Kawizx9r

iTrader: (2)

Ok so about the car;
1993 FD3S stock other than dual intake/cone filters, electronic boost controller, pre-cat eliminated, and suspension.

I've had this issue where it seemed like there was a dead spot these past few days upon acceleration. I've narrowed it down to the throttle position sensor but I've yet to get a multimeter (last one broke) to recalibrate and/or replace it.

Now I've got a new issue altogether.

It started when I parked at Home Depot, I let the car cool down for like 4 or so minutes+the 1 minute turbo timer built into the factory Ungo alarm.

Anyway, when I parked the car suddenly started idling crazy. It has always idled normally at 850rpm in park but this time it dropped from 850 to 550 and it kept fluctuating up and down.

First thought is, idle air control valve maybe? Or sensor? Not sure what this car uses exactly.

I pulled out cause I didn't want to stay there and decided to go home.

Car kept fluctuating in gear as well, at a stop light/sign and I had to keep a bit of gas on it in order to keep it from jumping alot. Car doesn't die but it comes close to dying hence keeping gas on it. Driving it home (1mile away) the car backfired a couple of times when decelerating and once I got home I parked it. Fluctuating idle remained, I checked all fluids (full), took a good look around and no disconnected lines as far as I can see.

Didn't feel like I had a misfire at all, though I wouldn't know how much different it'd feel/sound like on a rotary than a piston engine. No smoking from the exhaust, and again all fluids good and vacuum lines from what I can see.

I made a video to display what I was experiencing (also explained it if you didn't read everything).

http://www.youtube.com/watch?v=WO6G2WZYX9o

Would it be bad plugs? Fuel pump? Specific vacuum line that can cause this?

Sorry to ask but I wouldn't if I was much more familiar with rotaries. I do my own work too so I don't mind getting my hands dirty to trouble shoot stuff.

Kawizx9r

iTrader: (2)

PS when I said there was a sudden noise, it sounded...like Idk a short clank in combination with a gear grinding. Belt is still intact btw.

CAR IS AUTOMATIC, don't think I posted it in the first post.

MazdaSpeedDan

iTrader: (4)

I paid 8$ for a multimeter at Autozone. You can use your multimeter to check for dead spots when opening and closing the throttle body while hooked up to the TPS. If you think its the TPS (Which it looks like it possibly could be) Id say go buy one for cheap and test it out.

DaleClark

iTrader: (55)

Most likely your idle air control valve is stuck/dirty. Pull it off, clean it out with carb cleaner, lube with a little WD-40, give it a try.

A vacuum leak will cause a high idle and yours is low. Most likely the engine is starving for air, if the idle air control isn't opening like it should you'll get funniness like that.

Could in theory be the vacuum line to the MAP sensor off, but you'd typically get some rich smoke and stuff. I'd check that anyhow to make sure.

Dale

Kawizx9r

iTrader: (2)

I was thinking that, but that would still effect my RPM's while driving and the backfiring at slightly higher (2k+) RPMs while on the road?

I'll do the idle air control...if I find out which one it is lol

Kawizx9r

iTrader: (2)

MazdaspeedDan, I was in OIF2, 3, and 5 (3rd Bat 5th Mar) and was there during the push through Fallujah in OIF2!

Awesome to find other vets on here, but ok I'll grab a multimeter soon but did you guys watch the video? I explained that the rpms fluctuated while stopped while in 1st gear, and fluctuates when driving too (past the 1/4th mark where the TPS sensor gave me issues).

neit_jnf

iTrader: (17)

did you check the map sensor vacuum line?

Kawizx9r

iTrader: (2)

I've only checked what's visible (without taking anything off).

I'll check that too the minute I can find where it is.

I'm used to MAF vehicles, and my last MAP vehicle everything was out in the open. Is the IAC on the side of the throttle body closest to the bumper at the bottom edge?

Wish I had a repair manual, wouldn't be asking this stuff cause I like to trouble shoot before coming right to the forum.

I'll go look again, engines cooler to the touch.

MazdaSpeedDan

iTrader: (4)

Haha OIF2, so Im sure you might have memories of rolling soft top humvees and taking the doors off and launching 203's out. Now they wont even let the windows open in our new MRAPS haha. Thanks for your service to!

All my issues with my TPS and I have never had it back fire, I assume you checked for error codes and thats how you got the TPS? If not Id test for codes and see if its pulling any.

Also to see if it is a sensor you can disconnect the battey and hit the breaks a few times to reset the ECU, and if car acts fine for a few minutes then kicks back on it could possibly narrow it down to a sensor.

Kawizx9r

iTrader: (2)

Not a sensor, btw when the car idled for a good 5+ seconds..there was a slight screech yet it had a slight grind noise to it as if someone was killing their starter (as if you tried to start a car that's already on).

I had that noise during the video, happened once. Happened again now after 5-6 seconds of idle after resetting the ECU.

Thinking this is a good sign of what's wrong but Idk what the sound means?

Kawizx9r

iTrader: (2)

I try to search as much as possible quickly lol thanks!

It wasn't the vacuum line, the wire is kinked/broken. I pulled a bit of the sleeve off and twisted the wire, started it up and it's FINE!

I feel like an idiot but this is the kind of stuff that makes forums like this one so great.

Btw, did you remember the nasty rain storms we had? I was living under damn poncho's (I was in WPNS company, 81's platoon).

MazdaSpeedDan

iTrader: (4)

Is your AC on or off while this is happening? (Taken from Other webpages)

>...stalling when AC on at idle
I forget the name, but the stock air-bypass system effectively open up the throttle plates (ie allows more air flow to the engine) at idle/cruising when sensed load occur like AC, alternator, etc. If the ECU isn't seeing the load signal or the bypass isn't increasing RPM (or problem X) then the load will likely stall the engine.

Having a light flywheel make the problem very obvious.

--------------------------

Maybe Lower Intake Manifold Gasket?


This page might help ya out.....

http://www.fd3s.net/idle_adjustment.html

Kawizx9r

iTrader: (2)

That page for the idle adjustment was bookmarked since before I got the FD3S lol I book marked that and several other helpful links that comes with owning an FD.

Appreciate the help, not sure if you caught that but the orange (one of the 3) wire on the electrical end of the MAP sensor coming from the wire loom was kinked/ripped. I pulled the sleeve on both ends and tied them together and everything started up and idled fine (for 7-8 minutes).

I put a small zip tie on the vacuum line for safe keeping on the hard line that comes from the throttle body. Will tighten it later lol engines hot again and it's a pain in the *** pulling it tight.

neit_jnf

iTrader: (17)

hey! im glad it was something simple!

I remember when I first bought mine, the map vacuum line popped off and I thought I had blown the engine!

Kawizx9r

iTrader: (2)

Lol it's a rotary and being my first rotary, I'm over-thinking things and assuming I've done much worse than if a piston-engine was experiencing the same problems.

I remember on my turbo PT, I was pushing meth injection, aggressive timing, maxed out TD04 (tiny turbo, yes it's cute awwe), and so forth and the rubber seals between the intake manifold upper and lower blew out (2 of them). It caused an extremely high idle and massive backfiring, thought I blew something yet my A/F ratios remained at 11.8~at WOT. Been there too many times where I thought something screwed up.

My last car was an LS1 Trans Am WS6. A/C compressor crapped out on me and it 'choked' things up (it momentarily locked up causing it to stop the engine from spinning) and it shut down on the freeway. Thought my belt broke and I thought 'oh ****, my waterpump!' so I pulled over and sure enough, no belt...just a broken A/C.

Kawizx9r

iTrader: (2)

Just thought I'd share pics, all taken outside my house -

'Blue monster' PT Cruiser with mods listed above -



'Black beauty' WS6 I recently got rid of to get my FD3S -



383 Stroked Firebird, wife and I dumped the project and sold off everything, well almost...still have a stock hood I'm giving away. 1977 Firebird Formula hood -



Camaro I had for a short bit, FYI don't buy an LT1 f-body...if you want a 'maro get at least an LS1 -



My RX7 FD and my Celica (daily) -



Had many other cars but these were the last cars since after I got out of the marine corps.