HELP! wierd jumpy idle! URGENT!!
 

I NEED YOUR HELP PLEASE!!!

i am at my girlfriends place about 70 miles from home. i drove here fine this afternoon, everything ran perfect. i parked my car for a few hours, then it started up again fine. but after that i started to have problems.

(just for reference, i have newly rebuilt turbos and a factory replaced motor with about 10,000 miles on it. i have a power fc w/commander and full intake and exhaust.)

we drove about 20 miles to dinner, and when we were driving on the freeway at about 80mph, ~4000 rpm, my turbos still boosted fine according to the power fc commander (~.82 bar= ~12-13 psi) for most of the trip, but while i was gassing it nearer to our destination, i felt a strange bucking for only a second or two, and my revs dipped and fluctuated rapidly for a very brief period of time. everything seemed normal after that, except until we got to the first stoplight, my idle was very, very jumpy and it seemed like it would fluctuate from a very low 300-400rpm (almost stalling) idle to around 1200rpm every second or two. we ate a very stressful dinner that tasted like crap, and then started back home.

i started the car, and at first it seemed to stay at the normal ~1500rpm, which was good for a few seconds until it dipped to the low, jumpy idle again. this occured at every stoplight on the way back, but besides the idle, everything seemed to be fine and run smooth, except when my pfc commander unit read 12psi boost, i would only feel about ~4psi, and a strange grinding noise came from around the turbo area. it made me feel really sad.

i stopped off at a gas station near her apartment, and popped the hood. no detatched intercooler pipes or loose/snapped belts, everything seemed intact from the top of the engine bay, but there was a fairly loud clanking, washing machine-like sound from the turbo side of the engine, somewhere under where the y-pipe and intake piping is. i poked around a little, and the lumpy idle continued a mystery. i did not have access to any hand tools, so i couldnt take anything apart to inspect.

i think that possibly one of the turbo control hoses popped off or snapped, but would that explain the lumpy idle?? im pretty sure nothing happened with my engine's water seals, because my car did not get above 86C-90C degrees the whole trip and it runs smoothly besides the idle. the car still drives very smoothly and seems perfectly normal between 1200rpm and ~4500rpm. but when i come to a stop the idle is erratic, and when i boost, i get a good reading, but no kick. PLEASE give me some advice. could it be something else besides the turbo connections, such as the airpump or o2 sensor? i need your advice.

thanks in advance for your help. sorry for writing a novel, i just wanted to include all the details of what happened because it does not seem to be a common problem based on my search throught the archives.

You might want to take it to Ivan

check your MAP(Mean Atmospheric or Barometric Pressure)Sensor hose on the firewall behind the brake booster and left. It's a black pill-sized box mounted on a bracket with a bottom hose and labeled as a "boost sensor". The botttom-attached black hose pops off sometimes under boost if you don't zip-tie it. Sounds like it popped off and is giving a "rump-rump-rump* idle with a sooty exhaust from the richened fuel. It may take 3-5 minutes of driving for it to clear out after reconnecting it.
Let us know what you find out...

Grinding noise from turbo-area has me concerned as well..

If that's not it...another possibility is a bad intake manifold gasket. But since you just had the install that may not be the prob. Good luck finding out what it is. Hope it's nothing serious.

any other ideas??? im stuck here guys...

Pull the - battery terminal and push the brake pedal to reset the computer and see if that fixes your problem...

I doubt it the MAP sensor because the PFC wouldn't show boost if it was disconected...

I doubt it is the intake manifold gasket because Idol would be very high due to the vacume leak..

The bad news is I think your secondary turbo shit on you and is eating itself... The primary turbo is still spooling and that is why you are getting good boost readings, the secondary isn't and that's why there is no power... You'll have to take it apart to tell for sure, but for now don't boost it untill you know for sure.. Just take it easy on the drive home and stay at lower rpms. You don't want a bunch of aluminum metal shavings getting sucked in to the engine and if you find that it is one of the turbo's you will want to pull and clean out the intercooler just incase it traped some loose metal...

Hope I'm not to late
Chris

Chris

thank you all for your suggestions, but the problem still remains the same...
 

i took the car back home last night, but did not push it very hard. it actually felt perfectly fine the whole way home until i got to a stop, when the idle started to flutter like mad again. im not sure if the turbo is to blame anymore because the transition seemed smooth and didnt seem to be lacking in power anymore. but the rattling noise and crazy idle continued strong as ever ever i got to the stoplights in the city. i started the car up this morning and after it settled, the idle was just as bad as last night.

i am going to try resetting the comp after i get home from class today, hopefully that solves everything. if not, i am going to pull everything apart and check out the turbos compressor outlet, and all the hoses i can reach.

i have concluded that it was not the map sensor, the hose and wire harness were intact and boost read fine on my pfc, as dragon pointed out.

im pretty sure it is not the main manifold gasket, got a new one of those when i put in the turbos, and i didnt see any hot air coming from the turbos when i popped the hood.

does anyone have any other suggestions in case resetting the computer does not solve my problem? or anything in particular to look out for? please put in any ideas you might have.

Bad Idle
 

Well i would soft reset the car and see if it makes any difference!
but my car had a problem like that and it turned out to be a bad
tank of gas!!!!! pull the plugs to see if they are soaked with fuel
and carbon build up!! if that checks out o.k. ????? check all the
vac. lines

thanks for the advice, ill check the plugs while im down there too.

anything else to look out for?

mines doing the same thing
kinda of all of a sudden like what happened to you

everyone says bad LIM gasket that i talk to, but i havent gotten enough time while in dallas withe the car to take it all apart and look at it.

spray some carb cleaner around gaskets. if the idle surges you have a vacuum leak there.


let me know if you figure it out

thanks

i tried and tried, and thought i had it solved more than a couple of times, but it ended up with the rough idle again and again every time after the revs lowered down after the engine warmed up. my engine bay has emptied apart and snapped back together three times now.

spark plugs were fine, all the vacuum lines i could get to seemed okay, reset the ecu twice, checked ic and hoses for any debris and came up with nothing, the problem is still there.

i thought more, and thought, can it possibly be a problem with my throttle position sensor, wiring, or something glitchy in my power fc??? what else should i check, ive run out of ideas a few times now...

please help guys. i need more of your help!

:confused:

Go to the sensor screen on the power fc and see if any of them are highlighted and there for have an error or arn't working... also check your throttle position sensor voltages at closed and at open throttle..

Chris

which abbreviation sensor is the tps on the power fc commander display?

VTA1 - is Throttle position sensor1 full range
VTA2 - is Throttle position sensor2 narrow range

I am not sure if this will help but it fixed my problem. I had a really rough idle, high rpm spudder, but fine boost at lower rpms. I also had the different readout of boost from my PFC than my gauge. In the PFC settings go to PIM Volt, make sure it is set on "Normal" insted of any of the options. Then press next and make sure all the %'s are at 100. I don't know about that noise though, it can't be too good.

hey is the VTA1 readout supposed to be the same at closed throttle all the time??? mine read 0.64 at closed throttle when i checked it this morning cold, and 0.45 after i warmed it up for a while and the rough idle started to kick in. is this just a result of the double throttle after the car warms up?

the reading at wide open throttle seems to be consistant at ~4.25.
VTA2 seems to be consistent at ~1.02 closed to ~4.98 wot.

i really appreciate your help guys. thanks for chiming in too 7-sins, i will check that PIM setting right away.

Those #'s sound good so now you need to pull off the idol control valve.. It's the round cylinder shaped thing bolted to the intake by the throttle body and next to the fire wall... It's held on by 2 10mm bolts and has a white plug connected to it.. Once you get it off spray some brake cleaner or carb cleaner in it and remove all the carbon.. Then shoot a squirt of wd-40 in after the cleaner has all dried and put it back on the car...

Also pull off the PCV one-way valve and clean it out the same way as the idol control valve... this could also be your problem if it is stuck open...

If this doesn't help then adjust the idol down with the adjuster and reset the computer and let the computer relearn idol...

Chris

Your Car is possesed!
 

(I'm sure I spelled it wrong so no grammer lessons, thanks)

I could be a stuck valve thingy (must be technical). Try disconecting the vacuum hose to the double Throttle control. Plug the line if you can.

If this fixes the problem then it's the secondary plates in the throttle body trying to open or close or whatever when they are not supposed to.

It is designed to prevent dummys from hitting boost when the engine is cold.

anyone know what color wires the VTAs correspond to on the TPS??

VTA1 reads .57~.68 closed and 4.39 WOT
VTA2 reads .98~1.24 closed and 4.97 WOT

and i have a bunch of weird problems with idle and such.. thanks for the help!

...pete, you resurected a really old thread. rx7speed811, has a bad motor, bad seals...:(

i'm aware of the ressurection, but i used the search, like you are supposed to, and well, threads never die. And my motor is new.

So i'm still awaiting an answer on the color wires corresponding to VTA1 VTA2 on the PFC.

Thanks...

Haha, damn this thread is old. For any of you that care for an update...

Yep, the problem turned out to be bad compression (60-60-90) in the rear rotor. Unfortunately, I did not find this out until about four months and 3k miles later, after numerous repetitive trips under the hood and a few hundred dollars on replacing a few stock sensors and other devices I had hoped were to blame. Oh, and one more thing... two months and 1k miles after Mazda's factory warranty expired :(

Here is how I found this out... I finally took it in to a shop to get a compression check after the process of elimination led me to believe that the motor was just a lemon, which it was. That was the only thing left that could be the culprit of the problem.

After finding out about my bad compression readings and rough idle symptoms, the consensus from most rotorheads I talked to seemed to think it was bad engine prep and assembly on Mazda's part. Because the car was still running fine, and the power delivery was not (at least at first it wasn't) extremely weaker than normal, they said that the cause of the bad compression must have been a poorly set apex seal spring or a seal bit that was not up to spec with a new part. I was in contact with my local dealership, from whom I ordered the motor, at first for a few weeks, and then Mazda's corporate Remanufacturered Parts (or whoever the monkeys were that handled what went on in their mess of a reman and reassembly factory) office for a month, to no avail. Even though I noticed the problems with my motor a while before the warranty expired, they would not budge and compensate me for even a percentage of a new motor. I would never buy a Mazda reman again.

Just for any of you reading this...

If you have any problems that you cannot figure out after a week or two of tinkering, go get yourself a compression test. It might save you a lot of time, work, effort, bloody knuckles, and money. Plus, it might get you back on the road a lot faster than trying to guess the problem. Oh, and do NOT buy a Mazda reman if you can help it. If I had known that things would end up like this, I would have spent the extra couple hundred and gotten a motor built by a more reputable rotary tuner.

Who would have thought that Mazda doesn't sell the BEST replacement parts for their OWN cars??? It just doesn't make sense.