88 GT Standard……replaced fuel filter, and IAC valve. Cleaned the throttle body. That pretty much took care of the crazy idle hunting; however the idle is still wavering between 900-1000 RPMs. Also slight lag or hesitation when accelerating through 3500 RPMs.

Shouldn't the car idle at 600 RPMs?

Why the lag?

Care has 29,200 original miles on it.

According to the 88 FSM, normal idle speed for the 2.8l engine is 900 RPM in neutral and 800 RPM in gear for the auto trans and 900 RPM for a manual trans.

Yes, the 900-1000 rpm is normal. The lag is not, but it may take some work to find out why. Bad electrical contacts, mechanical problem, dirty injectors...etc.

edit: Can you help me understand what an 'original' mile is?

[This message has been edited by Gall757 (edited 06-28-2014).]

quote Originally posted by Gall757: Yes, the 900-1000 rpm is normal. The lag is not, but it may take some work to find out why. Bad electrical contacts, mechanical problem, dirty injectors...etc. edit: Can you help me understand what an 'original' mile is?

What I meant was no rebuild, unmolested, thats all. Thanks for your reply!

You might want to pull your distributor cap and inspect the rotor and inner terminals. If you plug wires are original they may be breaking down from age. Also check all your rubber vacuum lines and connections to see if any are dry rotted or split.

thanks Rick88. I was thinking the same so i ordered a cap and rotor. Wires are red, so not original. will check vac lines. plugs are new also. very clean. also ordered a coil.

I think its the coil. I replaced the distributor and rotor, wires and plugs and still had this problem. It would lag at certain speed and and almost seem to hesitate at times. Looks like the new coil fixed the issue

[This message has been edited by marc-alan (edited 07-06-2014).]

Wouldn't hurt to clean up the ground wires on the engine, especially the big one on the battery side.