weswisehart

My 305 tubing Camaro is stuttering only while the gas pedal is pushed under normal driving conditions. If I let off its smooth. While idel its smooth and if the pedal is to the floor it seems smooth. I'm not sure what could cause this. Thanks

coryprine

iTrader: (4)

Could it possibly be a misfire? My 2002 Camaro is doing the exact thing and it ended up being a cylinder 5 misfire under load.

Grumbles

Start with fuel delivery if the misfire thing falls through. Could be a failing pump or clogged filter.

weswisehart

I will change the fuel filter sometime this week but it runs fine during Odell and under full throttle so idk.

weswisehart

I purchased a new fuel filter and will install it this evening. Fuel prices went up and so have fuel filters ha ha

palmer90rs

hey my 90 rs 305 is havin the same problem, did that fuel filter fix the problem?

weswisehart

No it did not. I also changed my spark plug wires and it still stutters. I will pull out my plugs this weekend and see if that's the problem. I have no other clue what it could be.

weswisehart

I have changed the spark plugs the wires and the fuel filter and the car still studders. Any idea's as to what else could cause this?

weswisehart

car is still doing this and ive searched everywhere. Any idea's? thanks

G-reg

iTrader: (3)

How's the distributor cap? Since you changed everything else spark related, no point in overlooking that. Pull it off, see if there are any cracks, burn marks, wear, etc...

ASE doc

I would want to check ignition patterns at this point to look for low KV on one or more cylinders. This could point to one or more bad injectors, a common issue on the TPI cars, or a damaged pole peice or timing core in the distributor. Checking ignition patterns requires an ignition scope with a knowledgable operator who can decipher the patterns.

Another option is to visually inspect the distributor internals for signs of damage. Pay close attention to the metal "teeth" just beneath the rotor. These are the timing core and pole peice which may be damaged or loose on the shaft. Also, check the cap for signs of carbon tracking.

Check the injectors using a stethiscope. Listen for one that sounds dull compared to the others. this one may be partially clogged or have a damaged pintle. Injector and distributor failures are both common on these cars.

weswisehart

The dizzy is fine its about a year old. I pulled it off and checked it out and still looks really good.
this is a tbi not a tpi. I've looked at the spray patterns and they look good while idealing but can't put my head under the Hood while driving ha ha.
Could it be the pump? It only happens while trying to maintain a constant speed.

weswisehart

this video is at idel and i barely touch the throttlle and it dies
http://s71.photobucket.com/albums/i1...9-21-49-16.mp4

i took a longer video and when i barely touch it, it almost cuts off, then i give it more gas to keep it going
http://s71.photobucket.com/albums/i1...9-21-49-49.mp4

hope this helps. i didnt notice it did this until tonight. i only noticed it while trying to maintain a constant speed.

weswisehart

Would there be a better way for me to explain this or is it that no one has a clue either?

ckelton

Sounds like the Throttle Position Sensor is dropping out at part throttle. Grab a multimeter and check the voltage coming out of the sensor, it will start at .2x and go up to 5v when slowly opening the throttle, if you find that the voltage drops to zero the tps is bad.

If i remember correctly the brown wire is the signal wire.

weswisehart

Thanks I will check that out. I dropped my car off at a shop just after the last post so I can't get to it until Monday

ASE doc

Lol. Just noticed. Your profile shows it's a TBI.

There are a few common issues on the TBI cars. The most common is the fuel pressure regulator. This is more likely to cause an overall power loss and poor drivability. The pumps do fail. However, loss of fuel supply volume or pressure is more likely to cause issues at higher engine loads and speeds, when the engine is demanding more fuel. To check pressure(9-13psi) you will need the adapter fittings to "T" in between the disconnected pressure line and the throttle body.

To check injector spray pattern, I like to use a dial back timing light. The injectors on your TBI, as on TPI, fire every turn of the crankshaft. By dialing the light back to the proper point in the crank's rotation, we can see the injector spray in a strobe light. This lets us see the actual fuel droplets in mid travel. The size, shape and uniformity of the droplets and spray "cone" are a great indicator of fuel pressure and injector health.

To see the injectors respond to throttle changes, you dont need to be driving the car. Just snap the throttle while watching the injectors and you'll se them open up. The spay "cone" should touch the walls of the throttle bore and droplet size should shrink to a fine mist as pressure spikes.

One thing I have found a few times that will cause just what youre experiencing is clogged or restricted passages in the throttle body affecting accuracy of the MAP sensor. The MAP sensor signals the ECM of changes in engine load. If it does not signal these changes quickly enough, you will experience hesitation.

Another possible cause of throttle "tip in" problems is the TPS. It can be checked for glitches using an analog volt meter or scope. Of course, whenever I suspect fueling issues I always check temp sensors, both coolant temp and inlet air temp. The accuracy of these sensors is critical to proper fuel management.

You dont say if your ignition wires are new. If not, suspect them as the cause of your trouble. They can test good and still cause your exact symptoms.

weswisehart

Thanks a ton. I will check on these issues in the shop on Monday.

weswisehart

Well he is just now getting a chance to look at her so we should find out soon

weswisehart

It was the TPS. I bought a new one yesterday and put it on. Car runs great. Thanks everyone

billweber6

Hello, I am having the same exact problem. What is a PTS or "Pittie". How do I find it?

weswisehart

It is on the left side or passenger side of the throttle body. It has a plug facing straight up and two small screws. You have to take off the air intake to see it. If you can't find it I will take a picture of mine.

John91VertZ28

I had the same problem... I changed the fuel filter, plugs and wires, and it still did the same thing. I checked my timing and adjusted it to about 15deg and it seemed to help a little. I then put in a full tank of 93oct, by the time I got to 3/4 tank it seemed to go away and runs smooth now.

billweber6

Thank you Wesley. I found it and ordered a new one from NAPA. It will be in tomorrow. Keep your fingers crossed.

weswisehart

No problem. I hope it fixes your problem. Good luck

billweber6

Good Day,

I put in a new Throttle position sensor and calibrated the voltage to .62 volts. Problem persisted. I began checking my wires and got confused. I appeared to have a wire out of place. I juggled some wires and made things worse. I know the firing order but am not sure where cylinder # 1 is on the distrbutor cap itself. On some drawings it is the first lobe clockwise from the mounting screw on the front of the distributor. Looking where I had things it looks like cylinder #1 is the second lobe to clockwise from the mounting screw. Cap is not labeled. Any ideas. I assume that all 305's have the same firing order. Is that in fact he case?

weswisehart

I believe mine is the first one counter clockwise from the screw

ryan91rs

iTrader: (1)

im ordering a tps too. i have done EVERYTRHING and i get the mysterious stutter and its killing me when i need to get on the high way. anytime i get close to shifting at any speed or put i tunder load it fights me. hope this does the trick or im sending ti to the GM shop and giving up