I've been browsing the boards here for the last week or so, as I just purchased a 96 Z-28 last week. I love the car, but I have something that is bugging me.

I have been having a problem with the car bogging down/surging while driving at about 70mph and 2000 - 2400 rpm. This only happens while I'm driving on the highway after about 3-4mins. I had a code for the EGR which i replaced today and then wiped the code out of the system. I was driving in after that, and everything was fine for a while. I got on the highway put it on cruise at 70+ and then after about 4 miles maybe it would start surging up and down. I took it off cruise and dropped it down to about 65 and it did the same thing but not as harsh or noticable.

I was thinking this was being caused by the EGR, but it must not be. The guy i bought it from is a close friend, and he is leaning towards the fact that the optispark may be going out. I admit I know verry little about the Optispark, but why would the ignition be crapping out at anything over 70mph?

The car idles better now with the EGR replaced and it has all kinds of power at WOT. No problems at low speeds or any RPM ranges during low speed runs. Also, it has not thrown any new codes. If it had, then i would have an easier time finding something wrong.

Anyhow, I'm hoping I'm not the first to have this problem and someone can lead me in the right direction. just buying a new opti is out of the question for now due to the fact i had to buy new tires for the car $$$. Thanks in advance for any help guys.

Brian

 

well id have to say its probably opti, but how many miles does it have

if its somewhere between 90-130k miles

id have to say opti, if its past that i donno how the opti could have lasted that long and it would be on its second one which might be failing already... but probably not

but check sparks and plugs

does it backfire at all?

 

Just over 57,000 miles. Still the factory Opti. No backfire, just the high speed surging for now. It's drivable, but annoying.

 

According to Haynes repair manual, under troubleshooting section Engine surges while holding accelerator steady

1. Intake air vacuum leak
2. Fuel pump not working properly

 

Wow. I just came here to ask if maybe this could be related to the fuel filter being clogged up and starving the motor after running for a while. I'll be checking that first thing in the morning. Thanks