Isphius

Ok, my car(91 305 tpi) ran like **** when i got it, took it to insp for the hell of it. I only failed HCs by a few points. I replaced the injectors, plugs wires cap rotor, re connected the coolant temp sensors(none of the 3 were plugged in), redid the fan wiring, hooked the knock sensor back up, and a few other things. But i took it this time and failed horribly, but the car runs much better now and no check engine lights. Its getting like 12-14 mpg which is pretty low. Im guessing its running rich, but i have no idea why. My own knowledge is telling me i have a huge vac leak, or my timing is way off and i just cant tell. Im replacing the distributor because the cap hold down is stripped, held by a home depot nut and bolt for now. So that may be a cause too. After that im going to retime it and take it again. But any other input will help!

Here are the numbers. My wisdom tells me nox are a bad cat or something, HCs are from running rich, also explain my poor mileage, and CO is bad combustion for some reason...thats about all i know about emissions. Thats why i need some help lol

most recent/last check/what it should be

NOX - 3121-2265-879
HCs - 187-240-117
CO - .89-2.13-0.65
CO2 - 12.7-11.3
O2 - 2.0 - 2.2

jv9999

iTrader: (1)

Did you check for codes? High NoX is usually related to the EGR valve. Is it hooked up and working? The low MPG and high HCs do point to a rich mixture. You really need a scanner so you can see what it's doing. Without it you're just guessing. Sticking fuel injectors and a bad O2 sensor are two possibilies.

Russ-So Cal

I don't know if you are familiar with these cars or not, but to do the timing you need to unplug an electrical connection at the firewall on the right side, and set timing at 6 degrees btdc. If you don't unplug the connection first, the ecm will try to make adjustments to the timing while you are trying to set it. Don't forget to hook up the connection after you are finished. Check you fuel rail pressure. There is a fitting on the fuel rail in the crossover in back of the plenum with a schrader valve in it. Get a mechanical oil pressure gauge and a hose with a valve depressor to check your pressure with. You should have somewhere around 38-42 lbs, (I don't remember exactly). If someone has set the pressure up, that could cause rich running.

Isphius

Yes ive already set the timing once. The distributor needs to be replaced though so im not changing any parts till i do that. Misfires/bad timing (although it feels fine but you never know) could cause high HCs and CO. Im a bit short on cash but when i get paid ill get something to test the fuel pressure. is there a way to test the injectors without pulling them out? I already ohmed them and there all good. I just replaced them in the summer with used ones that were on a good running 305. And my EGR is in place but i dont know if its working. I got an EGR code before. How can i test that? any suggestions for anything else?

dj_justice

iTrader: (1)

As for testing the injectors you can do an injector balance test. Basically run the car as if you were going to change the timing by disabling the computer with the EST port, then while idling one at a time unplug the injectors and note the rpm drop. The injector(s) that cause the least rpm drop are doing the least "work" and are probably bad.

It looks to me that you may be having a lean misfire issue since your co2 levels are kinda low and nox and hc's are high. High nox is caused by high temps/pressure mainly above 2500 degrees farenheit lean conditions can cause cylinder heat and pressure to rise dramaticaly as the fuel actually absorbs some of the combustion heat. High HC's are from improper combustion either too lean or too rich.

Chevhead89

unpluggin the injectors one at time.. i dont think it would work right because when you unplugg number 1 its gonna have a greater effect on the engine then if you unplug number 5 just do to the fireing orderin.
might wanna check your plugs to see how there burnin. and the wires for any dry rottin or burns.

Russ-So Cal

Firing order will make no difference in how hard a particular injector is working. The injectors in our cars a batch fired not sequential, so it fires right bank-left bank-right bank or vice versa depending on when you start counting injector pulses. The test mentioned above may work for testing injector balance, but if the problem is a plugged up egr or an egr valve not working (all the ecm reads is the signal it sends to the egr sol. coil) you may not set a code.

IrocZ_85

iTrader: (1)

My 85 IROC LB9 failed worse than that. A new O2 and cat and I passed with lower numbers than our 91 Volvo!

rgarcia63

I've heard the ECM looks for a temperature drop that tells NOX is being reduced, but I don't quite see how if the only temp sensor it reads is on the intake.

Isphius

So i updated the first post with my new numbers. My nox went way up, but im lower, almost passing, on the other 2. I replaced the distributor, with new ignition module. I checked the fuel injector balance....they all mess with the idle evenly. They all still ohm within a few 10ths of each other. I fixed a huge vac leak which i thought would help, guess not. I still have not found a fuel pressure meter to borrow. Also, the co2 should be around 16 if my mixture is good...but its 12. could indicate rich or lean. the high CO And HCs also indicate overly rich A/F. And furher, all my numbers indicate i am running leaner than last test(fixed vac leak?) but not lean enough... Could the base timing too far advaned or retarted be doing this? thats the only thing i havent set properly, i just eyed it up at TDC then advanced it a tiny bit from there. Need to get a timing light but what else could cause rich mixture pending a fuel pressure test? is there any sort of data logger i can use with the ECU to read whats its doing while driving? is there a way to test the map sensor? thanks, Let me know!

305sbc

iTrader: (3)

That's not the way you set the timing, even if you could blink your eyes that fast.
Have you tried a new O2 sensor yet? or checking to see if the fuel pressure regulator is leaking fuel into the plenum via the vacuum reference line?

Isphius

I mean i set the motor to TDC, then i pointed the rotor at cylinder number 1. I then lined the cap up over the rotor, and put my number 1 plug there. Then i let it run with the EST disconnected and advanced it a little bit. I know i still have to do it the real way though! no im gonna get the o2 sensor from work tonight(autozone) and also price some other stuff. I have to get a gauge for the fuel pressure somewhere

dj_justice

iTrader: (1)

I agree replace the o2 sensor, set base timing correctly then get retested. When I had my emissions tested i was at 22 times the limit on HC's and twice the limit on Nox. After setting timing (it was advanced) and replacing the o2 sensor my car passed.

Isphius

Ok ill try that. I can get the o2 from work. There is 2 right? Or is that the later cars? i see one on the driver side header but thats it. It could be becuase of the timing. I think that would do it. I passed nox in the summer, only failed HCs. Ive only put about 400 miles on the car since then so im sure the emissions gear is still good. Just have to get all the dam settings right!

86T/A_Ram_Air

remember in jersey you only get 3 inspections and then they revoke your registration

Isphius

car had a different owner first time. So i should have one strike left...that sucks lol