JTOTHAP

Okay guys I am open for ideas. I have a 1999 C5 with an LS1 and its running on Cylinders 1,2,3,4 and not on 5,6,7,8. You can smell raw fuel and the car is running very rich. It sounds like there is a massive cam in it. I have changed the plugs and wires to see if that was the problem. I scanned it and I found out about the cylinders not firing. All the injectors are working and all of the coil packs are plugged in. No codes are being thrown at all.

Im open for ideas and/or suggestions. Hopefully somebody on here has had this issue and knows how to resolve it. Thank you in advance.

TooLateVTEC

iTrader: (2)

Are you sure its 1-2-3-4 or is it one back of cylinders (as in one side of the engine) ?

I find it really wierd to be firing on the first 4 numerical cylinders.

Sounds to me like the coil pack isnt getting told to fire or the connection isnt very good maybe.

JasonSS2000

iTrader: (1)

I would check the coil pak plug or grounds (all the grounds, engine & both the chassis connections, drivers side rear of head, etc.). What codes? With a C5 you can pull them up in the DIC. This will tell you just what cylinders are firing. A misfire will cause the check engine to flash as well.

Look for an O2 sensor code (bank 1, sensor 1 or bank 2, sensor 1 as the upstreams tell the PCM how much fuel to add to each side) as a bad O2 on one bank may cause the PCM to add to much fuel).

Also, the drivers side is 1-3-5-7 and the pass 2-4-6-8 so it would be really weird for 1234 to fire & 5678 to not as it would be alternating from the left to right side.

Give us more info.

Z28_LT1

iTrader: (2)

so the back four are firing but not the front?

JTOTHAP

I put the car on a scan tool from the chevrolet dealer here locally. The car shakes very badly and idles rough. You can smell raw fuel as soon as its cranked until it is turned off. When using the scan tool we turned off each cylinder individually to see what effect it would have on the motor. When we turned of cylinders 1,2,3,4 and it effected how the motor ran. It would bog down and almost die. When we turned off 5,6,7,8 it did nothing to the motor and had no effect on the way it ran. We tested the coil packs on the back two cylinders on each side and all four had very little spark. The car is throwing no codes and the scan tool registered no codes. The check engine light isnt even on. This is a very strange and frustrating situation to be in. It literally sounds like it has a massive cam and running like poo at the same time.

TooLateVTEC

iTrader: (2)

Has there been any work done to the car recently, or has it been run really hard when this happened?

I see your sig says mild cam, worst case scenario is maybe the cam is wiped on the back 4 cylinders.

Any metal flakes on the dipstick?

This is wierd for sure.

JTOTHAP

The car set up for about a week and I drove it to a local sonic. It is a 30 mph zone the whole way. I just cruised. No work has been done to it in a few years at least.

white2001formula

iTrader: (5)

If you are in fact running only on the first 4 numbered cylinders, the car would have died when you did this. (bolded below) How is fuel pressure? What spark plug wires and plugs did you get? Are you SURE they are connected? Those can be a PITA sometimes when headers are in the way. Do you drive this car daily, or every now and then?

Typically, you'll have problems related to one side like others have mentioned. It almost seems like it's something simple.

If you tested the coil packs and saw little or no spark on the rear 4, then you could always verify by changing for instance the front two coil packs with the back two and doing the same test. If the issue follow's the coil pack, you've found the culprit.

Hope it helps,
Chris

JasonSS2000

iTrader: (1)

Pull the DIC codes up....I bet it will show some. Unless the codes are all shut-off in the tune there has to be codes if it runs like that.

Pull them up & post them for us. :thumbs:

JTOTHAP

It ran so rough when I pulled up in the stall at sonic. I killed it and it didn't want to crank back up. Put some fuel in it just in case because you know how the corvette fuel gauges are. This problem was happening before I changed plugs and wires and yes I made sure the plugs were done properly and all the wires are on the plugs. The driverside #7 wire was the hardest but they are all fully connected. It is not shoing an engine light nor is it throwing any codes. I even reset the codes on the dealer scan tool to see if it would make them show up and it still showed no codes being thrown. I'm frustrated and have no clue.

Phantom_LS2

iTrader: (3)

My GTO does something similar to this. One thing I've noticed recently is it'll only do it when it's REALLY low on fuel. I'm planning on pulling my tank soon to check for garbage / water in the bottom of the tank, fuel pump, and filter.

JTOTHAP

I swapped the coil packs around and nothing changed so they are fine. Phantom LS2 I thought it was bad fuel as well but I filled up and ran almost through and entire tank and nothing changed.

trans_am7935

iTrader: (15)

Dude, i did the same thing to my car when i changed my push rods, check the coil pack plug. if it is not plugged in your car will still run but not fire on half the cylinders. i had the same issue and thought it was cool till i found out i was missing half my power. just check the coil pack plug in the middle on the coil pack on the backside.

Ferocity02

iTrader: (60)

I had this problem, but it was because the reluctor wheel on the crank was installed backwards, and it was running on four random cylinders. It idled rough, wouldn't rev past 1k, tach didn't work, smoked and smelled of fuel. This obviously isn't your problem.

I would check the crank and cam position sensor. Then check ALL the grounds.

Or just tow it to the dealer.

96blackta

iTrader: (7)

Check the Inj 1 and Inj 2 fuses.

JTOTHAP

Everything is plugged in. I have no clue. I had a mechanic come from the dealer to my house and scan everything and look everything over. I may just end up towing it down to EnglandGreen and letting them fix it. I am clueless.

HotSilverBird

Sounds like the PCM has failed, try pulling the fuses for the pcm with key on to reset it.

RsSean

iTrader: (27)

Something that maybe easy to check to is to see if the lobes wore off the cam would be to pull off the valve cover, and use a dial indictor to check lift on the front four cylinder on the spring retainer and then do the back and see if the lift changes. Compression test may help as well could have cracked cylinder wall between the rear cylinders. Highly un likely, BUT

joecar

Keep us posted.

96blackta

iTrader: (7)

But did you actually check the fuses and see if they are blown?