problem with ported 5.3L DBW TB

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Jun 2, 2008 | 12:56 PM

#11

BlackGMC

Resident Retard

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From: Fort Worth - TX

Quote:

Originally Posted by SS_bnoon_SS

If the throttle body has been ported incorectly and there is daylight around the edge of the blade when fully closed, the MAF test will fail because to much air gets by at closed position. Get it scanned with the TB in place if you get a chance.

From my understanding it will also fail that test if your MAF is reading more air than is in calculated... I had a similar problem with my ported TB that I ported, I kinda gave up on it...

Quote:

MAF Rationality Test: This table defines the maximum difference that is allowed between the calculated airflow (using MAP) and actual measured airflow (MAF).

So if your MAF table is not calibrated correctly then you will exceed this parameters, or like SS_bnoon_SS said if you TB is not correct (like what happened to me) you will fail that test and go into REP....

Jun 3, 2008 | 06:27 PM

#12

Mack201

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I ran some more experiments and this is what I find happening.
The computer is going into the reduced engine power with the ported TB.

If I pull the intake tube after the MAF off slightly so that not all the air runs thru the MAF, the idle comes down.

I let it run this way for a few minutes and slowly attempted to put the intake tube back on completely over the next several minutes but as soon as it seals and all the air is going thru the MAF the idle goes to 2K and stays there.

Are there any tuners in the central massachusetts area on this forum that will take pity on my issue and help me out?

Jun 4, 2008 | 11:14 AM

#13

rpav

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From: Fontana, CA

what codes do you throw?

Jun 4, 2008 | 11:40 AM

#14

Mack201

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I did not plug in a code reader however the instrument panel said "reduced engine power" the check engine light was on, and the rpm's were around 2K at idle.

Pulled the intake tube off partially and the idle came down

I am guessing the MAF table is seeing too much air at idle due to the porting.