89 5.0 ( 306ci ) surging , dieing, backfiring

[RedNBlack84Hatch]

Its got a 306, B cam, Cobra upper and lower intakes, 70MM BBK Throttle Body, 24lb injectors with i believe a 73MM mass air sensor. It has stock milled heads on it. Smog pump delete.
Car drives fine untill u let off the gas in gear and eventually sends a huge backfire out, also surging from 200-300 rpm up to 1200 or so and will even itself back out or die out on a surge, has holley adjustable reg.
Any ideas where to start looking ... pulling plugs friday morning hoping they tell me something, no appearent vaccum leaks anywhere... appreciate the input..

[Chas_svo]

What have you recently changed?

[RedNBlack84Hatch]

Nothing , starting to think blown gasket, possibly intake.

[CJ]

You said 73mm.. Is that a piece of shit C&L MAF? With the calibration tubes? If that is a C&L maf that's definitely your problem, they never work right. Does it run perfectly fine at WOT?

[RedNBlack84Hatch]

Its just the C&L housing , stock sensor, and ya runs fine at least half throttle havent gone wide open because of how its been running

[petyweestraw]

You try pissing on it?

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[91CoupeMike]

Its just the C&L housing , stock sensor, and ya runs fine at least half throttle havent gone wide open because of how its been running

Those arent that awesome, takes a lot if work to get them right. If you have stock injectors throw a stock maf housing on it and see if it runs better. From there get a pro m, unless you want a tune. If you want a tune then use the lightning maf. Or you can unplug the maf and see if the idle clears up.

But, a maf shouldn't cause a surging idle, that's more of a TPS, IACV or vacuum leak.

What's your fuel pressure set too?

[Spector93]

I have two c&l mass air meters 73mm and 76mm both have been great meters.

[RedNBlack84Hatch]

Forgot to mention when the car started surging for the first time, it would clear itselfs out and idle normal now as soon as I engaged the clutch starts to surge and will die out , possibilty of the idle controller being bad then? Car is on 24#ers not stock injectors as well
Edit - not sure on the fuel pressure

[CJ]

I have two c&l mass air meters 73mm and 76mm both have been great meters.

I've had two of them and they gave me similar problems to what he is describing, neither of them worked. I had someone call me with a similar problem a few months ago, told them to change out that C&L and it solved his problem also.

[sspstang]

If you weren't so far away, I would let you try my good 76mm maf. Im putting my money on a bad maf.

[CJ]

If you weren't so far away, I would let you try my good 76mm maf. Im putting my money on a bad maf.

x2, it's that C&L. And for the OP's reference all C&L's used the stock sensor, that's half the reason they never work right.

[sspstang]

x2, it's that C&L. And for the OP's reference all C&L's used the stock sensor, that's half the reason they never work right.

Exactly, my thoughts. I have a old Pro M on my car, and that is pretty much, all I have ever ran. They have never given me any issues.

[CJ]

Exactly, my thoughts. I have a old Pro M on my car, and that is pretty much, all I have ever ran. They have never given me any issues.

I also switched both of my cars out to ProM meters and never had another issue.

[sspstang]

I also switched both of my cars out to ProM meters and never had another issue.

Isn't it amazing how that works. C&L was always more expensive too.