L98 backfire in plenum

[luvmyc4]

Had to smog my 85. They didnt have a dyno and were revving it in nuetral. 10 mins after I left I heard a ticking noise I never noticed b4. Next day I have backfire that sounds like its poppin out the throttle body and poor low gear power. Wont do it on freeway, just on acceleration.MPG readouts way off now too...Hmm...exhaust manifold gaskets probably crap...cold or hot same prob...distributor? valve? egr? 02 sensor? any advice greatly appreciated:confused

 

[navy2kcoupe]

Broken intake valve spring maybe..............
Andy

 

[luvmyc4]

Thx will check out. Had the pleasure of removing dash to replace headlite switch. These cars arent for everybody. Gotta love it. Read something about checking distributor too.

 

[Schrade]

Was it burning badly before the test? Did they 'fix' something to get you by the test?

 

[luvmyc4]

No

Was it burning badly before the test? Did they 'fix' something to get you by the test?

No probs. AT ALL!!! thought I could save a buck.passed with flying colors. When i smog in AZ or CA they engage tranny. Told em rpm readout not accurate; so dont rev 2 high.These guys up here just hook up yer pipes; wheels dont spin. Like when u go for oil change and teenager doesnt put drain plug back in right."prove it" Cant do smog in my yard lol.Its 25yrs old please dont do that!!!!!ad

 

[navy2kcoupe]

Hey luvmyc4.......not to hijack this thread, but a few years ago I went to "Hot August Nights" in Reno.
MAN where there some CARS there!!!!
Andy
Hijack over........we now return you to your regularly scheduled thread.......

 

[luvmyc4]

Haha just spent the night with the Boozefighters on they're ralley at the sands.Local vette club meets blaH BLAH BLAH(3rd thursday at Bonanza)...hOT aUGUST nIgHTS......//////MY 1963 split widow/my 1970 Mako shark?/my 1978 indy pace??? LOL!!!! OH GOD YEAH and the fully restored C1's.....wow.

 

[GRAND SPORT #12]

if you were not having that problem before i would run a compression test then cylinder leak down test a lot of times when i have experienced a back fire audible through the intake its many times a timing issue so if timing is correct do the above test..

 

[GRAND SPORT #12]

oh yea sounds simple but make sure air intake to throttle body is tight i have seen unmetered air do the same thing

 

[luvmyc4]

and could I

if you were not having that problem before i would run a compression test then cylinder leak down test a lot of times when i have experienced a back fire audible through the intake its many times a timing issue so if timing is correct do the above test..

Could I hurt motor drivin it 4 a week at slow speeds?(till I get paid)

 

[luvmyc4]

Update

Ok so took it to a shop for diagnosis. was told I had a flat cam. DROVE it to this shop. Quoted 3000 for fix. Neighbor heard of my prob took me to his garage. Lo and behold he has a 64 85 87 corvette(s) in there. Called his guy; dude came with flatbed and got her(after other guy, who broke my steering column (wont admit it, but I would notice, come on!) then charged me $160 for "diagnostics")was told to leave it alone and not touch it.......New guy is doing ALOT of stuff for $1200; and throwing in alot of his own parts cuz he likes my "corvettes anonymous" sticker.LOL!hnoes

 

[vetteboy86]

What does this guy think the issue is?

 

[luvmyc4]

????

What does this guy think the issue is?

He got it this a.m. will know more 2moro.ad

 

[vetteboy86]

About a week ago, I started noticing some driveability issues. Mainly an intake backfire. I verified fuel pressure. I don't believe I have any vacuum issues as part throttle and idle the car is fine. I also verified timing with my scanning software as well as a timing light.

I'm really at a loss. I pulled the valve covers yesterday suspecting a damaged valve spring. I didn't notice anything out of norm, but will have to further inspect. I've got a buddy coming over to help diagnose. My wideband O2 doesn't show anything abnormal with AF ratio.

It really is the strangest thing. If I am driving normally than hammer the go pedal, I get strong popping out of the intake. If I am in neutral and rev the motor get popping not severe. If I bring the RPM's up slowly no popping at all. I'm going to look at the ignition components next.

 

[vetteboy86]

Any updates?

 

[G Winter]

Vetteboy, do you have an EGR ? I was doing some reading and exhaust pressure can blow the EGR off it's seat on some models, if the egr is failing.

Glenn

 

[vetteboy86]

Vetteboy, do you have an EGR ? I was doing some reading and exhaust pressure can blow the EGR off it's seat on some models, if the egr is failing.

Glenn

Glenn,

Thanks for the reply. I do not have an EGR. I did however find my problem. A buddy came over to troubleshoot the problem with me. We pulled the valve covers and found a loose rocker. It was on the exhaust side.

I'm going to put about 50 miles on the car and pull the valve covers again, and check, to see if something is amiss deeper inside the motor.