drjewalton

Hello everyone...just wanted to see if anyone had any feedback on an issue I'm having with my 84 z28.

While cruising in 5th gear at a steady speed, the check engine light will come on solid after several minutes. No noticeable change in performance while driving.
While the light is on, I can push in the clutch and rev the engine (or just floor it) and within 30 seconds to a minute, the light will go off and remain off, sometimes for 3-5 minutes, sometimes the rest of the drive.
I've stopped the car and checked for codes (with no light) and the code 44 is the only code that shows up. (lean exhaust).

I have replaced the following in hopes that I could resolve this, but have not succeeded:

O2 sensor
EGR valve
EGR solenoid
vacuum hoses between EGR valve and EGR solenoid
all spark plugs (and they were white, indicating lean burn)
PCV valve
mechanical fuel pump
fuel filter on carb

Would a vacuum leak cause this? How do I detect?
I run 93 octane from BP in the car....should I use 87?
I visually check the O2 sensor wires and they aren't close to exhaust manifold.
Rochester Quadrajet need fine tuning for lean/rich? Is it even possible?

Car history:

1984 camaro Z28 with 28,000 original miles.
Unrestored car....engine, hoses, etc all original
Car literally has new tires, battery, mechanical fuel pump, fuel filter and radio...that's it!

One side note.....car idles fine on cold start and after being warmed up (choke works properly). However, when I rev the engine, it spits and pops (especially when cold, not so bad when warm) and on rare occasions, it will noticeably hesitate and pulse temporarily when pushed to WOT.

Just trying to be complete. Tried taking it to a few places locally but no one seems to know anything about anything! Any help will be appreciated!

sofakingdom

iTrader: (1)

Sounds like a fuel delivery problem.

I'd suggest letting the tank run nearly dry; then pouring in a gallon of lacquer thinner. Drive the car for a mile or 2 to get it all in the whole fuel system; then park it overnight; then fill it up with fresh gas in the morning. See if that doesn't flush some of the varnish out of everything and help it run better.

If it doesn't, it's carb rebuild time. There is tuning available on it, however it's highly unlikely that it has de-tuned itself with no human intervention, therefore I'd STRONGLY urge that it be left alone until verified 100% non-defective. Few things will put you farther out in the ozone, to the point where you will NEVER be able to get it back right again, than adjusting on a defective carb.

drjewalton

Thanks for the input although I don't think I'm ready to put lacquer thinner through my car just yet.

I feel that this is either a carburetor problem or a vacuum problem. A friend of mine says EGR based on the specific condition of the light, but all EGR components have been replaced so I just don't know.

I wonder what the proper procedure would have been at a GM dealership back in 1984 if this condition were present....in other words, what's the step by step "flow chart" to diagnose this?

I don't want to jump right in to a carb rebuild unless it is the absolute next step. And I definitely don't want to run anything other than fuel through the fuel system in an otherwise pristine unrestored vehicle. Don't get me wrong, I believe there is an issue with fuel delivery somewhere because of the condition of the plugs when I replaced them, but it seems that I would be experiencing more consistent driving problems if it were poor fuel/varnish in system.

On a further note, I have put approximately 1200 miles on the car this season and have only used BP 93 octane fuel. The car runs about the same as when I started driving it this year. Again, there is no noticeable change when the light appears in cruising state, but there is a little popping when revving or when down-shifting to slow down.

Thanks for the input, keep it going...let's figure this out!

drjewalton

An update:

Purchased a replacement rebuilt Rochester quadrajet E4ME to install. Upon removing original E4ME carb, I noticed that the back 2 nuts holding the carb on were barely hand tight (vacuum leak?)

Since I had the new rebuilt carb in hand (and the original's gasket was wet with gas), I went ahead and replaced it.

After some fine tuning, NO MORE check engine light (code 44) !

Now the real question....if I had just torqued down the original carb, it may have fixed the problem.

Lesson learned: Check ALL possible things, no matter how small....I never would have thought about checking the tightness of the nuts that hold the carb down!

Just thought I'd share. --- I believe sofakingdom"s signature summarizes it all!