85 z28 tbi
 

so i just i got the car a few days back and the idle is really rough.
when stopped at the light it reads 500 rpms and feels like it wants to die.
the only time it dies is when its not hot enough.
my friend and i tought it'd be the spark plugs but nope.
the problem is still there, any ideas?
could the timing be off or something?

Are you sure the car is a tbi and not a tpi. Tbi was not put into camaros and firebirds with v8's until 1988.

What is the eighth digit in your vin#?

F= LB9 Tuned Port injection 215hp (only available with automatic) 1985 Camaro IROC Z28 7.0 sec 15.2 sec @ 91.0 mph 305ci/215hp Car & Driver 10/84
G= L69 Carb. Rochester 190hp (only available with stick shift) 1985 Camaro IROC Z28 4bbl 7.5 sec 15.4 sec @ 90.0 mph 305ci/190hp Car & Driver 10/84
H= LG4 155hp No performance figures found

my friend said it was a tbi? i dont know.
the eight digit is a H.

If everything is original an H means carb. 150hp and 240ft lbs of torque. Page 3-15 in the chiltons manual

Time for a crate motor! Open the box and put it in.
http://sdpc2000.com/details/gm-perfo...parts/19210009

But seriously. Does a TBI car have a computer in it? I'm just wondering if it isn't a sensor like a TPS or electric choke.

Yes a TBI car has a computer in it. TBI has 2 fuel injectors inside of what looks like a carb. TBI is also a VIN E starting in 1988 all the way until 1992.

Well even the carb'ed cars have a computor, as the carbs. were electronically controlled. My 84 LG4 had a small silver box for the carb. on the pass. side under the dash/kick panel.
If you have the "H" in the VIN this is probably what you have (the LG4 with two barrel carb.).

This is what the TBI looks like. http://www.chevyhiperformance.com/te...all/index.html

You are correct. My 83 trans am was a carb with a computer. I think the carbs started using a computer in 1981 which was the last year for 2nd gen. My TBI looks a little different, but mine is factory GM and I'm sure designs will vary just slightly.

I have an 86 z28 that does the same thing. When I am at the red light it sounds like the motor is going to stall if I shift it in neutral its a bit better but not much. I asked the previous owner if the cam had been changed, he said no. Would a cam last that long in a 305 I have 180 000 KM on it.

180k KM's is only 111-112k miles... so yes the engine is probably going to be getting tired by now (especially given all the botched emission stuff GM crammed in there). So that is possible.

However in both scenario's the timing could be off (and if its a true carb'd engine) you might have to make some adjustments to the idle set screw.

To check timing you'll need a timing light (unless you're old school and know how to listen to the motor... even then a timing light is highly useful to make sure). Behind the balancer on the crank (I forget which side but I'm thinking passenger?) should be a metal plate with a serrated type edge. That's your timing plate. You'll "shoot" the timing light in it and whenever you see the line across your balancer line up on that plate thats what you're timing is at. Adjust as needed. You can even play with turning the distributor (how you adjust the timing) with the light on so you can see how the engine timing changes. There's NOT a whole lot you can damage by screwing with the timing... the engine will just die if the timing is off (and could backfire/etc...).

Attachment 21225

To check the idle set screw have someone in the car (it can be off for this, probably better if you don't know what you're doing) and have them push the gas pedal while you look under the hood (with the air cleaner off) and watch the carb. You'll see something on the side move (rotate). When you see it have your friend stop pushing the gas and look where it comes to a stop. There should be a little set screw there you can adjust (usually a phillips head), try turning it 1/4 turn in (clockwise) then start the car.

Attachment 21226

It's mostly just a trial and error deal.

-Chris

(and PLEASE don't crucify me if my arrow is a little off on the carb... I've been stuck fixing my wife's Ford Focus for the last 2 years and had to remove some of my carb memory to make room for the useless junk required to maintain her POS)

i have a 85 z28 and its a tpi, were there two differnt motors put in to the same car?