I am wondering if anyone knows what the possible causes of this would be? It seems like it's only an issue when the engine is running from cold. If I warm it up and turn it off/on it seems to go back to normal. I have the P0455 that I'm hoping to fix this upcoming weekend, and I redid the PCV just over a week ago (unfortunately not soon enough to prevent major oil leaks) but it doesn't seem from Googling that either of those would cause this specific issue. I checked vac hoses, and they're all secure. What items should I be checking to diagnose this?
V70 T5 - Revs dropping to ~600 during idle in D or R only
BoxxyLady
1 - 20 of 20 Posts
I am wondering if anyone knows what the possible causes of this would be? It seems like it's only an issue when the engine is running from cold. If I warm it up and turn it off/on it seems to go back to normal. I have the P0455 that I'm hoping to fix this upcoming weekend, and I redid the PCV just over a week ago (unfortunately not soon enough to prevent major oil leaks) but it doesn't seem from Googling that either of those would cause this specific issue. I checked vac hoses, and they're all secure. What items should I be checking to diagnose this?
Joined
·
22,421 Posts
Whats your idle without load ie in park? Throttle could just be out of adjustment but if its only when cold an O2 sensor or MAF could certainly be the culprit.
Joined
·
22,421 Posts
Do a trip odometer/gallons at the pump calculation of fuel economy. A failing O2 sensor can cause this issue and will illustrate itself by a drop in gas mileage
Joined
·
22,421 Posts
Upstream O2 sensor. Not hard or expensive. It's probably original
Sent from my iPhone using Tapatalk
I'll vote against O2 sensor as your immediate problem, when the car is ice cold it doesn't even look at the sensor to figure out its fueling. Open loop all the way here. You could unplug it entirely and it will not change "cold start" behavior. When the car is warm it is in "Closed Loop" and relies on the sensor for input. No difference if the car is cold started then gets hot, or hot started. Still behaves the same when it hits closed loop. The plug on the O2 sensor will be date coded, nothing wrong with changing a sensor if it is 18 years old, it won't have good response time anyway.....
As to your problem, if the car seems to run at higher idle RPM when restarted, the only thing I think you've changed is a "cleaning cycle" of the MAF sensor wire and for the first little bit you are back to open loop. I'd lean more toward the MAF playing a role here. Not to challenge what you've stated but I suspect you have a host of vacuum leaks as well. Many are not that easy to find visually. All kinds of possible vacuum leaks on these cars, don't even get me started.....
That would be nice as the part is about $100 here (Canada) and I don't reaaaaally have that to spend on it right this second. I will definitely check the date and swap it some time if needed.
I forgot to mention that when we started it up after the PCV replacement, the MAF was unplugged and my friend plugged it in with the car running. Obviously you aren't supposed to do that (especially since it stalled the car), but it was working fine for about 4 days after that incident before I started to get the idling issues.
I agree that there be some vac leaks as well. I already wanted to replace those line ASAP as I had to cut some of them off their connection points to do the PCV work, so they're clearly very old if not original. Are the vac lines something I can replace with silicone hoses? I've seen on FCP and IpD that you can order lengths of silicone hoses for cheap. I have a budget of $0 this month, and given how expensive some of the PCV hoses were, that could significantly help reduce my budget overages
.Also, would the car still run with the vac lines hooked up to the wrong connection points? I'm wondering if that may have happened during the PCV job.
The car will run poorly if vac lines aren't hooked up correctly (notably turbo control valve and pcv canister). Neither should do anything to create a very low idle. I'm betting you have a giant air (vac.) leak in the intake tract.
To have such a significant RPM drop, I'd look at large hoses (boost hoses / intake hose) for poor fitment.
You could save yourself a lot of time in diagnostic if you could see the OBD values. A huge deviation of fuel trim values will point you in a specific direction....
To have such a significant RPM drop, I'd look at large hoses (boost hoses / intake hose) for poor fitment.
You could save yourself a lot of time in diagnostic if you could see the OBD values. A huge deviation of fuel trim values will point you in a specific direction....
Thanks! For OBD values, do you just mean scanning for codes? I have a very basic scanner that gave me the P0455 code, but I didn't get any more information from it. I am at work right now, but I can re-scan when I get home. I keep forgetting to re-scan it as the lambda came back on about 1 day after the RPM's decided to go all wonky.
P0455 is an evap code (the system that burns gas tank fumes rather than disbursing them into the air). Could relate to the low idle though I'd be rather iffy on that matter. It does indicate either a vacuum leak in the evap system or a leaking evap valve. I think your vacuum leak is much larger.
See if your code reader has "data", meaning it connects with the cars computer and can see the fuel trim, engine temp, rpm, etc..... It has almost every operating parameter of the car virtually real time.
See if your code reader has "data", meaning it connects with the cars computer and can see the fuel trim, engine temp, rpm, etc..... It has almost every operating parameter of the car virtually real time.
Purge valve is most likely culprit for evap issues.
If you have a mityvac pump, they need to hold vacuum on both sides. In a pinch you can suck it and hold it on your tongue (both sides), see if yours holds. It your current valve holds okay, you more likely need to locate a leak in the vacuum piping going down the radiator and back to the tank. Check hoses to/from.
If you have a mityvac pump, they need to hold vacuum on both sides. In a pinch you can suck it and hold it on your tongue (both sides), see if yours holds. It your current valve holds okay, you more likely need to locate a leak in the vacuum piping going down the radiator and back to the tank. Check hoses to/from.
Joined
·
22,421 Posts
Evap leak could also be a disconnected PTC element hose. Had that issue with my 99 pewter and when I put the snabb intake on it low and behold there was a hidden albeit large vacuum leak.
Sent from my iPhone using Tapatalk
Sent from my iPhone using Tapatalk
The original poster appears to have a '98 so won't have that weird double check valve plumbing associated with the purge valve. Should come straight off the manifold.
Good suggestion however on a hidden but fairly common large vacuum leak. I've had the hose detach from the PTC as well as the piping to the rubber J hose either break (plastic) or detach ('99 and later metal pipe). Disturbing the intake hose after years in one spot seems to make for problems....
Good suggestion however on a hidden but fairly common large vacuum leak. I've had the hose detach from the PTC as well as the piping to the rubber J hose either break (plastic) or detach ('99 and later metal pipe). Disturbing the intake hose after years in one spot seems to make for problems....
Okay, I will run out and check that tonight! I remember it being a little loose at one point. -.-
I couldn't even find my OBDII reader yesterday, so I am going to meet up with a friend who has one later this week and see if we can read that stuff.
Edit: I just checked and those lines are all snug as a bug. I can only see the top side though, and I believe there might be more on the bottom? I'm going to look up some pictures and stuff.
I couldn't even find my OBDII reader yesterday, so I am going to meet up with a friend who has one later this week and see if we can read that stuff.
Edit: I just checked and those lines are all snug as a bug. I can only see the top side though, and I believe there might be more on the bottom? I'm going to look up some pictures and stuff.
Where is this J hose? I'm not entirely sure what I'm looking for there.
The PCV pipe assembly runs below the intake manifold, then curves around the head, it terminates into the intake hose down near the turbo, the hose I am referring to is the short bent rubber hose that connects the pipe to the PTC orifice. It can become detached from the pipe, or more commonly from the PTC.
I hope you didn't use URO hoses when you did the PCV, nothing but headaches will result...
I hope you didn't use URO hoses when you did the PCV, nothing but headaches will result...
1 - 20 of 20 Posts
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
