Hopefully somebody here has experienced this and fixed it...

My 87 IROC-Z (350) has a slight surge while cruising. It feels as if the AC is engaging and disengaging. I did a search and found plenty of ideas, but most of them had to do with modified engines and such.

My car is bone stock with 12k original miles. At 6500 miles, the EGR valve and the EGR solenoid were replaced due to a code 32. They were both purchased at the Chevy dealer. I also recently replaced the plugs with AC Delco replacement plugs. I haven't replaced the fuel filter yet as I believe it could be a possibility, but not sure. I also thought about replacing the plug wires and O2 sensor, but I don't want to replace unnecessary things. The car used to be stored during the winter, but was stored with Stabil in the fuel tank, so crap in the lines has not come up as an option. Getting ready to put about 1000 miles on the car going to a show in Atlanta and would like it to ride smooth on the trip. As an FYI, I get about 15mpg local driving and about 21 highway. The 15 is because I can't keep my foot off the gas!!!

Any help is appreciated.

 

Mine was doing that. Ended up being #2 cyclinder not getting a good spark.

 

Nobody else has any suggestions?

 

Sorry, I don't have a suggestion, I'm experiencing the same sort
of problem-so I thought I'd watch your responses, if any.....

 

Bad EGR!

 

Already replaced less than 6k miles ago.

 

I had a surging problem in my white IROC. Turned out to be the brake booster hose was dry and split at the engine side creating a vacuum leak. Put a new hose on and all is good. Check all over for vacuum leaks.

 

Can you buy, rent, or borrow a scan tool? Other than a quick visual on plug wires and vacuum lines, that'd be where I'd go next. Just look for something that fluctuates in sync with the problem.

Can you see the RPMs change rapidly? If they jump by 200 RPM, but the vehicle speed changes slowly, then your torque converter clutch may have a bad connection somewhere, or the computer is telling it to do that based on bad sensor readings.

I've had both the EGR surge, and the burnt plug wire surge.

Mr. Millican, I sure hope someone worthy buys your car on Ebay. My car scraps [sic] with the stock ride height, hehe. {refraining from going into some uneducated sounding slang rant about fast cars and using words like hella, dude, and sick}

 

The RPMs don't fluctuate at all during this surging. It feels similar to the AC kicking in, but with no noticable rpm variation. I Would think that the vacuum issue is a non issue with 12k miles on the car. I will see if I can follow my vacuum lines and see how they all look. I did have some dry rot when I bought the car 5 years ago. The EGR valve and the tires were shot. All hoses have been inspected and were marked "good as new"

 

Just a follow up FYI...

I haven't driven the car since I replaced the plug wires, but plug 6 had a nice chunk out of the outer shielding. Looks like it was bit by a mouse and he didn't like the flavor of it!! I'm hoping that fixes the problem. Thanks for the help.

 

Sounds like a reasonable cause. One cylinder misfiring intermittently would probably result in a surging effect similar to the AC comp cycling on and off without any change in rpm. Have a fun trip to A-town - I'd love a good road trip right about now....
K