The idea that i came up with yesterday may be a possibility but its just a theory that i have.

Cylinders 2, 3, and 4 seem to be doing it the most while cylinder 1 seems to be more of a rarity. My theory is about the fuel pressure gauges sending unit (or whatever you call it). Its installed in the fuel rail in between injectors 1 and 2.

Could it be a possibility that once the fuel pressure climbs enough that its not able to pass enough fuel past this unit to get to injectors 2, 3 and 4?

Reason i ask is that the car ran a lot worse in the beginning to the point where it would stall out and die. My brother added this fuel pressure gauge after it started doing this. After replacing a bunch of stuff it runs a lot better but just has this misfiring at higher fuel pressures. I'm wondering if we fixed the original problem but only added an extra problem on top of the original with installing this unit into the fuel rail. And maybe that's why we are having such a problem fixing this.

So not willing to swap plugs? it is a cheap easy thing to do. Plugs do wear.



MD Motorsports

ive already stated its got brand new plugs in it... the same brand and stock number he put 20,000 miles on with absolutely no problem. I dont see how switching away from a plug that has given him absolutely no issues in the past with this supercharger is going to solve anything. I can give it a shot but i really can't see that solving the issue. It defies common sense to me.

re gap them smaller, just try it, if it doesn't work it at least rules someething out...

lol wow @ tech

Rob wrote:

Qwibby {T3H Old QBE} wrote:

spark plugs get used... so they wear down over time. Get new plugs, those NGK's and regap them to .035 and have a better day buddy....

random cylinders at random times - spark blowout

the GM 2.4 kits are notorious for it....

How is not gapping a plug to manufcature spec going to fix anything, and even if it did, you put a band aid on a broken arm. the problem is still there

He's correct on this.

meckster wrote:

ive already stated its got brand new plugs in it... the same brand and stock number he put 20,000 miles on with absolutely no problem. I dont see how switching away from a plug that has given him absolutely no issues in the past with this supercharger is going to solve anything. I can give it a shot but i really can't see that solving the issue. It defies common sense to me.

I can understand your reason of not changing the plugs, (BUT) he changed a bunch of other parts aswell. If it was and only the plugs he changed, then I would go with your route and look at something else.
Now the question is, are the new parts AC Delco?
I would look into throwing a good fuel system/injector cleaner along with the Delco R42LTS plugs.

Goodluck.



-----The orginal Goodwrench on the JBO since 11/99-----

"If you don't stand for something, you might fall for anything"

not all new parts are acdelco... most of the stuff i got through napa


i just tried all the spark plug theorys... different gaps and even tried the R42LTS plugs... problem still there.


The damn thing still sounds like a machinegun at 52psi and above in the fuel rail. I just dont understand it

oh.... completely forgot to mention that we found that one of the bolts to bolt in the supercharger to the engine was gone, and the one next to it was backed a quarter of the way out. All the other ones were merely hand tight it seemed. After i tightened these all down and replaced the bolt. thats when it started running better. It stopped stalling out and dieing after that. So all thats left is this damn misfire problem

Have you replaced all the o rings at the injectors ? Maybe one is ripped or torn and only when it pressurized it spreads and allows air in? Way far chance but something similiar happened to me

"So all thats left is this damn misfire problem" - - -

All along it has been symptoms of weak spark or bad spark plugs.

There's not any brand of spark plug that occasionaly doesn't have
some "bad ones".

I'd throw the current set and start with something new. Whatever
brand and plug number I wouldn't know.

I can try new o-rings tomorrow, its worth a shot. But i pulled them all out today and nothing out of the ordinary really.


And its not the spark plugs... ive tried three different sets gapped at different heights, not a lick of difference. So its safe to say we can rule them out.


Here are some engine values i got today that might help you guys with some ideas.

- At closed loop, Long term fuel trim is at -22%
- key on engine off.... the tps reads .55 volts with the throttle closed.... and 4.39 volts at wide open throttle


and i will repeat... this misfiring can happen to any of the four cylinders..... only under heavy load (in which the fuel pressures rises above 50psi)

oh and also...

we replaced the cat because it blew apart inside. pieces of it literally blew out of the muffler. This happened right after this all started.

and he replaced both o2 sensors with bosch brand sensors

If your LTFT is -22% you have a serious rich mixture, and it is telling it take away fuel. More than likely a leaking fuel iinjector




2004 Cavalier - daily driver 74k, still got the original tires on it

Looking to be running really rich for some reason if you actually blew the cat apart.

yeah the cat literally melted and blow the insides out the exhaust. when he removed the cat it looked like a bomb went off inside.


question for you guys.... since the cheapest i can find these injectors to replace the ones that came with the supercharger are $105 a piece... does anyone know if i can swap them all out for the stockers just to see if that gets rid of the rich problem? I'm talking about just temporarily... or is that a no no with that supercharger?

Super rich, start off with replacing that front o2 sensor with an ac delco

Being that I'm not there to physically diagnose the the car it is hard to determine the problem.

You said you put in a brand new set of R42LTS plugs gaped to 0.050 in. And still the same problem.

Keep the plugs in, and try a new ACDELCO coil housing and a set of ACDELCO coils. Also make sure that all 8 springs (housing/boots) are making good contact including connectors.



-----The orginal Goodwrench on the JBO since 11/99-----

"If you don't stand for something, you might fall for anything"

replace coil housing

I would not go with stock injectors. I do have a brand new set of 3100cc injectors never used I'm selling.



MD Motorsports

like they said, blowing a cat apart and sounding like a machine gun means very rich..too much fuel or not enough air. i would lean towards the injectors. frankly, i would just try to clean em. you could do a balance test, but what you're lookin at is too much fuel at high load, so we should start looking at something that would cause that. what did the plugs look like when you pulled em? all 4 black? only a few black?

oh, and bosch sensors usually don't work too well in our cars...different resistance ratings and such. all the computer reads is voltage, so if your bosch sensor is reading slightly rich, or even lean or anything, but the voltage that it makes at that condition is that of a different value than what the delco one puts out, the computer will read whatever it should if it was a delco sensor.