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Discussion Starter #1
Hi Folks,
Been struggling with a MAF sensor error code on my 96 Tracker. After warming up the little guy starts having an erratic idling issue and will often die going from drive to park.
Items replaced......MAF sensor
crank sensor
air filter

items checked and cleaned...gang plug connectors under the hood, ecm box pcm box, distributor
all chassis grounds that are visible
Alternator voltage and battery and the connections
trans fluid
vacuum lines and airbox hoses and routing
wires shorting to frame....you know ,normal checklist

Just can't seem to dump that code and correct erratic idling.
Other than that the Tracker runs smooth and revs fine

I am beginning to suspect the ecm not playing ball with the MAF sensor

After putting in a new MAF sensor the Innova code reader started talking to the computer box whereas it was not before. Interesting. Still have the check engine light and PO102 code.

Any ideas on this subject will be appreciated and my 17 year old can maybe drive the Track'

What did I miss?

Thanks , and stay well
Glenn
 

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Other than reading the code, what other tests have you done?

Potential causes for this trouble code may include:
  • Dirty or contaminated mass air flow sensor
  • Failed MAF sensor
  • Intake air leaks MAF
  • sensor electrical harness or wiring problem (open, shorted, frayed, poor connection, etc.)
Read more at: P0102 Mass Airflow (MAF) Circuit High

Do you have a live data scanner ??
 

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Poor grounds...you say it only started talking to the ecm after changing the maf. Thus is suspicious.

Check all your power supplies and grounds, especially the one on the body by the battery and the ones on the engine block.
 

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Discussion Starter #4
Thank you group....I am going to investigate every possible ground situation. I do not have a live data scanner, that may be the next step. Troubleshooting the harness is another avenue ahead...unwrapping and tracing. I know I had a ground situation with the Tracker years ago on the drivers side of the engine but I can't remember where that ground was..I will keep this thread updated.
Glenn
 

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Theres one on the firewall from memory that heads onto the engine loom. Looks ok but has been known to get rusty under the lug.
 

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Start with the scanner, look for +/-4g/sec at idle on the MAF..

You do not need to molest the harness, prove it out first..
 

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Welcome to the forum. See post #3 here, as well as Rhino’s link further down, and some of the conversation.
 

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Discussion Starter #10
Welcome to the forum. See post #3 here, as well as Rhino’s link further down, and some of the conversation.
Welcome to the forum. See post #3 here, as well as Rhino’s link further down, and some of the conversation.
 

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Moving along with this thread.....We have good news and bad news. 1st the good. The MAF sensor issue seems to be rectified. I found that the cheapo MAF sensor replacement from china did not work at all. The old original one was acting irrationally but has since settled down after a good bit of MAF cleaner (10 bucks, Oreilly) No PO102 code and no other codes either...hurray for that. Now the issue has returned to a very weird , erratic and ongoing condition. Let me elaborate,

Nothing seems to surface until after the car has been warmed and driven for a while. Then I will notice the engine start to miss at both slow and highway speeds. Thank goodness the Tracker always makes it home when testing. In the driveway and after a test drive it will do some weird stalling when shifting from D to P ,P to R, R to P etc.. The condition is worse when shifting slowly and better when a fast shift is performed. Nonetheless the engine will miss under load if just idling in R or D. Then sometimes it will just stop. Now if you start the car again it will sometimes be normal for a while then return to the aforementioned condition. Very frustrating. Once again , no codes ! I am open to all thoughts on this but I am gravitating towards a fuel delivery or injector issue. The filter is new , the pump is original. I also have to throw this in....the car had a head gasket replaced several years ago and that went well except I noticed a lot of slop in the reassembly process....loose grounds(several) and things not rebolted tightly, a hurryup and finish job for sure. The gasket job itself is tight.

Also I have two different ECM's and the condition is the same with both but a tad better with one (the original one.)

I am finding this difficult to diagnose.
My own thoughts on progressing.....fuel injector cleaning, new set of plugs and wires, check electrical on fuel injectors for a loose or dirty one.

I have to say when the car is cold the engine runs like a dream....good compression,acceleration and idle condition.
Chasing a gremlin here.
Thanks group. Stay away from cheapo MAF sensors.
Glenn
 

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I have to say when the car is cold the engine runs like a dream....good compression,acceleration and idle condition.
Chasing a gremlin here.
Thanks group. Stay away from cheapo MAF sensors.
Glenn
The engine runs better when cold is a result of the ECU being in "OPEN LOOP" condition (Factory presets), the failure shows when the engine warms (CLOSED LOOP) the ECU at this point uses the current DATA to adjust running conditions...
Proper diagnostics are in order, use a LIVE DATA SCANNER !!
  • Monitor the fuel trims at idle and 2500 rpm.
  • Monitor the S1B1 O2, active switching with no bias,
Post the results.. in graph mode..
 

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Discussion Starter #13
Moving along with this thread.....We have good news and bad news. 1st the good. The MAF sensor issue seems to be rectified. I found that the cheapo MAF sensor replacement from china did not work at all. The old original one was acting irrationally but has since settled down after a good bit of MAF cleaner (10 bucks, Oreilly) No PO102 code and no other codes either...hurray for that. Now the issue has returned to a very weird , erratic and ongoing condition. Let me elaborate,

Nothing seems to surface until after the car has been warmed and driven for a while. Then I will notice the engine start to miss at both slow and highway speeds. Thank goodness the Tracker always makes it home when testing. In the driveway and after a test drive it will do some weird stalling when shifting from D to P ,P to R, R to P etc.. The condition is worse when shifting slowly and better when a fast shift is performed. Nonetheless the engine will miss under load if just idling in R or D. Then sometimes it will just stop. Now if you start the car again it will sometimes be normal for a while then return to the aforementioned condition. Very frustrating. Once again , no codes ! I am open to all thoughts on this but I am gravitating towards a fuel delivery or injector issue. The filter is new , the pump is original. I also have to throw this in....the car had a head gasket replaced several years ago and that went well except I noticed a lot of slop in the reassembly process....loose grounds(several) and things not rebolted tightly, a hurryup and finish job for sure. The gasket job itself is tight.

Also I have two different ECM's and the condition is the same with both but a tad better with one (the original one.)

I am finding this difficult to diagnose.
My own thoughts on progressing.....fuel injector cleaning, new set of plugs and wires, check electrical on fuel injectors for a loose or dirty one.

I have to say when the car is cold the engine runs like a dream....good compression,acceleration and idle condition.
Chasing a gremlin here.
Thanks group. Stay away from cheapo MAF sensors.
Glenn
 

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Discussion Starter #14
I will try to do that. Not real up to speed on modern engine diagnostics. Is a live scanner something anyone can buy or is that what a shop uses? I'll try to get data on the forum but what you say makes perfect sense. Closed loop...current engine conditions...different behavior ,I get it.
Thanks, Glenn
 

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$15 elm based obd2 scanner and torque lite for android works for graphs
 

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While waiting for your new scanner, you may want to give some actual details as to how the car runs. As Philip says, when the engine is cold, not only is the ECU using preset perimeters for fuel delivery, etc., it is also providing extra air/fuel for the engine to warm up. So, exactly what happens when you start from cold? What is your cold idle? What does the idle do as the engine warms up? What is your warm idle, etc.
And please put your car’s specs into your signature, so everyone knows what you’re driving without having to search...;)
 

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Discussion Starter #17
While waiting for your new scanner, you may want to give some actual details as to how the car runs. As Philip says, when the engine is cold, not only is the ECU using preset perimeters for fuel delivery, etc., it is also providing extra air/fuel for the engine to warm up. So, exactly what happens when you start from cold? What is your cold idle? What does the idle do as the engine warms up? What is your warm idle, etc.
And please put your car’s specs into your signature, so everyone knows what you’re driving without having to search...;)
 

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Discussion Starter #18
Yeah sure....To be specific we have a 1996 Geo Tracker with the standard 16 valve in line 4. Car upon start... rpms are around 1300 (a guess using tach readings) then to about 1100 as car warms, settles in at 900 to 1000. The Tracker runs as would be expected(open loop) for about 15-20 minutes then goes into closed loop. This is when issues arise. It will start missing at idle primarily when in gear but also sometimes when not under load. The car will stall going from R or D to park consistently. No codes showing.The car also misses at highway speeds when in closed loop. I hope that helps. Thanks for the help.
Glenn
 

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I think there may be some confusion about open loop - open loop basically means that the ECU is not using the O2 sensor for its regulation of fuel/air delivery, but a preset perimeter. When the O2 sensor heats up, the ECU then begins to use its signal for fuel/air delivery. This happens well before 15-20 minutes.
Even aside from this, normally your engine should take much less time for the idle to drop to - what should be - 800 rpm warm idle. This shouldn’t take 15-20 minutes to achieve.
By the way, if you go to your control panel, you’ll see a listing for signature - that’s where you should put the specs for your car, so that it appears in the bottom of each of your posts, without you having to retype it.
Have you ever checked the timing of this engine? Done a compression test to verify valve timing? Checked to make sure your spark plugs are gapped to .028”? Everything is based on proper valve timing, and it would be good to know, before we start searching in other directions, that this engine is timed properly.
 

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Discussion Starter #20
Thanks Bex. The 15 minute warmup was probably an overestimate...like I said car does fine until the curse sets in. Recent head gasket replacement where critical engine specs were met. Like I said the engine sounds like a kitten purring normally and shows no symptoms of valve ,compression or timing issues...its all in the engine-computer interface or possible a fuel pressure thing. After reading your analysis of closed loop I am thinking a O2 sensor out of spec might create this issue. My local shoppe is going to do a live scan next week if I have not made any progress.
Take Care,
Glenn
 
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