85 olds 442. put on flowtech headers, now rough idle + die

[85oldzy442]

hi. i have an 85 olds 442. put on the flowtech short headers at least six weeks ago, ever since then the car seems like it is idling rougher at stops, dying sometimes. and just running roughly in general. often the car will bogg down when i hit the gas after a stop.

i think i have readjusted the idle screws since then, but im not sure.
sometimes in this northern IL winter, the car may die often for short travels of 5 minutes, i wasn't letting the engine warm up all the way, so it will die sometimes coming up to a stop if i dont hold the gas to about 2k+ RPM or shift it to neutral.

a week ago or so the car wouldnt start from normal "single pedal tap to engine start" method, and i had to hold the pedal in all the way until it sloooowly crept up to life, and then it immediately smelled like gas big time .. ive had to do this a few times... more recently though i had it die in a parking lot, after making a brief trip from my home, less than 5 mins and didnt really let the engine warm up.. it died two times in a row trying to leave a parking lot. after waiting a few minutes i had a b*tch of a time getting it going. i tried all my pedal manipulating changes to put different amounts of gas in it. then i open the hood to see if the choke is working... yes the choke plate is working and opens and closes at the proper times, but there was no gas in the carb at all .. .even after pumping the pedal a ton. this has now happened a couple times to me and ive had to get it running on starting fluid.... yesterday i let it warm up for 5 minutes, took a 5-10 minute drive to post office, left the car running the whole time and then came home.. so it was a total of 50 minutes running at least, then 10 minutes later i need to leave and as i am accelerating out of my street it dies on me completely and will not come back to life.. no gas in the carb again...very full tank o gas. i get it started with starter fluid, let it sit for a few minutes, the choke plate opens up signaling that it is warm, the pedal linkage and throttle assembly is working and connected well. i rev it up a little bit manually, and as it is revving down, the engine just dies. started it for work a few hours later and it was fine ... if i just baby it by slowly accelerating and decelerating it seems fine.

i bought a new fuel pump and will install that tonight. other thoughts appreciated

 

[FE3X CLONE]

What engine is in the car? Is it the stock 307?

Do you still have all the CCC computer stuff hooked up? If so, did you weld in an O2 sensor bung into the exhaust sytsem when you swapped in the headers?

If you did, and your still using the stock O2 sensor, that could be your problem depending on where you placed it. It's not a heated O2 so when the engine is idling, the O2 sensor is cooling off and not giving the computer an accurate reading.

I'd check into that assuming your still running the stock setup.

 

[84GP455]

When adding headers or changing exhaust (bigger pipes) or whatever, usually that means that you have to re-jet the carb because the engine is breathing more so it is getting more air. That's just my opinion of what it could be.

 

[85oldzy442]

yes stock 307. i believe 307 H.O.

headers was a project with my father, there is no o2 sensor in the exhaust system now, i dont know where it is actually, could be dangling somewhere or it could be in the trash .. hah

i'll check into re jetting also thanks

 

[FE3X CLONE]

Well, that's probably your problem. Its not going to run right if the O2 isn't hooked up. Although I would think it would be throwing a SES (service engine soon) light on the dash if it wasn't.

 

[85oldzy442]

after driving for about 5 mins a check engine comes on, which i did asssume was from no o2 sensor.. didnt think it would be responsible for starving my engine... is that due to the solenoid that is in the front that puts gas in the carb?

anyways, assuming i can easily buy an o2 sensor or find it in my garage ... can i install it anywhere? or can i somehow fool the computer in to thinking that it is working right without a sensor?

we ran the computer troubleshooting codes and its only for o2 sensor ... didnt think it was a big deal, guess this should have been my first stop.

 

[FE3X CLONE]

You need an O2. No way around fooling the computer other than getting rid of the computer system and swapping a non-ccc q-jet and distributor on the engine.
Without the O2 sensor hooked up, your engine has no idea how much fuel to add and is probably in a "limp home" mode.

Are these full length headers or shorty headers? I'm assuming full length since they're made by flowtech. Easiest thing to do is weld an O2 bung into the passenger side header collector. You'll probably have to extend the wiring since the O2 sensor is further away than where it was stock.

Its also a common problem for a non-heated O2 sensor to cool off too much when at idle or low speeds because its now further away from the heads and higher exhaust temps. This can cause it to read erratically. So keep that in mind. I don't have the link at the moment but I know Oldspower.com they were discussing the heated O2 upgrade a while back.

 

[85oldzy442]

okay we got a sensor but need to pickup a bung tomorrow, thanks alot for your help. also they are full length headers i believe

 

[Blake442]

If your choke is working properly, I'd be looking into the cause of it not getting any fuel first.

It sounds to me like it's getting vapor locked, and the thermostat is where I'd start.

I put headers on my '85 442 back when it had the stock 307 in it, and I did not put an O2 sensor on it.
I threw it in the trash along with the rest of the old exhaust and wrapped up the wire and tucked it away.
Everything else was still completely computer controlled. Carb, distributor, everything was all as the factory delivered it with the exception that the air pump was gone and so was the A/C.

The car ran like a bat out of hell (for a 307), and got 15-19 mpg if I kept my foot out of it.
You could drive it around town all day and it would not throw the check engine light.
Once you got on the highway, within 1 mile the check engine light would come on.
Turn the car off and restart it and the light was off again.

That 307 ran like a top all the way until I grenaded the sh*t out of it 4 months later... :lol:

 

[85oldzy442]

yep my 307 is still stock.. i drive it as easy as i can.. and the mileage is 12-14mpg .. so im sure something is messed up 🙁

yes i get check engine light only when i hit 50-60 mph, which is common for my daily route

almost done putting in new o2 sensor , *yawn* i hope that works otherwise ill be sad that i blew 40 dollars and cut a hole in my headers

EDIT: put on the o2 sensor and started it up. the temp got up to 220 before the thermostat kicked it down to 190, and its a 190 rated thermo i think.. so ill have to keep an eye on that.

also i havent adjusted the idling screws yet, any tips for reaching them?