my trans am has been acting weird lately. about a month ago the gages were bouncing around. i check all the grounds and they look good. regrounded some of them to be sure. my hids were flickering at night too. this morning it was "bucking" under load and the check engine light came on. as long as i drove slowly it seemed okay. can i just use another computer from a junk yard? reflash? 200 bucks? i have deleted my vats already... thanks for any input!!

 

So to add to this...this car used to be auto. when i did the conversion i didn't change the computer (pcm) and it ran for a couple days before not running at all. i then sent my pcm to FASTCHIP to have it reprogramed about 5 years ago. my question is__ if i get a pcm out of an another firebird M6 1993-1995 (1996 they started using dual cats) will i need to get it reflashed? as i dont have vats anymore.... help!!!! thanks!

 

The PCM from another '94/'95 F body should be fine if the engine is close to stock. If you think it might be the PCM, pull it up where you can get to it and, with the engine running, tap on it with a screw driver handle, etc, to see if anything changes. Even a broken circuit board in the PCM should not effect your head lights. You likely have a loose connection or broken wire someplace. Try wiggling the battery cables also. Flashing the PCM isn't going to help.

 

Could it be the optispark? i have an oil leak in that area and going to fix that soon. the funny thing is it doesnt do it all the time but when it does it starts jerking around with power going in and out for a couple seconds then its okay as long as i put around. which is what i am doing now. whatever it is my rpm and speedo is climbing like crazy and is very unaccurate. some of the other gages too. the reason i think it's the computer is that when a obd computer is hooked up the computer doesnt respond at all. i know just a reflash isnt going to help but i rather spent 75 bucks on a used computer than 75 bucks plus 200 for a reflash for the used computer. thats just too much dough! thanks. btw WRIGHT__damn your ride is fast!!

 

Do you not know somebody with an '94/'97 LT1 F body that would let you plug their PCM into your car for a few minutes to test that? I don't think that is going to be the problem. If you were around here close you could drop by and I would let you try another PCM. You shouldnt have to buy one to find out. No LT1 friends?

Btw, love the avatar!

 

Now, is it all the gauges or primarily the engine coolant gauge that fluctuates when the car surges? I'm curious...if it is, then it could possibly be the ECT (Engine Coolant Temperature) sensor or the wiring to the sensor. The ECT sensor on LS1's are located on the driverside cylinder head. I'm not sure if it is the same on LT1's or not.

Anyways, bad wiring to the ECT or Engine Coolant Temperature Sensor can cause a surging or jerking problem within a vehicle. "How you may ask?" Well, within many EFI engines the ECT sensor tells the PCM how cool or hot the engine is at any given moment. With this in mind, when the engine is cold (or upon initial startup) the ECT tells the PCM to dump more fuel into the cylinders, to bring the engine temp up to operating temperature. Now, if your ECT is not reading properly or is fluctuating a lot, it could be sending a wrong or mixed reading to your PCM causing too much or not enough fuel to the cylinders.
Now, bad wiring to the ECT is a more likely culprit because your surging does not happen all the time, only on occasion, then goes away shortly after. Also, when the ECT or it's wring goes bad, there is usually no Engine or DTC code thrown unlike; misfires, maf, or EGR issues. This makes it even more stressful when you don't know what's wrong with your vehicle.

I had a similar surging and bucking problem happen to me right after I got my cam installed at a shop. Now, I drove the car home (120 miles) no problem. However, it began to surge and jerk around for no reason. I couldn't figure out what the problem was because there was no Engine or DTC codes showing up. However, I noticed that all my gauges fluctuated when the surging happened, primarily the Engine Temperature Gauge. So, I trailered the car all the way back to the shop and it turned out to be bad wiring to the ECT sensor. They said that the ECT wiring was fluctuating and reading -38 Degrees when the engine was warm, which began dumping too much fuel into my cylinders causing it to buck and surge. I know this may not be the problem with your car. However, I hope this could give you an idea that your problem may be something small and minuscule like mine was.

 

Shouldn't effect his speedo. Btw, the LT1 coolant temp sensor is located in the water pump, toward the driver's side.

 

i probuly going to be chasing some wires lol. all my friend are into imports except two. one has a 2002 SS camaro and the other a 2003 zo6 corvette. maybe my salvage yard will let me borrow one.
i would hate to be showed up by a civic when this happens (worst case senerio) spellcheck. i sure he would brag to all his vtec buddies if it happened. a couple years ago i replaced all the wires coming off the battery not that it means they couldnt of gone bad. typical i have been working my *** off on painting it and buying tires and power window motors and now this comes up. never fails. thanks for the info so far.

 

Yes, correct, it shouldn't effect his speedometer. However, there are an array of things that could be wrong. Of course, I'm not there to analyze the situation. But anyways, what engine code did it throw? You said the engine light came on, correct? If you could tell what code it threw, then that could give you an idea of what is wrong...and thanks Ed_Wright for the info on the LT1.

 

That's how it goes with cars and women. It's always somthin'.

 

my computer isnt responding to the obd...that why i thought it was the computer. i have a feeling it has something to do with the charging system. i noticed as i push the pedal down and the rpms climb (not my gage as it will read 8000k at 2500k) the volts would drop. also it seems my car isnt starting up easy and i just put a new starter on it two months ago and it was working great. i tried to roll my windows up with my engine off and they are a lot slower. going to autozone to get it tested even though they tested my starter and told me it was okay but it wasnt. rookies.

 

Ok ive been looking all over for someone that is having similar issues to me cause it is driving me crazy! You guys seem to be kinda in the ball park as the same issues as me so maybe you can help me out!
Ill be as descriptive as i can, So first off I have a 1998 z28 that I just put a new engine into(stock ls6). About a day after I installed the engine I noticed when under hard exceleration and in the upper rpms, all the gauges would momentarilly fluctuate and then stop; nothing else.
I just took it on a road trip this weekend and it has slowly gotten worse to now all the gauges will fluctuate almost all the time. only randomly will the go to normal and everythings is perfect, then back to fluctuating. Along with the gauges fluctuating the engine spudders when bogged down.

Now, radio, lights, ect all act normal, Ive put a meter on the batt, and it is charging great around 14v. Starts great everytime so i dont think its a bad batt but will look into as i go through diagnostics. 2002 SS HUGG mentioned the temp sensor would had some similar issues; but like Ed Wright said, all my gauges are fluctuating so it shouldnt be that causing this.
I know i just put the engine in so I could of messed up some wiring somewhere but i have went through all of it and dont see anything obvious.

Does anyone have any idea or suggestions to help me out!?!?!?! Could it just be a bad ecu, is there a way to check that?

Thanks for the help!!!!!