I have a problem with back firing on hard acceleration, the car will die untill I take my foot off the gas and let it return to idle, then I can slowly keep driving untill it clears up. I JUST replaced the opti, plugs and plug wires, it made NO difference. I'm thinking it may be a bad MAF.
Any ideas?
Ron
95 Z28 Convert with 250,000 miles on it. All stock except exhaust and air intake.

 

The best way to observer the MAF is via a scanner or data logging software. If it was acting badly enough, you would probably get a trouble code.

 

A bad MAF didn't throw a trouble code our our LT1 here is my story; -->> Post #7 <<

 

Mine doesnt throw any trouble code either, but it does throw flames out the tail pipes when it acts up.
Ron

 

i would try to clean it first, get some maf cleaner and spray the snot out of yours. Than if its still f ed up, start calling junk yards or looking on ebay. You shouldnt have to pay more than 50 or 75 for one. If you want one new i *think* their 185.

 

Sounds like a fuel pump to me...

Get a gauge on it.

 

Well, I dont have a gauge but the reason I dont think its the fuel pump is, when it does act up and start the back firing, black smoke rolls out the back so it must be getting fuel, right??
Ron

 

I duno about that...

How often is this happening? Every time all the time?

You could unplug the MAF and see if that makes a change (after you un plug it you will hae to keep your foot on the gas for a minute or 2 to keep it running untill the computer adjusts for not having one.

Any codes in the computer?

Also might want to take a look at you 02 sensor readings.

 

This doesnt do it ALL the time, but pretty often when accelerating fairly hard. I have never replaced the O2 Sensors in 250,000 miles. There are no codes in the computer.
Thanks for your help.
Ron

 

Unplug the maf, see what happens. Your computer won't need to adjust to anything, it will just throw an error (no maf connected) and run in a speed density - like mode.

 

I takes a minute (maybe not a minute but at least several seconds) to go into speed density mode, during that time most cars will not stay running unless you give them some gas.


200k+ miles on 02 sensors is way too long, i think they should be changed every 50-75k miles. This might not be you problem but i am sure its not helping either.

What about your fuel filter? or Cats?
Just trying to throw some stuff out their for you to check.

The best thing to do is get a scanner on it and take a look at everything (or post it up here) and see what is out of wack.

 

OK, I unplugged the MAF and it didnt make any difference, when I started to accelerate hard it started back firing and died again until I took my foot off the gas, I then had to let the clutch out while I was still moving to get it started again.

 

it sounds like a fuel problem to me
You can get a gauge at the parts store for $15-25, this tool is a must if you are going to be working on your car.

Hook it up to your car and find a way to put on the windsheild (i used ducttape)
youe PSI should be right around 42 at WOT and mid 30's at idel

 

Hey, you dont know how much I appreciate your help. Thanks. Now, If I go buy a fuel pressure gauge how can I hook it up to the plastic lines? I've never tried to cut or splice these types of fuel lines. I have a cowl hood that is open at the rear so I could mount a gauge in the opening if I can figure out how to hook it up.
BTW, when the car is back firing and shooting flames out the rear, there is black smoke pouring out the pipes too. Still think fuel??
Thanks. Ron

 

black smoke hmmm, means rich. I duno man maybe when the pump is failing the computer is trying to open the injectors more and more to give the engine more gas and when to pump finaly kicks it runs really rich untill the computer readjusts to getting fuel.

The one thing that is reall really weird is that you dont have any codes in the computer, a car running as bad as you are describing should be throwing several codes i would think.

When you unpluged the MAF did the check engine light come on?
Are you just guessing that their are no codes or did you have the car scanned?

If you are short on cash then i would wait untill you can have the car scanned untill you buy anything.

ANYWAYS to hook up the gauge, first off buy a fuel presure TEST gauge.
it will have a hose on it that will screw into a shard valve (the type of valve that is on a tire)
Behind the intake is where the LT1 shard valve is, it has a plastic cap on it that unscrews, just screw the fuel gauge into that (becarefull because some gas will shoot out).

Also if you have the cash ($75 each) buy the 2 upsteam 02 sensors (dont by the bosh ones they are crap) 90% of time if these are bad they will throw a code, bt it is way past due for you to change them.

Also when you did the tune up did you replace the coil?
Double check you coil wire is on tight.