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Discussion Starter · #1 ·
Sup guys, Newbie here with his first post.
In Dec 13 I picked up my first 96 ss.
Check engine light was on code called to replace EGR.
Replaced & code cleared, passed smog like a champ, no known other issues.
Prev owner told me he only ran high octane. This I will continue.
Car has ran great up until I needed gas and the ONLY station around was AMPM.
So here's my situation: 2 weeks ago filled up with High Octane 20 gal AMPM, (Shame on me for the cheap gas, I know but nothing else was around, & I have always used Chevron before this fill up) & right after I went thru the pressure wash for a nice shine.
Drove fine that day. Next day car sat didn't move. Day after that I went to start & from nowhere the car wasn't firing right up (which has always been immediately). Wined for about 5 sec but never turned over. Took key out, tried again & fired right up no hesitation.
It did this every time I tried to start for the next 50 miles. (few days) So I thought to myself maybe the cheap gas was watered down & is causing the problem. So I purchased a bottle of techron & octain boost & put them in the tank. (Again 50 miles into this tank of gas)
Problem did not clear up. It hard starts EVERY TIME , but ALWAYS starts on the second try.
So I thought to myself just drive all this bad gas out and refill with Chevron ASAP and hope all clears up.
So about 100 miles into this tank and now Im getting a RPM surge when the car finally turns over, then slowly goes down to normal.
Now 170 miles into this same tank of gas & the check engine light comes on, Code P0400 EGR Flow Malfunction.
Now I personally replaced the EGR aprox 2 months ago.
Car does not miss, sputter, die out, run bad or sound bad.
No obvious leaks or known issues.
I could be far off here but My assumption is BAD GAS. But could that trip a code?
Any ideas would greatly help fellas, & thanks in advance

Mods & replacements if needed to help narrow down issue.
(All done within the last 6 months)

New water pump
New AC Delco Opti Spark
AC Delco Fuel pump
AC Delco Fuel Sending unit
AC Delco Fuel Filter
AC Delco Fuel Screen
Fuel Pump relay
New Serp Belt
New AC Delco plugs and MSD wires, full tune
New Magnaflow Cats
K&N cold air intake
HyperChip
 

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throw a fuel pressure gauge and see what it is when having the problem.

search will find lots of fuel pressure threads.
 

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Discussion Starter · #5 ·
will check on those as well & clean or replace if necessary.
I was just thinking bad gas because it happened the day after a fill up, & up to that date the car had no such issue.
Will report back with findings.
Thanks!!
 

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On the first thing to do list when I get off work!
See what she reads.
Thanks!
first off I own a 1996 and never used anything but 87 octane. next If you used bad fuel the engine would run like **** before you got back home...lets say it was bad fuel then I would use 2 bottles of dry gas to resolve this issue.

If you got gas because the fuel gauge was below 1/3 of a tank then you may have run it down to the point where the fuel pump got overheated and the fuel filter also may have picked up debris to foul/plug up the fuel filter. pressure gauge test may confirm this...

If you do not use this vehicle for several weeks at a time put fuel stabilizer at each refilling when the level drops to 1/2 a tank...

EGR code 400 is a tricky code some times.. this may mean the controlling solenoid or a vacuum leak to it...along with a leak at the egr gasket vac line to it. the intake manifold port to EGR maybe restricted with carbon deposits.

the EGR 400 code may take a few engine cycles to throw..

I would compare the old EGR to new on the force to open the EGR... also push the EGR to open and block the vac opening to see that the EGR stays open ..this will confirm the EGR has no vacuum leak on the power head..
 

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Discussion Starter · #7 ·
The car has been ran from the prev owner on high octane, So this is what I will continue to run, no since on changing that.

The tank was pretty low, I gassed up & squeezed in 20 gal so the new fuel pump and filter could definitely be in question now as well.
(Which is a bummer because they are both just a couple months old.)

The Impala is a daily driven vehicle so Its never really sitting more than a day.

Im deff gonna check for any leaks or cracks on all lines running to and from the EGR.

Thanks for the input, I will try to address all these factors with the vehicle today & hopefully find the issue.

Time to get dirty & have some fun :D
 

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The car has been ran from the prev owner on high octane, So this is what I will continue to run, no since on changing that.

The tank was pretty low, I gassed up & squeezed in 20 gal so the new fuel pump and filter could definitely be in question now as well.
(Which is a bummer because they are both just a couple months old.)

The Impala is a daily driven vehicle so Its never really sitting more than a day.

Im deff gonna check for any leaks or cracks on all lines running to and from the EGR.

Thanks for the input, I will try to address all these factors with the vehicle today & hopefully find the issue.

Time to get dirty & have some fun :D
using 93 octane will cost much more than 87 and is not necessary. I tried it and back about 18 years ago most with these engines [oem] said the highest to use was 89 because it provides no improvement or gain.

I use most times shell 87 octane or mobil . shell appears to keep the throttlebody/IAC clean ..good luck with your purchase... 18 years ago these where pretty reliable not so much now at this age. you will learn much about auto repair ..
 

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Discussion Starter · #9 ·
Update::

Yup, just as I thought, BAD GAS!!
Since this issue I have filled up twice with Chevron High Octane
& used a bottle of 20 gal Techron Fuel system cleaner in each tank.

In the past week, Hard start has simmered down and is back to normal.
Car has been starting up like a champ, FIRES RIGHT UP!!

RPM surge is gone as well.

My Conclusion: DONT USE AMPM GAS!
Also, Techron fuel system cleaner gets the thumbs up recommendation!
 

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Yup, just as I thought, BAD GAS!!
Since this issue I have filled up twice with Chevron High Octane
& used a bottle of 20 gal Techron Fuel system cleaner in each tank.

In the past week, Hard start has simmered down and is back to normal.
Car has been starting up like a champ, FIRES RIGHT UP!!

RPM surge is gone as well.

My Conclusion: DONT USE AMPM GAS!
Also, Techron fuel system cleaner gets the thumbs up recommendation!
Glad you reported back. Not many do when they find the issue. Change the fuel filter anyway.

Chris
 

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Yup, just as I thought, BAD GAS!!
Since this issue I have filled up twice with Chevron High Octane
& used a bottle of 20 gal Techron Fuel system cleaner in each tank.

In the past week, Hard start has simmered down and is back to normal.
Car has been starting up like a champ, FIRES RIGHT UP!!

RPM surge is gone as well.

My Conclusion: DONT USE AMPM GAS!
Also, Techron fuel system cleaner gets the thumbs up recommendation!

I just want to add that any fuel supplier can give you bad fuel. I got a tank full of shell gas for my truck in south Carolina and the engine was pinging.. when I refueled in north carolina engine ran perfect... also my gas mileage returned to 18 MPG with the bad fuel I only got 15 MPG.

I have used techron for many years every few thousand miles and the intake stays pretty clean..
 

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Techron is one of the only 'fix it in a can' products that I know of that works. It's not going to fix big issues, but small drivability issues that you can't seem to pin-down to a bad part or anything else it seems to help. My car always ran a little better after a couple tanks of Chevron so I told my Daughter to stop going to the no name 'save 5 cents a gal' places.
 
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