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Author
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Topic: Surging on startup
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stangin'
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Member # 514
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posted
 
 
I'm working on my friend's '93 Notch that has a bad surging issue that I can't seem to cure.
It has a stroker 347 with your standard HCI setup. The surging would only happen right after start up, cold or hot. It would jump to 1500, 2000, 2500, and finally idle like normal after about 30-40 seconds. It could idle for 10-15min with no issues at a sweet 800rpm. As soon as you shut it down and start it back up, it would go through the same routine. There is a check engine light for DTC 91 and 41.
I did the idle reset, cleaned the IAC, replaced the ECT sensor, cleaned the maf sensor, and checked for vacuum leaks.
I notice that the MAF sensor was a Ford unit mated to a C&L 73mm housing. I also noticed the blue top injectors which are 24lbers. I figured maybe the previous owner had a mismatched setup which was causing the surge.
I was able to located a Pro-M 80mm maf setup for 24lb injectors. Switching to this new maf only made things worst. I'm open to any suggestions.
Posts: 2993 | From: Bay Area | Registered: Oct 2001
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Fostang
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Member # 3752
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posted
Get it dyno tuned with the proM.
Your MaF transfer functions are out of wack.
You may mask it clocking the maf in various ways and making sure you don't have an open filter element.
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67' Fastback TT 408
67' Camaro Lsx
64' Corvette Fuelie
57' Chevy Bel Air Lsx
68’ Pony Convertible
66’ Pony Coupe
Posts: 3012 | From: Stockton/Danville | Registered: Nov 2003
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70stang351w
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Member # 9948
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posted
What's a standard HCI setup? just wondering
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1996 GT VERT /32v MOD - SOLD
1970 Mustang Coupe M-Code 351w
Posts: 1419 | From: 925 | Registered: Apr 2010
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SacStangDriver
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Member # 8304
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posted
tuning it will get rid of the surging issue. its common on HCI
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Need sidework done at great prices? I work on all makes and models from engine work to gears. Check engine light problems too. 916 912 3493
Posts: 1217 | From: sacramento | Registered: Mar 2008
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stangin'
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Member # 514
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posted
The HCI consist of the TFS top end kit with their stage 1 cam.
It's currently running a BBK fenderwell CAI with the C&L unit. The Pro-m 80mm unit has the huge filter which doesn't mate very well with the BBK elbow.
I tried clocking the MAF today and it only made things worst so I left it back with the sensor directly on top.
Do you guys have a recommended tuner in the Bay Area?
Posts: 2993 | From: Bay Area | Registered: Oct 2001
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Fostang
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Member # 3752
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posted
Not in the bay but Nate I hold in high regard.
https://starkweatherperformance.com
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67' Fastback TT 408
67' Camaro Lsx
64' Corvette Fuelie
57' Chevy Bel Air Lsx
68’ Pony Convertible
66’ Pony Coupe
Posts: 3012 | From: Stockton/Danville | Registered: Nov 2003
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phildog
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Member # 1214
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posted
Maybe try one of the idle air control adjustment plates, that go in between the IAC and the throttle body. It's a Ford product designed to solve idle issues. Last time I checked it cost about $50.
The IAC itself may be sticking as well.
Posts: 1554 | From: 510 | Registered: Apr 2002
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stangin'
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Member # 514
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posted
quote:
Originally posted by phildog:
Maybe try one of the idle air control adjustment plates, that go in between the IAC and the throttle body. It's a Ford product designed to solve idle issues. Last time I checked it cost about $50.
The IAC itself may be sticking as well.
I think that the IAC is functioning properly b/c when I disconnect it, the idle drops low and once plugged in it idles great. I believe the previous owner replaced it b/c the unit itself looks very new.
Posts: 2993 | From: Bay Area | Registered: Oct 2001
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LXjames
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Member # 10791
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If your running the cai with no fender portion I've heard c&l mafs don't like being filter mounted for some reason
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On Point Motorsport prez.
King Lx
Posts: 4761 | From: Pittsburg CA | Registered: Mar 2011
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92_5.0
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Member # 7624
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posted
The ford unit is fine to use with the C&L housing as long as the sample tube inside the C&L is calibrated for the injectors. I have used that same 73mm in the past with 42 lb injectors and had no issues.
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Infineon/Sears point? same difference!
11.8 @ 115 mph @ Sac Raceway
411 rwhp 402 trq (old set up)
540 rwhp 517 rwtrq (new set up)
ET's to come
Posts: 1629 | From: bay area | Registered: May 2007
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kuku93
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Member # 14014
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posted
The injectors could be the issue. I was told with a 347 stroker not to use 24lbs but to use 42lbs. Try switching them up
Posts: 154 | Registered: Apr 2015
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ed650
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Member # 9897
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24s too small for a 347 you need at least 36s
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410w Hatch
306Ci Coupe
Posts: 1744 | From: menlo park | Registered: Apr 2010
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Martinna
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Member # 12493
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posted
On modified EEC-IV motors it's common for the lower end of the MAF curve to need adjustment. 24 lbs injectors will support 325-350 flywheel HP on a NA motor. 30lbs injectors 400-450 flywheel. 36lbs 500 to 550HP flywheel. The EEC needs to be calibrated to spray less fuel during cranking when using larger injectors. When too much fuel gets sprayed when cranking, it can cause a big RPM surge on fireup that can cause an over correction and surging.
Posts: 1093 | From: City | Registered: Oct 2012
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