I've inherited an 84 Fiero SE with a 4 cylinder Iron Duke. It's been sitting still outside for the past 15~20 years, and has just shy of 50,000 miles on it. I just finished remounting the fuel tank the other day after cleaning it out and replacing the fuel pump. I got the engine to turn over and start, but it's idling really rough. If I feather the gas (while in park) so it's running above ~1000 RPMs it sounds a lot better, and as soon as I let off the gas it chokes and sputters for a good half minute until it eventually stalls.

I've been rooting around the web looking for rough Idle troubleshooting tips, but haven't turned up much that is useful. What should I check next? Any advice would be much appreciated.

Thanks,
-Spoonless

Did you change the fuel filter? I would suggest new plug wires and plugs. Buy some Sea Foam and use it according to instructions. You might have little critters and their nests in the exhaust if it was sitting where they could enter the exhaust.

here is stuff to look for this is written from the haynes manual for the fiero.. i would look at 1-4 first then go to 5-7 lastly look at every thing in those systems. and try to find the problem... the reason for 5-7 last it hard to rip it down and rebuild easier to just test and fix...

#8 engine lopes or idles erratically

1) vacuum leakage
2) leaking egr or plugged pcv valve (chapters 1 and 6)
3) air filter clogged see chapter 1
4) fuel pump not delivering or insufficient fuel being delivered see chapter 4.
5) leaking head gasket see chapter 2
6) timing chain and or gear worn see chapter 2
7) camshaft lobes worn see chapter 2

Whereabouts in Michigan?

south east out by novi

quote Originally posted by KurtAKX: Whereabouts in Michigan?

Western UP

[This message has been edited by Spoonless (edited 07-13-2013).]

Check your timing. I know my 84 duke is very picky about timing and idle.

Thanks everyone for your input, here's an update on what I've done thus far

- changed the air and fuel filters
- added some Lucas fuel treatment
- checked and cleaned the PCV valve
- checked the distributor cap for wear
- checked for ECM error codes (only got code 12)
- checked the spark plugs (they look oily)
- saw some dark smoke come out the tail pipe while the engine was running
- saw exhaust comes out the air intake shortly after the engine stalls out

I plan to check the EGR and vacuum next (as soon as I figure out how go about doing that)

Check your timing, I just fixed my rough idle and low rpm running issue by adjusting it and now it runs perfectly.

Well, I found the problem!

Following the advice of a friend I checked the compression on the cylinders. No. 4 (farthest on the driver side) registered 0 psi, so I pulled off the valve cover and discovered a bent and broken push rod.