89 383 "backfire" problem

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Aug 23, 2006 | 03:33 PM

89corvetteken

Thread Starter

Instructor

Joined: Jan 2005

Posts: 197

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From: East Amherst New York

89 383 "backfire" problem

I recently got up and running a new 383 for my a4.
The problem is when I step on the gas at part throtle it "pops" out
the intake.After a pop or two and a slight stumble it takes off excelent.
I did a scan and came up with (at idle):

TPS .52 volts
Block learn 108
integrator 116
IAC 160 steps
Sparke advance 19.9
inj pulse 2.0 ms
Mass air 12gr/sec

Any help here would be greatly appreciated.

Thanks

Aug 23, 2006 | 11:45 PM

drive it

Melting Slicks

Joined: Apr 2001

Posts: 2,115

Likes: 220

From: Ca.

Quote:

Originally Posted by 89corvetteken

You said that scan is at idle, not at the problem area. At idle you show rich, however you need to scan when it pops and stumbles. "Usually" a stumble when you step on it it's goin lean and giving you a lean misfire. Do you have a wide band? That would really pin it down. Take a look at the accell enrich tables. They affect "pump shot" for carb terminology.

Aug 24, 2006 | 07:32 PM

RRT vette

Le Mans Master

Joined: Feb 2006

Posts: 8,753

Likes: 9

From: Louisiana

Having the same sort of problem with my 86 stocker w/ exhaust mods. Out of the blue, when giving part throttle I hear a popping noise, kind of like a miss, but it comes form the intake. It was real bad and popped a few times in a row, but now only every once in a while. I'm running rich also (24lb injectors with 34 psi fuel pressure). I notice everytime it pops, I get a knock count.

TPS .55 volts
Block learn 108
integrator 126
IAC 26 steps
Sparke advance 22.5
inj pulse 1.74 ms
Mass air 8.28 gr/sec @ 750 rpm's

^ this is when at idle and 200* engine temp. The only thing I see on my scan when the intake pops is the knock counts get higher. At least your not alone on this one. Try posting this in Tech/Perf, you'll get more suggestions/comments.

Aug 24, 2006 | 07:42 PM

AZC4Guy

Drifting

Joined: May 2005

Posts: 1,302

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From: Tomahawk WI

what drive it said. Aside from all that computer mumbo jumbo.. this is a lean problem.

Oct 11, 2006 | 01:02 AM

coupeguy2001

Le Mans Master

Joined: Sep 2006

Posts: 6,050

Likes: 147

From: Phoenix AZ

2021 C4 of the Year - Modified Finalist

pop

sounds like an oxygen sensor problem or maybe a coolant sensor problem giving false info to the computer.
also try readjusting the valves again, it may be on the ragged edge when you give it gas, the raised RPM and warm temp might change valve lash
inspect your plug wires, check the inside of your distributor cap for cracks, or a messed up button that touches the rotor.
check the plug on the mass air flow sensor for tightness

Oct 12, 2006 | 04:27 PM

goldeneye_vet

Burning Brakes

Joined: Jun 2002

Posts: 1,001

Likes: 1

From: sd

Here is a link to www.thirdgen.org that describes your problem but you're going to have to do some chip burning to get it fixed. Good luck.

http://www.thirdgen.org/techboard/di...-has-lean.html

Oct 17, 2006 | 11:29 PM

johnnyevans

Drifting

Joined: Mar 2002

Posts: 1,251

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From: Thomson Georgia

Lean. Chip burning time, You'll need to work with the AE tables.

24# inj @ 34 psi. low fuel pressure, 45-50 with vac line off reg, i think would be a better choice.
johnny

Oct 19, 2006 | 02:05 PM

Dominic Sorresso

Le Mans Master

Joined: Sep 2000

Posts: 6,303

Likes: 714

From: Bartlett IL

Popping from exhaust on decel is too rich. Popping from the intake is not good. Lean. Look at bumping your AE pumpshot at lower TPS and MAP levels. You may also want to look at timing for too much advance but do 1 thing at a time.