i had my 95 z28 6sp rebuilt and replaced my cam with the lt4 hot cam kit.i didnt wanna go overboard on the rebuild at first so i also installed pacesetter headers and a new optispark.other then that the motor parts are all stock.since i got the cam installed i have been fighting a bucking issue while driving in town and at cruising speeds on the hiway. it feeels like it loads up and starts bucking,you get on it and it seems to run fine. it has thet typical rough idle but not miss or anything. i also had the ecm tuned but no help with the problem.i eliminated the secondary air injection pump.... i was told it wouldl cause any prob. i have no check ingine lite. any ideas im at whits end with this car makes me wanna get rid of it rather then stick more cash into it .....please help the closest thing i can think of to explain the feeling is like trying to drive in to hi of a gear and is gets to bucking on you

 

Who did the tune?

What RPM is it typically at when cruising and it starts to buck? In what gear?

 

Any gear between 1500-2100.

I sent it in to Sinister Performance to have the ECM tuned. its really noticable when taking off .but even once u get up to speed it does it ..like i said i can feel a power cut almost like its loading up some before it starts

 

I went through an episode of mine bucking a few years ago. Weak fuel pump. Can you get a pressure gauge on it when it is acting up?

 

no thats one of my problems i had all my tools stolen so im trying to buy again. but no i havent checked the fuel pressure

 

Good suggestions above.

Was the engine running with zero issues before the mods?

You still with stock size injectors?

You should not be having those issues with that cam. I have a CC503(slightly more aggressive) and it has some bucking under light throttle at around 5-10mph(for example in a parking lot looking for a parking spot or riding around a gas station looking for a pump).

Absolutely no issues when cruising on the highway in any gear at any rpm...no bucking or surging. The only other thing I've noticed is that the car runs in the 205*F range at cruise where it used to run 190*F. I'm about to install a 160* thermostat to try and help that.

Are you sure the cam was installed with the dots in the correct position?

 

no i had no issues before the mods .. other then headers the cam kit optispark plugs waterpump and cold air intake its all stock. i replaced one injector after the motor install due to a leaking one.. i removed the secondary air injection pump.. and a/c.. if it were the opti sensor would the care still run or would it not run at all? this whole thing has me baffled the car runs awsome other then this issue im fighting as far as the cam install i had a engine shop install it all so all i really had to do is drop it back in the car. since i got my ecm tuned the car runs about 180f. i have had it on a scanner and it shows no trouble codes, and now and then it smells ritch but no smoking or antyhing like that

 

What OBD-1 scanner did you (or a shop?) use to scan it? The 95 is a problem due to the 16-pin ALDL connector. And there are codes that don't turn on the SES light.

There is a free download available (see "sticky" at the top of the "Computer Diagnostics....." forum) of scanning software written specifically for the 94/95 OBD-1 PCM. It allows you to data log the PCM over an extended period of time. We can help you interpret the data log.

This would be extremely simplistic, but is there any chance the rubber elbow between the MAF sensor and the throttle body is torn, or is not fully over the front of the throttle body?

 

i used the newest snap on scanner. only code is for the a/c press cir..i have checked for vac leack and missing rubbers on the connectors and all seems good

 

But did you check the intake elbow?

 

yes i dbl checked all the connectors and breather elbows all look good and tight

 

The inlet elbow is not a vacuum line and not a "breather". We don't seem to be able to communicate.

 

yes i checked the intake elbow the hose clamps are tight there are no tears or cuts in the elbow. the whole thing is weird. i took it out today for a little drive i made it 10 min with no problems then started to buck

 

Check for a bad plug wire. I had one melt against a header tube and would buck in a very specific range. Then it would stop as the wire would swing away from the tube....