FDNewbie

iTrader: (10)

Hey guys

This is in reference to my 84 GLS, 1.1 carb. She's got 82K on the original motor, runs strong as a champ.

I decided to take advantage of the free 100 point inspection at the local stealership, so I dropped my car off earlier today. Got it back w/ only 3 recommendations (suspension, window motors & regulators, and slight leak from the rear main seal, but isn't bad enough to warrant taking care of now). Also, I just recently had my oil cooler resealed. That's the history.

The problem: Drove it fine for a good hour or so, and I drive her hard. No probs, everything's a-ok. I made some stops along the way, and everything was fine. She was idling just right. Then I get home, and I start to back down my driveway. Get to the bottom, and I notice the car's idling real high...around 1200rpm. Normally she idles between 400 - 800 I believe. Idle is pretty steady (so yea I'd say she's holding idle), and the engine sounds like an FD 13B-REW w/ a half bridge, minus the "brap brap' sound. So it sounds like this "brum brum brum brum" continuously. About 4 of those "brum" sounds a second, and the exhaust is backfiring pretty frequently (every few seconds). I pulled up to the outdoor garage lights, and I saw some smoke coming out of the engine bay, couldn't tell from where since it's so dark out. Smoke was light in color. Oh and I turned off the car, turned it back on, and it was still holding idle at around 1200 w/ the brum brum brum brum sound and backfiring. Oil pressure looks fine, ditto w/ the water temp.

I have NO idea what's wrong...I'm hoping something might have been taken off during the inspection @ the stealership earlier today and just not placed back on firmly, so it just came loose, but I don't know what or where to begin looking. I'm still learning my way around the FB... so any help would be greatly appreciated.

Thanks
~Ramy

GavinJuice

Sounds like an ignition problem, check your ignitors, plugs, coils etc. for anything loose, anything that would affect your ignition i would suggest. If that doesn't prove anything, i would backtrack from your sparkplugs with whichever doesn't have spark.

kettlman

iTrader: (2)

i would like to know how the dealership can tell the rear main seal is bad?
but i would check and see if the choke got stuck open. then what he said?^

FDNewbie

iTrader: (10)

I'm gonna have to wait for daylight before poking around in the engine bay.

They said it looked like there was a leak from the rear main seal. That's the second time I've heard that (guy at Jiffy Lube said the same). You wanna take a look? And I just resealed my oil cooler and degreased everything, so it's a diff leak...

As for the choke, I used it tonight to get the car started, drove home about 20 min, then the above happened. Choke's working fine. Plus, I'd think that if the choke was stuck partially open, the idle may be high, but it wouldn't make that weird noise, nor would it backfire... I use the choke ALL the time to start up the car in the mornings...

GavinJuice

oops i missed the high reving portion, so everything i said might be irrelevant.

Matty's first 1st Gen

Could definately be a vacumme leak, good luck trying to find it. I'm assuming your emmissions are still on?

FDNewbie

iTrader: (10)

Vaccum leak? Not exactly what I wanted to hear... some brake cleaner should make it easy to find (I'd hope). But would that explain the smoke coming from the engine bay? Oh and yes, I still have emission control equip. She's not 25 years old yet

RotorMotorDriver

iTrader: (1)

On my old 85 (as well as other cars Ive heard of), if the choke is on too long, or too much, it will actually flood the engine with gas and cause it to struggle to run (thus the weird noise and the high idle). It can also cause it to backfire because of the excess fuel in the exhaust. Just something to check, and something easy at that. Dont rule it out so quickly. The cable can bind if its routed wrong like if they moved it aside to get to something too, I know that can happen.

~T.J.

r0taryluv

I have to agree with RotorMotor with the flooding problem, and with Matty on the Vacuum leak. You guys are suggesting the right things but back up with info on how to go out it. Not everyone knows the tips and tricks. As far are checking for a vacuum leak NEVER use brake fluide on anything other than putting it in the master cylinder. Get a spray bottle with some soap water and while the motor is running spray the vacuum hoses (do this with the engine @ operating temps) and listen for a change in idle while spraying the hoses. The soapy water will temporarly block the hole and will allow it to idle better, plus after doing this you can just wash it off. As far as flooding check the float levels on the Carb, there are two of them. On the front of the car there will be a glass window to see the level of fuel in the flooat bowls. By this time they are very dirty and will be hard to spot...I donot have any photos but you will see two phillips screws holding it on. Pull one of the LEading spark plugs and see what color it is, if it is very black go ahead and replace all 4 of them with all leading NGK plugs from a 86 seven, these have a higher temp rating which will help give a cleaner and hotter burn. If nothing changes, pull one whire at a time from the spark plug lay it on the sturt tower and turn the car over, you will see if it arces over or not. If all 4 arch then nothing is wrong with the ignition or ignitors. Keep us updated.

Vern

Kentetsu

Do you have a timing light? If so, throw it on each of the plug wires and verify your spark. If you lost your leading ignition, then there would be smoke coming from the engine bay, but there would also be a huge difference in performance.

If this just happened since you got it back from the inspection, maybe you should just take it back and demand that they fix whatever they messed up. That's where I would probably start. But if you want to pursue it yourself, I would look for something that was replaced improperly, or adjusted.

Check these items; Distributor cap (sometimes can be misaligned), all plug and high tension wires, wires to coil, wires to ignitors. After that comes vacuum lines (sorry). Next would be possible adjustment of the carb, but you don't want to start there because if that's not the problem you might make the issue harder to diagnose.

Good luck, and keep us posted on your findings/results.

kettlman

iTrader: (2)

i don't think he was talking about brake fluid, i believe it was brake cleaner. that would raise the idle up if it hit any vacuume leaks going to the carb, kinda like propane or carb cleaner. i do like the soapy water method, would the soap change the idle any or do you just need to keep your eye on it?

r0taryluv

Honestly if someone messed my car up I would be least likely to take it back to them feeling that have already done me wrong and will do me wrong again. Yet that is just me. I dont feel it is a timing issue seeings he didnt say anything about it running like this when he first started it, only after operating temps (20 minutes) " As for the choke, I used it tonight to get the car started, drove home about 20 min, then the above happened." Something they would mess with would be idle mixture. But I would not recommend messing with that screw untill you ruled everything elseout. Kettleman as far as the Brake fluid cleaner or carb cleaner....keep one thing in mind, that stuff drys all your hoses out and will cause vacuum leaks to mature. Think when you get some carb cleaner on your hands....dries them out and burns doesnt it? ;] This is why I suggest the soapy water cause it willl raise the idle as you decribed above when the water hits the leak. The soap just helps the water hold onto the hose a little longer rather than just running off.

Siraniko

iTrader: (13)

sounds like the butterfly in the intake manifodl aint opening.

FDNewbie

iTrader: (10)

Vern, thanks for the how-to. I didn't get a chance to do the soapwater spraying today...any ideas where I should start spraying? Or should I just keep spraying all around until I find an area and try and localize it from there?

Also, I couldn't find that glass window you're talking about for the life of me. Does anyone have a pic of it's location plz? I don't understand tho how it could start if it was flooded... and I can kill the engine and start it up, no problems. It even sat overnight from yesterday to today, and I started it up, no problems. I thought flooded engines won't start??

Also, I dunno where the choke cable is :-/

I'll check the plugs when I get a chance (time's real tight right now...exams). And I'll try pulling the wires one by one to check for spark.

86...that's an FC, right? I take it just have the guy at the Advance Auto look up the part # and make sure they're NGKs, right? And you're saying all leading, so all 4 will be the same #, right? (like running 9s all around on FDs, right?)

What I did find was that on the driver side, near the firewall, there's a bunch of connectors from the main wiring harness. And against the fender (very close to the firewall) are two black boxes (relays?) that some connectors connect to. One of them was unplugged, dunno if that's new or not. I plugged it in, no change. There's one connector all the way at the bottom that's not connected to anything...and there's nothing for it to connect to, so I assume that's normal. Also, there's a little bag/pouch w/ connections in it, and I believe it has 2 or 3 that are connected, and one that isn't. I don't see anything that should connect to it. Again, I dunno if this is normal, but just sharing what I found.

Lastly, I called the stealership, and the only reason I would take it back to them is because they're one of the few stealerships that actually have a mechanic certified by Mazda to work on rotaries. It's the only dealership actually that ppl take their FDs too because of him. So I thought it would be in good hands. Long story short tho, the service advisor told me they did no engine diagnostics, so they're not accepting liability for anything. But he'd be happy to have the mechanic take a look at it and diagnose it for $90

And I'd check that how?

FDNewbie

iTrader: (10)

Go figure...after driving the car for 30 or so miles, it started to idle fine again, all by itself, out of the blue, as I came to a stoplight. Dunno what the prob is, but backfiring out of the exhaust = poor timing = running rich, right? So I'm thinking maybe the ignition solenoid is going bad? I figure if it is, this prob will get worse over time...but as of now, everything's a-okay...so I'm not complaining lol. I'll post here if it happens again...thanks for the help everyone!