Heard a pop then...

Fuel · Post by **Fuel** » Sat Jun 10, 2006 5:50 pm

Hey all,
Got an '89 GTU that's acting funny at the moment. Doing about 40 when I heard a pop go off, then severe loss of power. It'll start no prob, and idle nicely but she's worthless under a load.

Under the hood:
Found the vac line from TB to the canister off -
plugged it back in. Otherwise nothing
out of the ordinary.

Threw in some h2o remover and
inj. clearner but no change.
Went through diagnostic mode -
flashes 12 repeatedly and nothing else.

At the moment the plenum is off
and I'm checking FI. Front gasket
was cracked everywhere, back
gasket was fine. Have a new
PCV which I'll throw in.
Have cleaned and polished the TB
recently.

140K and never a problem. Real
strong and fast.

Trying to locate the TCC so
any other suggestions are
welcomed.

rweatherford · Post by **rweatherford** » Mon Jun 12, 2006 11:55 pm

If the upper plenum gasket was leaking bad and letting air in the engine, those cylinders would be lean and could cause an intake backfire, which would sound like a big "pop"

Fuel · Post by **Fuel** » Mon Aug 07, 2006 11:05 pm

Updating the board in case it may help others... problem still not licked

changed plenum gaskets, PCV
and plugs. injectors ok. unplugged
tcc. no vac leaks. still no fault codes.

seems like its running on 5 cylinders

idles fine and will drive, just chugging and loss of power, vibration etc.

leaning toward IAC, and ign. mod.
whatdaya think?

rweatherford · Post by **rweatherford** » Mon Aug 07, 2006 11:46 pm

If the plugs, wires and coils are fine then I guess you can try the ignition module. Some parts stores can check them.

berettajunkie1991 · Post by **berettajunkie1991** » Tue Aug 08, 2006 1:25 am

i had the same problem you may have dropped a valve into the cylinder i had no codes go off either the valve maybe smashed up into the head so check your split locks and springs

z284pwr · Post by **z284pwr** » Tue Aug 08, 2006 3:19 pm

Compression check?

Fuel · Post by **Fuel** » Tue Aug 08, 2006 4:32 pm

was praying to the gods of chevy
that it's nothing mechanical
but alas, these are things I
must consider!

will start doing the comp. check
today and update

thank you gentlemen

Fuel · Post by **Fuel** » Tue Aug 08, 2006 7:44 pm

1 - 150
2 - 152
3 - 140
4 - 152
5 - 155
6 - 155

may be a tad out of adjust.
all holding tight though

all plugs a bit black. something
is causing a rich condition.
but it seems the comp. would
register a fault code.

1988GTU · Post by **1988GTU** » Tue Aug 08, 2006 9:43 pm

Blown out fuel regulator?

rweatherford · Post by **rweatherford** » Tue Aug 08, 2006 9:43 pm

A misfire will cause a rich condition as well as some other things.

Compression is not terrible on #3, but there could be something going on there.

berettajunkie1991 · Post by **berettajunkie1991** » Wed Aug 09, 2006 1:25 am

yea i agree the cylinders are within of about 1.5% of each other so your pretty even, but once again i might consider something mechanical has gone wrong.
Also did it smell rich in the plenum, if it did i suspect something with you valve train how many miles do you have on the motor, i had a new short block and my heads were not rebuilt when they put the new block in and well the split locks cracked and gave out so check your valve train. i have new rebuilt 3.1 with 7000 miles on it, 175-180 psi in each cylinder so you do have some wear

Fuel · Post by **Fuel** » Wed Aug 09, 2006 8:23 pm

^ smelling gas at the engine
and muffler no visible signs of a
leak

at this point I suspect
the pressure regulator,
will need to get a
gauge to test though

here's a little something that
might help you help me...
when I start her up she runs
good for about 3 - 5 minutes
then all the hell that I mentioned
earlier breaks loose

rweatherford · Post by **rweatherford** » Wed Aug 09, 2006 10:31 pm

If you take the vacuum line group out of the TB (on the top) and no gas comes out with the key on, then the FP regulator is probably ok.

I think you may need a better scanner to figure this one out.

3-5 minutes is about when the car would go into closed loop.

Try pulling the battery cable off for a few minutes to reset everything. Unplug the oxygen sensor and see if it runs better for a day or two. If not then plug the sensor back in and see if it improves or gets worse. If no change then it may not be any good.

If none of this works you might see if the converter in the exhaust is plugged up.

Fuel · Post by **Fuel** » Fri Aug 11, 2006 1:02 am

^ seems like it ran a little
better unplugged, not
extremely noticable either
way though

no gas at FP reguator vac
line, prolly ok

just for the heck of it I
turned on the ac and
mad fumes where coming
out. a plugged cat would
definatly back things up
so makes sense.

not sure what that
pop was, unfortunatly nothing
visible. came from the
engine compartment
I know that

neway, the hunt continues

Fuel · Post by **Fuel** » Mon Oct 23, 2006 1:46 am

Updating the board...

Problem solved!

It was a bad coil (1and4)
Believe it or not, the car
still ran, drove, idled etc.
albeit crappy.

the computer was no help
so with new plugs I took it
out and drove it hard checked
and walla.

the pop was a misfire
which was the coil taking a
dump

hope this helps others
out there

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