I recently bought a V6 Camaro (1989) and I love her, she sounds great 'cause she came with a Dynomax cat-back. I put some work in her to get her runnin good. My prob. is that I have real bad gas mileage, like 12-13 mpg highway in moderate traffic. Once i come off the highway after a 50 mile drive, I'll get vibration at idle in drive and the rpms flucuate b/w 650 and 750 when stopped at a light. I've been reading old forums and this site has been great, I plan to own my f-body for a long time... here's a link to my reader's ride page : https://www.thirdgen.org/rides/index...ew&rideid=9833 Any help would be appreciated... sorry for the long message.... Thanks to anyone in advance.

 

I've been having the same issue with my 92 Firebird GTA, but only after I changed the EGR valve recently (which started throwing a MAT sensor error too). On a nearly full tank of gas I was only able to go 180 miles before I HAD to refuel and there's been a very bad vibration, only when it's in drive and only while stopped. Any ideas would be greatly appreciated!

 

plugs and wires? it could be any sensor going out, or gunk in your system... tell us more info

 

Same here, 90 firebird 3.1. Maybe squeeze 190 miles out of the tank at 80% highway driving...maybe. And that is feather footin it! Idle is erratic and jumpy as well (but has not stalled...yet). Recently passed CA smog and no check engine lights on. Runs smooth w/no bogging etc, and rpm's stay level while running at speed. Seems like we have the same problem gulf_coast_228..... I just got this car 2 weeks ago, prev owner said he changed the fuel injectors, so dk.

 

ever since i put the headers on ive had that problem too. With the backfiring it did before. i think i may have fouled a spark plug. it vibrates like crazy while stopped and in gear. put it in park, it all goes away.

 

First thing I'd try is unplug the EGR valve and see how it drives for a day or two.

 

i was told that if you dont have the egr valve hooked up it will burn up the head and the rest of the engine.

 

well i dont think it will in a day if you aren't to hard on it. or just take it for a spin around the block with it off and see what happens.
but first i would try stuff like new fuel filter, fuel injector cleaner, check the plugs and wires, basic tune up stuff might help.

 

got the same vibration when i stop at lights etc, tuned it up, still does it, usually doesnt stall but sometimes she does. maybe a handful of times a year. im in the process of seafoaming her now but any ideas? vaccum leak? i know my exhaust manis have a small leak on one side...but that woudlnt cause this?

 

Vacuum leak. All 3rd gens have that lousy brittle plastic for the vacuum lines, and it only really lasts for 10 years, so if you haven't replaced the vacuum system yet, its pretty cheap and easy to do. Just make sure all your brittle hard plastic lines are gone and then you can start from there.

When the car is in drive its still spinning part of the transmission. When you put it in park the tranny is held in place by the parking pawl so less stuff spins. Perhaps you guys need to check your tranny and motor mounts?

I had terrible vibration till I found a pinhole in my vacuum system on the fuel pressure regulator line...

Oh yeah and BTW your fuel use rate is directly proportional to the amount of vacuum applied at the fuel pressure regulator on the fuel rail. Less pressure means more fuel used as less is sent back to the fuel tank.

Replace your vacuum lines then get an inline vac meter stuck inline with your FPR and see if its within specs.

 

I agree with /l\. Check all your vacuum lines, cuz my plastic lines on my v-6 were all cracked. And i experienced the same rough idle you are experiencing.

 

when you replaced your lines, did that improve your gas milage also?

 

Before my car died altogether I was having the same problems. Where can I go to get new vacuum lines?

 

im just going to make mine with rubber fuel hose or something, and try to hide some of the lines better with the new stuff, just cut n go .

 

unhooked the EGR valve and the same thing still occurs.. my gas cap was very loose, after tightening it my milage improved.. vibration is still there.. will investigate the vacuum lines, i bet thats where its at. it wouldnt surprise me at all. if that fixes it i'll post it here!

 

that is a very good idea. saves alot of disgruntlness for something else.

 

Found the vibration, the hard way. Was pulling off the interstate when I heard a whining noise from the engine and electical smoke pouring from underneath the hood. I pulled over and popped the hood... my alternator was frozen up. Apparently it has been trying to for a while now. Got a ride to the Advance Auto Parts and did a warranty exchange on it (the thing wasn't even a year old), put the new one in and in about an hour I was back on the road. The vibration has also stopped completely and the car idles fine now. I'll be replacing my belt shortly as well.

 

I've also been having similiar problems since I did my 3.4 swap. Mileage took a dive and it vibrates at idle sometimes enough to make things rattle in the dash. Sometimes I can feel a slight hesitation while accelerating.

I wonder if I created a leak when I had everything in and out doing the swap. I did the test for the solenoid that I read about a few weeks ago, and it seemed to be working fine. Not getting any codes either.

Guess I need to hurry up and replace the vac system and see what happens.

 

any luck with any of ur vibration problems i'm on the same boat with u guys and i'm thinking it's either my maf or cts.

 

it's your sensors. after 15 years they tend to go bad lol. well, 89... 18 years now. replace your sensors with extra money, and write down when you did it and that type of good stuff in a notebook and keep it in a good place.

a lot of times it will be your mass air flow, idle air control, egr valve, oxygen sensor, all types of crap. either test all of your sensors with a dmm (digital multi-meter) and compare with readings from your chilton/haynes manuals and replace as needed... or just go to the auto parts store and start buying sensors, but they do get costly