RUF SS

I drove the car normal and it was fine! Austin was too hot that day (about 103F), the car did detonate for a small bit but all was fine! I stopped for about 3 to 4 hours and then took off. It was fine for a bout 15 miles. After that the car started to idle like a top fuel drag car. I did a leak down test, checked the plugs, and all was up to par. Everything seems to be fine regarding AutoTap as well except for the misfire that the car is having!

I have not idea what could cause this! Could a blown head gasket be the problem and not show up in the leak down test?

Any help is really appreciated!!!!

Thanks!

Visceral

iTrader: (1)

autotap results/codes or similar?

RUF SS

Well, I have tuning. Nothing seems to be out of wack! Only the miss fire! @ idle i get about 180 to 200+ miss fires. I am thinking I may have a blown head gasket, but the leak down test looks ok!?!?!?!?!

RUF SS

????

malibu350

If you had a blown head gskt...more than likely you would have water in the oil...have you checked any of your wires??? And is the SES light flashing a lot indicating mulitiple cylinder misfire???

Ragtop 99

iTrader: (7)

do the misfires occur badly on all cylinders or just one or two? ATAP current misfires for each cylinder.

If just one or two have misfires, try swaping coil packs and plug wires to see if the misfires move.

RUF SS

Thanks guys! The problem is that AutoTap is not giving me missfire per cylinder it is just giving me the total! I will start all over agin and see!

Could it be the crank position sensor?

VSGLS1

iTrader: (8)

I had this problem once. It was injectors for me. The car just out of no where started shaking and loping like a dragster. Took it to the dealer and they cleared the PCM. Got a mile from my house, and it happened again. Took it right back. I wound up getting new injectors and a reflashed PCM. Not sure which codes will lead you to ruling out the injectors, good luck.

RUF SS

The funny thing is, there is no code! Nothing!
What was your car doing? was it too rich or lean?
I may change them anyway just to be sure! This is getting me mad!

malibu350

I would try everything that doesn't cost too much money first...new injectors can be expensive...unless you have the money to just throw away on them...or you needed them anyway..then of course it's a good excuse to get them :p but I would try the coil pack swap first..if you can find out what cylinders are misfiring...but no SES light or anything???

H82BBad

I would check your valve springs. If you have duals one can break and fool you good while trying to find the problem.

JurisAg02

make sure they plugged all your vacum lines up behind the intake...I had the same problem one time Tom and it was because the vacum lines behind the intake were not connected...if you read a GM manual even for the LS1 under diagnosis for missfires you will see check vacum lines around and behind intake

driftwood

iTrader: (1)

Couple more options.If you have a bad head gasket,you can check for hydro carbons in the radiator.Also check your header tubes close to the head with engine at normal operating temp,a bad cylinder will show up out of average-i.e. cooler temp.
One last thing,if this is mainly occurring at normal operating temp,check your fuel pump flow rate.When it gets hot,it may be failing.
Good luck.

RUF SS

Thanks guys!
Well, this happens after 5 to 10 sec from start up! Very strange!
I am taking the intake and the valve covers off tomorrow! And we will see what disease it has!

Thanks again!

Visceral

iTrader: (1)

wait wait wait.... if it starts happening exactly 5-10 seconds after startup... look at the folowing:

1. Engine Sensor fuse
2. 02 sensors.

This happened to me before. Not sure how, but the engine sensor fuse was blown. Same as you...no codes. It was nice that it was a <50 cent fix.

chris

RUF SS

Thanks!!!! I will check that first!!

RUF SS

One more thing! Where is that fuse located?

Thanks!

RUF SS

The funny thing is, if I start the car and let it idle by it self, it is about 90% to 95% fine! After I rive the rpm over 2000 it will start to miss up!

FEAR THE LS1

iTrader: (1)

I am getting a similar problem. I am going through the tuning stages on my new engine.

I get misfires on all cylinders but the car idles fine. I can't hear anything wrong, but ATAP is showing misses on all cylinders. After about 60 secs I get P0106 code, MAP sensor low voltage, and the ASR turns its self off, which is normal if the MAP sensor fails. But if I let it idle about another minute the ASR comes back on. The misfires are not constant on all cylinders too, like I will get a bunch on them all then it stops and none, then a few minutes later I get misses on all again.

I am pulling my intake, valve cover and rocker arms tonite. I am going to recheck my head torque specs (ARP Head Studs) and also take a look at the vacuum hose and MAP sensor on the intake.

Let me know what you come up with.

Gremlins

Lee

RUF SS

I will!