when its cold outside, my car makes this really loud bang noise coming from what sounds like the intake. It wont "warm-up" properly, i seriously have to rev the engine at 4g's for 10 secs at time, numoures times. On the other hand, when it is warm/hot out my car starts right up no prob. runs perfect....tune up done yesterday and same prob. there are many plugs unplugged and i have no idea where they go...... btw its a 2.8 i have 3 DAYS LEFT BEFORE IT GOES.

 

C'mon guys/girls....dont wanna see my car go, if its not running fine in 3 days she's outta my garage =(

 

Check all vacume lines.

 

what vacuum lines can do that if it runs fine after it is warmed up....and there is a big a$$ round thing that has a whole lot of wires running out of it adn a throttle cable connecting them all....it was jus sitting there....where does it go?

 

Pictures of what you're talking about would be nice.

In general, things will only plug into what it is supposed to plug into.

What happened to get it into the state it's in now?

 

i have no idea..ask the guy i bought it from

 

Pics would help a lot. Also I would say, start by taking the unplugged wires and find where they go and plug them in. There is only so much we can tell you about where the wires go if we dont know which ones they are.

 

A box that would have throttle cable connected to it, and wires would either be the cruise control, or throttle body.

Not warming up could be several things. Not enough gas, vac lines, coolent problem.

No clue on "bang", unless your talking about a backfire which is usually valves or timing chain.


A picture is worth a thousand words.

 

sorry no camera available...mom took my cell

 

You said it runs fine when its warm...does it do the "bang" when its warm?

 

nope...not at all,where could those v-lines be?

 

Spark may be crossing over between two wires and firing on a cylinder at the wrong time. Too many people tie the spark plug wires together. Spread them out and see what it does.

Other than that maybe a broke valve spring.

 

no the bang is more of a backfire sound

 

so how much is your mom gonna sell it for? just kidding, i hope you figure it out.

 

Sounds like it is lean when cold, your reving the engine while lean is causing a backfire into the intake. Check fuel pressure, Coolant temprature sensor. If a MAF system, check for air leaks between MAF and throttle body. Cold engines can not tolerate the same lean condition a warm one can.

 

how do u fix the MAF?

 

First you have to figure out if that's the issue. Check for air leaks between the MAF sensor and the throttle body. Check the bellows especially.

 

sorry...not a big mechanic..how do u check it..put ur finger there?

 

do you have a repair book?

 

yea, haynes..but didn't say anything in v6 motor section

 

Well, if its stock you can put your ear to it and lissten for hissing, I would also use a flathead screwdriver to tighten all those hoseclamps (the round metal things, if you look a round a screw will be on one side) to ensure it is sealing.

Make sure the Mass Air Flow sensor(maf) is plugged in. Also if your camaro has the big "Y" shaped intake there is a plug on the back of it (facing the engine) make sure that is plugged in as well, that is your incoming air tempature sensor.

Do you have access to a timing light? If so I would check your timing for sure. It seems like a hard thing to do, But it is actulay realy easy. Hell, whoever you borrow the light form should be able to show you.

One more thing to check, above your heater or AC box (thing in the rear passanger side of the engine bay, it's black) should have a big wire cluster over it; Coming out of that is a little brown/black wire with a plug in it, That is your EST connector. To check timing you have to unplug it. However when you are driving it MUST be plugged in. Make sure it is plugged in. Without this your ECM (car computer) can't change your spark timing. The ECM needs to do this or it will cause problems like you are describing.

Here is a picture of the incoming air tempature (IAT) sensor.

keep in mind you won't be able to see the sensor part. Here is a picture i borrowed from some thread that shows the camaro intake. You can see just to the driver side of the intake pipe that white thing... THAT is the IAT.


Also in regards to vaccume lines. With a few exceptions this should be a map of your accessory vaccume. This will have nothing to do with your emmissions vaccume.

For testing purposes you can plug it up at the "T" connector on the back of the plennum. This will disable your Cruise Control and possably your heater vent control if you have a vaccume controlled heater car. If the situation does not change just hook it all back up, or leave it plugged up (your CC is probably broken anyway)

Another thing that could cause the symptoms you are talking about is the Throttle Position Sensor (TPS) being out of range. Now this is a bit complicated. The TPS tells the computer how much gas you are giving the car so it can add fuel accordingly. If the TPS is out of allignment it will put in too much or not enough fuel. Now, to test the TPS you will need a Volt/Ohm Meter (VOM). Should be able to borrow one of these from a car friend. If not they are less then $10 and it is somthing you WILL use alot.

The TPS is a resistance curcuit. The more it is moved the more current it lets through. When you are at idle it should have .54 volts (give or take .075) and when you are all the way on the gas it should let atleast 4.0Volts through. Also move it slowly through it's range, if at any time the voltage stops going up, spikes up or drops off you have a bad TPS. If it is not within that range loosen the screws and tinker with it until it is. I made a picture to help you out on how to adjust it so you know where to put the VOM wires. The red wire from the VOM should go to the blue wire on your car, and the Black wire should go to the Black wire.


I have some car work of my own to do but I will try and keep an eye on this thread today in case you need anymore help.

 

a backfire through the intake is not the air control... its a valve/lifter/pushrod or valve spring. something is too lose or too tight. if this is fuel injected... its going to be a huge pain to fix it. if you have about 12 hours to put aside, you can go ahead and start trying to fix it... but you will be just fine without fixing it. it is nothing that will kill your car. if its a backfire, its just an exhaust valve. if its an intake backfire, its and intake valve. you may have a bent pushrod or broken lifter for all you know. a pushrod is 1.49, a lifter is 4.49. very cheap, but the labor is going to kill you if you don't do it yourself.

if you hear a loud rattleing at the valve covers, you probably have a lose valve.

if you want to do it yourself:

take off the plenum, make sure you remember where all of the vacuum lines go
take off the injectors setup and lines
take off the upper intake
if you have the egr setup on the passenger side, take the ignition setup off, and the egr setup. also take off the alternator before doing this... and make sure you unplug the battery so the alternator hot wire doesn't spark anything. you may need to take off a hard metal line that connects from near the thermostat housing to the heater valve (this would be a good time to change your thermostat if you haven't already done so)
take off the valve covers (make sure you have lots of oil in the oil pan before doing this!!!)

put the upper intake back on, injectors, and plenum, and all vacuum lines, throttle, etc. egr setup, alternator, ignition

start up car

tighten any valves that you hear rattleing a lot (15mm or 5/8) but small increments at a time. if the engine bogs down and doesn't rev back up after a few seconds, it's too tight.

also, if you want, your engine takes 12 push rods... 1.50 each = 18$+tax... if you want to replace them. i didn't when i did mine, and mine is almost 18 years old. well, i replaced one that i bent lol (from tightening too much).

the lifters are below the lower intake, and that is a bish to get off and back on. so if they are all pushing up and down, your lifters are just fine.

also, you will want to get a gasket set from an automotive store for the intake manifolds and valve covers. also you will need some engine adhesive... i use "right stuff." its awesome. you will need to scrape the old gasket from the valve covers off and put the new ones on... only glue the side to the covers, do not glue the gasket to the heads... i glued all of my gaskets to the bottom of my intakes (bottom of plenum, but not the top of the upper intake. bottom of upper intake, but not the top of the lower intake. bottom of the valve covers but not top of the heads).

But, this takes a LONG time to do by yourself with no experience... trust me, i know! lol.

anyways, if your car starts fine, just run it. if its throwing a light... turn it off, turn the key to ON. put a paper clip in the computer hookup below the dash below the steering wheel in the upper right corner there are 2 metal pieces beside (not below) each other... put that paper clip in there and write down the codes... and example would be 22, blinks 2 times, waits a sec, blinks 2 times... waits a few secs and it may blink another code. if you get 1 blink, waits a sec, blinks 2 times and no other types of blinks and keeps blinking that same code... it is a code 12 it means that there are no sensor errors.


...


to check that, you may have to have the engine to "best operating temperature"... can someone confirm that?

anyways, replace whatever sensors the codes throw out to ya. if you have a miss, where you hit the throttle and it skips, replace your plugs and plug wires. plug wires are ~15-20, plugs are 1.5-2.00 each.. don't get fancy plugs, just get 6 AC Delco plugs for your car with the correct gap. you may have to set the gap yourself, its easy with a gap setter, they cost like 1.00$.

note: just do what i said if the other guys didn't help ya... because my way is the super long way and may not be the problem... but if it is backfiring, it is either that sensor or a valve.

--ScottieB

while the injectors are out, check and make sure they have all of the nipples on them. you will know what i'm talking about when you pull them. they are very sensitive, so seat them in very cautiously.

for the vacuum lines, check these pictures:

http://blackboard.vcu.edu/bbcswebdav...acuum%20Tubes/

also for everything else inside of yours and mine engine bay, it should look something like this:

http://blackboard.vcu.edu/bbcswebdav/users/bakersn/89%20Camaro/Under%20Hood/

 

Scottieb, a car can intake backfire from more then just what you mentioned, realy screwed timing or a bad firing order can also cause this. though i'll admit if you had a bad firing order you would probably know it, but keep in mind the Original Poster is quite new at all this stuff.

Also Scottie your post leads me to pointing out that when many Automotive begginers use the word "backfire" they mean "afterfire". alot of my tests are to cure a rich condition that would casue afterfire. this leads me to a question i should have asked before.....

Question:
twotonemaro89: is your car afterfiring or backfiring?

AFTERFIRE = the explosion or combustion of fuel in the exhast system. casued by the buildup of excess fuel in the exhaust system or the premature opening of the exhasut valve or late spark.

BACKFIRE = the Premature detonation or cumbustion of fuel in the intake manifold, casued by early spark, a valve remaining open, and other things.

the way to tell is where the bang is coming from. is it coming from the tailpipe or under the hood?

the answer to this question could rule out a few things. example if it is an afterfire you can probably skip looking at the valves until last. if it is backfire i would look at spark timing, firing order and then valves.

it is probably not valves... man i hope it is not valves... my engine was having an issue i improperly diagnosed as improper valve lash... spend a lot of time i did not need to spend under the hood. valves were all perfect. this was after 50K of me not touching them too, they were fine....

 

hey guys ive mine trying to fix this on his car...u can here a hissing noise but sometimes it gets louder like a blowout valve on a turbo.. the backfire sounds like a go karts backfire when you hold the throttle for a while...but his throttle feels loose..like when u step on the gas and step off the car revs up fast and comes down really slow..i dont know whats goin on with this car but after 2 min of reving and staring it it will run like a brand new car but the throttle still feels weird.. it only does this when the car is cold like it wasnt started in a day..

 

I am having a bit of trouble understanding your post. you are helping him work on it? or you are talking about your car?

the throttle taking a while to come down sounds like an Idle Air Controller valve (IAC). there is a tech article on the main page about how to adjust it.

however i have heard of this issue with alot of GM EFI cars and i usualy never hear about how anyone fixed it. my sisters old cavalier (2.8) and my brothers girlfriends pontiac grand am (3.1) both did it. we sold the cavi like that and despite all efforts my brother was never able to fix his girlfriends car and they also sold it with that known problem.

 

his car

 

I had almost the reverse problem as he did, ran fine cold but when it got hot things just went haywire. Bad maf sensor, but before you go out and spend $200 on a new one, check the relays first.

Is your car throwing any service engine lights?

 

I have to ask, how old are you, that your mom makes all your decisions, and takes your cell phone?

Sounds like if the car goes it doesn't matter, because you're not old enough to drive anyway.

 

I'd have to put my money on a collapsed lifter/bad lifter that is slow to pump up.

Just keep in mind that the car is not in front of me.

 

hes 16, could have his licence now but mom wont let him lol, the cars in good condition but the drivetrains shot he needs a new rear and tranny mount witch is a pain in the --- to find dealer wants 184...the rears 84.. but this lil baackfire probs killin him.. the service lights on but i think thats because of the previous owner bypassed the vat key and put a push button

 

He is just a kid, parents are parents. Mine were just as bad till i got out of high school. Though they never threatened to sell my car. Course, if they had paid for it, they would have had every right to

 

i had a darn tps ( throttle position sensor) go bad on mine and also had to replace the throttle return spring but im not going to have headaches by a 2.8 anymore because i ripped it out and am sticking a 350 lt1 i bought down in it

 

well, in most states from the age of 16 to 18 you are licensed to drive but mommy still has legal rights over everything you do.

 

LOL, My Mom couldn't tell me what to do, since I had my own job, and paid for everything myself. She also understood that if she threatened to take anything of mine, I would simply move out.

I actually did move out at 17, but was for other reasons.

I'm seeing this far too often anymore, overcontrolling parents, just because they believe it's within thier legal rights to do so. :roll:

The problem is, it doesn't really teach the kid true responsibility.

By the sounds of it, she's going to sell the car on him either way, whether it's running good or not, especially if she won't let him get his license. Again, my mom had no say in that, I payed for it, so I got it, she also knew that I would many years before have my license at 16, due to being raised in a car family.

 

you can get an energy suspension polyurithane (sp?) mount for 35.00 at baxters auto (or local auto parts store). they are WAY better then stock. rear end i would say junkyards or craigslist.

 

the "backfire" is coming from under the hood...

 

then its something to do with the valves i *think* because if you take off the snorkle, you can still hear it come out of the throttle body connected to the plenum. anybody else? i'm just tryin to help guys.

 

its a t-5 mount its not at the local parts store we looked everywhere its a big round mount huge..is that the energy one

 

THIS is what you are looking for. the T5 and the 700r4s use the same mount between the tranny and crossmember. Energy part number 3-1108. i have one on BOTH of my t-5 cars. the L98 (swapped in a T5, originally 700r4) and the 2.8 (factory 5).


when you say huge round mount.... is it made of metal and does it sit between the tranny and engine? if so this "mount" is called a bellhousing, and it probably does not need replacing.

EDIT* attached a picture of a v8 T-5 and bellhousing. the bellhousing is the thing infront of the tranny.

 

heres a pic he just sent it to me

 

I kind of have an idea about what is going on. My Land Rover is doing the same thing. Backfire when cold, and runs perfect when warm. I had it checked out, and was told that one of my catalytic converters was clogged. Mine sound just like a backfire out of the intake. This could be one option worth looking into.

 

went out to try and start my car today...it turned over after about the 10 try....kept trying to stall out on me...had to keep reving it

 

it might be the catalytic converter ill have 2 check on that.. because one of the cylinders were not firing so it might have built up in there like my car did ill have 2 gut it this weekend

 

mine used to backfire like that only when it was cold, everytime i shifted. turned out that it was an EGR vacuum line that was plugged. never threw a code either. just my .02 for ya. and if your mom is gonna sell your car, remind her that she will then have to drive you around if you need to get places. mine threatened to take my car away once, but with all the stuff i had going on, work and all that, they decided not to once i opened their eyes to reality, lol.

 

I know this sounds crazy, but are all the spark plugs tight? I had a shop change my my plugs for me and they didnt get the plugs tight enough and they backed out. When id hit the gas it would "hick-up" and backfire and would blow the air-cleaner out. But when the motor was hot it would run like a champ. This was on my 92 s10 2.8/5 speed. Also, has the car been driven or just revved in the driveway?

 

Your mother would sell the car before having a mechanic look at it? Or is this just one of many past problems that has finally put her over the edge?

 

my mom goes from one exteme to the other...w/ a little persuasion she now isn't gonna sell me car! and just revved in the driveway....it doesn't have a working rear-end

 

I think the energy mount replaces that round ugly one. Neither my T-5 mount nor my 700R4 mount looked like yours. I'll see if I can recruit some help from some CascadeCrew guys that don't generally visit the v6 forum and see if they can help....

 

I've never seen that round mount on an F-Body. My experiance shows the V8 Cars to have the ES style mount Tony posted a picture of, while the 6 cars have a crossmember with either 1 or 2 rubber essentially bushings that space between a second plate higher up.

The V6 and V8 style tranny cross members ARE interchangable. I had one on my '85 IROC unknowing. Had the same trouble finding a mount for it. Ditch the V6 one and pick up the ES mount for $35 and the standard crossmember from a boneyard.

 

My wifes 87 Firebird LG4 / 700R4 had one of those round tranny mounts. It mounted the same as the regular style mounts like in the picture above. I just bought one of the cheap Napa rubber mounts and replaced it.