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996 CEL Codes ....


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I went into the engine compartment and was digging around and found this little plug attached to nothing ... Part number 028 0130 092 ... what is is and where should it go?

http://www.chrisstutzcustomphoto.com/Mystery%20Part

The link is blocked by my company's firewall. Where is it located and how many pins? Can't find the part number either...

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there was no gromet there for the part ... it appears to not have been there. I installed it where is is supposed to go ...

RPM steady 770

Temp 84c (engine

As for the numbers:

Bank #1 #2

RKAT -1.78 -2.39

FRA .97 .98

Edited by stutzchris
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take a look at the attached. you do not have vacuum leaks becasue the DME is trying to make the mixture more lean.

Hi George, that is strange. My previous search suggested otherwise but I can't argue with the pdf you sent which is DME 7.2 specific.

Maybe the P1128/1130 codes means lean in one version of Motronic and rich in the other version?

I just searched Renntech again and saw P1128/P1130 interpreted BOTH ways!! Totally crazy.

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hello ahsai,

THe manual has two procedues for P1130, above limit and below limit. I noticed that rkat was negative so that means the dme is trying to make the mixture leaner. hence "below limit" so i attached that procedure. However, in stutzchris' earlier post of rkat they were positive which would indicate the opposite. i find that interesting. He also mentioend this problem occured after installing the aftermarket exhaust so i wonder if this included the cats and could the o2 sensers be mixed up.

The mass flow reading of 19kg/hr is consistant with the high idle, 770 rpm so there is no false air. i am not sure what would cause the high idle and if it is related to P1130. i had a bad voltage regulator (low voltage) and that caused my car to idle high.

any ideas?

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hello ahsai,

THe manual has two procedues for P1130, above limit and below limit. I noticed that rkat was negative so that means the dme is trying to make the mixture leaner. hence "below limit" so i attached that procedure. However, in stutzchris' earlier post of rkat they were positive which would indicate the opposite. i find that interesting. He also mentioend this problem occured after installing the aftermarket exhaust so i wonder if this included the cats and could the o2 sensers be mixed up.

The mass flow reading of 19kg/hr is consistant with the high idle, 770 rpm so there is no false air. i am not sure what would cause the high idle and if it is related to P1130. i had a bad voltage regulator (low voltage) and that caused my car to idle high.

any ideas?

Thanks, George. It's even more weird than I thought then. So you're saying P1130 (and maybe P1128 as well) splits further into "above limit" and "below limit" that mean the total opposite? The former indicates a lean running engine and the latter indicates a rich running engine. Do both cases use the same "361" code or the "above limit" case uses a different code? This is super confusing.

Agree that 770rpm is consistent with the MAF reading and seems there's no false air. His RKAT and FRA are good and within spec I think. I could definitely see that a bad alternator can load up the engine like in your case.

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I must clarify the "after market exhaust. I purchase this car back in January. The muffles were what came on the vehicle. The cats appear stock but the mufflers are not. They look like a fab speed clone ... there is no branding on the mufflers.

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  • 2 weeks later...

(fingers crossed) The CEL has not returned. I removed the evap canister and cleaned the contacts and the valve itself. Also, I gave the MAF a thorough cleaning as well. I have put in 10 days of driving since my last post and about 1500-2000 km no codes.

Thanks to all for you input and wisdom ...

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Glad to hear problem is solved.

I was wondering why the RKAT values were negative at one time and then positive another time. You would think that the problem was would make the mixture either rich or lean but you had both. Also, I was wondering why the diagnosing procedure for listed the purge valve in only the error for “below limit”.

I think I know why. When the car sits the carbon canister gets loaded with hydrocarbons from the fuel evaporating. When you first drive the car the purge valve opens and these hydrocarbons are sucked into the intake manifold and burned. Eventually, after running for a while, there are no more hydrocarbons remaining and the valve should close or partially close. If the valve is sticking open then it is the same as an intake leak and the lean threshold is reached. So that explains how the “above limit” is reached. The DME also performs oxygen sensing with the valve closed to establish as baseline mixture adaptation. If the valve is stuck open during this adaptation when the canister is loaded I can see how the “below limit” is reached since extra fuel is being introduced. It seems like the purge valve should have been listed as a possible cause on both procedures. Just something to think about!

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George, if you go back to post #29, the RKATs although negative, they were only at ~ -2%. Seems too small to call that running RICH, whereas in post #8, the RKATs were positive at 4+% so a stronger indication that the engine is running LEAN.

As to your second question, if the EVAP purge valve is leaking, all the vapor adds to the fuel so the engine will always run RICH hence the valve is check only under RICH condition (or "below limit" condition). There's no end to this because the fuel keeps evaporating, especially if you give it vacuum (will evap even faster).

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Yes, the adaptation was not as negative as it was positive. However I thought it was odd that same fault code appeared and the adaptation was negative one time and positive another time. You would think that the fault would be always one or the other. With this being said, another important point is that we don’t know how much time elapsed from CEL to when the adaptation was read. We would need freeze frame data to know what the adaptation was when the fault occurred. I assumed CEL was due to lean threshold being reached one time and rich threshold reach another time. This may be an incorrect assumption because we don’t have the freeze frame info.

Yes, if the purge valve is stuck open it will always introduce extra fuel because the fuel is always evaporating as you said but it also introduces air. So the question is “what is the mixture being sucked into the intake”, is it rich or lean? If the valve is stuck and not able to modulate, the mixture will high in hydrocarbons at first and leaner as time goes on. So even though the purge stream contains fuel the mixture could be leaner than the required mixture making the adaptation go towards rich. I know the DME modulates the purge valve but not sure what is looking at to control it, fuel tank pressure or oxygen sensing. My guess it looks at oxygen sensing, it keeps the valve open if oxygen senses a richer mixture and closes if it senses a lean mixture. With Durametric you can see the mass of air being measured by the MAF and the total air mass, the difference is the air through the purge valve. Interesting stuff.

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FYI .... Ran the Durametric again a couple of days ago just to observe and here are the numbers ... after driving .... car was at operating temps ...

RPM 770

BANK 1 BANK 2

FRA 1.0 1.01

RKAT -1.80 -2.10

MAF 17-18 kg/h

Still a little rich???

Edited by stutzchris
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Yes, the adaptation was not as negative as it was positive. However I thought it was odd that same fault code appeared and the adaptation was negative one time and positive another time. You would think that the fault would be always one or the other. With this being said, another important point is that we don’t know how much time elapsed from CEL to when the adaptation was read. We would need freeze frame data to know what the adaptation was when the fault occurred. I assumed CEL was due to lean threshold being reached one time and rich threshold reach another time. This may be an incorrect assumption because we don’t have the freeze frame info.

Yes, if the purge valve is stuck open it will always introduce extra fuel because the fuel is always evaporating as you said but it also introduces air. So the question is “what is the mixture being sucked into the intake”, is it rich or lean? If the valve is stuck and not able to modulate, the mixture will high in hydrocarbons at first and leaner as time goes on. So even though the purge stream contains fuel the mixture could be leaner than the required mixture making the adaptation go towards rich. I know the DME modulates the purge valve but not sure what is looking at to control it, fuel tank pressure or oxygen sensing. My guess it looks at oxygen sensing, it keeps the valve open if oxygen senses a richer mixture and closes if it senses a lean mixture. With Durametric you can see the mass of air being measured by the MAF and the total air mass, the difference is the air through the purge valve. Interesting stuff.

George, agree with what you said. Acording to the serivce manual, the purge valve modulation is indeed done by monitoring the oxygen sensing.

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