mark kibort

you could have some leaking injectors..... Erik has the right idea.. plugs tell a lot.
your AFM has voltages as well (pin to pin volt measurements) you can tap into that and go for a drive. i think 8volts was full throttle and idling was around 2 volts. thats if the AFM is drowning your engine. BUT, as i said, the o2 sensor should keep things really dry and clean due to the closed loop operation. if things are that rich, then something is not working there and injector duration changes via the Ljet, is not properly regulating them.. (i.e. they are still leaking)

have any hard start issues? black smoke on start up? wet looking plugs that smelll like gas, flooding? those are key signs.
how are you getting that much gas in the oil??????? HUGE question. even too rich, the gas will be pumped out the exhuast ports and plugs will be wet. going by the rings, if compression is good, is unlikely. if so, then the gas is filling the cylinders after turn off due to the leaky injectors ... get a fuel pressure guage on the system and see the fuel pressure decay time.... should be about 30mins.. if the guage falls instantly, then the fuel is going somewhere......... fuel pump check valve broke, (common) or injectors leaking........

o2 sensor should make mixture go full lean to full rick about 5-10 times every 10 seconds. if it doesnt , then thats a problem.
there are meters that check that , and are easy to install..... 3 wires.... one on o2 sensor and power and ground..... do this first!!!

there is also an injector duration function that taps into an injector, you can see injector duration that way

also, you can see , with the mixture AFM meter, to see the hunting between lean and rich (averaging out to 14.5:1), and then when WOT switch is activated it goes closed loop, indicating about 12:1. check that too!!!!

pulling the o2 sensor should make it go OPEN loop and go right to about 14:1 and stay there. also the idle should smooth out and raise up 100rpm or so.

Bruno DeSousa

green wire is brand new.. i replaced it about a week ago.. hoping it would solve the mystery... just did a fuel press test.. flawless.. 32PSI at idle.. when i crack the throttle it drops to the 27psi range.. i remove a FPR vacuum hose and it goes up to about 35PSI or so... leak down test also went fine..

AFM has been tested by the guy in costa mesa arizona Kevin.. he said it was fine.. i also have another AFM that i swapped just to see if there was a difference.. no change.. conclusion.. NOT an AFM problem.. i have done all the ohms tests at the L-Jet plug.. all check out in range..

just tested the temp sensor again during the fuel press test.. it read in the 320 range . motor was warmed up.. also checked the temp sensor ohm reading at the Ljet plug.. same 320 reading.. conclusion.. NOT a temp sensor issue...

just swapped the ignition box with one from my parts car... no change.. actually the car ran worse.. haha... conclusion.. NOT a spark box issue..

im going to tackle the distributor/cap/rotor/wires tomorrow..

i have checked the plugs... all 8 are black(rich) condition... with the good fuel pressure test and knowing my injectors have been cleaned/flowed.. my guess is a problem with the ignition...

also disconnected the O2 while the car was running and it started to run worse... i am to assume the O2 sensor is working properly... i have also swapped L-Jet brains with a good unit... no change.. conclusion... original L-Jet brain is working fine..

i have removed the CSV from its "port" to see if it was leaky while the car was warm... it was NOT leaky at all... also removed the hose from the AUX air valve to make sure it was closing when the motor warmed up.. and yes.. it closes just fine...
thanks again for all the responses !!

Bruno DeSousa

hmm after i had the injectors cleaned/flowed.. i reinstalled them and checked the connectors with a noid light, they all had pulses.. BUT im not sure what a "Good" or "Bad" pulse looks like... from what i remember the pulses looked kinda dim and very rapid..almost continuos... ill have to recheck them cause logically that doesnt seem to be correct..can i check the pulse with a stethiscope? what should i try to listen for?.

umm what would cause a bad injector pulse?.. you mentioned a failed O2 sensor and also the Ljet brain... is that all? i have yet to replace the O2 sensor . so it could be bad.? i have swapped Ljet brains and no change in performance.. the AFM has been tested by kevin at injectorlabs.. ill have to check the spark plugs again just to make sure the injectors are NOT leaking when shut off. Fuel pressure leak down went fine.

oh and i currently know that the alternator is not working.. would that have any possible chance to be the cause? i doubt it but im thinking out of the box..

also how about a bad fuel injection relay??

do these cars have a crank sensors??

thanks again!

GlenL

To solve this you need to listen to what people are suggesting and strongly consider that something you think is working and "can't be it" actually is it or is part of "it" as you may have multiple problems.

Dave928S

Yes ... correct voltage is vital for everything electrical, just as good earths are also essential. It's pointless checking injectors, sensors, etc, for correct operation if you have low voltage.

This is good advice ... don't assume anything.

Bruno DeSousa

yes dave i was just thinking the same thing.. if there isnt proper voltage the readings for the o2 are going to be off.. since the o2 reads voltage to help lean and richen the mixture.. makes perfect sense why my injector pulse light(noid) seemed to be giving off a low dim very rapid flash..(low voltage reading from O2 => rich mixture signal to the L-Jet brain... hmm

the alternator is being rebuilt as we speak.. it is the SEV france unit. not the bosch.

i am not assuming much of anything.. i test and confirm to diagnose each part.. just havent tested the O2 sensor yet.. with the alternator out of the car i am kind of stuck now til i get it back in and working. i could remove the O2 and do a bench test to see the voltage readings.

thanks again guys!! once i get the car running correctly i owe you all a drink! lol

mark kibort

you dont need an alternator for it to run right. also , the o2 sensor is probably not the issue , but it could be....... did you do the fuel pressure rate of pressure decline test???? this would arrest my suspicion that the injectors might be leaking? but i would think that might only be one or two . tell tail sign, would be the rapid pressure decay after the car is turned off.... should be 30mins, but if you watch the guage drop after you shut it down, that might be the issue. everything is working well, but if the injectors are leaking, all bets are off.
you are VERY rich if you can accumulate 2 quarts of gas in the oil!!!!!! something is very wrong. this is not an o2 sensor issue. AND, when you unplug it, it shouldnt run worse. it should actually smooth out and run slightly higher RPM , like maybe 100rpm higher. the fact that it runs rough with o2 sensor disconnected might be due to a leaky injector that the closed loop system cant fight when disconnected.

there is no crank sensor. its a very simple set up. these things should run like a top and very clean. could your cold start injector be stuck open ?
your WOT switch and idle switch working? WOT switch stuck open would enrich mixture 15% or more and that could cause richness issues at part throttle , as well as make the system go open loop when you dont want it too.

Bruno DeSousa

fuel pressure stayed up when i shut the car down.. and stayed for 30 min after.. i will do it again to confirm.. ive tested the CSV and it does not leak when the car is running or off..

i just tested the WOT switch at the prongs ohms were 2.. i didnt test the reading at the Ljet plug yet.. with the car running at idle i use my finger to snap the WOT level and the car immediately boggs down.. perhaps too much fuel.. does this tell me it is working correctly? i would still like to test for continuity at the Ljet harness plug.

perhaps the O2 is not fully malfunctioning.. maybe its working 50%? .. i still believe that the alternator not working might have something to do with the issue..ill find out when i re-install the rebuilt unit this week.

thanks agian!

mark kibort

the WOT switch doesnt do much if activated at idle, so if it boggs down, that is a sign of too much fuel. if its doing something , its working. no ohms there, ist just a switch. on off. could be o2, but it should run fine without it.
idle switch doesnt do anything, other than cut off fuel on off throttle until rpm gets near idle, usually, i disconnect that entirely for the race car. but WOT switch is essential, and enriches under 75% throttle or more. sounds like injectors are not leaking down, so i dont know how you end up with so much unburned fuel in the engine oil.... that is the mystery!

dr bob

Raw gas smell at the exhaust is most common to cars with weak ignition. A good spark will fire a rich mixture, and the tailpipe smell isn't particularly a problem especially if the CAT is functioning. Meanwhile, a lean mixture and/or weak ignition won't fire well, so the unburned fuel passes through to the tailpipe.

The oxygen sensor on the car is a narrow band device, with a target ~~0.4 volts with stoich combustion. It effectively measures CO in the exhaust, proportion changes with more or less fuel, but the reading is only good when there's combustion. So a weak spark, weak ignition, weak combustion won't significantly change the reading from the sensor. So follow others' advice and look at the plugs immedialtely after running the engine with a little load, then shutting it off directly. Combustion is leaner is lighter tan, richer is darker brown, miss has dark soot on the plug tips.

Bruno DeSousa

correct, the WOT is at 0 ohms when not in use BUT when you click the lever the continuity is there.. which was about 2-3 ohms.. to me sounds good.

keep in mind the gas in the oil didnt happen overnight.. the car has been running like this for a while.. the PO had changed the oil perhaps 2 months ago.. i just changed it last week.. so the extra fluid in the crankcase(gas) has been accumulated over the last couple months.. during his tests and now my testing..

definitely smells like raw gas out the tailpipe.. my eyes get irritated its so bad.. and im outside not in a garage!!.. i need to swap distributors from my parts car to see if it makes a difference..

the plugs after i run the car are BLACK with soot...all 8 plugs!.. and there is a slight hesitation and misfire... definitely sounds like an ignition problem.. but i will test the O2 as well just to make sure everything is working properly

thanks guys!

Bruno DeSousa

ok guys. quick update on my running rich issue.. i finally got a bosch reman alternator off my parts car and installed it onto my 81 928 Ljet usa car.. i am finally getting a charge.. the gauge reads a little over 12 at idle and goes up a little when i throttle the pedal. anyways it didnt make much of a difference on the running rich issue. i let the car run at idle til it warms up and it is still wayyy too rich!.. i disconnect the O2 and car runs worse.. the only way i can keep the car running at idle when it warms up is to have the hose from the AUX air valve off which allows the motor to keep sucking in air with the aux air valve closed(warm motor) to compensate for the large amount of fuel in the combustion chambers... i do not know if the PO had messed with the Idle adjustment screw BUT im ready to check everything at this point!!

1. what is the idle adjust screw suppose to be set at?
2. how do i adjust?
3. would a wide open idle adjust screw be the cause of my running rich mystery?

thanks again guys... im almost done!! if the idle screw is not my problem.. the only things left to check are distributor and cap / rotor /o2 sensor(but im sure it is working properly... and possible coil / wires but i have already swapped these from a parts car and it made no difference in performance..

mark kibort

the car should be running at 13.5 volts when the alternator is working. 12 volts without an alternator (12.5 nominal when the car is off)''
it should run better with o2 sensor disconnected. thats a clue that something is not working right

check temp II sensor

worst case, AFM might be the problem. doubt the little air screw on the AFM could be a culpret... you can check it though. see how many turns its back out, and tell us... its just a bypass air hole in the AFM. not significant. also see if you can pull out the AFM a little to get some false air flow and lean out the idle mixture. if thats the issue, it has to be the Temp II or the AFM itself but that is doubtful as they usually never go out of adjustment. (or someone has tweeked it by taking it apart)