92 fox 24lb injectors - Forums at Modded Mustangs
 
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post #1 of 10 Old May 26th, 2015, 05:59 PM Thread Starter
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92 fox 24lb injectors

helping a buddy out with his 92 5.0 fox. has idle and running issues, lowest I can get the idle is 800-850rpm. and the idle stumbles. driving let of the gas it backfires to shift and then getting back on the gas backfires again. power also seems to be only be from 3-4grand and rest bogs.


here are the mods he has done.

24lb injectors
b303 cam
c&l maf cheater tube.

timing is set at 10 idle is set by the book.


From what have looked up he needs an adjustable maf and a tune to run what he has. or just go back to stock 19lb injectors to solve his problem.

or is there anything Im missing in getting it to run right


'00 Mustang 266hp 305 ft/lbs Sold
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post #2 of 10 Old May 26th, 2015, 06:18 PM
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if that's the only mods I would stick with the 19's and bump up the timing
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post #3 of 10 Old May 26th, 2015, 06:19 PM
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You can get away by just getting a 24 lb calibrated maf as most foxbody guys do but getting a custom tuned ecu for the b303 cam and 24lb injectors will give you the best driveability....

Or simply go back to the 19 lb injectors
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post #4 of 10 Old May 26th, 2015, 07:05 PM Thread Starter
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thanks for the quick replys


'00 Mustang 266hp 305 ft/lbs Sold
'14 Mustang premium with track package
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post #5 of 10 Old May 26th, 2015, 10:03 PM
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A few questions...
1. Is the exhaust stock? cats? Does it smell rich?
2. Does it idle surge or just stumble when you let off?
3. Has the tps been touched?
If so, I'd make sure the tps is set at .95v, clean the maf and iac (idle air control valve on the side of the throttle body), make sure the throttle cable isn't sticking keeping it from going back to rest position on the throttle stop screw, and last pull the battery cable for 10 minutes and let the eec relearn...
I know you said the timing is set but have you checked tdc? Pull number 1 plug and bump the engine to tdc and check to see if the rotor bug is at number one just to make sure timing hasn't jumped....
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post #6 of 10 Old May 27th, 2015, 02:24 PM
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Quote:
Originally Posted by sam03rc View Post
24lb injectors
b303 cam
c&l maf cheater tube.
Most common mistakes with C&L...
1. Incorrect sensor. It needs to be the sensor used with the stock MAF/ecu setup. It should be an 'F2VF' part number for a non-cobra ecu, IIRC.
2. Incorrect Sample Tube. It should be color coded on the aft/outlet side.

24's should work just fine with that setup, assuming the MAF matches.
Are you getting any codes?

TPS isn't going to fix anything, unless there is a code thrown for it.
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post #7 of 10 Old May 27th, 2015, 04:09 PM
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I would either do a koeo koer scan or a base idle reset/followed by a 15-20 mile drive/then run a koeo koer scan.Codes can be present without the check engine light being on & you can do the koeo koer scan without a scanner.If any codes are present,they will help you diagnose the problem. Did the problem just start out of the blue or did he install the c&l meter & injectors recently and then the problem began??If its the latter of the two,the c&l meter might be the cause as mentioned by other guys.If it began to have issues after the MAF was installed, I would swap the stock MAF & injectors back in to see if the issue stops.Its as easy as pulling the upper intake and putting the stock injectors back in place.He doesn't need 24lb injectors anyways.The 19lb injectors are good up to 304hp @ 40psi.Its most likely running rich with the 24lb injectors.

Summarized/Corrected Base Idle Reset Procedure

DIY KOEO/KOER/Cylinder Balance Self-Test Procedure

91 LX 342ci (10.5:1)
TFS 190cc (stage ll)
TFS Track Heat
Lunati 61011(.549"/.565")
Flowtech 1 3/4" Shorties
QA1 Coilovers
Weld ProStar XP'S

ISIT EVER ENUFF
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post #8 of 10 Old May 27th, 2015, 07:40 PM
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I've had TPS issues with no code on more than one car. That's why I mentioned it... since he had the intake off changing injectors it's possible to knock the TPS around and not realize it. Definitive? No. Possible? Absolutely.... He said he was surging; also can be TPS issue... more so in combo with IAC but I also mentioned cleaning it. I do agree 24lb are excessive with the current mods but since they are there, why not keep them.. the cycle/duty rate will go that low if he has everything else lined out and he keeps the fuel psi stock.
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post #9 of 10 Old May 27th, 2015, 09:41 PM
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He can check the tps to make sure its functioning correctly.

TPS Codes 23/53/63 Troubleshooting

91 LX 342ci (10.5:1)
TFS 190cc (stage ll)
TFS Track Heat
Lunati 61011(.549"/.565")
Flowtech 1 3/4" Shorties
QA1 Coilovers
Weld ProStar XP'S

ISIT EVER ENUFF
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post #10 of 10 Old May 28th, 2015, 09:12 AM
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unless there is a code for the TPS, it cannot cause surge issues. the TPS just doesn't have enough influence in the code to do that... the ecu doesn't use the tps signal that way.
Joels writeup linked to by wbrockstar (above this post), has a TPS mythology thread which will discuss this in detail.

24's won't cause the car to run rich, unless the MAF/Inj/ecu setup is mismatched.

I would leave the 24's, but confirm part numbers and color code of the sample tube in the MAF. If no color code is visible, pull it apart and measure the inlet/outlet of the sample tube.
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