fcChrisk

i just bought a 86 fc n/a about two weeks ago and from day one it had problems. well i bought it for 2000 so i guess there was a reason why it was so cheap. when i first got the car it ran ok but then sometimes the engine wouldnt idle or it would be jerking or just not running right. when i checked it out the next day i figured out that there were wrong spark plugs in it. instead of one trailing and one leading spark plug on each rotor it was all the same. plus the plug thing connecting to the spark plugs were on wrong. both trailing wire thingys were on one housing and the 2 leadings on the other. i got the right spark plugs and plugged it in right so it ran pretty smooth after that. so it ran pretty good for a week until last night where my car overheated for some reason. i dont have a thermostat, i have to put a new one in, so i cant really control the temperature i guess but ive never seen the temperature go past halfway so it was alright but then it overheated. i got the car home taking breaks when it heated up a little past halfway and today i just put a new radiator cap on cus the old one sucked and it ran pretty much normal again. except that it runs cooler than normal. i took the freeway down to work and it ran fine going about 70 no problem but when i tried to push it a little more the engine started jerking again. maybe the computer is getting confused cus the temperature is being random going up and down. my engine was heating up and then cooling back down so when i tried to push the car a little more i guess the computer thought it was in a starting mode? i dont kno the car seems fine right now but im just wondering wats going on. please help this is my first car. im 17 so i dont kno much. thanks

RX7MAVEN

On a 20+ year old car, especially one that was not maintained properly, start from scratch. Get a good manual. Then check or replace every vacuum line. Make sure you check the small vacuun control/delay valves. These are the small plastic, usuallly two colored, devices in the vacuum lines. Check the timing. There are leading and trailing timings. Run a diagnostic making sure all the engine control devices are working properly. Go to church and pray.

clokker

iTrader: (2)

First thing to do is install a thermostat.

On your S4 "normal" operating temp is about 1/4 on the cluster gauge.

helghast7

iTrader: (6)

put an oem thermostat in, as surprising as this may or may not seem you need one. period. what alot of people dont understand is that without a thermostat your car will run hotter.

I know...your thinking...wtf is he talking about?!?!? but its true....think about what a thermostat is really for.... it keeps the coolant in one place until your engine gets too hot right? so whats the rest of the coolant doing while the coolant in the engine is warming up? its cooling down. without a thermostat your going to have nothing but warm to hot coolant with not time for it to cool off because its going to recirculate too fast...plus since your engine never really get to normal engine operating temps, thats not good either.

and like what RX7MAVEN said check all your sensors...theres a strong possibility one of your sensors has taken a dump on you

socalrotor

iTrader: (1)

Go to the west section for local help. I have a few people that are lined up when I get back, but maybe I can swing through WH. Get a oem/mazda tstat to start,The jerking might be 6 ports or clogged injectors to start with. Sparkplugs could also be dead.

clokker

iTrader: (2)

Although your advice about the thermostat is sound this entire paragraph is wrong.

helghast7

iTrader: (6)

please explain then i wish to be enlightened

pfsantos

iTrader: (1)

Some good advice in previous posts. Maybe I can add to it. Yes, OEM Thermostat and cap (caps if you also have one on the top of the radiator). I believe the cap near the thermostat shoud be 13 psi. It looks like you know a bit about these cars, but not enough, but you'll get there! Your temps varying are due to the missing thermostat. The overheating could be due to the bad cap(s). Make sure the clutch on the fan becomes stiff when things get warm - it will provide resistance when you try to turn the fan. Make sure you have the underbelly pan. With engine cold, start it up with the cap off and see if a lot of champagne like bubbles form. You may have overheated it to the point of coolant seal failure - the coolant seals between the housings, but don't panic unless sure.

As far as the driveability problems, adjust your TPS sensor, using a rig made up of two LED lights plugged into a particular plug. See archives or search "TPS adjustment". Also check your water thermo sensor for the EFI mounted at the back of your thermo housing (resistance with different temps.). See FSM in my sig. for more info.

P.S. Did I mention OEM thermostat and cap(s) only?

clokker

iTrader: (2)

The coolant is always circulating (as long as the waterpump is functional anyway), the question is "Where"?
Think of the thermostat as a proportioning valve- when the engine is cold it causes the coolant to just cycle through the engine block until the thermostat's operating temp (in our case 180°F) is reached and then it opens to let coolant flow through the radiator.
The thermostat is always in a state of flux, slightly varying the degree it's opened to keep the coolant at a steady temp.

The biggest myth is the idea that coolant gets colder if it sits in the rad for a longer amount of time (the "recirculates too fast" statement) and that the thermostat is a restrictor that "slows down the flow".
Water to air heat exchangers (which is exactly what a radiator is) operate most efficiently the higher the temp differential between the coolant and the air flowing through the rad.
In a perfect world our radiators would be smaller and you'd just increase the speed of the pump but that can't be done since pumps begin to cavitate at "x" speed and since a car's waterpump speed is RPM dependent (belt driven pumps are at least) you have to leave some headroom for high RPM operation.

This is why a racecar can benefit from an "underdriven" (i.e., smaller) waterpump pulley...it spends the majority of it's time at high RPM (not to mention typically in a much narrower RPM range) and could cavitate if driven with a stock pulley.
A street car has to be able to pump effectively through a much wider RPM range than a race car- from long periods of idling to occasional bursts of redline.

Now, back to the radiator.
As the water enters the rad, the difference in temp 'tween the water and the cooling airstream is greatest and the exchange of heat is therefore the greatest.
As the water travels through the radiator and is cooled, the amount of heat transferred from water to airflow decreases, so you can see that "holding the water in the rad" becomes less efficient the longer you do it.

In theory, given the choice between doubling the size of the rad or doubling the speed of the waterpump, the second option would be the most efficient but, for the reasons mentioned above, that's usually not practical.

How easy this would all be if the engine RPM were fixed, airflow through the heat exchanger were constant and ambient temp never varied.
Not gonna happen though.

helghast7

iTrader: (6)

ok so that makes perfect sense, i understand my fault and although you would agree i am not 100 percent wrong i will 100 percent agree with you that i was not correct in my statement, i put too much importance on the thermostate and not enough on the rest of the cooling system, although it is a vital part of the system it is no more or less important than the rest of it.

i beleive we can all agree that you need one?

clokker

iTrader: (2)

Oh yeah, no doubt about it.
You weren't 100% wrong, it's just that every time I see the concept of "slowing down the coolant" I go nuts.

I'm on several PC hardware forums and you should see the neverending arguments about this as it relates to watercooled PCs.

Suiicidalpenguin

Seen the Asus board with coper tubing for heat dispersal mmm mmm match it with sum good ol water coolins (or my favorite the redneck AC against the case)

fcChrisk

first of all thanks for all the help cus like i sed i really dont know much about cars. but im slowly learning more so thats good i guess lol. i put in the new thermostat. a 180 one the company is failsafe? i dont kno the difference. i thought it would the temperature would be about halfway on the temperature guage thing but like clocker said it is about 1/4 on the gauge. now its running pretty good except that wen i dont drive it for a couple hours it doesnt idle right away. i work about 5-6 hours and end around 10 so its kind of late but after work it usually doesnt just start and idle. itll start and then die so i have to heal toe home. manually idling the car at like 2000 rpm. im going to get new vacuum lines and new radiator hoses. oh about radiator hoses. i dont kno if its supposed to look like this but its one size at where the hose is clamped on and the part of the hose where its not clamped is kinda bigger than where its clamped. is it worn out or wat. its kind of bulging

XxJaPxOxNeEs23xX

changed spark plugs, plug wire connection was wrong, changed his radiator cap, and thermo, but problem from here is after the engine is in op temp the car does not want to rev up higher then say 4k. any opinions? im believing maybe the cat is clogged.

helghast7

iTrader: (6)

check sensors, tps, map, afm. they could be the problem.

my tps was my problem, i hade troulbe with hot starts occasionally, pluss i was getting about 180 miles to the tank wether it was city or highway driving, and idle issues. like i said check them all they could all make your idle go stupid, its easiest if you have a modis scan tool from snap-on. or a friend or something.

fcChrisk

what are the sensors, tps, map, and afm. i dont kno wat those mean... sry. oh i just passed smog today lol. only thing that didnt pass was the gas cap thing. the gas cap couldnt hold the pressure or something but i bought a new one there and then it passed so yay