wingedZ

Hey everyone im new here and wanted to see if anyone could give me advice on my car.
I have a 94 Z28 with the LT1, auto trans. I got it last summer and it has had an intermittent "surging" problems. What i mean by this is I will be cruising and the engine will jump up and down several hundred rpm and continue to lose power for very short times over and over. It also happens occasionally at idle, and here the rpm will jump up sometimes to 2500 all by itself, needless to say when this happens at a stop light it is not good lol.
I originally thought TPS sensor, and replaced it and the car ran well for several weeks then started surging again. That was the end of last summer and this year when i took it out of storage it was acting up on the first day so i bought a new TPS thinking maybe the 1st I bought was faulty. The car has been running great for the last few weeks but again now it is acting up.

The wierd thing is this problem will come and go at random. I have noticed that overall it is more likely to do it the longer i drive it, especially if i drive somewhere turn it off and then drive home it will run bad coming back. Also if im going down the road and its cutting out and surging if i floor it it clears out and pulls all the way up no problem, as soon as i come back down to cruise it surges again.

Thanks alot please give me some direction if you can

djjab57

iTrader: (17)

May be something simple, check your elbow for tears or leaks

TexasNative

Being that it's a 94 I know your scanning options are somewhat limited but do you have any idiot lights or have you tried scanning or reading any codes that may be present? I had a 94 TA that would do something similar to this and I went nuts looking for possible vacuum leaks but it turned out to be the fuel pump on it's way to taking a dump on me.

wingedZ

I dont have any check engine light, but i do have an ABS light that comes on sometimes and a low coolant light (I checked the coolant its fine). I havent ran any scans

Mongoose_TA

iTrader: (2)

Low coolant light might be dirty. Won't solve your surging issue but if you are sure your coolant level is fine, then the sensor is either dirty or bad. If you unplug the sensor on the radiator the light will turn off, But you're gonna have to keep an eye on the coolant yourself.

TexasNative

Forgot to mention earlier but check your egr valve out while you're at it. That can cause the symptoms you're seeing as well. I've seen that happen on more than one occasion on several of my LTx cars.

shbox

What you need is some live scan data when it is acting up. Quit replacing parts just because you think they might be bad.

TexasNative

Shoebox is right on the money here. Check all of the obvious stuff and run a scan to see if you get anything before just throwing money at it. If you don't have a cable and datamaster, freescan or something similar then some of the Autozones might be able to scan it for you.

wingedZ

Alright thanks guys ill see if I can get a scan and go from there

TexasNative

DO check your EGR valve though. It's a simple test and it's a likely culprit for something like this. Next time you have the surging issue try reaching behind the intake manifold (not necessarily an easy feat without long sleeves and/or gloves) and see if the diaphragm is stuck. If that's not the issue then a scan is your best bet. You can also check it when the engine is cold to make sure it moves freely but it's best to do it when you're having the problem. Good luck and let us know what you find so that others can have a reference in the future.

Tampa_97_SS

iTrader: (6)

I am guessing that it has the original engine in it; so how many miles are on the car? Have you replaced any other parts in the past? Is your check/service engine light on?

Have the car scanned for trouble codes first before you spend anymore money.

I am thinking maybe a vacuum leak or a fuel dilivery issue like a dirty fuel filter.