Pennock's Fiero Forum
  Technical Discussion & Questions
  weird MAP sensor reading.

Post New Topic  Post A Reply
Email This Page to Someone! | Printable Version


next newest topic | next oldest topic
weird MAP sensor reading. by lou_dias
Started on: 05-02-2025 04:38 PM
Replies: 8 (131 views)
Last post by: cartercarbaficionado on 05-05-2025 04:50 PM
lou_dias
Member
Posts: 5360
From: Warwick, RI
Registered: Jun 2000


Feedback score: (3)
Leave feedback





Total ratings: 67
Rate this member

Report this Post05-02-2025 04:38 PM Click Here to See the Profile for lou_diasSend a Private Message to lou_diasEdit/Delete MessageReply w/QuoteDirect Link to This Post
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).]

IP: Logged
PFF
System Bot
Vintage-Nut
Member
Posts: 1542
From: California
Registered: Apr 2020


Feedback score: N/A
Leave feedback

Rate this member

Report this Post05-03-2025 10:29 AM Click Here to See the Profile for Vintage-NutSend a Private Message to Vintage-NutEdit/Delete MessageReply w/QuoteDirect Link to This Post

------------------
Original Owner of a Silver '88 GT
Under 'Production Refurbishment' @ 136k Miles

IP: Logged
Frenchrafe
Member
Posts: 501
From: Locmiquelic France
Registered: Feb 2017


Feedback score: N/A
Leave feedback

Rate this member

Report this Post05-03-2025 11:09 AM Click Here to See the Profile for FrenchrafeSend a Private Message to FrenchrafeEdit/Delete MessageReply w/QuoteDirect Link to This Post
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.

------------------
"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).]

IP: Logged
lou_dias
Member
Posts: 5360
From: Warwick, RI
Registered: Jun 2000


Feedback score: (3)
Leave feedback





Total ratings: 67
Rate this member

Report this Post05-03-2025 02:26 PM Click Here to See the Profile for lou_diasSend a Private Message to lou_diasEdit/Delete MessageReply w/QuoteDirect Link to This Post
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).]

IP: Logged
Frenchrafe
Member
Posts: 501
From: Locmiquelic France
Registered: Feb 2017


Feedback score: N/A
Leave feedback

Rate this member

Report this Post05-04-2025 01:18 AM Click Here to See the Profile for FrenchrafeSend a Private Message to FrenchrafeEdit/Delete MessageReply w/QuoteDirect Link to This Post
And if you can, check the voltage on your logs for spikes or fluctuations.

------------------
"Turbo Slug" - '87 Fiero GT. 3800 turbo. - The fastest Fiero in France! @turboslugfiero
https://youtu.be/hUzOAeyWLfM

IP: Logged
Vintage-Nut
Member
Posts: 1542
From: California
Registered: Apr 2020


Feedback score: N/A
Leave feedback

Rate this member

Report this Post05-04-2025 10:47 AM Click Here to See the Profile for Vintage-NutSend a Private Message to Vintage-NutEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
To be safe I ordered a new MAP sensor from the Fiero Store.


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...
IP: Logged
lou_dias
Member
Posts: 5360
From: Warwick, RI
Registered: Jun 2000


Feedback score: (3)
Leave feedback





Total ratings: 67
Rate this member

Report this Post05-05-2025 03:18 PM Click Here to See the Profile for lou_diasSend a Private Message to lou_diasEdit/Delete MessageReply w/QuoteDirect Link to This Post
Eek! Are you saying the Fiero Store one in not a good one?
IP: Logged
Vintage-Nut
Member
Posts: 1542
From: California
Registered: Apr 2020


Feedback score: N/A
Leave feedback

Rate this member

Report this Post05-05-2025 04:05 PM Click Here to See the Profile for Vintage-NutSend a Private Message to Vintage-NutEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
The Fiero Store carries quality replacement parts that meet or exceed OEM specifications.


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}

IP: Logged
cartercarbaficionado
Member
Posts: 888
From: cusick, Washington, USA
Registered: Sep 2023


Feedback score: N/A
Leave feedback

Rate this member

Report this Post05-05-2025 04:50 PM Click Here to See the Profile for cartercarbaficionadoSend a Private Message to cartercarbaficionadoEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by lou_dias:

Eek! Are you saying the Fiero Store one in not a good one?

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.
IP: Logged

next newest topic | next oldest topic

All times are ET (US)

Post New Topic  Post A Reply
Hop to:

Contact Us | Back To Main Page

Advertizing on PFF | Fiero Parts Vendors
PFF Merchandise | Fiero Gallery
Real-Time Chat | Fiero Related Auctions on eBay



Copyright (c) 1999, C. Pennock