Missfire I think..getting worse, please help

Ryleighsdad · Jan 3, 2013

Ok, well I have another problem with this car now. It started a couple days ago. I noticed under steady throttle that it would "miss" once. Well its been getting progressively worse. I say its a miss because the car looses power and the rpm needle drops 100-200 rpm then right back up again.

Its intermittent though. Sometimes it runs just fine, then all the sudden it will miss once, maybe twice, then be fine for a few mins and do it again.

Tonight I left my mothers headed home and got in it. Ran to redline in 2nd gear. Well after that is when it started getting bad and I could barely drive it home. It was missing, bucking, jerking, and all manner of crazy.

I could only manage about 45mph out of it.

It has the following new parts due to another problem:

air filter
fuel filter
plugs
wires
cap
rotor
dizzy
coil
alternator
battery
Timing set, re-set, and double checked at 12*
Maf cleaned
TPS cleaned
EGR checked for operation
Searched for a vacuum leak to no avail

Please please please help me guys. I just started back to class yesterday, and I really need help figuring this out!!

Thanks for any help in advance.
Logan

toyman · Jan 3, 2013

When was the last time you physically checked the battery to engine and engine to chassis grounds? Check not only the terminal ends but also peel back about 1/2" of the sheathing to check for corrosion of the cables. The best way to check for vacuum leaks is a 'smoke test'. The better shops usually have the equipment to do this. Vacuum leaks can occur where you can't see them or effectively test for them. Also keep in mind that all sensors will eventually start to fail and cleaning doesn't help in these cases. That's where pulling DTC's can help.

Ryleighsdad · Jan 4, 2013

Car is not throwing any codes.

So today I took the TFI in to be checked and it failed 3 tests. Got a new one swapped it out. Problem still there.

It was dark so I decided to check for arcing in the engine bay and noticed a new problem. After only 2-3 mins of running the car I noticed the drivers side header was getting red hot. The passenger side was not!

This car sat for 4 years only having 1000 miles put on it in that time. Whats the chances I have a clogged cat causing this issue? Stock Hpipe.

Ryleighsdad · Jan 4, 2013

This is not my car, and this is a V6, but my car is doing EXACTLY THIS SAME THING!

toyman · Jan 5, 2013

Ryleighsdad said:
Car is not throwing any codes.

Where did you test from? The under dash one is not hooked up on the GT's. The test port is in the engine bay on the passenger strut tower. There is at least a 111 pass code but never no codes.

So today I took the TFI in to be checked and it failed 3 tests. Got a new one swapped it out. Problem still there.

Okay, surprised as the TFI's on the SN's are not prone to failure.

It was dark so I decided to check for arcing in the engine bay and noticed a new problem. After only 2-3 mins of running the car I noticed the drivers side header was getting red hot. The passenger side was not!

Discussion on this over the years has been inconclusive. Some say it's a lean AFR condition other say a rich AFR condition. The performance shop that built my engine says it's common for the headers to glow at idle. We just don't notice it unless it's getting dark.

This car sat for 4 years only having 1000 miles put on it in that time. Whats the chances I have a clogged cat causing this issue? Stock Hpipe.

Clogged cats are possible but I would look somewhere else first. PIP failures are common and are starting to show up more often as the cars age. There is quite often no code with a PIP fault.

Ryleighsdad · Jan 5, 2013

Tested with scan tool under hood. Passes all tests, but going to do it again today. No CEL.

I watched the machine report a low rpm and high rpm failure. The car has been sitting for four years with only 1000 miles on it in that time. The thermal grease on the TFI was dust.

Wonderful, so that doesn't tell me anything.

Car has a brand new distributor. I know new parts fail but I dont have money to start replacing all these brand new parts again...

ratio411 · Jan 5, 2013

I'd be more interested in the cylinders not glowing red...

You have replaced most everything that could be a culprit, however, brand new parts are known to be bad out of the box, so it's no garantee.
Also, when you replace so much at one time looking for a shot in the dark, you can have a tendency to install things incorrectly, as in leave connections loose or what have you, out of frustration. Been there, done that.

Go back and double check everything you did.
Look for loose, broken, dirty connections, check clearances (spark plug gaps too), and grounds.
Check voltage on new sensors such as the TPS, for example.

ratio411 · Jan 5, 2013

Ryleighsdad said:
This car sat for 4 years only having 1000 miles put on it in that time.

Bad gas?
Gasoline is only 'good' for about 6 months with modern formulations.
It will still work after that, but with decreasing reliability as it gets older and older.
Fuel tanks that sit, tend to rust as well. You could have 'crap' in your pump sock.
I have also seen the insides of pumps rust from sitting...

Even if your gas is not terribly old, if it was bought during summer, and then run in the winter, you have to wonder about the fact that gasoline is reformulated throughout the year depending on weather. You might be trying to run fuel that was formulated for weather totally opposite of what you have now.

Ryleighsdad · Jan 5, 2013

Thanks for trying to help me figure this out. I swapped all those parts one at a time trying to figure out an "intake backfire" issue. That turned out to be the coil.

Ive run a dozen or so tanks of premium fuel through it since I purchased it, as well as chanced the fuel filter.

Checked again today and got codes:

DTC211
DTC212

So Looks like I need another new distributor. Good thing it has a lifetime warante.

Ryleighsdad · Jan 5, 2013

Just poppped the Dist. cap and looked for problems...Found this...

toyman · Jan 5, 2013

Car has a brand new distributor. I know new parts fail but I dont have money to start replacing all these brand new parts again...

Brand new as new or new to you. Was that a reman distributor? My guess is if you pull the distributor you will see signs of where the PIP sensor is making contact with the vanes.

Ryleighsdad · Jan 6, 2013

It was a reman unit. All they had at the time. New distributor fixed the problem. Thanks for all your help Toyman.

toyman · Jan 7, 2013

Ive run a dozen or so tanks of premium fuel through it since I purchased it, as well as chanced the fuel filter.

87 Octane should be fine with timing between 12*-14*. Don't confuse octane numbers with quality. Higher octane fuels just burn slower which is required in higher compression engines or boosted applications.

Missfire I think..getting worse, please help

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