Fiero Domain Forum

Ok so I just got my first Fiero after admiring them forever.I bought a pretty sweet 87 with 109xxx miles.I heard it run a couple months before i bought it then the fuel pump went out and the kid didnt want to fix so I got it cheap.I put in a new pump,sock,filter and MAP.Heres the problem,It fires right up idles a little rough but not too bad.Press the gas and at about 3800r's it acts like it's running on 2 cylinders.Ive done all the normal tests,timing,spark etc. and it all checks out fine.This duke runs super strong until i hit 3800 then it craps out.If anyone has a clue please let me know what 2 do.I have read on PFF that these cars are picky and there are little tricks to them so if you know a trick to fix this or even an idea of the problem,throw a guy a bone and I'll try it.Thanks.

Welcome to the Fiero addiction  ;D

Have you done anything to the car ignition-related yet? Plugs, wires, distributor cap and rotor, ignition coil and module?

Do you get a check engine light?

I installed new plugs,wires and cleaned the coil packs up.i do not get an engine light which is what is baffeling me.I would think that a problem like would throw a code.It's really got me puzzled.

Replaced the Fuel filter? If its clogged that could cause this issue.

Yup new fuel filter and sock.Im gonna try a couple things tommorow if it dont rain on me.I'm thinking on dropping the tank and replacing the little rubber hose between the pump and steel line,I have heard this will cause this kind of trouble.While I got it in the air  I am gonna take some measurements for a v8 swap.If I cant make the duke run right its gonna get dumped out for a (dare I say this) a Mopar crate 360 that I have just laying around.I would really like to get the duke running proper so I can get other projects done but this one is priority.If anyone has a suggestion please let me know.Thanx.

If its not that hose I'm not quite sure what else it could be, I'll have to check around a bit. I've never had that issue with my previous Iron Dukes.

Perhaps something with the EGR is going wrong when it opens, I don't remember how the 4cyl egr works at the moment.

Man I've checked it out as well and its fine.I just dont know what else to do.It was raining most of the day so I didnt get a chance to drop the tank but I plan to do so tommorow weather permitting.I'll post more tommorow if I figure something out.

Ok so the tank is on the ground and I am about to install yet another after market pump, Bosch this time since nobody on the planet can get me a delco pump this month.Will post results in a bit.

New fuel pump same problem.While I was turning wrenches I also relplaced the egr gasket and valve cover gasket.I did however discover that this car comes with a couple of "hidden" options,bloody knuckels and severe headaches.Sorry just a little humor,trying to make light of an omnious situation.Not to mention the I got the wife telling me I told you not to buy it speech,lol.Any more ideas feel free to share.

I'll search around the web to see what I can find for you, you've replaced/checked nearly everything I can think of  ???

I have searched on PFF and find alot of similar problems and tried their fixes but nothing seems to help.I wonder,could it be that even though the compression check came out great,could the lifters be floating out at high rpm's?I have had this problem with a few of my big-block Mopar motors and it kinda acts the same way.I dont do much GM work I'm Mopar or no car born and bred,but I really like this car and would love to put it down the street as a daily driver,but if something dont change I'm just gonna put a for sale sighn on it.

Could be some sort of mechanical issue, the Duke is a low-rpm motor as it is. What is the red line on that engine anyway?

The redline is 5000.I did notice while i was running it earlier that the fuel spray at idle was a fine mist cone pattern.As I accelerated it became a tighter higher volume almost stream and it was backfiring through the exhaust.Is this spray pattern common?

Possible the injector is bad, not finding much useful info on what the spray pattern should be at high-rpm.

As another possibility, how old is the catalytic converter?

No cat,no muff,just a fart can.Not my idea that is the way I bought it.

Given fuel injector cleaner a try yet?

Just throwing out ideas at this point.

Yup,1 bottle in the tank with 5 gallons of fuel,no luck.I do appreciate your help with this mess and I'm sure it will work out it's probably one of those silly little things that takes 2 seconds to fix and 2 months to diagnose.It is what it is.

As a last ditch effort you could try swapping the ECM, I spent months and hundreds of dollars on my Formula replacing parts and sensors to fix a running issue.

Replaced the ECM on a whim and the car suddenly ran perfect. Unfortunately I don't believe there is any way to isolate the ECM as the issue, just a swap it and see type of deal.

Any idea on what would cost.I have heard they can get high dollar and I'd hate to drop a ton of $$$ to find out it wont help.I just read on pff that a gent was having similar trouble swapped out his o2 sensor and cured it.Is there a test for the o2?

I got my ECM used for only $15, you can find them on ebay as well. Rebuilds are quite a bit more.

For the O2 sensor, you can test it with a volt-meter. The voltage from the O2 sensor should vary quickly between 0 and 1 volts once the engine is warm and running.

IIRC , you just set the multi-meter to Volts DC and connect your positive lead to the O2 connector and the negative lead to ground.

If you haven't already replaced it its probably worth doing anyway. I believe Denso is the recommended brand, Bosch is known to have issues.

I think I'll get the O2 tommorow and try it first.I also found a few ecm's on ebay so if the O2 dont do it then I'll grab one up.

Ok it's been a couple days but I have been bustin hump at work and have 0 time to spend on the car.I would like to say I have an update but I dont.I am picking up the O2 and TPS tommorow and slappin them on and gonna give it a go.I will update 2moro.

Hope one of those takes care of it, if nothing else you'll have a whole lot of new components on your car.

Xanth may be on to something. A blocked cat can cause stumbling issues too. My first fiero was a duke. The spray pattern should be consistent btw. It should tighten up a bit but not to the point of a stream. The injector might be screwed up and not atomizing the fuel correctly. If you have a bad injector and a partially clogged cat the lack of proper fuel atomization and the engine choking due to the clogged cat might be the issue.

Nothing new to report,just too damn busy.I havent had time to go out and fire it up.Maybe someday next week I can get something done.

Ok new update.Installed a new o2,tps and fuel pressure regulator.Absoloutly no difference.I guess throwing new parts at it aint the answer either.So any suggestions are welcome.

Sorry for the delay, been busy and neglecting the site  :'(

Do you have a compression tester? You could try checking the compression across the cylinders and see if they're close to each other.

One of the first things I tested was compression.Highest cylinder was 128, lowest was 123.I am starting to wonder about the coil packs.They look old and are cracked in spots.Could it be them causing this kind of trouble?The car still acts like way too much fuel not being burned in the cylinders and it smells more rich than normal.Maybe I'll throw some more money at it and buy some soon.I'ts only money right?If nothing else it will have a bunch of new parts on it when I'm done,lol.

I can't be certain with my limited 4cyl experience, even less so with distributor less systems.

Worth giving a shot anyway.

Ok I'm stumped.New coil packs didnt do it either.I am out of ideas.

Hey Xanth,I just read your comment on PFF where your Fiero stumbled and ran poorly when the ecm took a dump.Is it anything like the trouble I'm having?I am trying to get signed up there but I remember my username for my att dsl and it wont let me sign up on my yahoo email account.

The situation is similar, though my car stumbled across all rpms. My car ran like junk all the time, not just at high rpm.

If you need an email address I can give you a FieroDomain.com address that will allow you to register on PFF.

Well I kidna figured as much.If the ecm took a dump it would run bad all the time but it was worth asking.That would be cool if you could hook me up so I can get on pff.I could really use some help with this car cause it's driving me crazy trying to figure it out.I noticed that there are alot of 4 banger guys there that may be able to help me out.I saw the bulletin about the stolen fiero convertible,I was not aware that any were ever built.It looks really good,I hope they dont find it smashed and decimated.It would be a shame to destroy something like that.

I sent you an email with your FieroDomain email info  8)

Thanx for the addy,I will keep everyone informed as to the progress of the car.Who knows somebody else may run across the same trouble some day.I thank everyone for their help so far and in the future,lord knows when you own a Fiero you need all the help you can get.

Hey Xanth I fixed it.It turned out to be the dis module all along.