I finally got my Bird flying again and I am having a couple of issues.. its a 355 vortec superram. When the car first starts up, It idles fine, nice and strong, a couple little hiccups here and there but basically waking up. After a few minutes I put it in gear and it acts like it wants to stall out, and more often than not, it does. Even when I am driving it and I come off the accelerator to hit the brake it will die then also. And sometimes when I get it back home, I put in park and then I have a high idle for a long while usually around 1500 rpm.. Does anyone have any ideas what my problem might be here and what is be the best action to rectify this.. Thanks

 

Any vacuums leaks?

 

None that I can locate.. I did the spray bottle with water to find it stumble, then the brake cleaner to find the surge.. Nothing. I thought pcv valve, but 90% of whats under the hood is new.. So I am not sure.. I dont hear any hissing in the engine bay, besides the air filter suckin air n2 the motor

 

I had a similar problem a few years back. It ended up being the Throttle Position Sensor. I had swapped in a crate motor and had purchased a brand new TPS sensor from a GM dealership and installed it while putting in the new motor. Every so often when I came to a stop, the car would die. I checked it out with a multimeter and the TPS was a dud.

 

hmmm.. i tested it a few days ago and it seemed fine.. voltage was at .55 so Im not sure that would be it.. Did yours read any voltage when it went out or no? Honestly that is something that hasnt been replaced when I did my build.. Let me know.. Thanks

 

Does your speedometer work? Both on the dash and to the computer. You'll need a scan tool to check the computer.

Have you reset the TPS and IAC according to the tech article?

You might just need a custom chip to go with your setup.

 

you got me interested cause i have the exact problem... but with a bunch of mis-matched crap under my hood.
stupid previous owner and me not having any money...

to me, in my car, it feels like a TPS issue or MAF kind of thing.
i dont know exactly your circumstances, but does it kinda act like there is no real 1-5% throttle range?
mine kinda skips over that area and then takes off.
also, before the engine warms up enough, if i tap the gas in neutal or park the engine cuts out for a beat then revs up.

i dont know much about electronic FI and computers but to me this says that there is a disconnect between how much fuel/air the engine thinks its getting and how much it actually is...

something to consider in your case.

lemme know if you make any headway in this
id love some other opinions.





on the side, how exactly does one go about testing a TPS?
is it basically a resistor and i test the voltage coming out and look for any jumps or dead spots in the range or is there more to it than that.
also, where is it?
throttle body?

 

Hey Kevin.. Thanks for jumpin in. The TPS has been tested for proper adjustment as I said earlier, but the IAC has not.. I know for a fact that Im goin to need a chip burned but I figured something like this wouldnt effect the chip. I could be mistaken tho.. Its funny you mention the speedo, because no it doesnt work either.. I was goin to bring that up in the transmission section of the org since I pulled a code 24 which is the VSS. So youve got me curious now... What are you thinking here?

Hey Red Dragon Hows things goin.. Sounds like in your situation you are experiencing a lack of throttle response.. In all other RPM ranges your car performs well correct? In a throttle response situation.. You definitely want to make sure your timing is dead on, your TPS is adjusted properly and your not MAF power and burnoff relays (located under the hood against the firewall driver side corner) are functioning well.. Check those out and let us know what you come up with. Also if you know what your setup is under the hood, that might help us get better picture of what your workin on or with.

Anyone Else got any ideas..

 

hey!
first of all, i got the car for $500.
the previous owner was a roomie of mine, and he wanted to sell it and i bought it.
as for the engine, the block is a 350 block from a 70-something pickup.
he pulled the tpi off the 305, and some old guy made him a chip after running the car down the road a few times.

as for whats in the motor, i have no clue and he doesnt either.
his best description is:
new flat pistons
big cam (real descriptive... i know)
chevy bowtie II heads (whatever that means...)


im guessing the bottom end is stock.
thats all i know.


as for checking things, this is my first camaro and i havent had it all that long. my previous car was a 84 caprice with a carbed v6 engine. the only electronics were a TPS and O2 IIRC, so there wasnt much to worry about.
the point is i am going to need more or less explicit directions on how to check stuff.
electronics and i dont get along at first, so this will be interesting.



as for exactly what is happening, i think it can mainly be traced to a bunch of different people not knowing how to fix what is wrong and doing what they think is best.

once the car is warmed up fully, it idles in Park at 1200-1500 and in D at 750.
cold, its at 750-900 in N and wont stay running in D without a bit of gas.
now i know there is a 9th injector so im thinking that if this isnt working it may be partly to blame.

also, it seems like the engine isnt "recovering" once you put it in gear.
in my caprice, in neutral its at 900 and in drive its at 800 once it steadys out.
the camaro is completely different.
IMO, it shouldnt go from 1500 to 750 by putting it in drive

 

True.. First off that car should idle (according to the emissions label under the hood), at around 5-600 rpm.. Sounds low, but thats where it should be.. THat can be adjusted via the throttle body, top of driver side where the throttle cable is.. There is an idle control screw there. That may need to be adjusted.

Second, are you throwing any codes though the ecm.. Is ur check engine light on at all? If so we got dig into that and see what may be causing a problem there. If not the cold start injector is located on the driver side of the motor in between the runners, make sure that connection is good and solid.. Also there is a cold start sensor on the front of the intake with a similar clip to that of the injector. That may need to be replaced or check for a good connection.

You mentioned a big cam.. I know you have no specs or idea as to what the duration may be, but how is the idle...smooth, choppy, lopey? This may be a reason why your idling so high.. might be just to keep the car running, which means you dont have enough vacuum going through the engine..

I hope any of this info is helping you at all.. Feel free to post a video if u can and we can watch it and better help with the diagnosis

 

The computer adjusts the IAC based on your speed. Without it, the computer doesnt know what to do to keep the car idling.

 

ok. this is the idle adjustment method i am familiar with. but ive heard some things about how with the TPI you have to use a multimeter or something and something else to do it "right"

i can check the codes, but ive never gotten a check engine light with the engine running.
it goes on (solid) when the ignition is on and the engine is off, but after that i dont see it any more... i guess this is good... who knows... either way ill check the codes.

ok. i dont recall seeing this injector, but i will check for it.
is there a way to tell if it is connected and working besides pulling it out and spraying it into a cup or something? any way i can check with a multimeter?

once the car warms up and settles down (before the idle gets up to 1500 and after it begins running smoothly... there is a window of time here) it is smooth-ish but sounds like a muscle car... cant really explain it.
part of the problem is that i have leaky collectors to the Y pipe, so it is louder than normal, but i feel like i can hear the individual pulses... its not like on new cars where the pulses all blend together. there is a definate
bap bap bap bap bap bap
its not what i would call "choppy" or "barely running" though.
another thing is that i recently went and replaced every piece of vacuum tube under the hood.
it didnt help.
if i get a chance i will borrow my uncles vacuum meter although we will see. i am pretty busy with christmas and all.

yes. thank you very very much.
i really appreciate that you guys take the time to help someone out the way you do.
it would have been a lot less work to say "do a search" or "buy such and such book"

ill get back to you on this when i get back home but for now i am at my parents house for christmas...




oh, and sorry for hijacking...

 

Your on the right track which is basically maintenance.
Get all leaks intake/exhaust (before O2 sensor) repaired.
Read the IAC & TPS adjustment in the Tech article before attempting to adjust the idle screw remember this is a computer control engine.

If the 9th injector isn't working you'll experience extended cranking times when cold.

 

Kevin.. I will investigate the IAC and I believe i have an extra laying around I will put it on and test it also.. will get back to you.

Dragon.. The 9th injector has the same electrical clip, but different look as far as injectors go. To be 100 % honest I dont know how to test it. Personally I never had to. It sounds as tho it isworkin if the car is running when cold.. Before I did my build for the car, I went through three or four cold start sensors, the one I said was on the front of the intake. Maybe that could be something to think about.

As far as testing the TPS and IAC go.. there is a tech article here on the site.. Go back to the home page and the list of places to go on the site are located on the left hand side of the page, go down to Tech articles.. There will be an article entitled "TPS and IAC Adjustment" or something close to those exact words. That will show you how to check and adjust both of those components.

Definitely get a vacuum gauge and work on that AFTER you check ur TPS and IAC.. then well go from there.

 

thanks guys.
found the article.
will do.
i wonder if harbor freight has any vacuum guages.
im kinda broke... ya kno what i mean?

 

ok, so here we go.
i set the IAC and the thing ridles a heck of a lot better once its warm.
until then, its the same nasty sob that it was before but possibly worse.

on a hunch i jumped the a and b pins on the aldl with the engine running and semi cold and although i still had to keep it running it ran smoother.

once it was warmed up the wire kept it running even smoother but it ran fine without it.
by smoother i mean that the engine didn't sound as harsh from under the hood, and from behind the car, it sounded almost civilized but still a bit choppy.
without the jumper, under the hood its still the same bap bap bap bap bap bap and from behind it sounds like it could be a 57 chevy with a 3.5" dual exhaust system...
its weird.


anyway, i thought that i would set the TPS voltage, but when i plug in my multimeter, i get NOTHING
i tried every combination of the three pins i could think of and got 0.00 volts every time.
i then went from idle to WOT and still 0.00 volts...

maybe i am doing this wrong?

 

ok, so i tried plugging the connector into the TPS and poking my Multimeter leads into the wires coming out of the connector and this is what i got:

idle: 0.550v
WOT: 3.874v
voltage increases linearly

without the connector attached i read the ohms of resistance in the TPS and it increased from around 3.9 kOhm to around 7.5kOhm.
this may not be right but i forgot to write these values down.




now heres what i have.
when its warmed a bit, i have to start it and hold it at around 1000 rpms for a while and gradually let the throttle out to around 700. then the idle picks up to around 900 and gets smooth.
i then let it out to about 600 and hold it for a second then slowly let it go to rest at 550 or so.
i cant say what happens when the car is cold yet but i will tell you tomorrow.

the nice thing is that it idles in P-N at around the same rpm as as R-D-3-2-1.

so i fixed something.


one thing is that i found a disconnected vacuum line after i went and calibrated everything so i had to connect the vac line and re do everything.
it no longer runs like a 57 chevy.
sounds very civilized for what it is now.

it still kinda hiccups when i blip the gas though.



anyone got any ideas?








my speedometer is working but very miscalibrated.
could this be to blame?

also, i have a megashifter and have not installed the relay thing that they recommend you install.
the wiring diagrams they provide arent really all that great.

nobody really seems to know what those other two wires acutally do anyway.

 

one other thing.
i cant find the 9th injector or any hole where it should go.
any pics with it circled or something?
thanks all