perfectroller89

First let me start by saying hi to all here at ls1 tech. Since im a new member I thought that was due

Second im sorry if I posted in the wrong area and respectfully ask to have my post moved if this is the case

Now on to my problem I own a 94 trans am gt it has 180,000 on it and has been my daily driver for 3 years with in the last month the temps out side have been in the high 90's so my car dosent take long to reach operating temperature

The problem is once it hits around 180 it will surge back and forth seems to do it more on the highway but will do it at idle to. While warming. Up it runs great starts fine every time and drives like a dream

Now before I list what I have tried to fix this I know I need to stop throwing money at it which is why im here

I have replaced
opti
Tps
Iac
water tempature sensor
water pump
Both o2's
plugs and wire as of yesterday
maf
coil
icm
Ignition switch (old key)
PVC
oil change
Heater core
Have done cooling mod to icm

I have also tested spark from opti harness, ohms of fuel injector's, pushed in egr and it did stumble , fuel pump engages and primes., run datamaster and fast scan no codes fuel trim seems low at around 16 at idle 6 or 8 when egr engages . Problem is constant though power enrichment mode at wot I can also confirm it is switching from open to closed loop properly

I have no means of checking fuel pressure or compression I have done the carb cleaner test on all vacuum lines with no change

Some others info that may be of use is its stock except moroso cold air intake and the cats been punched (live in none emission state )

It seems this problem is beyond my knowledge and beyond the 10 mechanics that my step dad has working for him (two of which have a 94 and 99 t/a)

Lastly I thank anyone willing to help and oppligize for the long essay I have just wrote
have a great day

Alexdaredevilz

I don't know much about these engines but I had a similar problem once, and it turned out to be a blocked cat

perfectroller89

Thanks for the reply but it can't be a blocked cat because mines hollow im basically running straight pipes again thanks for taking the time to look over my post

shix

wouldnt hurt to check your cats.

Camaro350Z28

iTrader: (6)

what do you mean by surge back and fourth? rpms keep jumping up and down? or?

perfectroller89

Best way to describe it would be like a violent jerking of the whole car to be honest never watched the rpm as it did this since it always happens on my way to work and im just focused on making it there

Also I happens roughly after about 7 to 8 minutes

Just climb under the car (not to easy with the jack at the house ) smacked the cat a couple times sounds hollow still car had cat internals punched out when I got it 3 years ago

95 mystic ls

iTrader: (12)

Might be a $15 fuel filter?

License2Ill

iTrader: (1)

check the plug wires...also who is their make?
who is make for the replacment opti?

perfectroller89

Fuel filters got less the 1000 miles on it didn't mention it cause is not completely new I do have another waiting to go in

Parts are ac deco and cost me a fortune

gatorhead

iTrader: (4)

Should I be the third one to ask about a blocked cat after you clearly stated it was punched out lol.

Would you describe the car like it was a six speed and you are at a stop sign and trying to take off in sixth gear? Does it quite running when this happens?

I have a few ideas but I want to know these first.

perfectroller89

Its a A4 it does it in all gears usally shows it self sitting at a light rpm will drop down to about 400 the it acts like it will stall usally if I power brake the gas I can keep it alive (not always) then while im driving it acts almost like a engine govener kicking in where the whole car will jerk its very diffacult to explain so I understand ur confusion never had a car do this

food nd cars

def sounds like a fuel issue to me.. maybe one or a few bad injectors, also check fuel pressure as my fuel pump failed on me at 125,000 mi.
btw it is very easy to swap fuel pumps.

gatorhead

iTrader: (4)

I was asking if it felt like a manual trying to take off in the wrong gear lol kinda like that jerking shuddering, stuttering........anyways I will leave you with a few things as it could be one or many things regardless of whether you just replaced them or not. Bad parts come in new boxes, ask me how I know lol.

I agree with checking the fuel pressure, start there. If thats not the problem I would move onto diagnosing the problem and since you are saying it seems heat related then I would have to go to the ICM. If there is an Advance Auto near you they can test them, make sure they run the test 5 times in a row, that way it tests after getting warm. If it test good before putting it back on do the ICM COOLING MOD. It may help, but it cant hurt and it is cheap or free depending on what you have laying around.

Test the ICM harness. Use the ground in that harness when testing the other wires. Use shbox.com for the test procedures. Thius will verify your spark

Now, I just remedied a similar problem and I checked everything and I found ALOT lol so I cant tell you what exact thing caused it but I know of several that contributed. I had a weak ground, the grounds that mount behind the ICM are prone to this due to their mountings. Check them good.

Does the car run hotter than what the gauges show? This is also typical. The dexcool usually by this time has been introduced to air and the clay that was in it turned the fluid brown and dispersed into the system. The remnants of it is like a sludge and it gets in the heater core and radiator and uses that space instead of coolant. I flushed mine (water only!)and got alot out and changed the thermostat at the same time, old one was weak. My car runs a helluva lot cooler now.Also check the temp sensor in the water pump.

I found that the elevated underhood temps were heat soaking the ICM. I did the cooling mod and flushed the cooling system so it reduced the temps. Along with fixing the ground it fixed the problem. ICM tested good btw.

I also worked on someone elses car awhile back and it did the same thing and it turned out to be the sensor in the opti was getting heat soaked and quitting. That was a bitch to figure out as it threw no codes and everything was showing good. I had to use an oscilloscope to see that one acting up.

Gojira94

iTrader: (4)

You said temp sensor- the sending unit for the gauge or the one that talks to the PCM? (LH head between cyl 1 & 3 or in the water pump?)

IronOutlaw

iTrader: (4)

If your dad has 10 mechanics working for him Im sure one of them has a fuel pressure gauge you can borrow. Id also start checking all of the wires under the hood. Maybe something is getting hot and giving off crazy readings.

bizerk1

did u change thermostat and check your coil wire, any more info on the tranny other than its a a4, this problem sounds fimiliar and double check your 02s maybe u got a faulty one or a wire got burnt

95 mystic ls

iTrader: (12)

I think your trans may be a good place to look. If your trans is not unlocking the converter, it can kill it at a light. Also if your soliniods are kicking it in the wrong gear on take off it will feel sluggish. Third if the trans is sending the signal that it needs to shift down, it may be were you are getting the surg from. Take it to a trans shop, the will most likely take it for a test drive while hooked to a computer so they can see if the electronics are working right.

License2Ill

iTrader: (1)

are you sure your MAF is not on backwards?
could be a bad opti altho if it is genuine AC Delco would be tuff to beleive.
But as someone else posted bad parts do come in new boxes sometimes.

Sometimes too wide a gap on the plugs can stress a coil out...it's not widely advertised but is technically possible due to the current draw.

x2 for a vote against possible tranny issue......does any of this happen while in park....or neutral? Try to throw her into neutral and coast the very next time it does it.

(correction on above---vote is towards Not against)

95 mystic ls

iTrader: (12)

Even in neutral and park, if the soliniods aren't un-locking the converter it may still do it.

License2Ill

iTrader: (1)

Hey man I meant to write TOWARDS not against... stupid brain!!
So perfectroller the tranny could be culprit sorry to confuse.

Altho im not sure on when in P or D.
Mystic cant he disconnect the solenoids to rule that question out?