Check engine light diagnostic help

Hi all, I'm looking for an extra set of eyes to help me troubleshoot a check engine light. The car is a 2000 Carerra with a 3.4, bone stock powertrain, no mods. Stock air filter, all maintenance up to date. It had a major engine out maintenance cycle a bit over a year and ~1000 miles ago (that included a new AOS and accordion hose). My wife has been driving it lately, and yesterday she reported a check engine light. She didn't observe any strange noises, smoke, odors, etc. The car ran great, and continues to do so. When she got home, I pulled the codes and got a P1128 and a P1130: oxygen sensing adaptation idle range bank 1 and bank 2. Some quick googling of Rennlist suggested this indicates a lean running condition, likely caused by too much air entering the system. Since it is both banks at once, it suggests that it is the plenum or something upstream. If I understand it, this could be caused by a number of things including vacuum leaks, loose intake hose clamps, a failing MAF, a loose oil cap (or bad cap gasket), failing AOS, etc. I cleared the codes and will have her monitor for recurrence. I verified that the oil cap is on tight, the dipstick is firmly inserted, there is no visible damage to any components (like the intake hose, plenum boots or oil fill tube), and I looked for anything else that was disconnected, loose, out of place or broken (nothing was). The MAF connector was connected solidly. I removed and cleaned the MAF sensor with MAF sensor cleaner, let it dry and reinstalled it. Then I made sure the connector was firmly attached. I'd like to rule out vacuum leaks, but do not have a smoke machine. I'd like to test the AOS, but don't have a manometer (well, I do, but it was made for balancing throttle bodies on motorcycles). I am ALWAYS open to buying more tools though (admitted tool junkie). Do you have any make/model/supplier recommendations for a manometer and smoke machine? I'd be looking for DIY grade, but decent quality, not pro grade or junk, unless it is unavoidable. One post on Rennlist suggested that the Dwyer Series 476A is the same tool as one of the vendor supplied manometers at a much lower price. Are there other things I can be testing in the absence of these specialized tools? I know there is a test where you try to remove the oil cap to see if the AOS is going - would a failing AOS result in a cap that comes off with difficulty or too easily when running? Are there changes in engine noise or idle to pay attention to while doing this? Would disconnecting the MAF tell me anything? What would I look for? I have both a Foxwell handheld reader and a Durametric cable, so I can monitor real time values. Are there values for things like MAF that I can use as reference ranges for a properly working sensor, as I monitor? Are there other real time values that I could watch? If so, any guidance on what to monitor, what conditions (idle, under load, certain rpms) and what value indicates a properly working sensor? My wife is falling in love with driving this car, so I'd like to make sure it is headache free for her. Thanks in advance for any advice you can offer.

An 02 with a 3.4 or 3.6? Check the gas cap rubber seal for cracks.

Good call, Bill - I mixed my cars up. It is a 2000 with a 3.4. (I also have a 2002 with a 3.6, not quite as bone stock, lol). I'll fix it above. Gas cap is tight, seal looks good, no damage. I think that is a different code too (maybe P0455?) .

I picked up this Man-o-meter a few months ago: https://www.amazon.com/gp/product/B06WP2Y9VY/ref=ppx_yo_dt_b_asin_title_o09_s00?ie=UTF8&psc=1 https://www.amazon.com/gp/product/B06WP2Y9VY/ref=ppx_yo_dt_b_asin_title_o09_s00?ie=UTF8&psc=1 Seems to be adequate. Can't help with smoke machine. I have used one at work, but that unit would be quite costly. My typical home testing involves WD40 or carb cleaner. I'm sure you know how to test with either. I had the same codes as you when I first brought my car home. I suspect the MAF wire caught in the air filer box was the cause (slightly compromising the seal). After all the work I performed, the fault has not returned.

Thanks. That manometer looks like a sweet deal ($85+ for that other one I mentioned). I have a spare oil cap form my parts engine, so I can just drill a hole, and grab a barbed fitting and some hose from the hardware store. Any idea what range of values (in HG of vacuum?) I should expect if the AOS is happy?

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You won't even need to buy a barb fitting - one comes with it. Just drill a hole in your spare oil cap. I don't know the range off the top of my head. I think the specs are in the listing.

There are a few threads here that mention the proper range I think it's 4-5 in. is acceptable off the top of my head - but check it - don't take my word for it.

I use the same manometer, which is great 4-6 inches of water when idling with no load fully warmed up. May have more clues if you read the FRA and TRA (or RKAT) values from Durametric.

Thanks, guys. It's on order, love that Amazon Prime. Ashai, any threads about how to interpret FRA and TKA (or RKAT) ? Sounds like a world language... I'll do some searching too, but if there are handy threads you could point me to, that would be awesome. I googled up a good article here: https://www.callasrennsport.com/blog...im-information Just measured (at idle: 1044 rpm): Mass Air Flow -> 22 kg/h FRA bank 1 -> 1.00 RKAT bank 1 -> 0.00% FRA bank 2 -> 1.00 RKAT bank 2 -> 0.00% Based on the above linked article, the RKAT should be 0% (x > 0 lean, x < 0 rich) and the FRA should be 1 (y > 1 more fuel being added, y = 1 no adjustment to fueling). So I think we are ok, and don't have an air leak. But... mass air flow should be ~17 kg/h +/- 2. So 15-19 range... Mine is 22 kg/hr. What does that tell us? Another good bit of information (from another forum - http://forums.pelicanparts.com/boxst...g-numbers.html ): The RKAT values near idle are used to change the length of the injector pulse to account for deviations from ideality (ie intake leaks) to maintain the proper O2 sensor reading. The RKAT value is an additive factor and can deviate by +/- 4.5%. The FRA value is a multiplicative factor and can deviate by 1.32 to 0.70. The positive values or values greater than 1 increase the injector pulse length to account for a lean mixture, and negative values and values less than 1 are to compensate for a rich mixture.

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1044 rpm is way too high for idle speed (should be ~780rpm) if the engine was fully warmed up with a/c OFF (what the spec numbers assume). Were the measurements taken at cold start? Also all the 1.0's and 0's look suspicious. Did you just reset the DME before you took the measurements?

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It was cold start, so maybe I was in a closed loop state? Not sure if the AC was on. So maybe those numbers are garbage. Let me take it out for a warm up drive in the morning and take new readings with ac off. I had cleared DME error codes. Does this reset the DME?

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Yes and yes. You will need to drive it for a few days and put some miles on it for the DME to adapt. Then you can take the reading on a warmed up idling engine. Since the MAF reading varies with rpm, you need the rpm to be at ~780 to compare with the spec MAF value .

Thank you. I really appreciate the help you've provided. I'll do that and report back. Thanks!!

I took the car for a good drive today, then took new readings. AC off. RPM: 774 1/min Mass Air Flow: 15.3 kg/hr FRA bank 1: 1.0 RKAT bank 1: 3.56% FRA bank 2: 1.0 RKAT bank 2: 3.61% So, both sides running lean? Air flow reading OK, so MAF probably fine. I have an air leak in the system upstream from the plenum?

Those numbers look great and are all in spec so they don't confirm an intake leak. I would say recheck in 100miles.

Will do! Thanks.

Anytine

CEL returned after 100 miles or so: P1128 Oxygen sensing adaptation, idle range, bank 1. Only one bank though... That is different than before. My manometer should be here shortly, so I can test the AOS. I need to either buy or rig up a DIY smoke machine to check for leaks.

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So what are the MAF, FRA and RKAT readings then? It's the best time to check those values because the CEL has been tripped. It's possible 1130 may also be coming so it may not be different than before.

Wife just got home with it, so I pulled the codes while warm. You were spot on, today it threw the other code (P1130) again too. So it has both P1128 and P1130. Just measured (at idle: 790 rpm): Mass Air Flow -> 15 kg/h FRA bank 1 -> 1.03 RKAT bank 1 -> 4.45% FRA bank 2 -> 1.01 RKAT bank 2 -> 4.50% The manometer arrived today, so hopefully I can get that tested soon too. Just need to find my extra oil cap.

Duplicate, please delete.

The readings are interesting that the RKAT is only ~4%, which should not trip the 1128/1130 codes. I wonder if you have an intermittent vacuum leak. It may he worthwhile to do a test drive and monitor the MAF and RKAT in real-time (perhaps with a helper). It does seem to point to an intake leak or a MAF with intermittent signal drop off.

I'll see if I can get my wife to take me for a drive this weekend while I monitor. Any tips on what to monitor and what changes would point to particular root causes? Would I be watching short term fuel trim for both banks and MAF? I'm guessing MAF would go to 0 if/when it fails? Would short term fuel trim go up when it experiences an intermittent air leak because it is running lean? AOS test today, smoke test once I find the bits to make a smoke tester (or order them on amazon).

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Amazon has become one of my favorite places for many things. Even an oil fill cap. Free shipping on most of my orders, really make it easy to justify. https://www.amazon.com/gp/product/B00A400RPY/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&psc=1 https://www.amazon.com/gp/product/B00A400RPY/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&psc=1

Not to muddy the water, but does your Durametric read stft values as RKAT or TRA?

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Thanks. They're my go to as well. I know I have a spare somewhere in the garage though. The best way to find it is to buy a new one, then I'm almost guaranteed to stumble into the one that is already in the garage. Lol

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That's a good question that I don't have an answer to. I've been using my Foxwell scanner since it is more convenient than dragging out the computer. The Foxwell shows it as adaptation, range 1 or 2 with FRA and RKAT in parentheses:

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To maximize the resolution, you want to plot the reading in Durametric in real-time, choose the highest sampling rate and monitor as little number of parameters as possible. So I would just monitor rpm, MAF voltage (in voltage, which is the raw measurement, as opposed to calculated values), and FRA and RKAT on both banks. The MAF reading should never drop to 0v (if it does, you have an MAF with intermittent failure. I saw a case like that before). The RKAT will vary in much more than the FRA but it should stay within a few +/-% (your current reading is ~+4%). To trip the 1128/1130, I think RKAT has to go to +/-27% or so but perhaps someone else can confirm. I just want to see whether your RKAT goes beyond the +/-27% then goes back to normal during the drive. In any case, a smoke test will be more direct to check for intake air leak. However, keep in mind you still won't be able to verify any leak in the vacuum system (evap, intake resonance flap) because there's a one-way valve that prevents the smoke from reaching those components. To test those components, the only way I know is to use a vacuum pump on the vacuum line that plugs into the intake plenum.

Wow, you're really a lifesaver here. You're a massive asset to this community. Thanks for all of the time and energy you're putting in to help me. I'll use Durametric to log the drive and see if I can get any clues. Fingers crossed.

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Yep - I have many duplicate tools and parts as a result of this...

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Yes. Yes he is...!

Happy to whenever I can

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Load Range 1 near idle is called TRA before ym2000 (986 996) and is shown as injection time +- 0.36 Ti (set point) in DME 5.2.2, after my2000 it is called RKAT and shown in % with set point being 4.50% in DME 7.2, in DME 7.8 (996.2) the set point/adjustment has a wider window , although I can't remember the exact number. FRA is load range 2 for the upper rpm range.. . Yes he is, Ahsai is a very good troubleshooter and understands the DME/fuel control very well !!!

Just off idle, not warmed up, manometer reading from oil filler cap looks like about 3.0 in h2o. I'll take a warm reading later.

Thanks to PT3 and Ahsai for all the valuable info. I have a '99' so that explains my question concerning different types of values. You probably know this, but real time logging requires Microsoft Excel loaded on the laptop. Something I hadn't installed. Can CDS record O2 voltage as well?

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I didn't know that I needed Excel installed!! Once I install Excel, does it come up as an option in Durametric? I need to read the manual that I printed out...

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I don't know the answer to that. I contacted Durametric to find out why nothing got logged on to my laptop. That's what they told me. I did logging the old fashioned way. Had my wife drive while I noted actual values. If you get a chance can you jot down your O2 readings? Thanks.

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I'll see what I can do. Any particular readings you are looking for? And under any particular conditions (warmed up, idle, under load, etc)?

Warmed up at idle. Just curious as to what voltage would show up. Lean or rich after cat. Doubt this will help diagnose root cause of fault though.