deebee

I just bought a 1996 Z28 with about 67000 miles on it. The car is mint, well taken care of, previous owner changed the plugs and there are no check engine lights. It runs perfect, no stumbling or hesitation.

BUT, at idle it seems a bit lopey/rough to me? Is this normal? I have owned an LT1 before and can't recall if it did this. It doesn't stumble or stutter. Does the factory cam give a bit of a "cammed" type idle?

Injuneer

No. Smooth as butter.

Fatdog2

Same scenario here.When I picked up my God ugly 1993 with the ugly black top and black mirrors,I did the plug and wire change first off.Still had the rough idle.Then I changed the map sensor,still there.Then my neighbor who has hot rods suggested the fuel injectors are clogged up and said I should put fuel injector cleaner in the tank at every fill up till it smooths out.And I did,and it worked.Costco has the Chevron injector cleaner (techron) by the 6 pack.Use it at every fill-up till it's gone.Is your car a daily driver?If so you will see quicker results but mine is a garage queen only driven every week or two for 20 miles or so and this took a little longer but it works.I would change the gas filter after a couple of months.Also, if you can take the rubber elbow off the throttle body,I would spray some (throttle body cleaner)(the safe kind) in there to clean the blades as they get all black around the edges and should be cleaned.I used Q-tips the plastic kind so as to bend to clean out all the little orifices there as well.Hope this helps.

deebee

Oh boy, thanks guys. I thought it was normal when I bought it.
Thing is, it runs perfect. No hesitation, pulls hard has hell.

I will try the easiest things first - fuel injector cleaner then clean the MAF.

The guy who owned it before me put about 3000 miles on it in 5 years so he never drove it. Wonder if something buggered up. He changed the plugs but not the wires.

And I drive it as much as I can. A couple of times a week at least for some good drives. Hopefully that injector cleaner helps. Or at least they can diagnose it as there are no check engine lights on.

lt1-xjs

Post a video, it may have an aftermarket cam.

deebee

I will post a video soon. I don't know if you can even hear it, it is so slight. My g/f couldn't tell until I pointed it out to her. It is more of a "feel" as opposed to sound. It almost feels like a slight miss but it runs/accelerates perfectly. It idles steadily...

Unfortunately it is difficult for me to get Chevron Techron here so I had to order some from Amazon. I went to GM today and bought some ACDelco 88861012 and when I run my tank dry I will add it to the next fill and see what happens.

Order of attack:
Fuel injector cleaner
Clean MAF - check CAI for proper install
New fuel filter

And if none of that works then take it to the mechanic to scan for codes, although the check engine light isn't on.

Other than the CAI, the car is bone stock.

Fatdog2

Please please please do not run out of gas.The gas gauge on these cars are inaccurate and when you see 1/4 tank of gas it is really about one gallon or so left in the tank.You can and will burn up the fuel pump as the pump needs gas to keep it cool.If you burn up the pump it will cost big bucks and cause some financial drain.The fuel additive is good for about 10 gallons.I would also check for vacuum leaks.You have the onboard diagnostics 2 so you might want to pick up a code reader (harbor freight and tool) about $69.00 or so.Vacuum leaks can cause a rough idle and these cars are aged and the rubber hoses do go south.Sorry for the rant but nobody else chimed in and I think these things will help.My02.

deebee

Fatdog2, thanks for the info and I will definitely follow it.

I will run my car close to empty and fill with 10 gallons of fuel and the additive and go from there. If the injector cleaner and cleaning the MAF doesn't do anything then I will look for a code reader.

The car is 20+ years old and lived most of its life in northern Canada so lots of hot summers and very cold winters, which it was parked for more than likely months on end.

Will the car still throw codes if the check engine light doesn't come on? I always thought codes would trip the dash light.

deebee

Will this work on my car?
AutoLink AL301 OBDII/EOBD Code Reader | Princess Auto

I live in Canada so things cost a little more up here and can be harder to find.

Fatdog2

Experts on code readers would be Injuneer,GaryDoug,and Shoebox and others for OBll.Hope this helps.

shoebox

I did a quick look on Amazon and what looks to be the same reader (another brand, though), you could get two of them for $25.

That is a pretty basic unit if all you want to do is check codes and clear the check engine light. Better would be a unit that also did live data scanning. That's how you learn how things work. A basic reader should be cheaper than $70.

You can also get an ELM327 DLC plug-in that can use a free app (Torque) via bluetooth on your cell phone. It will read codes, monitor data, clear codes and more.

deebee

shoebox, thanks for the info. I bought an el cheapo from Amazon for about $30 CAD.

Is this the ELM you are referring to?
https://www.amazon.ca/dp/B00W2HYGUE/...d_i=B00E3VDL80

shoebox

Yes, that is the type of device I referred to.

deebee

Appreciate the pointers.

If I can't improve the idle doing the simple things I will buy that. It looks like a neat little tool and pretty cheap as well.

Injuneer

The description of the problem seems a bit contradictory.... "at idle it seems a bit lopey/rough" vs. "I don't know if you can even hear it, it is so slight". I minor misfire, not on a regular pattern would seem like the most likely cause of the "I don't know if you can even hear it, it is so slight" issue. Marginally dirty/leaking injector, bad valve, faulty plug or plug wire.