Just recently, my Fiero started to stumble or misfire or something when on the throttle under light load and the car would buck and the tach would dip and bounce and come back. I continued driving home and it kept getting worse. I couldn't cruise at 50 mph as the car would be constantly stumbling so I had to accelerate and coast to get home. By the time I got home even at idle it felt like it was misfiring. I have an idea of what I think it might be, I'd like to get your thoughts first in case there might be a quick fix.
Check the contacts on the inside of the distributor cap for white deposits. Scrape the contacts clean if they're not. Clean the rotor tip as well. I've done this many times since 1984.
[This message has been edited by David Hambleton (edited 09-12-2015).]
Gall757, it is hard to tell but it seems like it falls for a split second then jumps high and falls back to cruising speed.
pcgold, I know it isn't the exhaust. I had the problem start happening about a mile before I replaced my exhaust with a complete new one. I had already had the cat out as it rusted through and was falling down. I put in a new cat with short tube headers from westcoastfiero and a 2.5" exhaust all the way back. The drive back from the shop was what I described in the original post so I can rule out the exhaust.
It ran fine while I was on the highway doing 70 so I don't think it is the pump or ecm or coils. Once I got off the highway and was doing slower speeds with low load I started experiencing the problem again and it got worse as I drove.
I thought about a distributor issue, but why would it be the distributor if the problem goes away when I accelerate briskly? Also, can I take the cap off and clean without re-timing? I've never had ignition issues on this car yet so I haven't had to deal with the system.
My thought was that it might have to do with my timing chain. I don't think there is a chain tensioner so that can't be the problem. I'm skeptical that a slacked timing chain would develop this issue so quickly though. I have 76k on the clock now and, as far as I know, the timing chain has never been replaced.
I also wonder if it could be a fuel injector. Would a bad fuel injector seem to work fine under heavy load, but not work under light load?
I'm afraid to drive the car any more though. Is the 2.8 an interference engine? If the timing chain breaks am I looking at rebuilding the engine?
I think gall57 is right on this. Do not drive very far until you check that pick up coil. Had a Toyota truck that did the same thing and when it cuts through the wiring you'll be stranded unless you have a knife or wire stripper and some electrical tape. That's easiest check you can do. I don't know if fieros have fuel returns off the fuel rail but if they do you can pull the return line off the pressure relief valve and use a container to catch fuel while having someone start the car. If no fuel is coming out you have a fuel pressure problem. But from what you described it is a firing problem.in the pu where the tach picks up its signal.
I thought about a distributor issue, but why would it be the distributor if the problem goes away when I accelerate briskly? Also, can I take the cap off and clean without re-timing? I've never had ignition issues on this car yet so I haven't had to deal with the system.
I've had the erratic ignition issue many times over 31 years of driving my '84 SE and a couple of times in my '88 Formula.
The effects would be most significant when humidity is high. During the first few minutes of driving, the only way to have the engine run reasonably well would be to accelerate then coast. Don't know why... thought it might have something to do with the timing advance during acceleration. The 'contact' point would be slightly different.
After a few minutes, the problem would disappear. I assumed it was because the moisture in the cap had dissipated, so there was less arcing.
A new cap and rotor would resolve the issue; but a few 'cleanings' could be done with the same result.
Removing the cap and rotor have no effect on timing as long as they are reassembled in the same orientation as they were prior to removal. Don't remove the wires from the cap & it should be obvious how it goes. The rotor will only go one way.
Anyway, it's a simple thing to check and free to clean off the deposits. Maybe it'll work...
[This message has been edited by David Hambleton (edited 09-12-2015).]
Thanks guys, sounds like it isn't difficult to clean the distributor so I'll start with that. Is there a procedure and specification for testing the ICM and pickup coil?
Icm is doing its job. Tach is still receiving it's signal. Most icm's are expensive but pu coils are cheap in comparison. Start with the cheapest part first. Rotor button, ig coil wire, distributor cap are relatively inexpensive. Go to autozone to check icm or oreileys but I'm not sure if they can check this part. You can check the gap between the pu coil mag and the rotor but other than that it's just easier to replace it on most cars unless you have to remove distributor to do so.
[This message has been edited by Silvertown (edited 09-13-2015).]
So I haven't had a chance to look at the car yet, been really busy this week. I was thinking though and wondering why the car would seem to run okay under load and misfire at low load/idle if it were an ignition issue? If I had a bad pickup coil or some other ignition issue, wouldn't it be more either a constant misfire or a random misfire?
So I haven't had a chance to look at the car yet, been really busy this week. I was thinking though and wondering why the car would seem to run okay under load and misfire at low load/idle if it were an ignition issue? If I had a bad pickup coil or some other ignition issue, wouldn't it be more either a constant misfire or a random misfire?
That helps in diagnosing the problem. When you say under load do you mean when you give it gas or climbing a hill? Either way could be a fuel issue. At idle there's not enough or too much fuel causing it to stumble and when you press the accelerator it alleviates the problem. Does this happen during warm up or all the time? A leaking cold start injector could cause this but that doesn't explain the tach symptoms. Older distributors used springs and weights to compensate advance but I'm not familiar yet with the fiero distributor. But after reviewing a wiring schematic of an 88 fiero ( Internet site/reliable?) The tach receives a feed from the coil.
I was wondering why the car would seem to run okay under load and misfire at low load/idle if it were an ignition issue? If I had a bad pickup coil or some other ignition issue, wouldn't it be more either a constant misfire or a random misfire?
That's what I've wondered all the times I had that issue & fixed it by removing the white deposits in the distributor cap. Still wondering!
Silvertown, I only drove it back from work before I parked it. That's about 20 miles. During the drive it got progressively worse. It started only happening when cruising around 2000 rpm. Then it started happening cruising at almost any rpm. Then, as I got home, it was doing it at idle too. If I was holding a steady 50 mph (~2k in 4th) it would be lurching alarmingly (sudden deceleration followed by acceleration). If I put my foot down and accelerated then coasted it wouldn't do it, so that is what I did the remaining few miles until I parked it.
I do plan to get to it shortly by starting with checking plugs and wires and back through the distributor for resistance and cleanliness.
Silvertown, I only drove it back from work before I parked it. That's about 20 miles. During the drive it got progressively worse. It started only happening when cruising around 2000 rpm. Then it started happening cruising at almost any rpm. Then, as I got home, it was doing it at idle too. If I was holding a steady 50 mph (~2k in 4th) it would be lurching alarmingly (sudden deceleration followed by acceleration). If I put my foot down and accelerated then coasted it wouldn't do it, so that is what I did the remaining few miles until I parked it.
I do plan to get to it shortly by starting with checking plugs and wires and back through the distributor for resistance and cleanliness.
Thanks, Ultimoblaze
Did it start up right away when you left work? I don't know when your fiero goes into closed loop. If it happens before or after will make a big difference in diagnosing the problem. Next time you drive it listen very closely to the exhaust while it's doing this. Have you ever heard it backfire through the exhaust?
[This message has been edited by Silvertown (edited 09-16-2015).]
Did it start up right away when you left work? I don't know when your fiero goes into closed loop. If it happens before or after will make a big difference in diagnosing the problem. Next time you drive it listen very closely to the exhaust while it's doing this. Have you ever heard it backfire through the exhaust?
No, but I'm right next to the highway so it would have been under load until I got off. I've never heard it backfire before. Unfortunately, like I mentioned above, I just had a new exhaust put on so it sounds different than it used to for other reasons so I can't distinguish if it is unusual sounding or not.
Sorry Gall. I should have been paying closer attention to previous posts. Is that an actual Fiero distributor in the diagram.
That is a 4 cylinder Fiero distributor. Just add 2 prongs and it would be a V6 distributor. The OP should test both the pickup coil and the ignition coil. The condition of the distributor cap may be a problem......too much gap for idle speeds, but works under load.
My 86 GT did the same thing. I changed every relay, switch, and sensor imaginable without any change. It turned out the I (the car, that is) had a vacuum leak.
I'm having the exactdame issue on,my 87 gt 2500-3000 rpm though whole maintain around 50 mph I replaced my,plugs wires cap and rotors when I got the car but I recently found the wires are arcing in going to replace them again and see if it changes anything tested icm it tested,good I'm just confused as to why if i,hold,the car above or blow this rpm range the issue is gone
No, but I'm right next to the highway so it would have been under load until I got off. I've never heard it backfire before. Unfortunately, like I mentioned above, I just had a new exhaust put on so it sounds different than it used to for other reasons so I can't distinguish if it is unusual sounding or not.
When you say new exhaust does that mean headers, exhaust or both? Make sure they put the bung holes in either if fiero required them. Some cars take the reading of o2 sensors at the headers, some before the cat and some after. Some use 4 locations. But I'd be surprised if the fiero had more than one.
I'm having the exactdame issue on,my 87 gt 2500-3000 rpm though whole maintain around 50 mph I replaced my,plugs wires cap and rotors when I got the car but I recently found the wires are arcing in going to replace them again and see if it changes anything tested icm it tested,good I'm just confused as to why if i,hold,the car above or blow this rpm range the issue is gone
More to that distributor than the cap and rotor.Where is it arcing, at the distributor end of the wires or near the spark plugs. If it's near the spark plugs then check plugs for fouling and gap. Also one of the plugs may be cracked and the fire from the distributor is not going to ground where the spark plug screws into the block therefore creating the arc you are seeing. How long ago did you replace the wires.you need to inspect them for any burn through from the exhast. Fiero engine compartments are hot enough, at least mine is, to cook a set of wires over a short period of time always use dielectric grease when installing plug wires. If the grounding is not correct this will shorten the life of the wires. So that means making sure the engine is properly grounded
[This message has been edited by Silvertown (edited 09-17-2015).]
I'm having the exactdame issue on,my 87 gt 2500-3000 rpm though whole maintain around 50 mph I replaced my,plugs wires cap and rotors when I got the car but I recently found the wires are arcing in going to replace them again and see if it changes anything tested icm it tested,good I'm just confused as to why if i,hold,the car above or blow this rpm range the issue is gone
So your at 50 mph and the revs are between 2500 and 3000? In what gear? My 88gt is at 2000 rpms at 50 mph in 5th gear and it damn near runs perfect except for a o2 sensor throwing the check engine light on.
[This message has been edited by Silvertown (edited 09-17-2015).]
Silvertown the car is an automatic to start with so it's on third sitting around 2500 at 50. The plugs,wires,cap and rotor were replaced 6 months ago when I bought The car along with the front side exhaust manifold and cat delete. The arcing is at the cap side of the wires they are,arcing between them selves on the cap and also jumping to the intake I'm going to replace them and the cap and rotor. In just confused basically everything is bad already kind of confusing
Silvertown the car is an automatic to start with so it's on third sitting around 2500 at 50. The plugs,wires,cap and rotor were replaced 6 months ago when I bought The car along with the front side exhaust manifold and cat delete. The arcing is at the cap side of the wires they are,arcing between them selves on the cap and also jumping to the intake I'm going to replace them and the cap and rotor. In just confused basically everything is bad already kind of confusing
Start by going to auto zone. Have them check the charging system. The battery and the altenator. You need to practice basic car maintenance fundamentals with an older car. Once you've established the charging system is fully functional then move to the ignition. You said the plug wires are warranties so get those replaced. Did you put new spark plugs in? Have they ever been changed? If not you need to check them all for fouling and gap. Did you remove spark plug wires from distibutor? If you did, were they put back in the correct order and if not did you get the cap on right. You could have it on 180 degrees in the wrong direction. Once you know all this is correct you can take the next step out to the pu coil for continuity and gap between the rotor and pick up. Do you have a feeler gauge. If not get one. It can be used for both pu coil and spark plugs.
Start by going to auto zone. Have them check the charging system. The battery and the altenator. You need to practice basic car maintenance fundamentals with an older car. Once you've established the charging system is fully functional then move to the ignition. You said the plug wires are warranties so get those replaced. Did you put new spark plugs in? Have they ever been changed? If not you need to check them all for fouling and gap. Did you remove spark plug wires from distibutor? If you did, were they put back in the correct order and if not did you get the cap on right. You could have it on 180 degrees in the wrong direction. Once you know all this is correct you can take the next step out to the pu coil for continuity and gap between the rotor and pick up. Do you have a feeler gauge. If not get one. It can be used for both pu coil and spark plugs.
Silvertown thanks for the suggestion but I already verified the charging system and battery with the equipment I have at work. I have gone through the basic maintenance on the car the plugs were changed with the wires cap and rotor when I got the car. I warrantied the cap rotor and plug wires today upgrades to the better wires the plugs are delco. I tested the icm it tested good multiple times. How do I check the pickup? Also today I was able to get the car to do this in the driveway while holding it at 2500 now it is accompanied by a notable pop from the exhaust as well.
Ok so I removed the distributor from a parts engine I have and it was the cage style pickup luckily the parts store stocks the pickup for this style so I bought one installed it times the engine and my problem is solved thanks for all the help
Ok so I removed the distributor from a parts engine I have and it was the cage style pickup luckily the parts store stocks the pickup for this style so I bought one installed it times the engine and my problem is solved thanks for all the help
That's great. Drive it like Ricky Bobby. Before I tear into my distributor did you have to set the gap or was it plug and play?
It was plug and play in my case but measuring is never a bad thing I'm going to order the pickup coil for the star style distributor and re install that one since over heard that style is more efficient than the cage.
I feel I should add that my parts engine/trans came out of a reck/project someone cut in half to make a trike I bought that had less than 1/3 of,the miles my car does so the distributor had a lot less usage than mine. 329658 on my car which I'll have to make another thread about my odometer quit working today
Wow! That is incredible. I hope I can get that far with my Fiero some day. Only 76k on mine...
So I took off my plug wires and the distributor cap. The pin in the center of the cap came out with the ignition wire. It is fairly corroded inside. I see a little spring sitting in the center of the rotor, not sure what that is for. I also don't know how the ignition pin connects to the rotor. I think something might have broken when I was taking it off and a piece flew off somewhere. I orderd a new MSD cap and rotor from the Fiero Store.
Some pictures:
[This message has been edited by ultimoblaze (edited 09-19-2015).]
nice! what is kind of funny about that is the distributor I pulled from my parts engine did the same thing when I pulled the coil wire I had never seen a cap corroded that bad before then. im going to do the same thing though get a msd cap and rotor im not very trusting in the borg warner one I have now
So I received my new distributor cap and rotor. I also bought the viton seal from NAPA for the housing. I put it all back together and luckily I put enough marks on things I was able to line it back up since I don't have a timing gauge on the timing cover. It started right up and drives just like it used to. Problem solved!
