That wouldn't be anywhere near close to the top few causes I'd consider. Why jump to THAT conclusion?

 

 

"little erratic" needs more explanation. One mans "erratic" is another mans "slight hiccup."

In my experience, you may get the occasional (slight) stumble with the accompanying blip in idle rpm. This is due to the batch (bank fire) arrangement in the L98.

Some purests will argue that there should theoretically NEVER be a bank fire stumble, but I find it part of the charm of the Chevy small block.

Put a vacuum gauge on the engine. If the needle hold steady you are good.

 

 

On my 1988 Coupe the idle became much smoother after I replaced the set of fuel injectors. I had a leaky one that I knew about so I changed the whole set. The result for me was a rock steady idle AND better starting.

Just a thought, you mentioned that you had replaced many parts already and if you changed the injectors already then ignore this post.

I doubt that your timing chain could do this at 52,000 miles, I also doubt that your timing gear is worn as your mileage is too low. My car has over 100,000 miles on it and the motor is still tight. When I ran my compression tests at 100k miles they were very close on all eight cylinders.

I wish you the very best of luck in finding this gremlin you are dealing with.

 

 

Can you post up a vid of the idle? Maybe one near the engine (hood open, obviously) and another with the camera (mic) positioned near the exhaust outlet so we can hear what you're describing?

 

 

One more idea, have you ever done anything to the car's EGR (Exhaust Gas Re-circulation) system?

A bad EGR system can cause issues with your idle and off idle performance. EGR valves fail frequently and are a pain in the butt to replace. I would keep it on the car and working properly myself but there are many who remove them and make a change in the chip to avoid getting codes.

First check to be sure that the EGR solenoid is getting vacuum and that the solenoid itself is in fact working. If you have the FSM set then you can follow their testing procedure just to verify that the EGR is not playing with you.

When my EGR failed I found out by failing my states emission testing. I don't know which went first but my EGR Solenoid had failed as well. On my 1988 the NOX was way out of range which points to the EGR. There are several ways for these valves to fail but you can rule them out following the FSM procedure for testing the EGR system.

I am sorry to hear about your Father, that makes everything 10 times harder on you personally. I hope that things get better and time appears for you to get this Vette sorted out so you don't have to sell it. They are far more fun to own...

 

 

I had a faulty ignition module that caused a similar issue once. It drove me nuts trying to figure it out.

 

 

The grounds sound like a likely cause. What do you have for plugs and wires cap rotor etc. If you don't run the car hard I would go for a projected tip plug 1 heat range warmer. Personally I like 8mm spiral core wire with around 800 ohms per foot. I have historically had the best luck with Moroso wire as they are local to me and very fairly priced. Standard Ignition makes a good cap and rotor especially for the money. The coil could always be suspect as could the wiring leading to it. Have you loaded the engine down to see if it skips under a load. It can be as simple as left foot on the brake and right on the gas if an automatic. If a stick car just go down the road in first and left foot the brake to load it down without going screaming down the road. You even have something as silly as carbon under exhaust valve seats if not driven often or not driven reasonably hard with consistently fresh gas. If seldom driven it is not a bad idea to run 94 octane unleaded race fuel with no ethanol in it.

 

 

Read this thread to see if it gives you any ideas. What you describe sounds like an earlier stage of my symptoms. I still need to try the suggestions provided in the linked thread.

I think you are on a better track looking at an electrical/ground issue vs the worn distributor you originally hypothesized.

EDIT: Also, what does your voltage show on the dash? Is it steady or wavering? If it's wavering a bit, keep in mind the computer has to compensate by varying BPW of the injectors to maintain a stable idle. Varying voltage COMBINED with the inherent cycling of a O2 sensor MIGHT contribute to unstable idle. 88 ECMs aren't THAT fast you know! Could be an issue with ground and/or voltage regulator (in the alternator) spinning slower at idle.

 

The negative battery cable runs to the frame; from the same point where this cable attaches to the frame, I run another cable directly to the engine block or bellhousing...it eliminates a bunch of potential problems

 

There are several ground straps on this car and they are all important. You should verify that your engine ground is the same as the battery ground. Simply put the red lead on the battery + and the black lead on the engine steel or other conductive metals. If you engine is not grounded solidly then the sensors have no frame of reference. I would also try going from alternator output cable with the red lead and check the engine.

On my 1988 the interior of my car was not grounded well and I saw all sorts of weird voltages. Once I redid the grounds I cleaned the terminal block near the battery to be sure that the "Fusible Links" were getting the proper voltage. When done my radio and other accessories all had full battery voltage available. Funny thing, accessories that had never worked right started functioning properly.

Having a good ground at the fuel pump and even the antennae is critical, loose a ground strap and problems pop up everywhere.

I hope that you are on the right direction and that this car will purr like a kitten for you, soon.

 

Guess you figured something out since you are selling a new dizzy?