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Re: P1128 & P1130 codes They're back!

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It's been a while but codes P1128 7 P1130 are back on my 2000 Boxster S with 40k miles. Runs great.
Happened at Palmer Motorsports Park DE last weekend. (Oxygen sensing at enrichment limit, idle) . Shop manual says fault is air intake leak, fuel pressure supply too low or dirty injectors. I have found no exhaust or intake leaks using the carb cleaner test. Haven't checked fuel pressure or volume since i expect they would affect high RPM running, too.

Got some interesting data with the PST2.
Manual says air mass at diagnosis condition >35 kg/h. PST2 reads 26 kg/h

O2 sensor resistance bank 1 before CC 0 - 64 ohms (changes from 0 to 64 every few seconds)
" " " " " after " 64 ohms
" " " " 2 before CC 0 - 64 ohms (changes from 0 to 64 every few seconds)
" " " " " after " 128 ohms
Adaption Range 2 FRA Bank1 1.09

Have some other data that may or may not be relevant.

Comments, suggestions? Could one O2 sensor cause codes for both banks?

Thanks,

Ed B confused smiley
Quote
Ed B
It's been a while but codes P1128 7 P1130 are back on my 2000 Boxster S with 40k miles. Runs great.
Happened at Palmer Motorsports Park DE last weekend. (Oxygen sensing at enrichment limit, idle) . Shop manual says fault is air intake leak, fuel pressure supply too low or dirty injectors. I have found no exhaust or intake leaks using the carb cleaner test. Haven't checked fuel pressure or volume since i expect they would affect high RPM running, too.

Got some interesting data with the PST2.
Manual says air mass at diagnosis condition >35 kg/h. PST2 reads 26 kg/h

O2 sensor resistance bank 1 before CC 0 - 64 ohms (changes from 0 to 64 every few seconds)
" " " " " after " 64 ohms
" " " " 2 before CC 0 - 64 ohms (changes from 0 to 64 every few seconds)
" " " " " after " 128 ohms
Adaption Range 2 FRA Bank1 1.09

Have some other data that may or may not be relevant.

Comments, suggestions? Could one O2 sensor cause codes for both banks?

Thanks,

Ed B confused smiley

The current MAF reading is not likely the reading at the time of the error. For that you need to pull the freeze frame data and the error code that caused the freeze frame data to be logged. This will give you a "snapshot" of the various engine metrics at the time of the error.

Probably not the AOS as I think it has been several months since your last go around with these errors. Unless you have not been driving the car at all since then I think the AOS would have given clear signs of a problem by now.

However, I have to note though with the 2nd AOS failure it took almost 2K miles of driving after the first appearance of error codes before the AOS finally got to the point -- billowing (and non-stop) smoke at cold start -- that it was clear the AOS was bad and the reason for the error codes over the previous few days and 2K miles was obvious.

You checked for air leaks using the carb cleaner trick but did you check the oil filler tube cap for leaks? For this no carb cleaner was needed just a good listen while trying to move the cap about while the engine was idling. Concurrent with the engine mildly reacting one could hear an air leak at the cap.

Two times now this has leaked on my car and had to be replaced. It is a small leak and really only comes into play at idle. Above idle the amount of air allowed in by the leaking cap is inconsequential compared to the air that is flowing past the MAF.
Marc,

The oil filler cap was OK the previous time I had the codes. I didn't check it this time. will do. I can't confirm this, but the codes seem to appear after some track sessions when the engine is hot.

Ed
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Ed B
Marc,

The oil filler cap was OK the previous time I had the codes. I didn't check it this time. will do. I can't confirm this, but the codes seem to appear after some track sessions when the engine is hot.

Ed

40K miles is low miles and based on my experience quite a few miles below which the oil filler tube cap on my Boxster needed to be replaced. Still it doesn't hurt to check it. I missed it the first time and replaced a perfectly good MAF. Fortunately I saved the old but good MAF and when the replacement MAF acted up I used the saved MAF and it is doing a fine job still.

Been going through boxes at teh house and found my OBD2 reference.

For P1128 (and the same goes for P1130): Fuel/air mixture is so lean that the control is up to the enrichment limit. Possible causes: Air intake leak. Fuel pressure too low. Fuel injectors contaminated. Fuel supply volume too low.

That last one... Tracking of course uses fuel like crazy. While the fuel level may not low enough to cause a fuel supply problem at the injectors at the end of a track session the fuel is likely very hot and likewise the pump is also very hot. If nothing else proves to be of any help you might consider running more fuel trying to keep the fuel level from getting too low, say below a quarter of a tank and keeping it higher than that might be even better.

There is a service note: Air leaks ahead of the oxygen sensors can leak to a fault in adaptation. I believe this is referring to a possible air leak in the exhaust. Again I note the errors occur at the end of a track session and if the exhaust system because it too is very hot is leaking...

At some point also you really need to think about checking fuel pressure by operating the fuel pump manually. You can do this by removing the fuel pump relay and bridging terminals 30 and 87 (identified as 3 and 5 on the relay panel) with a fused shop-made test harness. The fuel pump should run and deliver fuel. With engine off fuel pressure should be 55psi +/- 3psi (3.8 bar +/- 0.2 bar). With engine running 48psi +/- 3psi (3.3 bar +/- 0.2 bar).

Note the test port seal is not replaceable, the cap must be replaced after removal.

Next test the fuel pressure regulator, vacuum connection and fuel return line. (I actually like the "vacuum connection" as the problem...)

Remove vacuum line from fuel pressure regulator. Connect vacuum hose to a vacuum gage. Start engine. Read 0.4 to 0.6 bar. If the value isnot reached check vacum system for leaks and check vacuum line to fuel pressure regulator for restriction.
Thanks for all the suggestions. I'll get back to it next week. I do have the full set of factory shop manuals.

The car is driven between DE events, varying from a hundred to a thousand miles. The first occurrence was coming back from the 2015 Parade.
I normally run DE's starting with a full tank. It was over half full when the codes appeared this time.
If it's an exhaust leak before the cats it will have to be the exhaust manifold gaskets.

Just finished extensive repairs on the '95 Audi S6 with 200k miles. I ned a little break before I get back to the Boxster.

Ed B
FWIW, when I had a p1128 years ago, I just replaced the MAF and the code never popped up again.
My Boxster OBD2 reference doesn't list the MAF as a possible fault. But I think my Turbo OBD2 reference does list the MAF. Might help to see the freeze frame data.

I'm reluctant to suggest a MAF replacement because a new MAF is so expensive.

Up to the OP what he wants to do. Fuel supply issues due to tracking heat kind of long shot admittedly. Doesn't have to be a failure due to heat though, could be a vacuum leak at the fuel pressure regulator. The "vacuum connection" I stressed in my previous post.
Marc,
I ran diagnostics again this morning with the PST 2. Referring to factory diagnosis manuals (Group O, part 1). For DME set points, some of the numbers I get don't agree too closely with the manual.
I'm looking at pages 24-D53 thru 24-D55 issued in 1998. My Boxster is a 2000 S. I have the supplements through #3, issued in 1999.

Is there a later supplement that covers the "S" and if there is , where can I get it?

Other data.
I checked the vacuum lines again, including the fuel pressure regulator and the ones to the sport muffler valves. The oil cap is tight and moving it and lifting it make no difference in the idle. The dip stick is tight, also. Removing the cap affects the idle.
I cleaned th MAF, too. I haven't checked the fuel pressure, yet. Probably this PM. Fuel pressure is more likely to affect high speed running than idle, but. I don't have a new cap for the port, but there is a check valve under it. It's probably a Porsche
CYA item or a profit center.
I've reset the codes and it runs fine. A lille burble in the exhaust, but that may be the sport muffler.

Ed B
Fuel pressure with engine off and at idle is within spec.

Ed B
Quote
Ed B
Marc,
I ran diagnostics again this morning with the PST 2. Referring to factory diagnosis manuals (Group O, part 1). For DME set points, some of the numbers I get don't agree too closely with the manual.
I'm looking at pages 24-D53 thru 24-D55 issued in 1998. My Boxster is a 2000 S. I have the supplements through #3, issued in 1999.

Is there a later supplement that covers the "S" and if there is , where can I get it?

Other data.
I checked the vacuum lines again, including the fuel pressure regulator and the ones to the sport muffler valves. The oil cap is tight and moving it and lifting it make no difference in the idle. The dip stick is tight, also. Removing the cap affects the idle.
I cleaned th MAF, too. I haven't checked the fuel pressure, yet. Probably this PM. Fuel pressure is more likely to affect high speed running than idle, but. I don't have a new cap for the port, but there is a check valve under it. It's probably a Porsche
CYA item or a profit center.
I've reset the codes and it runs fine. A lille burble in the exhaust, but that may be the sport muffler.

Ed B

Oh, by "my OBD2" reference I was referring to the book OBDII Engine Guide Porsche Models 1996 to 2004.

The factory OBD2 reference that came with my set of factory manuals I don't have ready access to. My set of Boxster factory manuals, all 60lbs worth, is currently boxed and scattered about my apartment. I can't begin to guess where the box is that contains the folder with the sections you list.

Also, there were a ton of supplements, well a 3-ring binder inches thick with supplements and updates, and what have you that I never bothered to search out where they belonged and inserted them. I would be doing that still I fear. As for how to get supplements I have no idea. About all I could recommend is you visit a local Porsche dealer parts department and ask about how to obtain supplements.

I read in another post you have checked the fuel pressure and found it within spec. That is good to know.

You checked the oil filler tube cap and it doesn't leak. What about the oil filler tube? These can develop a crack I read or a split and leak but somehow in a rather intermittent fashion.

My references do not list the MAF as a possible cause of these errors. An online search turns up some cases where the MAF is listed as a possible cause. I don't know if this info is from some "official" source of something the poster put together on his own. Certainly the MAF is a critical piece of hardware and its proper operation is vital to the proper fueling of the engine but my reference doesn't list it as a possible cause.

Assuming the MAF can be the source of these errors what I suspect is that the MAF is acting up intermittently. At some point it's performance degrades to the point the fueling gets so bad that the errors are logged. The presence of the CEL then causes the driver to change his driving style, possibly even shutting off the engine. This "fixes" the MAF.

As an aside, years ago I had an intermittent CEL appear triggered by some O2 sensor error. But when I checked the O2 sensor readings they were good. Only when I because familiar with *when* the error was about to appear and could then view the O2 sensor readings in real time did I see readings that clearly were not right and only then was I confident enough to throw new sensors into the car.

This leaves me with the same problem as before. I can't recommend a new MAF based on my info. Whether disconnecting the MAF at the wiring harness then road testing the car to see if the error codes return or stay away would be worthwhile in this I can't say. Generally this technique works best when the error codes can be made to appear almost at will. Just seemingly random appearances of error codes is more difficult as one can disconnect the MAF and possible drive the car a number of miles and the codes stay away just because the necessary conditions have not all come together. Then the MAF is reconnected and as luck would have it the codes appear and the MAF gets blamed and replaced and afterwards here come the codes. Again. The new MAF was for naught.
I checked the oil filler tube in the trunk and didn't find any cracks., I did find evidence of mice though, and took approbate action. No damaged wires! I looked in the engine bay earlier, butI can check again.
The Pelican forum has a thread on these codes caused by the MAF unit. Since mine doesn't show codes often, I'll see what happens next.

Ed B
MAF and throttle body cleaned recently?
Quote
Ed B
I checked the oil filler tube in the trunk and didn't find any cracks., I did find evidence of mice though, and took approbate action. No damaged wires! I looked in the engine bay earlier, butI can check again.
The Pelican forum has a thread on these codes caused by the MAF unit. Since mine doesn't show codes often, I'll see what happens next.

Ed B

While wiring is at risk of damage from mice infestation they are just as apt to attack/gnaw rubber and plastic hoses. I'm thinking of the smaller diameter plastic and rubber hoses bu they'll go after bigger things too.

A tech showed me the damage mice did to the vapor recovery plastic tube. The tube had a small hole gnawed into it. The rodent stopped gnawing when he got a snoot full of gasoline vapor. This tube runs down from the tank area to the engine compartment inside the mini tunnel. This area is covered by a large plastic panel but of course there is plenty of room above the panel and the car above the panel for the mice. It is in fact a nice large but enclosed area and the plastic panel is like a 4 lane freeway for mice to use to go back and forth.

They also gnawed the large rubber sheeting that makes up the radiator ducting at the front of the car.

Check the wiring but you have to check all rubber/plastic hoses in the engine compartment and under the car and even in the passenger fender where at least some of the vapor recovery system hardware is located. You also need to check the air box tubes and such because a hole could be gnawed into the intake system between the MAF and the engine. A hole could be in the section *before* the MAF, too and while this isn't an air leak per se -- the air is measured by the MAF -- it is unfiltered air and this can affect the MAF. The MAF is very resistent to the finer stuff that might pass through the stock air filter element but if the stock air filter is not filtering the air that is some air due to a hole is unfiltered then the MAF can suffer from the possible accumlation of dust.
Marc,
Thanks for the additional tips. The mice here seem to prefer older Porsches and Audis. This is the first time they they have picked on the Boxster. At least they have good taste.

Ed B winking smiley
... they will go after any year car!
I just had a 2013 Carrera 991 with extensive damage due to mice. Damage to the tune of $2650!
They really like the new cabin pre-filter cubby to build their nest which the make from all of the surrounding foam parts.
If you live in a place where there may be mice put some rodent-deterrent in the trunks and engine compartment.
Happy Bolstering,
Pedro

Pedro Bonilla 1998 Boxster 986 - 287,000+ miles: http://www.PedrosGarage.com
PCA National Club Racing Scrutineer - PCA National HPDE Instructor - PCA Technical Committee (Boxster/Cayman)

Racecar spelled backwards is Racecar
"Racing is life. Anything before or after is just waiting" ... Steve McQueen as Michael Delaney in "LeMans"
"If you wait, all that happens is that you get older"... Mario Andretti
"Being second is to be the first of the ones who lose" ... Ayrton Senna
Quote
Pedro (Weston, FL)
... they will go after any year car!
I just had a 2013 Carrera 991 with extensive damage due to mice. Damage to the tune of $2650!
They really like the new cabin pre-filter cubby to build their nest which the make from all of the surrounding foam parts.
If you live in a place where there may be mice put some rodent-deterrent in the trunks and engine compartment.
Happy Bolstering,
Pedro

$2650 damage is light by rodent standards. In one case a 996 Turbo cab had rodent -- rats in this case -- damage and the engine had to come out and the engine wiring harness replaced. There was other damage too. The critters had gnawed a tunnel from the cabin back to the engine compartment. I don't know what the total bill was but I was told it was enough that the car owner turned the claim over to his home owner insurance rather than pay it out of pocket.

In another case, the one I mentioned in a previous post, the car was a late model Cayman S. Again the damage was quite widespread, a hole gnawed here, a hole gnawed there, carpets ruined, plastic air ducts in the engine compartment and A/C system, radiator duct damage, that the cost to fix climbed way above what the owned was prepared to pay out of pocket and he too turned this over to his home owner insurance.

Putting rodent deterrents in the car is ok I guess, but I prefer to try to avoid them even getting into the car in the first place.

My advice, based on what I gather from people (experts) more knowledgeable than I, is to where the vehicle is parked to arrange to get all boxes and stuff up off the floor. Rodents like boxes along the wall cause they'll chew through the boxes and make a tunnel. With no boxes they are exposed which they don't like.

Then use traps baited with just a smear of peanut butter. Once a trap has done its job toss in the garbage and buy a new trap.

For rats they are so quick they can jump back before the trap snaps shut so the rat trap needs to be placed on something slick. In one case when I had to deal with roof rats that invaded my house (and the houses of my neighbors) after some old houses nearby were torn down I was told to put the rat trap on top of the dryer. Its enameled paint was so slick the rats could not get traction to jump. That first night caught one the next night with a new trap caught the 2nd and that was the end of the roof rats.

Seal up any tears/openings in foundation ventilation ports and where pipes go in/out of a foundation wall plug the gaps with steel wool. Up at the roof do the same with attic vent openings. Openings up high entice squirrels to invade your attic/home.

In the garage where water pipes go through the sheetrock again seal the gaps with steel wool. Avoid leaving pet food out at night as this brings the critters to your back door. And the larger ones will use the doggie door to go in and out of the garage so don't even leave food out at night in the garage. Store bulk pet food in metal cans, small metal garbage cans.
Mice and I have been at war for years. Current weapons are "Decon", "Tomcat" and peppermint oil. Been through moth balls and "Bounce".
Had them build a nest in the air filter of my F250 diesel. Got a CEL for low boost.

Ed B
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