Hey every one. I have recently acquired my Fiero and begun work on it. It is a 1985 Fiero GT with 3spd auto. The car ran great in fact it ran well all 1800 miles home. Then I ran into a problem the Cat clogged and I had it replaced. I also installed a new cap/ rotor, plug wires, and NGK plugs. The car ran well but after a while started bucking almost while I was driving but only while cruising. If you try and maintain speed its like a cylinder randomly cuts out for a split second then comes back. so what you get is a momentary loss of power and a rough running Fiero. I replaced my TPMS sensor with one supplied to me by a local friend that he got in a parts car that should be new. The car ran a little better but still doesn't like cruising. I also still feel I'm not getting the fuel economy the car is really capable of. If any one has any thoughts please let me know. Right now I'm suspecting a bad injector but have no idea how to track it down since it seems to be an intern mitten problem only detectable while cruising at speeds over 55. Get up around 80 and it seems to be alright though.....
On the original problem get the fuel pressure tested.
Has the fuel filter been changed?
Fuel mileage will vary greatly. Some get only 15+/- around town. I used to get 25+ with an 85 SE V6 auto. (Back before ethanol) Now I have trouble getting that much with a V6 4 speed.
Is the Tac filter missing? It's the little condenser shaped thing usually mounted below the coil and has white wires coming from it.. It would be interesting to know if the Tac is flickering when the bucking problem is occurring.
What do you mean by "optimistic" on the temp guage....high or low reading?
Fuel guage----- Unfortunately that is almost normal on these cars.
Try reseating the speedo connector on the trans. It's the one on the passenger side trans out put shaft housing
The ECM relies on the tach signal, so check your tach filter. Also, Fieros don't like "fancy" spark plugs. If you put in "platinum" or other fancy plugs, that could be your problem. Stock AC Delco or equivalent work best. I use standard (not fancy) Champion plugs in my V6 Fiero because they are plated and resist rusting. I have AC Delco plugs in my duke Fiero.
check your plug wires!!!!!!! even though you changed them they might have come in contact with some thing hot. what you described is exactly what me car was doing and a set of new wires cured it. at night spray water with a spray bottle all around the engine if you see arcing then you know you have a bad wire. if that isn't it the the pick up coil could be to blame
Thanks for all the responces guys Ill start from the top.
The Fuel filter is only a thousand miles old because it was our first suspect when the car was bogging and it turned out to be a backed up cat.
The Temp gauge bearly gets off the far left when under normal driving. Now I do have my radiator fan wired to a switch instead of working on the thermostat since the thermostat was more then likely bad. (Original owner mod) If you leave the fan off the temp climbs but I feel like even with the fan on it should rest some where in the middle when warmed up not on cold.
I did Sea foam the car recently and it seems to run better but not fixed (Just thought I would throw that detail in there) http://www.youtube.com/watch?v=bqa4YPabdEo <- Link to a vid of the madness
The plugs are Iridium I believe a friend bought them for me as a congrats on the Fiero thing.
Ill check my wires again and see if there is any obvious damage.
I did buy one of Rodneydickmans tack filters but after plugging it in the tach still thought 5 grand was 0 and stared fighting with my oil pressure gauge which reads in the middle at idle but burries to the right when you accelerate (Thus I said it didnt work right because there is no way that engine generates that much pressure) I then un plugged it in fear of damaging anything.
I'm fighting the same issue (bucking at constant throttle) and i've gone thru the paces, finding a bunch of stuff wrong along the way.
You can check if your ignition is misfiring using a timing light, if you have one. Just hook up the light to the common coil plug and watch for misses. I found out my cap was bad using this method.
Pickup coil can cause a misfire as well.
I just sent my injectors off to be professionally cleaned so I will report if that helps or not.
The EGR is supposed to open at part throttle cruise. Although I don't know how a malfunctioning EGR valve would affect a car at cruise. I'm thinking it would malfunction at all times.
Personally, I've never heard of a fuel injector only acting up at a certain RPM. You can always have them cleaned and flow tested. It's much cheaper than replacing.
Have you tried misting the spark plug wires at night to see if they arc? Just a light water spray from a squeeze bottle will tell you allot. It's a free test. The standard auto parts house plug wires have been known to arc even when new.
Havent pulled em to check but appon googling NGK iridium plugs it looks like they have a very small tip there. I did some reading and ran into a thread here saying that Fiero ECMs are designed for certain Spark plug electrode sizes and etc. This causes them to run funny if they arent sparking exactly like the old delco plugs exampled being hotter or bigger spark caused by "Fancier" plugs.
Personally, I've never heard of a fuel injector only acting up at a certain RPM. You can always have them cleaned and flow tested. It's much cheaper than replacing.
My problem, at least my current theory, is that my injectors don't flow correctly at really low duty cycles (light throttle) such as a cruise condition because their dirty or maybe because I'm using disc-type injectors instead of the original pintle ones. It sounds like the same problem the OP is having, just a suggestion since I've done a ton of other things to my car and the problem remains.
I would get your injectors cleaned before I bought new cheap ones. I tried the same thing you are suggesting and the car didn't run quite right with the new injectors. I had bad results from Fuel Injector Connection and would not recommend them although many others have had good experiences with them. I am currently getting mine serviced at InjectorRX, $120 for the set of six including return shipping.
so you where having cruising issues as well? Because driving around under 55, wide open, acceleration, and deceleration is smooth and fine its all high speed cruising stuff.
well I misted the engine bay and got no arcing. So plug wires must be good. Ill see if I can stop by Autozone after work tommorow and pick up some run of the mill delco spark plugs for it.
.....for what exactly? Sorry not to clear on what exactly the EGR does any way and how it could cause my problem.
Sorry for not explaining. My EGR was stuck and my symptoms were exactly like yours. When accelerating and decelerating it would be ok. However as soon as I started to cruise especially when in 3rd gear it would just start to buck back and forth. Add a little gas or release a little and it stopped. So I suggest you should check your EGR if it works.
so you where having cruising issues as well? Because driving around under 55, wide open, acceleration, and deceleration is smooth and fine its all high speed cruising stuff.
I was having the issues anytime and any speed in 4th gear.
How do I check for a non working EGR? I also changed out my plugs today with standard AC Delco plugs and the car ran a well for a while then started running wierd again. The plugs I pulled out the NGKs with the sharp point electrode where covered in a thick layer of dark soot. These plugs are completely finished and their only a thousand miles old. Any Ideas?
Are you getting any check engine codes? The plugs you pulled all black and sooted up is definitely indicating a problem. Also you said a lot of your gauges were reading wrong. If that's the case, your computer is likely getting bad data as well. I would check that your sensors are good and the wires are at least clean and intact. You said you had replaced a bad cat earlier. Probably ruined by the conditions you are experiencing now. Good luck and let us know what you find.
As a side note regarding exotic spark plugs, I have been running E3 3.40's in all six spots for about 35,000 miles now and they seem to do well on my otherwise bone stock, high mileage engine (280,000 miles!) The stock AC's worked well for me too but I didn't like that the body would rust away evertime it rained and the water sits in the spark plug sockets until next time I ran it. Guess it's time to do the water shield on the front side of the hatch!
How do I check for a non working EGR? I also changed out my plugs today with standard AC Delco plugs and the car ran a well for a while then started running wierd again. The plugs I pulled out the NGKs with the sharp point electrode where covered in a thick layer of dark soot. These plugs are completely finished and their only a thousand miles old. Any Ideas?
If you can get your hands on a WinALDL cable and a lap top you could diagnose it fairly easily. Couple more items to check:
Ground strap from the engine to the right deck lid hinge mount. Is it in good shape and clean connections? Do you have a 195 thermostat in it? Does your check engine light work? Has it come on while cruising. If so have you tried to pull the codes? //www.fiero.nl/cgi-bin/main.cgi?ECMCodes Check both the temp sensors and make sure you have good connections. There's one for the gauge and another for the ecm. The sooty plugs indicate that POSSIBLY the engine is running in the "cold" mode and that maybe your gauge isn't too far off.
As far as the EGR I agree that the symptoms that you are describing could normally be caused by an engine getting too much egr. But the GM V6 set up that is run by a solenoid usually fails in the closed position. It's possible that a p.o. could have swapped in an aftermarket valve that has a required orifice washer missing and is allowing too much egr at light throttle. BUT it should have been happening all along.
I replaced the Coil with another ignition coil of unknown age and exact condition supplied courtesy of Marine1981. In any case The car on a short test drive did appear to have a bit more pep and it cruised at 55 up and down a one mile strech twice with no problem. Ill let you guys know more when I get to actually freeway test it. It did actually smell rich when I started it with this new old coil including a blast of grey smoke in the air when I first started it. My friend in a Text said perhaps the computer is having to adjust to a better working ignition coil and it will go away the more I drive it. Fingers crossed. though.
Just wanted to say that you aren't alone... I'm going through the exact same thing... Exactly!
So far I've done.. New distributor, cap, rotor, wires, champion spark plugs, EGR replacement... And now I have new injectors...well, rebuilds I found off eBay for 80 bucks with a garuantee for exact flow. Just need to put them back in.
But before it was at full throttle, it would buckle (but at long high rpm not with the quick first and second gears), instead of cruise... Found that it was the wires... So I thought, but now... Who knows. And the smog sniffer is due next month. I'm worried about the cruise portion now..
Please keep us posted... Mines a 3.4L P/R
Even though the distributor is new... Maybe it needs a new pickup coil... Oh, I replace the main coil also. I had a MSD.. Now it's a stock one from autozone
[This message has been edited by unboundmo (edited 09-10-2012).]
just went through the exact same symptoms. I had used brand new AC Delco plugs and AC Delco wires. It ended up being a resistance problem in teh #2 cyl setup. It would arc occasionally from the lower boot to the heat shield yeilding that same cutout of one cyl. I replaced the wires (lifetime warranty) and put new plugs in....problem gone.
Well after changing out the Coil and test driving it some more the car seemed to drive perfectly for a while doing well at 55 and 45 mph cruising however after a breif period of 70-75 it started again. Now considering I dont know for certain the condition of the coil I put on or its Milage I think Im going to order a brand new coil and see if it permanently clears up my problem. The coil I swapped in was a little beaten looking and aged but the car did run better for a little bit. Perhaps it was a coil that was on its way out but not as bad as mine when it ended up in my friends parts box when he bought his Fiero. My question is should I buy the standard 25 dollar ignition coil from Fiero store or pay the extra money for the MSD one? I have 7mm wires and now the stock delco plugs. I dont want a coil that is some how over kill and starts another problem.
Respectable people say don't use fancy coils either. I put an Accel 40k coil in my SE, along with tuneup, new (cheap) module failed weeks later, but after that it ran well for a year, module failing after a long time sitting. Have to admit it's not starting now, but the tach moves fine when cranking, I suspect fuel this time.
On GT I also installed 50k MSD coil along with Taylor 8mm wires and Bosch Iridium plugs, same as the SE. Did get a mileage bump on the GT. Both cars sounded nice and smooth with the new plugs and so on for a short time, otherwise not a big difference. Very few miles on the GT after tuneup. Have to admit not much to recommend fancy plugs, wires, coil, etc.