hi iam having major problwms with my 91 305 tpi, iam running pig rich, all started on decal from the highway i noticed it was running rough so once i got back to the city it would almost die at lights and could smell gas bad
i have not drove it since then just tring to fix, at frist i found a vac leak on the pass side at the plenum, got that fixed, checked for more vac leaks and did not find any
i had a vac gauge hooked up and it was pull 17 psi at idle but map was showing only 1.5 volts, does not add up compared to the chart vader posted for me, also ecm 852 shows the blms stuck at 108 in closed loop and cell 4, i have changed o2, gaskets on drivers side thinking there was a leak, changed ecm`s and tps with a different one
fp at idle shows 38-39 and with vac line off 47(holly afpr) when shut off it holds pressure then slowy starts to drop off
now i have a sdpc vortec intake base and i have been reading that an injector can ground out on the base if touching, i know a couple of injectors are close so if ones touching will it ground out that one or will ground out them all causing them to stay open and run rich?
funny thing about this is when cold and in open loop it will idle ok, u can still tell its rich but does not stumble but when it goes into closed loop all hell breaks loose, idles like crap and shakes the car badly,
really has me stumped, i also have no a.i.r or egr and chip is programmed to see that, was running good untill that day, i have a new cap, rotor , coil, pick up coil, and wires and i know theres good spark there cause i have shocked my self atleast 3 times checking lol, hope someone can help

 

check to make sure the metal vacuum fittings in the plenum are secure. check to make sure the vacuum line to the map is getting enough vacuum.

if you have headers.. you can check for a "dead" cylinder real easy.

start the car, let it run, get a squirt bottle and shoot some water on the exhaust runners, if the water boils away fast, its fine, if it sits there or takes its time to evaporate, then you know you have a problem.

also make sure you have not burned through an spark plug wire.

i had this problem 2 times.. 1 was a damn spark wire that was touching the block, couldnt see it visually, the second time was the vacuum line to the MAP wasnt connected securely.

hope that helps

 

Have you checked fp when problem is present. When my fuel pump started to go out it would intermittently run like crap and smell very rich. Then it would run fine some of the time and fp would read fine.

 

yep fp should be fine it was replace not that long ago and i have had a fuel pressure gauge hooked up most of the time i have been trouble shooting and it never misses a beat, steady

 

for vacuum does 17hg(dont think that the right turm but i know its not pounds either) seam right for a 305 running with a lt1 cam, i know its in the green range on my gauge but i think its seams low, maybe to do with a small vac leak still? and also when i pull off the line from the purg can off the side of the tb the vac jumps up too 19 from 17 and idles a bit higher? does that seam right also? i thought if i pulled it off the vac should drop not rise? thanx for the help

 

Pulling another vac line off creates an air leak, making the engine idle higher because it's getting unmetered air. The higher engine speed creates additional vacuum.

This is why it's pretty tough to diagnose a vac leak w/ a vac gauge.

With your scantool, check the Engine Coolant Temp reading and report back. If that's reading normal versus the thermostat you have and the fan on/off temps you're configured for, you're OK there.

Then check your Throttle Position Sensor voltage at idle...should be in the 0.54VDC range.

After these, move on to the injector swappage test I posted in your other thread.

17"Hg sounds about right for your engine as you described it.

 

Like mentioned before check plug wires, also check plugs to see if they are all firing.

Also what grade gas are you using?

 

Great Avatar!.
If you're a member or former member, all the better.

 

iam using 91 octane iam going to check the plug wires alot closer this time, i know iam getting spark to them all but iam going to check when its dark to make sure none are arking out one me, thanx alot for all the help so far, i will also be away from the car for acouple of days so i will check them wires once i get home, i will post after that