Do all 3800SC idle poorly? (Page 2/3)
Dennis LaGrua JUL 26, 06:48 PM
I've had issues with rough idle in the past and it was always ignition related. Remove your coil packs, lift up the module and clean the mounting surface with a wire brush and or emery cloth. Wipe residue with a clean cloth and electric contact cleaner (if you have it) Make sure that this surface sees a solid ground or run a separate ground wire there (3800s had a ground strap there). Put coil packs back on the plate ( don't use thermal grease) and tighten firmly but not excessively tight or you will break or strip out the 5.5mm screws. I did this and the idle is now perfect.

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" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

[This message has been edited by Dennis LaGrua (edited 07-28-2024).]

fieroguru JUL 26, 07:40 PM
If your CAI used an oil lined filter, you might need to clean you MAF. The oil from the filter can get on the MAF element and skew the readings.
Frenchrafe JUL 27, 03:10 AM
Mine's not S/C but turbo.
Different cam, no balance shaft, etc...
And it idles like a race car!
Not smooth at all.

I have to do the throttle blip to keep it from stalling at idle as well.

Other than that, it's fine

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"Turbo Slug" - '87 Fiero GT. 3800 turbo. - The fastest Fiero in France! @turboslugfiero
https://youtu.be/hUzOAeyWLfM

fierofool JUL 27, 02:10 PM
Not a 3800 but my 3.1 has the occasional pop at idle, otherwise runs fine. It may not be anything to be concerned about.
Sir Sdv JUL 27, 03:58 PM
I always assumed that the 3800SC just idled rough while sitting because of being Supercharged. I have two F23/3800SC swaps. One I have had for 10 years that idles rough just as you explained, but when I drive it, it runs smoothly. My other one is in the process of being swapped. Crazy thing is I thought this same exact thing if my second swap would idle the same way. I guess I'll find out in a few weeks. With everyone saying a stock swap should not idle rough, I may have to investigate further on my first swap.

Thanks for the information
jelly2m8 JUL 28, 02:37 AM

quote
Originally posted by Patrick:

Sounds good. What is the idle speed there, and what has the exhaust system been made up of?




Umm I'm an idiot, and you know that lol.. umm what ever is stock, yes, I should know, my attention when I start it is on oil pressure... What ever stock OEM is, 750, 800? The exhaust is somewhat simple / convoluted. ZZP power logs front and rear, Home build 2.5" manifold to homebuild 3.5 inch long ' mini convertor' down into a homebuild muffler mimicking the 2.8 muffler ( think making everything internal bigger' ) OEM tail pipes

[This message has been edited by jelly2m8 (edited 07-28-2024).]

Dennis LaGrua JUL 28, 02:38 AM

quote
Originally posted by fieroguru:

If your CAI used an oil lined filter, you might need to clean your MAF. The oil from the filter can get on the MAF element and skew the readings.



x2 found out the hard way. Those K & N permanent air filters last a long time but the oil in them WILL throw off the 3800 MAF readings. MAF cleaner corrects the problem there but with the stock Fiero engine all should be OK as it uses a speed density system without a MAF sensor.
jelly2m8 JUL 28, 02:48 AM

quote
Originally posted by Dennis LaGrua:


x2 found out the hard way. Those K & N permanent air filters last a long time but the oil in them WILL throw off the 3800 MAF readings. MAF cleaner corrects the problem there but with the stock Fiero engine all should be OK as it uses a speed density system without a MAF sensor.




Yep, I went a bit too far on my last K&N, 10 years no oiled cause I don't want issues. one day I though hmmmm seems a lil low on power

tossed that, put a new one in, 7 inch long one this time, all the Wirrrrrrr noises back
Patrick JUL 28, 05:24 PM

quote
Originally posted by jelly2m8:

What ever stock OEM is, 750, 800?



Thanks. I thought maybe it was idling smoother because it might've been idling a bit faster.


quote
Originally posted by jelly2m8:

The exhaust is somewhat simple / convoluted. ZZP power logs front and rear, Home build 2.5" manifold to homebuild 3.5 inch long ' mini convertor' down into a homebuild muffler mimicking the 2.8 muffler ( think making everything internal bigger' ) OEM tail pipes



Sounds good while idling. Does it drone at any RPM while driving? I put an aftermarket exhaust system on my turbo Subie. I love the sound of it 90% of the time. The other 10% of the time, the drone gets kind of annoying.
Stingray92 JUL 28, 07:03 PM
I've owned 2 3800's, 1 N/A, the other S/C. The S/C I bought new and can't recall ever having any complaints about idle. The N/A motor is at 170K and still idles smooth. Have you looked over the vacuum lines/gaskets? Next I might look at the injectors. The rubber hose on the N/A we're worthless, took care of all the rubber and thats where I'm at.

Stingray92