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Discussion Starter · #1 ·
The problem:
• The car stumbles under load in all gears, bucks and pops if you give it more throttle. It idols “ok” not great, but under load it stumbles and even back fires/bucks.

The setup:
• EFI 302, AFR 165 Heads, TFS Track Heat intake, 30lbs Ford MS injectors, 76mm C&L (30lbs cal tube) stock mass air sensor, 40lbs fuel pressure, Acufab 75mm TB, CompCams XE274HR roller cam (specs http://www.compcams.com/Technical/Search/CamDetails.asp?PartNumber=35-518-8) , base timing @13 degrees, stock distributor and ignition (new TFI), MSD coil (6AL needs to be replaced!), 4 into 4 headers, O2 sensors in tubes 1 and 8, heat range 24 (one lower than stock due to the heads) plugs.

I have searched the forum for this kind of problem and they mostly point to spark. I think the spark is there, but what I am missing is the magic air/fuel bullet. I will be installing a Tweecer RT this weekend to try and get into the Ford A9L computer and see what is going on in the air and fuel department.

Any words of wisdom???
 

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Do a forum search for C&L. The symptoms you are describing sound very much like what others have experienced with C&L meters. If you can borrow a Pro/M, that would be a cheap way to troubleshoot.
 

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If you can borrow a Pro-M meter to rule out the C&L that would be a good first step. The symptoms you describe sound a little much to just be the C&L but it could be.

On the subject of mass air meters. There are a few things that can affect the C&L style meter where the air is metered just on one side of the opening. This is not unique to the C&L the Pro-M bullet is also sensitive. Depending on how you have your air intake set up you may be getting uneven or turbulent airflow through the meter. Sometimes just rotating the meter to move the metering tube around in the air stream will improve things. Ideally the meter needs at least a few inches of straight tubing before and after the meter to allow the air flow to become even and consistent. I had a problem in my Mustang with fan wash causing all kinds of erratic behavior. A simple sheet metal 'shield' solved the problem.
 

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I think a Holley will solve your problems.....and possibly give you some new ones!

Ahhh...memories of EFI hell.

Did you put the spout connector back in after you set the base timing?

Did you pull it when you set the base timing?

Sounds like a lean stumble to me. I would check all your clamps on your mass air tubing. I would check all your bolts on your lower intake manifold. Re-torque them all.

Check your TPS voltage KOEO ( Key On Engine Off ) and make sure it's .998 or something close to it. While taking the reading on your DVM, try moving the throttle and see if the voltage from the TPS jumps suddenly, or alternately doesn't seem to increase in a linear fashion.

Did your car EVER run well? You may have a wiring issue with one of the wires in the harness. I had to ground one of my wires in order for the EEC to see signals from my any of my sensors. I can't recall which one it was however. I think it was white with a black stripe, but don't quote me on that one. Maybe somebody else here can help.

WADE?
 
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