High-load, low RPM misfire(?)

[Wayno]

Car:
• 1995 Camaro Z28 (LT1) M6 with ~69k miles
• Hurst shifter
• SLP intake & exhaust (dual conical K&N air filters)
• Intake airfoil
• Performance Friction race pads - front (they dust too much)
• Performance Friction street/track pads - rear (I prefer these)

Symptom:
When the engine is at low RPMs (~<2k) and throttle position is greater
than 3/4 in a higher than ideal gear (a co-worker of mine referred to
this as "lugging the engine") the vehicle car starts to shake. I
think that some of the cylinders start missing as the source of the
shaking appears to be from the engine.

Other indicators:
None; this is what is confusing me since the engine should set the
"Service Engine Soon" indicator if it detects a misfire.

Troubleshooting steps:
I did add some fuel injector cleaner but it doesn't appear to be
helping. I think the problem has more do with spark. This condition
is reproducible every time I'm on the highway cruising in 6th gear and
then mashing the throttle. Shaking galore! Lower gears also work but
RPMs have to be low. Hard accelerations from a stop (ex: 0 to 60) do
not cause this to happen and the car's 0 to 60 performance appears to
be the same as it ever was. I've noticed no decrease in fuel economy.
I tried getting the local AutoZone to pull the codes from the ECU but
their reader was not able to link up.

My request:
I have a service manual, but it's buried somewhere in my storage and I
have not been able to locate it. I would appreciate troubleshooting
suggestions or possible causes for this symptom. Thank you very much
for your help!

[4 GOOD@earthlink.net BAD 4 GOOD]

I also had this problem with a recently acquired V-6 (3.4) 95 F-bird.
Around 1500-2000 Rpm in overdrive...the shakes/missing.
It would also sometimes miss at a red light at idle.
Dropping out of O/D would clear it ,
until it was under a load again in O/D.

My cure was replacing the plugs and wires....( 3 plugs were only in hand
tight )

My guess is it was blowing by the plugs on my car under a load.

Hope this helps........Stan

"Wayno" <wptas...@yahoo.com> wrote in message
news:b8239792.03091...@posting.google.com...
> Car:
> . 1995 Camaro Z28 (LT1) M6 with ~69k miles
> . Hurst shifter
> . SLP intake & exhaust (dual conical K&N air filters)
> . Intake airfoil
> . Performance Friction race pads - front (they dust too much)
> . Performance Friction street/track pads - rear (I prefer these)

[rbc]

could be plugs&wires need to be changed. Also the cap&rotor. Make sure your
water pump is not leaking antifreeze on your cap. That could cause it to
crack, letting antifreeze in and causeing a missfire. good luck

"Wayno" <wptas...@yahoo.com> wrote in message
news:b8239792.03091...@posting.google.com...
> Car:

> . 1995 Camaro Z28 (LT1) M6 with ~69k miles
> . Hurst shifter
> . SLP intake & exhaust (dual conical K&N air filters)
> . Intake airfoil
> . Performance Friction race pads - front (they dust too much)
> . Performance Friction street/track pads - rear (I prefer these)

[Omegaman]

"rbc" <r...@stny.rr.com> wrote in
news:4738b.52150$yG2....@twister.nyroc.rr.com:

> could be plugs&wires need to be changed. Also the cap&rotor. Make sure
> your water pump is not leaking antifreeze on your cap. That could
> cause it to crack, letting antifreeze in and causeing a missfire. good
> luck "Wayno" <wptas...@yahoo.com> wrote in message

Correct me if I'm wrong, but I think that year LT1 has a distributor-less
ignition (ie. no cap or rotor). Good luck with the plugs... they're
impossible to get to by mortal men.

-O

[Gary - KQ6RT]

"> Correct me if I'm wrong, but I think that year LT1 has a distributor-less

You are in fact wrong. Lt1's use what it called an "OptiSpark" distributor.
It mounts on the front on the timing cover, behind the water pump. This
setup was used only on the LT1 and LT4 engines. If they used the standard
rear mounted distributors in the 4th gen cars you would have to remove the
engine just to change the cap and rotor. - Gary

[Ray]

LOL - I never even thought about that. I thought changing the plugs
on an LS1 was a bitch.

Changing the distributor cap & rotor on an L98 93 Camaro:
option a) drop engine
option b) remove windshield and top of dash pad. Sawzall a hole
in firewall.

Sometimes I miss my 70 Buick. Enough room to pull the tranny out
from the top - no need to remove the engine. ;)
--
Ray

[Zuhalter]

I don't beleive that a L98 was availible for a 1993 Camaro.

"Ray" <r...@yourisp.net> wrote in message
news:3F611DFF...@yourisp.net...

[Wayno]

Thanks for the suggestions guys. I'll get to work on this tomorrow
after swaping the front brake pads. Do you think that I should still
try to get an OBDI diag tool reading or just jump into replacing the
plugs/wires and perhaps cap and rotor? Any suggestions on replacement
parts (speciflically the plugs and wires?)

Thanks again,
Wayno

[rbc]

You are indeed right, but it works the same.
"Omegaman" <ThouShal...@nospam.com> wrote in message
news:rbednc9dJ_O...@wideopenwest.com...

[rbc]

I should have said, Cap and rotor as we once knew them. The Optispark works
the same way.
"rbc" <r...@stny.rr.com> wrote in message
news:ULG8b.29488$3t2....@twister.nyroc.rr.com...

[Wayno]

I found my service manual this weekend! Woohoo. Bad news is that it
looks like changing these plug wires is going to be a major PITA.
Have to take off the PS pump and drain the coolant! I think I'm going
to call around to find out how much the local places will charge me to
do this before I spend a whole weekend on it.

Anyone know where I can find a Tech 1 to borrow for a few minutes?
Auto Zone has OBD readers but the will not link with my car due to the
OBDII connector (I think). I'm currently in the Detroit area.

Also, I looked into replacement wires this weekend AZ had the MSD
wires but I hear that they do not find into the stock guides. The
other choice was Bosch, which also were custom wires. Any comments?
Also, has anyone tried the Platinum +4 plugs? Are these worth the $
or are iridium (sp?) the better way to go? Thanks!

[Wayno]

Darn,
I was just quoted $695 for changing the plugs and wires by Midas. 6
hours labor!!! How much time should this take them to do really?

[bikerbob]

At 50.00 per hour, and I am not sure what the going rate at Midas is. That
leaves 395.00 for parts! That in my opinion is A little expensive. Do you
know what there rate per hour is? A couple of years ago I had a new water
pump, optispark, plugs,wires and fuel filter installed at the Chevy garage
here in town and if I remember the labor required was a little over six
hours. The bill came to 900.00.

"Wayno" <wptas...@yahoo.com> wrote in message

news:b8239792.0309...@posting.google.com...

[Wayno]

The dealers in town charge $75/hour. Midwas is supposedly at $65/hour
if I remember right.

I've been thinking about this issue that my car is having and am
confused to the logic why this would be caused by either the plugs or
wires. Wouldn't I have problems all over the RPM range if that were
the case? Why only at high loads at near or at WOT? Just trying to
get it straight in my head. Thanks!

"bikerbob" <bb@f%&kspammers.com> wrote in message news:<nRBcb.3292$dG3....@twister.nyroc.rr.com>...

[The Man of Steel]

I was able to change all my plugs and wires by getting to several of them
from underneath by dropping the pipes. No need to do anything with the ps
pump or coolant.

Superman

"Wayno" <wptas...@yahoo.com> wrote in message

news:b8239792.03091...@posting.google.com...

[Wayno]

Thanks.... I noticed that this is what was stated in the F-Body FAQ,
I'm surprised to see that it conflicts with the service manual.

Question... If I get an 8.5mm wire will it fit in the looms? What
about an 8.0mm? If no, how does one get around this? I hit the local
Auto Zone last week but was lost at which plug wire I should purchase.
I'd like to get the High Performance MSDs but I don't want to make
this job any harder that I already know it is going to be....

Thanks!

"The Man of Steel" <supe...@autoearnings.com> wrote in message news:<vooch2r...@corp.supernews.com>...

[Wayno]

Well I tried my luck chaning the plugs/wires yesterday. What a PITA.
I ended up braking the first two bolts when I tried to take off the
Y-pipe, even after soaking them with liquid wrench overnight. After
that point i decided to give up since any more broken bolts would have
left me with a car that I couldn't drive. Instead I ended up chaning
the oil/ air filter/ PCV valve. Looks like I'll be paying a shop to
do the plugs/wires for me.

Thanks for all your help!
-Wayno

wptas...@yahoo.com (Wayno) wrote in message news:<b8239792.03102...@posting.google.com>...