This is topic Surging on startup in forum Tech Talk at Northern California Ford Owners .
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Posted by stangin' (Member # 514) on
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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.
Posted by Fostang (Member # 3752) on
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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.
Posted by 70stang351w (Member # 9948) on
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What's a standard HCI setup? just wondering
Posted by SacStangDriver (Member # 8304) on
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tuning it will get rid of the surging issue. its common on HCI
Posted by stangin' (Member # 514) on
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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?
Posted by Fostang (Member # 3752) on
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Not in the bay but Nate I hold in high regard.
https://starkweatherperformance.com
Posted by phildog (Member # 1214) on
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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.
Posted by stangin' (Member # 514) on
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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.
Posted by stangin' (Member # 514) on
:
quote:
Originally posted by Fostang:
Not in the bay but Nate I hold in high regard.
https://starkweatherperformance.com
Thanks, we'll check them out for sure.
Posted by LXjames (Member # 10791) on
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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
Posted by 92_5.0 (Member # 7624) on
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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.
Posted by kuku93 (Member # 14014) on
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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
Posted by ed650 (Member # 9897) on
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24s too small for a 347 you need at least 36s
Posted by Martinna (Member # 12493) on
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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.
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