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High positive fuel trims, low maf grams at idle

Old 01-11-2014, 03:25 PM
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I am still trying to figure everything out, maybe it is normal I don't know. Another guy out here who has an rx8 says his fuel trim is always at about 20 long term with short term around 5 or 6. So either we both have issues or it is normal for vegas?

I just learned that I guess the 2009 rx8s do not have the extra engine warranty at least according to the dealer I called. Also my powertrain warranty ended on 9/2013 which kind of sucks as I now have a transmission leak that has been there a while but I only just noticed. The news just keeps getting worse lol.
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Old 01-12-2014, 02:28 PM
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Originally Posted by Charles R. Hill View Post
Has this particular vehicle had a compression test performed lately?
Yes , before the owner bought it he did one . Said the results were fine but I didn't quizz him on what they were.
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Old 01-13-2014, 01:01 PM
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Originally Posted by xexok View Post
I just learned that I guess the 2009 rx8s do not have the extra engine warranty at least according to the dealer I called
Originally Posted by myMazda.com
RX-8 Rotary Engine Core Limited Warranty Extension
Mazda Motor Corporation is extending the warranty coverage on Rotary Engine Core Components on all RX-8 vehicles produced after the 2004 model year. The warranty coverage for the Rotary Engine Core Components is extended to 8 years (96 months) from the original warranty start date, with a 100,000 mileage limitation.
fyi....
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Old 01-13-2014, 03:09 PM
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Originally Posted by Charles R. Hill View Post
I wonder, in this particular engine's case anyway, if the relatively low MAF readings are from poor sealing due to age, etc.?
All I was doing was a reflash , mainly to delete the cel from fitting your coils . Would have liked to investigate further but he wasn't complaining about any issues so ......

I remember another member here with a turbo setup chasing a low maf reading for years , he never did get to the bottom of it . After changing , sensors , maf tubes and even engines he was still at a loss.

Last edited by Brettus; 01-13-2014 at 03:25 PM.
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Old 01-13-2014, 03:33 PM
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Originally Posted by Brettus View Post
All I was doing was a reflash , mainly to delete the cel from fitting your coils.
Is that a non-USDM thing, because the coil installation typically doesn't create a CEL on any USDM car that I know of? Or did you mean catless midpipe instead?
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Old 01-13-2014, 03:47 PM
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Originally Posted by TeamRX8 View Post
Is that a non-USDM thing, because the coil installation typically doesn't create a CEL on any USDM car that I know of? Or did you mean catless midpipe instead?
Yes ... it's a JDM thing . All 4 coils throw a cel . Interestingly .... removing the cat doesn't throw a cel on early JDM models . Go figure ..............

Last edited by Brettus; 01-13-2014 at 03:50 PM.
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Old 01-13-2014, 03:49 PM
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ok, thx for clarifying
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Old 01-17-2014, 07:58 PM
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Originally Posted by Charles R. Hill View Post
I wonder, in this particular engine's case anyway, if the relatively low MAF readings are from poor sealing due to age, etc.?
Just came across another 8 with really low g/s at idle . Only this time there was also a rattle which I traced to a loose SSV shaft .
Perhaps the extra clearance on the shaft is a significant vacuum leak ..................
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Old 01-18-2014, 03:24 PM
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Originally Posted by Charles R. Hill View Post
Sounds like the carb cleaner/propane leak test might be in order.
For sure . I must get some.
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Old 01-18-2014, 06:01 PM
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I had the leaky clunky ssv actuator issue. Unfortunately I have fixed a few annoying vacuum leaks over the years.

Op, just make your own. I use this:

RX-8 Hymee Supercharger Install - Smoke Tester

Posted From RX8Club.com Android App
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Old 01-20-2014, 09:48 PM
  #36  
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I'm sure it's already been said, but the simplest answer is the MAF is failing or dirty, and it's reading low, so the fuel trims have to be adjusted upward to compensate for the larger real air-mass going into the engine.
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Old 04-06-2017, 02:24 PM
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Xexok ever found the problem?
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Old 12-19-2018, 04:10 AM
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SSV, VDI, and VFAD issues might be at play as well as the tune. Ordered new ones after testing and all failed, but similar problems were present when took to dealer and mechanics and "fixed". If tune was optimum (with communication to/from solenoids) and timing was advanced (probably around -15 to -20 and slightly rich the OEM solenoid design would likely be optimum. Thought of circumventing solenoids by splitting intake vacuum directly to both manifold actuators and adding electric and/or non-electric assisted velocity fans before and after MAF to increase air flow (correcting a resulting sloped torque curve instead of the advertised relatively flat optimum torque between 4,000 & 8,000 RPM due to simultaneous activator function) and encouraging system to make fuel mixture richer (with increased velocity before MAF), and circumventing VFAD and purge with vacuum from one of the ports to the "high rise" port of the manifold and making sure any resulting open lines were capped. You also may want to check PCVs as mine were completely clogged.
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Old 12-19-2018, 04:43 AM
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Also thought of circumventing air pump solenoid by using "high rise" port to activate pump and hooking up sensor to port.
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Old 12-19-2018, 03:49 PM
  #40  
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Is there even a PCV on our Series 2? If so, is it called something different?
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Old 12-20-2018, 01:37 PM
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Originally Posted by jkinard View Post
Also thought of circumventing air pump solenoid by using "high rise" port to activate pump and hooking up sensor to port.
Something that seemed to be "circulating around ('pun' intended)", it might be a good idea to use a check valve if running vacuum off the ports that the air, VDI, and SSV solenoids attach and it is possible the solenoids wouldn't need to be replaced if there were check valves going into them.
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Old 12-20-2018, 03:12 PM
  #42  
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You bumped a long-dead thread with some oddball word salad. Then add another reply. Then quote yourself while ignoring another reply...

Are you just a bot having a conversation with itself?
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Old 12-20-2018, 06:51 PM
  #43  
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Just in case anyone is curious...

Series 2(and from what I have searched, Series 1 as well) RX-8 doesn't have a PCV valve. The system is literally just the rubber hose that connects the oil filler neck to the intake accordion.


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Old 12-20-2018, 07:31 PM
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VDI, SSV, and air pump solenoids.

erased as meant to be direct reply.

Last edited by jkinard; 12-20-2018 at 07:40 PM. Reason: Intended to be direct reply to post.
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Old 12-20-2018, 07:37 PM
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Originally Posted by jkinard View Post
Something that seemed to be "circulating around ('pun' intended)", it might be a good idea to use a check valve if running vacuum off the ports that the air, VDI, and SSV solenoids attach and it is possible the solenoids wouldn't need to be replaced if there were check valves going into them.
When looking at the catch box, if using the solenoids the PCV addition before might delay response with "locked" optimum timing from computer.
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Old 12-20-2018, 07:41 PM
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Originally Posted by NotAPreppie View Post
You bumped a long-dead thread with some oddball word salad. Then add another reply. Then quote yourself while ignoring another reply...

Are you just a bot having a conversation with itself?
Dates seemed recent. Later posts didn't seem directly related although replies to "self" seem relevant to context if others are arguing situation for optimum performance at time.
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