P2188 code, what would be better to do?

thedarkoneirc

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2004 Mazda 3 2.0L
P2188, what should I do?

I've had a P2188 (fuel system too rich at idle) check engine code for a couple months now, initially after I got it, I was doing some diagnoses and found that there was oil on my spark plugs, so I changed the valve cover gasket, no more oil but still P2188. I checked the purge solenoid, no problems there, replaced the spark plugs and air filter, no change, HO2S sensors seem to be fine, they respond correctly to fast depression of gas pedal and release of gas pedal, MAF is readings are fine, then I changed my oil and the check engine code went away for about 1300 miles, after which it has been on and off ever since.

Before my oil was changed, symptoms included the engine feeling really bogged down (not accelerating at nearly the rate it normally does), and when it felt extra bogged down, in 1st, 2nd and rarely 3rd gear i would get (what i think is) backfiring. And of course LTFT was sitting at -20.8% at all times, and short term fluctuates. After the oil change for the most part it runs properly, acceleration is a little bit slow at times, but nowhere near what it was at, and no backfiring, and LTFT moves around a bit, but stays -% at almost all times (unless fuel system switches to open loop with 99% engine load), and STFT is all over the map.

I was wondering would it be a better next step to check (and adjust) my valve clearance tomorrow (from calling the mazda parts dept. at one of the dealerships near me they have no idea what part I am talking about for the tappets [I had read that the 2004 mazda 3 has shimless tappets with the shim built into the tappet, wtf?] or shims for the tappets [in the event that what I read was wrong and they do have shims], so if the clearance is off I would need to take the shims and/or tappets out to measure them and bring them to the dealership so that they can actually check for and order the part), or take apart my intake manifold and check the PCV valve, or any other ideas on something that would be a better idea altogether?

Thanks in advance
 
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I don't have an answer to your question. I have a 2008 shop manual, I don't think there were any major
mechanical differences between the two. From the manual description it appears the valves do use shims.

Step 15 of the adjustment procedure is quoted. "Select the proper adjustment shim.

New adjustment shim = Removed shim thickness + measured valve clearance - Standard valve clearance
(IN:0.25mm (.0098 in.) EX: 0.30 mm (0118 in)"

That description is about like I have seen on other engines that I have worked on that used valve shims.

I'm trying to relate the changing oil to the engine running better? I do understand that changing oil
fouled plugs will help the engine run better.

I don't know if a vacuum leak could cause a P2188 code, I do know vacuum leaks can cause many
different problems. It may be a good idea to check for vacuum leaks if you haven't already done it.

In the P2188 possible causes I see a PCV valve malfunction can cause the code, it doesn't mention
vacuum leaks, but I wonder? I assume you have already read the complete list of possible causes.
I did notice valve clearance isn't mentioned.

Hope you get it worked out, please post what you find.

Clifton
 
See that's what throws me off, aside from the parts dept. saying they don't have either part in their computer, in the workshop manual page for TAPPET CONSTRUCTION [LF] it says

"• The tappet is a shimless tappet which is integrated with the shim.

• The tappet surface is phosphate-coated to smooth the attaching surface to the cam and improve abrasion resistance.

• The valve clearance can be adjusted by replacing the tappet. There are 35 kinds of tappets depending on the thickness. The tappet kind can be determined by the engraved identification mark. "

However in the valve clearance inspection/adjustment pages, as you said they say it uses shims...I have to say I have seen better workshop manuals than the one for mazda :)

I was surprised that the oil change made a difference too, my best guess for it could be something related to Cylinder 1 timing advance and the pressurized oil used to adjust that? or if mazda 3s did use HLAs for the valve clearance, which i've read mixed reviews on that, it could affect that as well.

The only things from the workshop manual for P2188 that I haven't checked are the PCV valve (as that will take several hours having to remove the entire intake manifold), and the EGR valve, because I need to figure out where that is in my engine :)

I was going to check my valve clearance on my brother's suggestion, as if the exhaust valve were hanging open during combustion of the gas, or opening too early, the combustion could continue longer than ideal, causing it to appear too rich. Aside from that, ensuring my valves are in spec can never be a bad thing :)

If I do find my valve clearance is out of spec, I'll be sure to post photos of the procedure, as I haven't found any photos online to refer to yet :)

Looks like tomorrow will be a long day, unless it rains... :p

Oh, also I forgot to mention in my original post that one other symptom my car is having is occassional misfires, usually no more than 1-4 any given driving cycle though, could be related, could be unrelated, I won't know until I figure out why I'm running too rich :)
 
Ok, so far I may or may not have made any improvements.

Upon checking the valve clearance, it was all in spec, so there was no need to do anything there.
While I have not had time yet to take apart the intake manifold to check the PCV valve, what I did do this
previous weekend was cleaned the throttle body and as far as I could reach into the intake manifold with
the throttle body removed.

Upon starting my car my engine rev'd to about 3000 for a while at idle and then lowered down,
after resetting the ECU via removing the negative battery terminal for a minute, I have not had a
P2188 code fire off yet in a couple days (whereas when I had the ECU reset when doing the valve
clearance check, I recieved a P2188 within 3 hours), however behaviour still looks to be a little bit off
(i think).

At idle without doing a long drive with the A/C on (engine still at full temp.) my LTFT was sitting around +-2%,
which is great, but then when I switched the A/C off, the LTFT started dropping down to about -15%.
After I was done driving for about 45 minutes, with the A/C off during a period of idling for ~15 minutes,
my LTFT was between -13.28% and -9.38%, averaging at -10.88%, STFT was between -5.47% and 5.47%
averaging 0.13%.
Afterwards I turned on my A/C (increasing absolute engine load from an average of 18% to 25%) and waiting
a minute or two for the fuel system to catch up to the engine load change, over a period of around 7 minutes
my LTFT ranged from -9.38% to -4.69% averaging at -7.1% with STFT ranging between -5.47% and 6.25%
averaging 0.09%.

From what I have read my fuel trim should probably be a bit higher than that (~10-15%), although it's good
that it's not going low enough to trigger the check engine code. I'll probably check the PCV valve 2 weekends
from now, as I won't have time until then, although I should probably figure out how I can test it (applying
vacuum and subsequently applying pressure) as I do not have any equipment for this.

Anyone else with any ideas, always welcome and appreciated :)
 
Sounds like a vacuum leak or maf problem to me. Check the seal on the o-ring on the MAF. Check the wires and electrical connection on the MAF sensor too. Helped someone with that code before and it ended up being maf wires.
 
MAF wires are fine, they were replaced by mazda due to the issue with the ground wire a few months ago, I did clean off the MAF sensor and IAT sensor the other day, no difference, seal on the MAF is also fine atm. Right now my car is all apart, took off the intake manifold (I really hate how ford/mazda put the PCV valve under the intake manifold, and how some bolts are blind to get to), and the PCV valve seems ok, however the O-Ring is missing from it, so that's no good. Also the EGR Gasket is getting a bit worn down, so replacing that too. Hopefully when I get everything back together on Tuesday it will be fixed. I'll get a new O-Ring for the MAF too when I go buy parts tomorrow just for good measure.

If it's not fixed, the only thing from the P2188 diagnostic steps in the workshop manual left is the EGR, but it's kind of unclear on checking it, and provides no locations for the solenoid, has anyone checked EGR on a 3 before?
 
It's right above the main giant coolant line. You have to drain the coolant and remove the main line to get to it. The bolts are behind it.
 
So update on the situation so far. I replaced the PCV valve, the EGR gasket, and the O-Ring for the MAF, to no avail, 6 hours of removing and reinstalling the intake manifold later, the P2188 code came right back after 10 minutes. So only thing left to check in the EGR valve (for causes from the manual)...

Also on an unrelated note, from above, I did verify with the parts dept. at a different mazda dealership that the valves do use shimless tappets, meaning anything out of spec. requires purchasing a $15 tappet for each valve out of spec.
 
Hm. I wouldn't think it's the EGR valve unless it's somehow stuck open. Have you checked the fuses? I had a CEL for an oxygen sensor once and it ended up being a blown fuse.
 
Had same code it was a vacuum leak. I was also throwing code 2187 now it's much better. I would check all hoses really well first.
 
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