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| weird MAP sensor reading. (Page 1/1) |
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lou_dias
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MAY 02, 04:38 PM
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Has anyone else experienced wild MAP sensor readings that seem off at high rpm?
I've done a bunch of dynos and it seems my MAP goes from reading 100 down to the 30's which then causes my fuel to cut down drastically?
I've mitigated the problem by increasing fuel across 4800-6000rpm at low map readings but my fear is that I'm having a valve-sealing issue.
You can see on the green chart I sett the fueling higher at low reading and that smoothened out the power curve but it didn't fully get rid of the issue.
The spike at the end is because I thought the dyno operator was gonna cut off the reading so I fluttered the pedal a bit.
 [This message has been edited by lou_dias (edited 05-02-2025).]
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Vintage-Nut
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MAY 03, 10:29 AM
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Original Owner of a Silver '88 GT
Under 'Production Refurbishment' @ 136k Miles
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Frenchrafe
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MAY 03, 11:09 AM
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I had faulty MAF and MAP sensors for quite some time until I found out that my alternator was giving out 17V spikes for a few miliseconds from time to time!
When comparing the voltage output, on a rather elongated graph, you could see the MAF readings going haywire at the same time as the alternator voltage spiked.
The MAP just stopped working and needed to be replaced.
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"Turbo Slug" - '87 Fiero GT. 3800 turbo. - The fastest Fiero in France! @turboslugfiero
https://youtu.be/hUzOAeyWLfM[This message has been edited by Frenchrafe (edited 05-03-2025).]
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lou_dias
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MAY 03, 02:26 PM
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Sorry, I thought everyone was fairly familiar with my build. No MAF sensor as this is an iron-head V6 w/7730 and DIS build.
You do bring up a good point. I should check the sealed quality of my hoses and sensors...maybe by forcing smoke thru the TB to see if it leaks out anywhere...
To be safe I ordered a new MAP sensor from the Fiero Store.
Edit:
Thanks for the diagram Vintage-Nut![This message has been edited by lou_dias (edited 05-03-2025).]
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Frenchrafe
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MAY 04, 01:18 AM
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And if you can, check the voltage on your logs for spikes or fluctuations.
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"Turbo Slug" - '87 Fiero GT. 3800 turbo. - The fastest Fiero in France! @turboslugfiero
https://youtu.be/hUzOAeyWLfM
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Vintage-Nut
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MAY 04, 10:47 AM
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| quote | | To be safe I ordered a new MAP sensor from the Fiero Store. |
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BTW
Years ago, GM discontinued the original MAP sensor and revised it which the newer sensor is more accurate.
The GM part number for this revised MAP sensor is 12569240 {ACDelco part number 213-1545}
To me, don't buy a 'cheap' aftermarket unit, get a genuine GM MAP... 
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lou_dias
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MAY 05, 03:18 PM
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Eek! Are you saying the Fiero Store one in not a good one?
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Vintage-Nut
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MAY 05, 04:05 PM
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| quote | | The Fiero Store carries quality replacement parts that meet or exceed OEM specifications. |
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Call Matt at the The Fiero Store and ask if their MAP sensor is Genuine GM unit OR an aftermarket?
If aftermarket, ask if he will tell you the brand?
Some members care more about 'the price' and I care more about quality....
{The ICM is a good example}
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cartercarbaficionado
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MAY 05, 04:50 PM
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| quote | Originally posted by lou_dias:
Eek! Are you saying the Fiero Store one in not a good one? |
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ive had more than my fair share of DOA parts from them and others. its not their fault its the manufacturers for the most part. i do blame them for how awful the ocelot kit fits together though and for the money i could have had something better so never again no offense to them.
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