V8 Stingray

Just purchased a new '89 vert and it finally landed here in Ireland today. I absolutely love it, and it came with a hard top as well.



Upon driving it home after picking it up, I noticed the car was hesitating and a bit of a vibration through the car when I was driving. Seems to drive fine under heavy acceleration, and over time it seemed to get better the longer I drove. Its still there now, but not as noticeable.

Once I got home, I noticed the idle was a bit lumpy/erratic. Not sure where to start first, so any pointers?

I have a '88 coupe that I also just imported that that drives like a dream - so I do have the option of changing over some parts to diagnose (i.e. 02 sensors etc).

Here's a video of the idle... at around 20 seconds in you'll hear it more clearly.

3D-Aircrew

Looks very clean ... Standard tuneup items are distributor cap and rotor, plugs and wires. Perhaps the ICM but that's is usually a go or no go item. Does it have the service engine soon light on? Check the vacuum hoses and connections for cracks and leaks.

billschroeder5842

Beautiful car. The video was great and there was a slight miss.

I say drive it for a while and put clean gas in the tank. As you have imported the car, do you know when it was actually drive regularly? You say that the car idle has improved some since you have driven it and I think there is truth in that. Put a few miles on it and I be it clears up.

V8 Stingray

aklim

Check fuel pressure and spark. For spark, I'd change the plugs, cap and rotor and probably wires.

billschroeder5842

I'd also second AKLIMs recommendation. A fresh tune up is always a good idea. You will want a maintenance base line anyway.

aklim

That would require gaskets. You take the TB off, connect the coolant hoses to bypass the coolant flowing into the TB. Take the top plate off, take the IAC off, take the IAC housing off and then you can clean all the passages and housing. DO NOT PUSH THE PINTLE ON THE IAC. Spray with brake cleaner on the pintle and GENTLY WIPE IT. Reassemble with fresh gaskets.

Edit: IF your injectors are MULTEC and you have ethanol in the gas or anything but pure gas, I'd change the injectors. Get something from FIC over here. He has the gaskets you need also. Multecs were not engineered with ethanol or anything but pure gas in mind.

65Z01

Indeed beautiful ride.
You might clip a timing light in turn onto each spark plug wire to isolate, if it's an ign problem.

topfuel67

I bought my 89 convertible a couple years ago and she too had a rough idle. It was the vacuum lines on mine. Theres a vacuum connection under the top of the intake manifold by the distributor. It has 3 ports. One goes towards the brake booster and Ts off again. It goes to the cruise control, from cruise control to inside the car for the heater/ac and to the front of the car to a vacuum reservoir. All of these hoses were severly rotted. I replaced the T fittings as well. Hope this helps.

SLVRSHRK

I ended up replacing a bunch of vacuum lines on my car as well to cure idle issues (among other things). I found that by removing all of the vacuum taps from the manifold and capping, I could quickly determine if the vacuum leak was on the engine (if the rough idle continued), or in the connected hoses (if the idle smoothed out).

Also check your plug wire routing. On my 86 they route the plug wired right next to the EGR pipe from the passenger exhaust manifold. With the insulation deteriorated on that pipe, the heat melted the insulation on the plug wires causing an intermittent miss for me on all cylinders of the passenger bank. I spent weeks chasing this as a transmission problem due to stuttering in overdrive at highway speed under light acceleration.

Best of luck

V8 Stingray

So, have driven the car this weekend to see if it would run out of it, but no joy. I swapped out the distributor, rotor, plugs and leads today as I had a bit of time - and didnt make any difference at all.

Then I noticed this! (that's oil on top and coolant below). This is just above cylinder 1 on the manifold by #1 Injector. I also checked the rad expansion overflow and found that there was copper grease in the coolant and some sludge, but it looks to have been there for a while. I suspect the copper grease is there from a previous piece of work and dont think the head gasket is at fault.... I forgot to check the OBD codes... but am going to get a compression test done later this week at some point to get some surety on the issue. Funnily enough, the "Service Engine Light" was really only coming on when the car was going up hill... went off then a few moments later... not sure if thats got any relevance?

unclet1

Beautiful car ! Looks like mine. Sorry no help with what's wrong. You'll get it though.