Engine shuts off when i remove oil cap or pcv valve... could be a problem - Mazda MX6 Forums: MX6 Forum
Mazda MX6 Forums: MX6 Forum User Control Panel
 


» Auto Insurance
» Featured Product
Wheel & Tire Center

Go Back   Mazda MX6 Forums: MX6 Forum > 2G MX6 (93-97) > 2G MX6 General
Register Home Forum Active Topics Garage Garage Photo Gallery Arcade Mark Forums Read Auto EscrowAuto Loans

Mx6.com is the premier Mazda MX6 Forum on the internet. Registered Users do not see the above ads.
Reply
 
LinkBack Thread Tools
Old 4-9-05, 19:30   #1 (permalink)
  Total: 10 Power: 5
 
Join Date: Apr 2005
Location:
iTrader: (0)
Engine shuts off when i remove oil cap or pcv valve... could be a problem

This is my first time posting on here, I just got an MX-6 a few weeks ago, its 93 2.5 L 5-spd, but anyway, here's my problem: I was checking my PCV valve yesturday just as it says to do in my Haynes manual, so i pulled it out with the engine running but like 1 second after i pulled it out the engine shut off; wasn't sure if this was normal or not so i started it again, pulled out the PCV valve again but this time got my finger in there in time for it to stay running, it did have suction and my PCV valve rattles, so i'm assuming that's fine too. Then earlier today i was changing my oil and i was adding this oil thickener (cuz im burning oil) and it said to add it with the engine idling, so i started the car and took off the oil cap, as soon as i did that the engine shut-off, it was probly less than a second. I'm thinking it's a compression problem but i don't know for sure and even if it is i dont know whats causing it, so any help would be greatly appreciated, thanks.



PS I did a diagnostic's yesturday and at first it was giving me codes 15, 16, 17, 23, 24, 41, and 69... but i didnt like all them so i reset the ecu and then i only got codes 41 and 69, dunno if that info helps or not, just thought i'd throw it in there.
bman64 is offline   Reply With Quote
Sponsored Links
Advertisement
 
Old 4-9-05, 20:14   #2 (permalink)
  Total: 766 Power: 5
 
Join Date: Feb 2004
Location: Chelsea, Canada
iTrader: (0)
Welcome to the board!

It's absolutely normal for this engine to stall if you unplug the PCV valve, remove the oil filler cap, or even pull the dipstick out. All our cars do this. They are very sensitive to vacuum leaks.

Be careful with those oil additives. Nearly all of them are bad.
NickR is offline   Reply With Quote
Old 4-9-05, 20:41   #3 (permalink)
  Total: 1352 Power: 5
 
Mike 94PGT's Avatar
 
Join Date: Sep 2000
Location: Canada
iTrader: (0)
NickR's right and here's why it happens:

First, the airflow measuring device on these cars (call the "VAF") has a sliding core that moves back in proportion to airflow. When there's not much airflow, such as at idle, the core doesn't move much at all. In order to move the core back even a little, there must be a pressure differential across the VAF's measuring core.

Second, the PCV system in these cars is, as the name implies closed. Fresh air for the system is taken from the air inlet ducting downstream of the VAF. It's drawn from that duct, into the crankcase and discharged into the intake manifold after having circulated in the crankcase.

The problem is that when you open up the system by venting the crankcase when you remove the dipstick or the oil cap, you essentially also vent the back of the measuring core of the VAF. The pressure drop across it falls to zero and the core closes, telling the PCM that there's no air entering the engine. So on top of a massive vacuum leak, the fuel delivery actually drops causing the engine to stumble and probably stall.

As NickR said, it's normal. You might have noticed Mazda even went so far as to put an O-ring on the dipstick to help keep the system leak-free.

Don't add "thickener". If you cannot fix the source of the burning, at least just buy a grade heavier oil. If you run 5W30, try 10W30 or even 10W40. It's odd to hear of a KL engine burning oil...it doesn't happen that much even with elevated miles on the car. Are you sure it's not leaking? With all those codes memorized it certainly sounds like the car has had an interesting past. Aside from the 41 and 69, have any of the others returned?

The 41 indicates a possible problem with the solenoid controlling the #1 VRIS valve. The 69 indicates that the ECTF (engine coolant temp - fan) temperature sensor is probably disconnected. How many temperature sensors do you see near where the upper rad hose connects to the engine. You should see three: one with a single wire going to it and two with two-wire harnesses. If you only see two sensors (a single- and a double-wire unit) you might not have the original engine in the car.

Mike (94 PGT - sold)
2002 Mustang GT Kenne Bell Intercooled 1.7L Twinscrew @ 9psi | Comp 262AH cams | Steeda C/B | Accufab 70mm T/B | FRPP 3.73s | ~450HP at the crank
2002 VW GTI 1.8T | GIAC X+ tune | APR R1 DV | N75J | Evoms V-Flow | APR TIP | Techtonics DP | TT SS | Helix projectors w/6000K HIDs | TT front brakes | MFA sport cluster conversion | OE Nav
Mike 94PGT is offline   Reply With Quote
Old 4-9-05, 22:03   #4 (permalink)
  Total: 137 Power: 5
 
Join Date: May 2004
Location: North of Mass, MA, USA
Age: 29
iTrader: (0)
Mike, if I were able to give you karma, I would! Ive always wondered why the car stalls whearas some cars you can take the VC off and watch the oil spew all over the place.

Last night I dreamed I was a muffler... needless to say I woke up exhausted.
AAlonzo is offline   Reply With Quote
Old 4-10-05, 7:30   #5 (permalink)
  Total: 1352 Power: 5
 
Mike 94PGT's Avatar
 
Join Date: Sep 2000
Location: Canada
iTrader: (0)
Quote:
Originally Posted by AAlonzo
Mike, if I were able to give you karma, I would!
Thank you.

Quote:
Ive always wondered why the car stalls whearas some cars you can take the VC off and watch the oil spew all over the place.
FWIW, back when I had the MAF on my PGT I could remove the stick and oil cap and it wouldn't stall. It seems to be a peculiarity of the particular setup with the VAF...

Mike (94 PGT - sold)
2002 Mustang GT Kenne Bell Intercooled 1.7L Twinscrew @ 9psi | Comp 262AH cams | Steeda C/B | Accufab 70mm T/B | FRPP 3.73s | ~450HP at the crank
2002 VW GTI 1.8T | GIAC X+ tune | APR R1 DV | N75J | Evoms V-Flow | APR TIP | Techtonics DP | TT SS | Helix projectors w/6000K HIDs | TT front brakes | MFA sport cluster conversion | OE Nav
Mike 94PGT is offline   Reply With Quote
Old 4-10-05, 11:31   #6 (permalink)
  Total: 10 Power: 5
 
Join Date: Apr 2005
Location:
iTrader: (0)
Well it's good to hear that it's not anything important.... it's bad to hear that oil leaking is more likely than oil burning. When i first got the car i was told it was leaking oil and to change the valve cover gasket, that turned into like a 6 hr job because the 2.5 is way too complicated. I'm thinkin my head gasket might be bad, but i really dont wanna replace it cuz then I'll have to replace my I.M. gasket, my valve cover gasket, and my head gasket... correct? I could be wrong, in which case I'll feel like a dumbass, but just need to make sure. Also if anyone else has done this, how long did it take you and would i be better off just taking it to a mechanic (which i'd rather not do because I'm cheap). Thanks for all your help guys and the friendly welcome, hope to hear some opinions from you all on my new issue soon.



FYI - I had 2 previous Honda CRX's that i did a lot of "hooking up" to, so i know a pretty good amount about doing engine work and stuff like that, so I'm not a newb at it or anything.
bman64 is offline   Reply With Quote
Old 4-10-05, 17:49   #7 (permalink)
  Total: 1352 Power: 5
 
Mike 94PGT's Avatar
 
Join Date: Sep 2000
Location: Canada
iTrader: (0)
Quote:
Originally Posted by bman64
Well it's good to hear that it's not anything important.... it's bad to hear that oil leaking is more likely than oil burning.
It should be fairly easy to distinguish between burning (blue smoke out the back, fouled plug(s) etc) and leaking (oil spots on the ground under the car, oil on the undercarriage or on the bottom of the engine etc...)

Quote:
When i first got the car i was told it was leaking oil and to change the valve cover gasket, that turned into like a 6 hr job because the 2.5 is way too complicated.
It shouldn't take that long. Removing the intake manifold is really not that difficult (the coolant doesn't even have to be drained...). After that, the VCGs are just a few bolts away.

Quote:
I'm thinkin my head gasket might be bad, but i really dont wanna replace it cuz then I'll have to replace my I.M. gasket, my valve cover gasket, and my head gasket... correct?
Well, don't guess about what the problem is. Find out first if the car is leaking or burning. If it's leaking, find out from where. You might have to take the car to a shop and have them steam-clean the engine underside and pour in a flourescent dye. Run the car a day or two and take it back...they'll use a blacklight (UV light) to illuminate the underside of the engine and the dye will show exactly where the leak is. Head gaskets may leak oil externally but more likely you'd see loss of compression, water in the oil and steam in the exhaust. Head gaskets are pretty rare problems on KL engines unless, I suppose, the engine has been overheated and the heads warped.

If the engine is burning oil, not when and how much. Under acceleration? When pulling away from a light? On cold start? Consider a compression and/or leakdown test to isolate a bad cylinder. How many miles on the car?

Mike (94 PGT - sold)
2002 Mustang GT Kenne Bell Intercooled 1.7L Twinscrew @ 9psi | Comp 262AH cams | Steeda C/B | Accufab 70mm T/B | FRPP 3.73s | ~450HP at the crank
2002 VW GTI 1.8T | GIAC X+ tune | APR R1 DV | N75J | Evoms V-Flow | APR TIP | Techtonics DP | TT SS | Helix projectors w/6000K HIDs | TT front brakes | MFA sport cluster conversion | OE Nav
Mike 94PGT is offline   Reply With Quote
Old 4-10-05, 23:01   #8 (permalink)
  Total: 10 Power: 5
 
Join Date: Apr 2005
Location:
iTrader: (0)
Quote:
It should be fairly easy to distinguish between burning (blue smoke out the back, fouled plug(s) etc) and leaking (oil spots on the ground under the car, oil on the undercarriage or on the bottom of the engine etc...)
Yeah I kinda knew all that, but that's why I'm confused: i dont have ne smoke out of the exhaust, but i also dont leave oil spots (there is oil on the outside of the engine but i think thats from my last oil leakage experience. I guess I should take ur advice and take it to "professionals", even if i am a cheapass. Yeah i dont know exactly why it took so long to do the VC gasket, I just always have problems with any install (took 8 hrs to do shocks/coil-overs on my crx somehow, that was a rough outting), but if i need to i guess i'll give it another shot and hope for better luck... or skill. Thanks again
bman64 is offline   Reply With Quote
Old 4-17-05, 19:30   #9 (permalink)
  Total: 10 Power: 5
 
Join Date: Jan 2003
Location: Milledgeville, GA, USA
iTrader: (0)
Any high rpm engine is going to burn some oil....but younger engines you dont even notice the loss if you do regular oil changes....i just hit 110k miles and im starting to burn oil like a bitch...it sucks cause i dont know if i want to keep an oil burner when im at UGA next semester...i might just have to get truck

Anyway...Before i sell it ill probably just put the cat back on to cover the oil burning up a lil bit. lol

95' Mx6-Ls currently- Top speed:as fast as one can roll it, 0-60 depends on the hill.
quarter mile: depends on the tow truck
RaVen_X6 is offline   Reply With Quote
Sponsored Links
Advertisement
 
Reply

Thread Tools

Posting Permissions
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On



Powered by vBadvanced CMPS v3.2.2

All times are GMT -5. The time now is 12:28.



Powered by vBulletin®. Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
SEO by vBSEO 3.3.2
Garage Plus vBulletin Plugins by Drive Thru Online, Inc.
Copyright 2000-2010, MX6.com
MX6.com is in no way affiliated to Mazda Motor Corp.
All views expressed in this site are the personal opinion of the author and not necessarily the owners of MX6.com.