? think its bad?

kevinc

If you're pulling a 108 BLM, the ECM thinks you're pig rich and it's pulled out all the fueling it can. (450mV is stoich, anything greater than that is rich, lower than that is lean)

What injectors are you running?

What is your fuel pressure at idle with the fuel pressure regulator vacuum feed disconnected and capped?

billyhoss

iTrader: (1)

according to ecm 852 my o2 is seeing anywhere from 600mv up too 800mv most of the time, once in a while it will drop to high 400`s for a split second
iam running lt1 injectors and the chip is programmed to that #
fp at idle is 38-39 and at 47 capped, using a holly afpr, no fuel coming out of the vac line when off either so its not leaking past there

kevinc

Possibly a leaking injector or two. Alternate is a contaminated O2 sensor (coolant silicon will poison the sensor and cause it to read rich).

Troubleshoot the injectors by leaving the fuel press gauge in place, shut off the engine, and see if pressure holds for a while.

If it goes to zero in a few seconds, pinch off the fuel return hose and repeat. I use an piece of old radiator hose and ViseGrips for this, the old rad hose keeps the Grips from damaging the fuel hose. If it still goes to zero, you got injector probs.

If this test passes, pull the O2 sensor and inspect for white grainy deposits. They'll be small and crystalline depending on what antifreeze you run, or the sensor may just be discolored white. White O2 sensor = bad.

If your sensor is white, pressure test the cooling system. Free loaner tester available at AutoZone.

billyhoss

iTrader: (1)

injectors seam fine, when i shut off it will hold pressure for 5 min then slowly start to bleed off,
just changed o2 sensor thinking the same thing, old one looked fine so i installed my new 3 wire heated one anyways and same, also changed gaskets thinking maybe a leak
iam going to recheck wires and make sure there all firing when they should be, thinking maybe if one is bad then it could be dumping the raw fuel in the header and o2 is picking that up and saying that its rich,

kevinc

If your O2 sensor is in one header primary, it's only sniffing output from those four cylinders. Try moving the injectors...just swap all 8 bank to bank. If the O2 sensor starts behaving normally and your BLMs go back toward 128, you know it was one of the four injectors previously servicing that bank.

billyhoss

iTrader: (1)

ok i figured out the major problem, i had a broken proform roller rocker in #7 intake, so now i got that fixed but it showing that its running lean now lol, i hook the vac gauge up again and it showed 18 hg but the volts to the map showed 1.25 which would mean about 21.75hg, is my map messed up and causing it to think it have more vac then what it does causing it to run lean now, it was fine before this all happened, lean rich wise that is, also i got a new heated o2 sensor in it but just have it hooked up for the one wire to read to the ecm, i never got a chance to hook up the ground and power for it yet, but i do not think that would cause it to do this, thanx

kevinc

Get your power and ground(s) hooked up before wasting more time troubleshooting...heated sensors are designed to be heated.

We're seeing cases on LS1s where even heated O2 sensors not receiving enough exhaust heat give improper readings (cycle slowly on switching rich/lean) and die prematurely.

billyhoss

iTrader: (1)

lol yep i will get that done, its just that i was so happy to find out what was wrong with it to begin with that i was tired of working on it for the day thanx for the help