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| Sat For 20 Years...Need Help With Diagnostic For Rough Running / Stalling (Page 1/6) |
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CampyBob
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JAN 09, 07:28 PM
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OK, first post so forgive me if I'm in the wrong topic area. Mods move at your pleasure.
I've been a design engineer for 40 years and I'm the guy that designed all the Fiero suspension arm dimensional gaging and tooling for Pontiac and Entech back in the day. Back when GM was throwing millions at stuff like that...private jets, topless restaurant dinners, gallons of booze...but, that's another tale for another day.
Anyway, in doing all that work on the Fiero project I got hooked. Actually, I was hooked when I saw the prototype Fiero's while touring the new 'Vette factory back in 1984. So I bought one. A brand new silver 1985 2.5, 5-speed. I loved it.
Then life changed. I eventually moved out to a farm and in 1999 drove my Fiero out to the new house we had just built and parked it in the garage. 27K miles on the clock. Looks like new. Underside is spotless. No rust anywhere and probably the best storage conditions this side of a heated, dehumidified room. Put a breathable car cover on it and life went flying by me. If you've done the math the thing sat without even so much as the doors being opened for 20 years.
Fast forward to last month when I decided it was time. Time to drive the old girl one more time before I end up in a hole in the ground. Parked it with a full tank of gas, of course (had it ready for a honeymoon, but ended up taking another car on that trip). Dropped the gas tank to find about an inch deep couple gallons of nasty, stinky stuff and proceeded to flush the tank out over and over and over. I then installed a new fuel pump and filter sock. Stuffed the tank back in place and test fired it up while still on jack stands with 5 gallons of fresh gas in the tank.
Success! Or so I thought. It ran fine that first time for maybe a minute or so as the memories flooded back to me, hunkered down in the sheepskin covered seat. But, the next day...hard starting...wouldn't idle...stalled repeatedly. The only way I could keep it running was by rapidly pumping the gas pedal. Crap! Tripped the code with a paper clip and got a 22.
Replaced the inline filter, the injector nozzle, the throttle position sensor. Only a little better. The more it warmed up, the more it wanted to die. Spray carb cleaner down the throttle body everywhere I could get it. No better.
I think I'll check the idle air valve next and replace the MAP sensor (will check for vacuum leak). I don't think it's the temp sensor telling it to go too rich or too lean, but I've been wrong twice before in replacing the TPS and the injector nozzle.
Doesn't smell rich. Can only hit about 3,500 RPM and once got it to 4,100 RPM. When engine starts slowing down it seems like it's not getting enough gas, if anything. No backfires or really noticeable timing burps. Once it 'catches' again the engine accelerates more or less normally and even stutters and picks back up fairly smoothly.
It has a hot spark, spark plugs look good.
Am I headed in the right direction or barking up the wrong tree? Any advice is appreciated.
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calvan5154@att.net
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JAN 09, 07:45 PM
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My 86 2.5L was doing that and one of the 2 vacuum hoses coming off of the air filter was bad. It does sound like it may a vacuum issue. Only a suggestion.
Hope this helps.
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Patrick
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JAN 09, 08:01 PM
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| quote | Originally posted by CampyBob:
I then installed a new fuel pump and filter sock. Replaced the inline filter...
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It's a hassle with the duke, but it's still worthwhile checking the fuel pressure.
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Notorio
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JAN 09, 09:18 PM
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| quote | Originally posted by CampyBob:
I've been a design engineer for 40 years and I'm the guy that designed all the Fiero suspension arm dimensional gaging and tooling for Pontiac and Entech back in the day. Back when GM was throwing millions at stuff like that...private jets, topless restaurant dinners, gallons of booze...but, that's another tale for another day ...
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Bob, welcome to the Forum. I can't imagine what it must have been like to work on the Fiero design! You will certainly be getting lots of questions from us, as well as advice. I am familiar only with the 2.8L so take this with a grain of salt. If the gas turned to sludge in the tank and lines shouldn't it also have done that in the fuel injectors et al?? Perhaps you may need to remove them and send out for cleaning and calibration. If you decide you want to do that I can post the contact info for the place I and several of us before me used.
John
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Patrick
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JAN 09, 09:32 PM
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| quote | Originally posted by Notorio:
...the fuel injectors et al?? Perhaps you may need to remove them and send out for cleaning and calibration.
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The duke only has one. 
| quote | Originally posted by CampyBob:
Replaced the inline filter, the injector nozzle, the throttle position sensor.
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CampyBob
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JAN 09, 09:37 PM
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John, I replaced the single injector nozzle. It's a throttle body. Spray pattern did not change.
Patrick, I have no fuel pressure gage, but the 2.5 only needs about 10-13 PSI per what I've read online. Pulling the fuel line into the throttle body the thing really pumps out a lot of gas in a short period of time. If nothing else the flow rate is great. Can't tell if the pressure is good enough to trip the pressure return valve. Should it trip normally? Gasoline is coming out clean and clear into the catch can.
I didn't actually design the suspension stampings. Those were done in Hartville, Ohio by Teledyne Monarch. My company designed and built the LVDT (transducer) gaging that dimensionally measured the stamped and welded suspension arm assemblies. Starting with a Chevy Chevette lower control arm and modifying it for the Fiero's front lower control arms things were whacky from the get go. As the design was twice reworked things got better, stiffer, stronger. But the money GM tossed at us was simply insane. Especially for a vehicle not really designed in-house. Test track sessions were fun. The un-built mules and prototypes were just wild. It's the T&E money that was just insane to a once young aerospace engineer assigned to work with an automotive project. I also remember the assembly line shut down for a few days (more than once!) because pieces parts did not even fit on the chassis going down the assembly lines. Hop a fast private jet from Akron-Fulton Airport to Pontiac and 20 minutes later all hands were on deck trying to get things working again! Fun times. Lots of red and white 1984 models (probably assembly line rejects) with huge numbers on the doors that anyone in need of transportation around the factory complex could jump in and drive to a meeting or whatever. Pretty cool stuff.
I really want to get the old girl back on the road for one last Summer fling. All four calipers are sticking from sitting so long, but that's child's play to loosen up or replace. The engine rough running, stalling thing has me stymied for now.
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RandomTask
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JAN 09, 10:46 PM
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Did it sit with gas for that long? When I revived a 85 a while ago, the fuel hose that was in the tank from the pump to outlet turned to mush from sitting so long. May be something to consider.
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fierosound
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JAN 10, 12:30 AM
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fierosound
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JAN 10, 01:23 AM
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oops... [This message has been edited by fierosound (edited 01-10-2020).]
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Patrick
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JAN 10, 02:01 AM
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| quote | Originally posted by CampyBob:
Patrick, I have no fuel pressure gage, but the 2.5 only needs about 10-13 PSI per what I've read online. Pulling the fuel line into the throttle body the thing really pumps out a lot of gas in a short period of time. If nothing else the flow rate is great. Can't tell if the pressure is good enough to trip the pressure return valve. Should it trip normally? Gasoline is coming out clean and clear into the catch can.
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Bob, I discovered that my '84 wouldn't run properly with 4 psi of fuel pressure. The symptoms I was experiencing were somewhat similar to yours. If you wish, you can read about it Here.
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