A long time lurker, here. I recently bought an '86 GT with an automatic. It's been a bit nippy out to really troubleshoot some of the issues I have with it, so I thought I would tap you guys for a little wisdom.
1) Driver's side headlight sticks up about a half inch after retracting. I have to push it down for it to sit flush -- no resistance when I push it down. Could this be an adjustment issue, or do I need to rebuild?
2) Long, 2-4 second crank time when the engine's cold. Sometimes it idles all the way down to 500 to 600 rpm for a few seconds immediately after starting. No issues on a warm start. However, the idle hunts a bit after a long drive....maybe 50 to 100 rpm. No CEL
3) Rough trans engagement from park to drive or drive to reverse. 1-2 shifts seem snappier than I'd expect, but it's been a long time since I've driven another vehicle with a TH-125 for me to compare.
4) Seems a bit squirly going faster than 60 mph, but I'll be checking the tie rod ends, wheel bearings, etc when it warms up a bit.
5) Cruise control seems slow to react, but maybe I'm too used to modern cruise controls.
I've searched the forum, but I can't really find my situation regarding the headlights, and the cold start, low idle/ idle hunting information is all over the place in terms of finding a solution.
Welcome to the forum. On your questions and issues, the "Search" function is your friend. Having said that however, at times it can be a bit of a word game.
Issue 5. Cruise system: The cruise control is vacuum powered. Any vacuum leak will impact the system and response times.
Issue 1. Headlights: Could be stripped gear or weather related considering your location this time of year.
I'm sure others will chime in with suggested fixes.
ditto on the search, and make sure you search all areas especially the archives. And ya welcome aboard the nut house, anyone that owns one of these has to be out of their mind. my memory is shot or I could remember more for you, hell half the time I forget to put pants on when I leave the house.
Steve
------------------ Technology is great when it works, and one big pain in the ass when it doesn't
Detroit iron rules all the rest are just toys.
[This message has been edited by 84fiero123 (edited 02-26-2014).]
2) This is a longshot, but it's possible you have a bad fuel pump relay. When you turn on the key, do you hear the fuel pump come on for 2 seconds? You should. If that relay is bad, the fuel pump will still be activated by the oil pressure switch. But this won't happen until after the starter primes the oil pressure, and that takes a while. Depending on your oil filter, it might be quicker to build oil pressure when the engine is warm but the oil may have drained back after it sits for a long time. Hunting is a frustrating thing many people struggle with. Sometimes it's been reported to be caused by vacuum leaks. Some have also found it to be caused by bad grounds. Since yours only happens at a hot idle, a more obscure possibility is that it doesn't have the original fuel injectors installed, and the ECM isn't calibrated for them. This calibration issue becomes significant with short injector pulses, and the injector pulses are at their shortest when the engine is hot idling. However, 50 to 100rpm doesn't sound like much - this ECM is primitive and I'm not sure how smooth it was even when the cars were new.
3) It might be normal, I'm afraid it's hard to say without direct comparison. The TH125C does engage more harshly than most modern transmissions do. The idle speed can make it worse - it's common for Fieros to idle at 1500rpm or so when cold. It should drop to 900rpm when warmed up. After getting my 86GT, I noticed the same as you about the 1-2 shift. It was quicker/firmer than what I remembered from 4cyl cars I've had with this same transmission. I didn't mind it, but it was interesting that it was different. I assumed either it's in better condition, or maybe it's a normal difference from being the heavier duty (V6) version of the transmission. I don't know for sure. In any case, I suggest doing a transmission fluid and filter change, since there's no telling when it was ever done last. At least then you'll know the fluid isn't 28 years old. In my car, I had some roughness when the TCC was locked, which got better after a fluid change.
4) Common on these cars due to the age of all the suspension components. Rear can especially make the car feel squirrely. When you go over all this, also consider the rubber bushings that mount the engine cradle to the frame. That rubber has deteriorated, meaning the whole rear end can float around. There are polyurethane and even aluminum replacements available for those rubber bushings.
5) When I got my car, the cruise control was intermittent. Seems it just wanted to be loved, because it "fixed" itself after I kept using it. But I've never had a problem with it being slow. Mine reacts much more aggressively than I'd like. Takes off too hard and is too choppy on/off trying to maintain an exact speed. If yours doesn't feel like a teenager is driving then it's probably not working quite right. Maybe it's a vacuum leak, as Cajun suggested.
Yep, the FP relay kicks in as it should....I wonder if the cold start injector is having an issue....I might run some Chemtool or MMO through the gas tank for now. Another thing I've noticed -- and forgot to mention -- was that the coolant temp gauge doesn't go passed the second or third mark from the left. Heat is luke warm. The previous owner said he changed the thermostat because he thought it ran too hot (but said gauge needle never got into the red). So, I'll check the thermostat and sensor while I'm at it.
I might go ahead and spring for an ALDL cable, too.
I ran 160* thermostats in my cars in the winter here and they always put out enough heat. You could have a collapsed heater hose or partially clogged heater core. They tell me that cool of a thermostat cause higher fuel consumption, but that was never a big deal to me. I think OEM is 180 or 190...he could have put a lower one in because of overheating issues. The fan dont normally kick in till almost 235* unless the AC is on.
I wouldnt change the trans fluid unless you get a real problem. Chances are its never been changed, and changing it could flush out all the stuff in it thats keeping it going. Ive seen lots of auto trans fail soon after a flush and refill. The only times Id change it is if I bought the car new, or I know about the care it recieved prior. Otherwise I just drive them till they quit. It could also have a shift kit in it which would make shifts crisper (and better for the trans ). Quick shifts good, sloppy or mushy shifts bad.
The long cranking time sounds like a bad cold start injector. The only purpose of the cold start injector is to add fuel during the cold cranking cycle to improve starting time. The injector itself could be bad or clogged, or the switch may be bad.
My Fiero has always had a slightly fluctuating idle, 50-100 rpm is nothing major. I think its just characteristic of the engine and relatively slow computer controls.
Roger --"I wouldnt change the trans fluid unless you get a real problem. Chances are its never been changed, and changing it could flush out all the stuff in it thats keeping it going. Ive seen lots of auto trans fail soon after a flush and refill. The only times Id change it is if I bought the car new, or I know about the care it recieved prior. Otherwise I just drive them till they quit"
I'm sorry , but that is just bad advice. I can't see that being a good idea period. I hope that it was a joke.
Roger --"I wouldnt change the trans fluid unless you get a real problem. Chances are its never been changed, and changing it could flush out all the stuff in it thats keeping it going. Ive seen lots of auto trans fail soon after a flush and refill. The only times Id change it is if I bought the car new, or I know about the care it recieved prior. Otherwise I just drive them till they quit"
I'm sorry , but that is just bad advice. I can't see that being a good idea period. I hope that it was a joke.
ABSOLUTELY NOT. I used to change fluid in my own used cars all the time thinking it was good. It wasnt, I paid for quite a few transmissions that went out weeks later. Anyone who works on transmissions will tell you the same thing (unless its one that you will pay to flush and refill it of course). I stopped doing that and havent had a single transmission failure since. (several hundred cars), many with over 200,000 miles on them. If you buy a car new, then by all means feel free to change it per factory recommendations. If you know the previous owner did that too, thats fine. If you got a 100,000 mile used car you know nothing about, flush and fill it at your own risk. Ill be the first one to jump in next month and say 'told ya so'. If you already have a major problem like slipping, missing gears, etc...its ok because you cant hurt it any more and could 'possibly' help it. Myself I leave the original fluid in till it goes out completely in 250,000 or more miles.
Roger --"I wouldnt change the trans fluid unless you get a real problem. Chances are its never been changed, and changing it could flush out all the stuff in it thats keeping it going. Ive seen lots of auto trans fail soon after a flush and refill. The only times Id change it is if I bought the car new, or I know about the care it recieved prior. Otherwise I just drive them till they quit"
I'm sorry , but that is just bad advice. I can't see that being a good idea period. I hope that it was a joke.
I agree with Roger on that one, if it hasn't been done all along it can cause catastrophic damage when you flush it just once in a 100 or 200,000 miles.
Steve
------------------ Technology is great when it works, and one big pain in the ass when it doesn't
Well, I have to respectfully disagree with you. I too have had many vehicles in my almost half a century. Starting with my Plymouth Duster at 14 (I miss that car!) and have only had 1 auto trans go..On a Chevy 4x4 I bought used @180K (those early 700r4's sucked). My Suzuki (with no real replaceable filter) is still running today with over 400+K on it and I dare say it's long life is due to yearly trans fluid changes (and my OCD PS,brake flushes etc) I believe if a trans is bad enough to slip after a fluid change, it was going to fail anyways (and when you are the farthest away from help!)
There's different opinions out there about transmissions. I know it's a common viewpoint not to touch the fluid on an old transmission, but I find that unduly defeatist. In the case of a mechanic, they don't want to be held liable for a trans that might be about to die, so by not touching it they can't be blamed. Stirring the pot could indeed hasten it's demise, hence the liability. But I figure if a transmission is so far gone that changing the fluid is going to screw it up, then it was going to die anyway. Personally I don't accept this (IMO rare) scenario as a rationale to never let an old transmission see fresh fluid again.
I've multiple times seen fluid changes make old transmissions behave better, not ruin them. I've also seen a disassembled trans that was sludged up. But yes, there are also people that have had transmissions die shortly after changing fluid. I just don't think the option of not changing it would have done them much good. If one was really worried that a transmission might be sludged up, then I suppose you could start slow. Crack open the pan and drain only a small amount, like say 1 quart. Add a bit of new fluid up top, drive it for a couple weeks or whatever and then repeat. People sometimes run into the same concern with sludged up engines. Changing the oil raises fears of dislodging too much gunk. But if I ran into an engine like that I'd still change the oil.
Anyway, since this transmission has no apparent problems and has been described to have snappy shifts, I see no reason to think it's on death's door.
Yeah, guys, I don't plan on flushing it. From my experience -- and a lot of other people's experiences -- flushing can hasten a high-mile transmission's demise. I might consider simply changing the fluid and filter, but definitely no flush job. She has about 154k, but only 10k was put on the car within the last ten years judging from the VIN report.
I'm probably going to do a 3.4 DOHC or 3800SC swap sometime in the future. But for now it's going to be a DD. Since it's already an auto car, the L67 and its 4-speed might end up being a little less of a hassle when all is said and done. I'd only want the LQ1 if it had a 5-speed beside it. I wouldn't even mind a 3.4 PR if I could cheaply get 200-220 HP from the crank without spending a fortune or losing EFI.
Originally posted by jbs2212: Another thing I've noticed -- and forgot to mention -- was that the coolant temp gauge doesn't go passed the second or third mark from the left. Heat is luke warm. The previous owner said he changed the thermostat because he thought it ran too hot (but said gauge needle never got into the red). So, I'll check the thermostat and sensor while I'm at it.
If the previous owner's concern was the peak operating temperature, a better solution is to change the fan switch. The factory fan switch doesn't activate until 235F (plus who knows what the tolerances are on that measurement). Rodney Dickman's web site sells a replacement switch that triggers the fan at 210F. http://rodneydickman.com/ca...th=22&products_id=88 An added bonus is that the fan switch also controls the trunk fan which blows air over the alternator and ignition coil. So this keeps those cooler as well.
Also check your radiator cap. The correct radiator cap should have a spring that holds the valve closed. If it flops open with gravity then it's the wrong cap and should be replaced. Many Fieros have the wrong cap installed, because it was listed incorrectly in parts catalogs for several years. The wrong cap can cause some coolant loss when the car is parked.
I have to agree with new transmission fluid too, if the old fluid is all thats keeping a transmission operating, the parts are so worn and out of spec that its not going to last much longer anyway.
What's in old fluid that isn't in new fluid? Clutch pack material, metal particles, moisture? MAYBE having some clutch pack material in the fluid is helping provide grip to a worn clutch, but again, it's because the clutch is worn in the first place. And if there's that much sediment in the fluid you can imagine how clogged up that pan filter must be.
The fluid properties, such as viscosity and all of the antiwear, antioxidant properties, degrade with age and use. So clean old fluid is absolutely worse than clean new fluid. Not only that, the transmission was filled back in 1986 with Dexron II fluid. New Dexron VI fluid is far superior than old Dexron II.
I would drop the pan, put a new filter in, and refill it. I suppose flushing it could dislodge chunks of sediment and force it where it shouldn't be. Just adding new fluid will give it time to slowly dissolve deposits.
FWIW, I put new fluid in a TH125C in a 89 Beretta and shift quality improved tremendously, the 1-2 shift had a shudder that went away with new fluid. I've also done it on a bunch of other old vehicles and its never hurt anything.
" if the old fluid is all thats keeping a transmission operating, the parts are so worn and out of spec that its not going to last much longer anyway."
EXACTLY what Im saying. You dont know how long it will last....maybe a few months, maybe a few years without messing with it at all. If that is a problem, you just end up speeding up its death.
One I had, a 77 Dodge full size van I bought new, I had the fluid changed because it was recommended...and it had no problems at all. After the change the trans went out in a week and wouldnt move at all. It was done by the Dodge dealer I bought it from. That one cost me $2000.
my memory is shot or I could remember more for you, hell half the time I forget to put pants on when I leave the house. 
