Idle problem , cutting out please help!!

[uscmx3]

Ok would really like some help..

my brother has an mx3 same as me but hes is a 1.8 v6. hes had a new engine put in as the ring when on old engine.

he had an idle problem on the old engine it kept reving at 1500 rpm then sudenly drop to below 0 and all most cut out !! infact theres a few times it has cut out and we have no idea why its doing it. even mechanic said hes not sure what it cud be.

it has a fse power boost vaulve and the temperture sender is broke so the gauage reeds high all the time. i know we need to fix the temp sender but wud this be why it cuts out??

ive checked all throttle body and vaf for air leaks they are all fine

please help

cheers

[marcdh]

Hmm I think that the temp sender that feeds the guage is purely for that guage, the ecu has its own sender.

When my 1.8 car did what you describe it was the idle adjust screw on the TB. I screwed it right in, then took it back a few turns, reset the ecu, then jumped TEn and gnd and set the idle to 650. Other things that would be on my mind are: tps, IAC, cleaning out TB and IAC and can never rule out the VAF. Hopefully someone else will take a more precise guess.

[uscmx3]

yeah cheers i wasnt sure if its worth buying a new vaf and see it that works.

what shud the standard setting be for the idle screw??

it seem to be worse when i approach junctions lol and turning into my drive without reving lots it wud cut out

if i blip the throttle say to 2000 it then goes down and drops below 0 sounds like its about to stall but then creeps bk up to 1000 and sits between 1000 - 1500 rpm

any help

[mazdags94]

I would second that with marcdh. Take a look into the TPS as well as the VAF. Basically, something is preventing your car from idling smoothely. Rough idle is usually an indication of some type of restriction. How many miles are on the engine and have you ever replaced any of the vacuum lines? My rule of thumb is to start with troubleshooting the cheaper parts and go on from there. Even check your pcv valve as well. Definitely try cleaning your throttle body bc there may be gunk built up on the inside that keeps the inner disc stuck open and when you 'flick' the throttle, it may get the disc passed the gunk and cause it to catch when it is closed to being closed; this may cause your air restriction. You will want to reposition your idle but don't do this unless you're in diagnosis mode (TEN & GRND jumped). This will update your ECU as well. Good luck.

[uscmx3]

ok you will have to bear with me on the techincal side.

tps ??

also its a new recon engine but the old engine was doing the same thing??

how do i get the car in diagnosis mode (TEN & GRND jumped??

any pictures would be brill

cheers

[mazdags94]

Hmm, if the old engine was doing the same thing, maybe its an electrical problem. Or if you switched the engine and hooked up the vac lines the exact way they were before, or if theyre worn, then it would produce similar results. Did you swap the IM from your old engine? Another question would be, are you using any parts transferred over from the old engine. That just may pinpoint it right there.


TPS --> Throttle Position Sensor, which is located on the left side of your throttle body (you can also go under the V6 FAQ and click on 'TPS')

TEN - "Test Engine"
GRND - "Ground"

Jumping them, or establishing a wire connection between the two, will put the car in diagnosis mode. Jump it first, then turn the car to the ON position (dont start it).

These terminals can be found in your engine bay near the firewall behind the battery area. Theres a box that says "DIAGNOSIS" on it. Take the cap off and that's where you'll find TEN and GRND.

As far as how to adjust the rest, you should find a detailed explanation in the V6 FAQ link.

Hope this helps!!

[uscmx3]

engine was installed by a pro mechanic and im lost for answers as to why it idles upa dn down

[mazdags94]

engine swaps are tough when you don't do the work yourself.... this may sound backwards but MANY people on these boards report having to troubleshoot some type of issue, and many do know what theyre doing. The problem lies in the fact that someone else installed it and you have to rely on them to tell you what they did, and they can troubleshoot more effectively. is it under warranty?

[onlytrueromeo]

Mine does this too but it idles high and boucnes from 700-2k. I'm pretty sure our problems are the same - I also think I know what the problem is but I've been too busy to fix it!

Search for "adjust TPS". Basically you need to reset your idle screw and whatnot. Also change your pcv valve and check for air leaks.

[uscmx3]

ok ive cleaned up most of the parts listed above including the pcv.

can anybody show me some pictures of the IAC?? and also pictures on where i can find the diagnostic box ???

also ive been reading the various idle threds on here vai the serch , but still dosent sound like mine ive found most idle problems are found to be the car idleing too high. The major problem we have is when slowing down or coming to a junction soon as you dip the clutch the revs drop belom 0 and the it goes back up sometimes it trys to cut out but only cut out one or twice most of time it picks upagain.

but why does it dip

im going to adjust the tps but need pictures and more help cheers

[Newfie_dan]

I am having somewhat of an idle issue myself, the idle air control is located underneath the throttle body. My problem is that I can get thar car to idle with no issues sometimes and then others it idles up to 1500 rpm and then bounces down to 1000 and back up again. My throttlebody was pretty dirty when I got the car. Mine is a 96 gs v6. I cleaned the tb and the iac but I am still having the issues. It also takes like 3 seconds or so when I stop at a light for it to drop down to 650-700rpm which I find odd. Might just be that I require a second iac cleaning. I pulled the codes with my obd2 scanner and got nothing for codes which I also found odd. Anyone else have this issue?

[TOOgreezy]

I am having somewhat of an idle issue myself, the idle air control is located underneath the throttle body. My problem is that I can get thar car to idle with no issues sometimes and then others it idles up to 1500 rpm and then bounces down to 1000 and back up again. My throttlebody was pretty dirty when I got the car. Mine is a 96 gs v6. I cleaned the tb and the iac but I am still having the issues. It also takes like 3 seconds or so when I stop at a light for it to drop down to 650-700rpm which I find odd. Might just be that I require a second iac cleaning. I pulled the codes with my obd2 scanner and got nothing for codes which I also found odd. Anyone else have this issue?

Iam having a similiar problem... mines drops a lot mostly when im pressing the brakes it'll just start dropping and wont stop i have tried a couple things but i think its the Idle Control motor... my car useto idle around 800rpm so when it dropped it would drop to about 400-500 which sounds like its about 2 stall.. i adjusted the idle so it idles around 1300-1500 so it sumwhat fix the dropping but it still drops once in a while but now it only drops to about 1000 so it doesnt effect my drivving when it drops... so my machanic said all id have to do is change the idle control motor which i can get one for around 60 bux but im doing an engine swap so ill probably just leave mine for now

[Dalur]

When you did the swap, did you keep the same Distributor? I had the same issue with mine, Idle rough and then die. I swapped out the internal coil and the problem went away, I also changed a wiring harness that looked dodgy. It fits with the electrical suggestion. Good luck.

[mazdags94]

It sounded like a vacuum leak until you mentioned pushing the brake. Pushing the brake places a load on your circuit and the load could be just enough to dip your idle down. Your engine needs to work hard to accomodate additional electrical output. Your alternator is belt driven and works with engine rpms. It's meant to output 14V (12V to run your vehicle's electronics and 2V to help recharge the battery). If thats not working right, the electronics won't work sufficiuently either (i.e. distributor). Have your alternator tested, its worth a look.

[Daninski]

Just because I'm in a good mood. This should take you about 1/2 an hour to do.

TPS Adjust (mechanicl)
Engine off.
Detach TPS connector.

Wire Colour & Purpose
P= +5V reference
Y= TPS position signal to ECU
BR= TPS idle switch
BK/DB= sensor ground

Connect ohmeter to 2 bottom pins (BR and BK/DB) and you should get continuity. If not, loosen 2 TPS retaining bolts and rotate until continuity has just barely been achieved. Semi tighten 2 TPS bolts.
Insert .006" (0.15mm) feeler gauge between the throttle stop screw and throttle lever. This should not break the continuity. If it does break continuity, slightly adjust TPS rotation again to regain the continuity. Insert the gauge in and out a few times to verify.
After confirming continuity with 0.15mm feeler gauge, insert a .020" (.50mm) feeler gauge. This should just barely break continuity but completely. If not re-adjust TPS rotation again. Re-confirm by re-inserting feeler gauge.
In essence, continuity on initial connection to TPS.
Continuity with .15mm gauge inserted.
No continuity with .50mm gauge inserted.
Tighten down TPS retaining bolts.
Re-connect TPS connector.

Once you've adjusted the idle and or TPS let the car run for 15 minutes sot he ECU can learn the new settings.

Idle Setting
Before adjusting remove the screw and ensure its clean and not damaged.
The screw on the top of the throttle body is what your looking for. Start by adjusting it about 3 turns out then start the engine. With the engine warmed up turn it in till the engine starts to die then gradually turn the screw out untill you read 650 RPM in Diag mode (Ten and Grd jumped). If you turn it too far out your engine will be less responsive so if it feels sluggish afterwards readjust the screw.