misfire and no SES.....

[Fierotom]

Hello friends,
I'm new to the board (see my thread at the lounge forum)

here is my problem:
my 1999 Camaro with an 3,8L L36 engine and A4 trany starts to misfire.......:(

if I drive with less throttle it runs fine and the fuel economy is very good!
Idle is very smooth at 750 rpm in "D"....

But if I floor the gas pedal to WOT the exhaust make a popping sound and the engine has less power...
same happend if I drive uphill with more throttle.....

The engine has 28k on the odo and is complete stock (okay, I put a K&N filter in months ago)

I have read a lot of threads about misfire and most people see the SES in the cluster..... but my ECU don't set a code! I have scanned it with two different scantools, the ScanGaugeII from LinearLogic and my AutoEnginuity tool says "NO CODE" and the misfire history is clear (????)

This is what I don't understand.... the misfire is heavy at WOT and above 3000 rpm...... It feels like the block detonate.....

Okay, first I try to change the spark plugs and the wires!
My choise are plugs from NGK - Iridium IX and a set of wires from MSD, but I haven't them yet..... I'm looking at summit, but they want $23 handling fees for oversea delivery.... hey, $23 to fill out the CN22 USPS Custom Declaration...

another opinion is a vaccum leak at the intake manifold or one or more injetors...
how can I check it for vaccum leaks? Is the stethoscope method helpful or can I spray WD40 around the gasket area?

how can I find out if I have a bad injector without a misfire code for a specific cylinder?

last not least. I change my coils and the ICM

any other opinions?
thanks!

[Fred]

Re: misfire and no SES.....

I would start seafoaming it and by changing out the spark plugs and wires first.

[loser]

Re: misfire and no SES.....

did you check the plug wires for cracks/burns? even a little bit can do it. a clogged fuel filter could do it to, but with those kind of miles i dont think so.

[99camaro-3.8]

Re: misfire and no SES.....

im having the exact same problem i just put in a brand new engine with only 2000 miles on it and its doing the exact same thing. one other thing i am thinking it may be is a lean air fuel mixture. this can be caused by bad sensors causing the computer to think there is less air so its not giving the engine enough fuel for the amount of air coming in. a lean condition such as this will seem like a misfir and feel like one without throwing codes nor will plugs and wires help it. this would also explain why it only does it under heavy load. during normal driving a slightly lean condition is ok but under heavy load more air is coming in and the bad sensors are not allowing the computer to adjust and give it more fuel. im going to check out my car tomorrow and see if this is really the problem. i will post with what i find

[white98mo]

Re: misfire and no SES.....

First, let me say welcome. I joined this group a few weeks ago and have found it very useful in diagnosing my problems.

One thing I noticed in your summary was the car only has 28K miles. The computer will eventually throw a diagnostic code if the misfire continues long enough to damage the catalytic converter. Since you are not seeing a code and the car has obviously been driven very little ( I'm jealous of your low mileage ) have you checked or replaced your fuel filter? The time the car was not being driven may have lead to a situation where the moisture may have enetered your fuel system. Is there something like Stabil fuel stabelizer there in Germany? We use this product for things like boats where the engine is stored over the winter.

Beware of randomly exhanging parts. If the misfire is not bad enough to throw a code keep your part buying to the cheaper things like you mentioned. Spark plugs, coil wires and even coils can be used later if they don't fix the problem but if you buy something like an Ignition Control Module and you don't need it than you coul've spent your money on something more fun.

Enjoy that Camaro, I still have my intake disassembled so I'm driving my truck to work until I get back together.

[Fierotom]

Re: misfire and no SES.....

thank you very much!

I see, a nice and helpful forum, you are great :)

to replace the fuel filter is an easy job, I do it first!
Yes, the car has very low miles, because it sat at the dealer until March 2002...

99camaro-3.8: I wait in suspense to your result (is this correct formulated?)

Fred I have read all about seafoaming.... do you think I have carbon build-up at only 28k miles?