fbomb

hey guys i posted up on the tech forums about this and they told me to check my ecu, then i searched through here and i've read a few other things, i tried doing some work to my car and now everythings messed up, i put headers and a y-pipe on with a spintech muffler, no o2 sensor or any smog equipment or cat, the car starts and runs nice but backfires like crazy when running, it isn't out of the intake, and it is intermittent, but pretty loud. I've read to check if the car is running lean,, and adjust the timing, and bump up the fuel pressure, also that i may need to tune my prom, i also have to check for exhaust leaks, any other suggestions, or places i can go to see how to do these things.


i also noticed when i stated it back up that it has low oil pressure and i've been told to check the oil sending unit, i bought a haynes manual and i can't find a diagram to find where it is. wondering if someone can help me out with htat, i;ve read that there is one behind the intake and one near the oil filter.

camaronewbie

If you still have the ECM connected, it's having a hard time - it can't find any info on anything since you have no more EGR or O2. The ECM takes readings from O2 to adjust timing and fuel - O2 senses unburnt gas, and changes gas/timing accordingly to adjust for rich/lean conditions. I'm not enough expert to know what direction the fuel and/or timing would have to be adjusted. Regardless of where you set either, the ECM is going to change them based on the readings (or in your case, the lack of readings) it gets from the sensors (such as O2). I'm not sure what to do to retain the ECM and remove the O2, since it's a major contributor to the ECM's decision on timing advance and fuel.

The OPSU can be in either spot - depending on the car. My 1990 and 1992 have them just above the oil filter, but other had them on the China Wall behind the intake and dizzy.

fbomb

so pretty much i need to hook up my o2 sensor again and see if that fixes it??

liquidh8

I would use the o2 sensor, the ecm uses the readings to make sure it is running with the right air/fuel ratio. Get a good one, install it, and take it from there.

ShiftyCapone

iTrader: (7)

As stated you must use the O2 sensor. It is needed for proper closed loop function. I am not sure why people have the tendency to remove them.

What are the mods to your engine? Is this set-up on a 400 as your info suggests? If so what chip, and fueling mods have you done. What is your base timing? It sounds like your car is horribly out of tune with miss matched parts.

fbomb

right now it is a 305 i'm building the 400 for later this summer, i'm just throwing the headers on for the time being, everything else is bone stock, i'm gonna try installing the o2 sensor again to see if it fixes the problem

ShiftyCapone

iTrader: (7)

After you install your O2 double check what you base timing is with the EST dissconnected. It sounds like you may have a timing problem as well. What did you set the base at?

fbomb

i straight haven't touched the timing since i got the car, i really haven't driven it at all, i took it out for a quick ride to test how its running, and with the o2 just hooked up and not actually in the exhaust the backfiring is much less, but the car is rediculously doggy, like to the point of not even being close to as quick as my lumina
p.s. what and where is the esp

ShiftyCapone

iTrader: (7)

The EST is the link that connects the distributor signal to the ECM. You have to set the timing with the ECM out of the picture. Set your base at 0° and go from there.



The EST is found behind the passenger side strut tower and has a weather pack with a brown/tan wire.

fbomb

after i get it set at 0* where should i go from there??

ShiftyCapone

iTrader: (7)

See how the car runs. 0° is the base setting. There isn't a need for any serious amount of advance. You need to get your car back into a "stock" state of tune.

fbomb

alright , go ahead and flame me to death, two of the plug wires were crossed, and one of the wires is stright broken, i swithced them and took it out again with the broken wire and the o2 still hanging the car seemed to have much more power then before and ripped a pretty mean posi mark for me

i've been convinced by a friend to go carbed, i'm going to use an Old holley 750cfm carb (i know i'm scared of that number too, but the guys a really good performance mechanic and said we could detune it for now) a stock manifold with a carb adapter for now since i'm just going to swap everything onto my 400 eventually, and i bought a hei off of ebay that looks pretty sick ( the one claiming a 65k coil)

question: for the fuel pump i'm going old school with the mechanical pump, again because of the 400 later, i've read some threads about it and i think what i'm gonna do is drop the tank and just throw a longer feed line in there??, i know there are other ways but this seems to be the easiest????

another question real quick, i have a chance to buy some supposed 350 heads off of a caprice (impala ss style 91?+car) the kid told me the casting and the only thing i remember is the suffix was 187, and the only heads i could find were the lo3 heads, which i have and obviously suck *****, they are vortecs so i dunno if thats them or not but i haven't been able to find any other vortex with that suffix code, and also i've heard to never use a 350 head on a 305??? i was told that the valves i think, will hit the cylinder walls and start messing everything up, please help me, i need knowledge!!!!!!!!!

ShiftyCapone

iTrader: (7)

That was an easy fix and we have all made that mistake. If you want your car to run normal you still need to plug in and use your O2.

Why is that? I can see it to a point for the 400 but why the 305?



187 heads are stock LO3 heads which some caprice cars had. They are the same heads you have on your motor now. Caprice heads (pre '96) are 193's (for the 350 TBI option) and are basically the same as your 187's excpet they have a larger intake valve and have a larger chamber. Find out what year caprice you are getting heads from. Better yet, double check the casting number. If you have '96+ heads you could have Gen II LT1 heads which will not work for your application.

You don't need to replace the heads yet. Your car has other bottlenecks.

What data do you have to suport that? Dewey316 has already proven that you can achieve 300hp on stock untouched 187 heads.

Results here

193 heads are not Vortecs.


People say that because most "350" heads have larger chamber which will in turn drop the compression ratio of your 305. The larger valves are fine and 1.94's will not hit the cylinder walls.


What are you trying to do with the 305? You need to step back and have a game plan. Work with what you have and make it run right. Just throwing miss matched parts and unplugging stuff does little to help you learn. Take some time to read the stickies above as well as searching for specific threads in the TBI forum.

fbomb

basically my game plan is to run the 305 till the 400 is ready, which could take some time depending on what i want to do with that power wise, in the meantime i'm trying to find parts i might want to use for it that may also help my 305

the reason for the carb swap is because i've seen it done by a few friends and it seems to work pretty well for them, also i'm hoping i can grab some more power out of that setup, i know i could with the tbi but i can grab more power out of a carb setup on my particular budget, plus getting the car set up for it now will save me later(fuel pump and i can rip some wires out when the engines out)

i'm still learning alot about american engines, i've owned an 88 toyota 3.0 turbo for the last 3 years so it's a little bit of a change, understanding all the different head combos is tricky, but i do want to find some nice heads for the 400, and if i can find some nice stock styles and throw them on the 305 for now and then have them done over and bored out for the 400 later that'd be cool. i dunno if that could be done and thats what i'm trying to get at

as of right now i'm doing all mainly bodywork to it, seeing as thats what i'm in school for and can get a free paint job, so it's gonna be tbi till after i'm done moving it around for that. the car isn't registered and won't be driven legally for a few months probably (don't worry i'll grab a dealer plate to get where i need to go) , so for right now it runs pretty good, i have the o2 hooked up but not cut into my headers yet, which i'm reluctant to do, and as far as i've been able to gather all that that is doing to my engine is making it run more on the rich side, which i beleive will be fine for the less than 150 miles i'll have to drive it back and forth to school

Gladstoneiroc

iTrader: (1)

You should ask yourself “why is it running rich”? “Is it because the 02 sensor is reading atmospheric oxygen counts?” “Oh yes it is.” Now the ecm dumps fuel and still no change, time to dump more fuel.
Do you even know what type of headers you have? Most headers have bungs already welded in and all you have to do is remove a little metal.

You don't bore out cylinder heads. Don't buy any more parts until you do some more research. Just fix the 02 and stop for a while, before you go ripping wires out.

ShiftyCapone

iTrader: (7)

The stock TBI unit can support 300 hp. You don't need a carb. You need a properly running car. Swapping to carb will waste your money if you don't do anything else to the motor. You would need to buy a carb, vacuum advance distributor, carb intake, and carb. Why do all that to yield the same power that your car already makes? You need to plug in your O2. You car is begging you to do it. It is there for a reason.


If you want a poor running engine that won't make proper fuel changes than by all means leave it unplugged. We all like sputtering fuel eating daily drivers.

If you just want your LO3 to provide you with solid transportation until the 400 is done that just fix what is wrong with it. Why guess what the problems are and then throw miss matched parts at them in an attempt to cure them. This surely is the wrong way to go in your quest to learn about these motors. You will only make equally poor choices down the road on your 400.

fbomb

they are hedman headers and obviously don't have a o2 bung i'm dumb not blind bud, i realize it's not great to run it that way but i'm moving it in 2 days, then i'm switching to carb, i'm getting the carb for free along with the intake, i'd rather have carb for my second car, not a daily driver, and at this point i'm just looking for information, i'm not actually buying stuff and throwing it on my motor, it's still all stock stuff acept for the headers, if you guys wanna help with the questions i have then i'm pysched you wanna help, thanks