surging under acceleration

[tatersalad]

351w EFI has just started surging while accelerating hard, my first thought is clogged fuel filter... Only does it while accelerating any thoughts on this? Also if it is the filter what is the procedure for replacing an efi fuel filter that is pressurized? never done it.. The filter is the one that came with my BC deluxe fuel rails

 

[EFI Guy]

Do those rails come with a test port?

I suppose it could be the filter if you aren't having any other issues. The easiest way to test would be to attach a fuel pressure gauge to the test port and see if your fuel pressure is dropping when you get the surge. Most gauges come with a pressure release button.

To relieve the pressure disconnect the battery and press the schrader valve in on the test port, use a rag or something to shield you from the spray.

 

[tatersalad]

the BC kit came with a fuel pressure gauge, I will pop the hood and see if I can replicate the issue while not moving

 

[tatersalad]

Okay, I ran a KOER and came up with the following codes 12, 94, 44, 33 and cylinder 8....

 

[tatersalad]

the rim harness instructions said I would have some codes, but what do you guys think is happening?

 

[Viperwolf1]

33, 44 and 94 are codes that are related to air injection and EGR. Don't worry about those if you don't have those devices installed. Code 12 is related to the IAC. You may have a problem with the IAC but I don't see it affecting accelleration. It may be gummed up inside. Fuel and ignition are the things to look at.

Did you get an 8 code after a cylinder balance test? That would indicate #8 is not contributing equally. Check spark plug.

 

[tatersalad]

Thanks Viperwolf, I will look at that plug and I am going to change out the filter also as a precuation as it was a new tank and the aux. tank could have had some debri being that its original

 

[tatersalad]

so i finally had a chance to work on this. I pulled the #8 plug and it looked like it was burning hot, pulled the fuel filter and it was fine. I pulled the tfi and it looked new still, pulled the distibuter cap and cleaned it and the rotor, the rotor had some carbon build up, put it all back together, pulled the spout connector and reset the timing to 10 btdc. Now that I backed off the timing it is really running like sh#t, hiccuping
and idling rough. I was following another thread last week with similar issues which is why I checked the tfi, any suggestions?

 

[tatersalad]

oh yeah the timing was at 16 btdc prior to the issues and ran fine for about a year and a half. the maf that is being used is f12f-12b579-aa if that helps. The motor is stock but was bored .10 over

 

[Viperwolf1]

I don't recognize that MAF sensor which is probably a bad thing. What computer and injectors are you using? Did you look at fuel pressure?

 

[Aso544]

Had a similar issue with my full size bronco with a351. I chased it for months and it ended up being a hair line crack in a spark plug. I only found it when I put it in a jet black dark garage and left it running and could then see it barely arcing off the block. Not all cracks in plugs are clearly seen by the naked eye. I was convinced it was fuel related..... I changed filter, tested fuel pressure, tested the throttle position sensor, even rebuilt all the injectors.

 

[EFI Guy]

oh yeah the timing was at 16 btdc prior to the issues and ran fine for about a year and a half. the maf that is being used is f12f-12b579-aa if that helps. The motor is stock but was bored .10 over

Are you sure it's not F1ZF ?? Is it still in a stock 55mm housing?

 

[tatersalad]

I don't recognize that MAF sensor which is probably a bad thing. What computer and injectors are you using? Did you look at fuel pressure?

I am running an A9s comp with RJM harness, 19 lb injectors (orange), fuel pressure stays around 35 lbs at idle and after I rechecked the MAF with my reading glasses on the third letter was a Z and not a 2..

 

[tatersalad]

Are you sure it's not F1ZF ?? Is it still in a stock 55mm housing?

yes it was a Z, and the housing is 55mm as far as I know.

 

[tatersalad]

What I do know is that I have an exhuast tick coming from around cylinder #5 at the header, I have replaced that gasket twice but it keeps burning out the gasket. I ordered the stage 8 header gaskets, locking fasteners and wire boots from Wild Horses last night to finally fix that issue once and for all hopefully. I also ordered their Bronco script valve covers as the mustang ones I was utilizing didn't have a spot for a PVC valve, so that will address that issue too. The #8 plug that I pulled seemed to be burning hot as in a lean condition. The plugs, wires, cap, rotor, coil, TFI and TPS all have about 5K miles or less on them. The injectors were cleaned and o rings replaced, the MAF is used as is the throttle body.

 

[Viperwolf1]

I assume this is with the truck lower intake and probably BC adapter/car upper? Otherwise you would have a PCV hole at the rear of the lower intake. Lots of potential places for a vacuum leak with that setup.

 

[tatersalad]

I assume this is with the truck lower intake and probably BC adapter/car upper? Otherwise you would have a PCV hole at the rear of the lower intake. Lots of potential places for a vacuum leak with that setup.

that is correct

 

[tatersalad]

So, I guess that I will get out a can of WD and start trying to find a vacuum leak. It might be the vacuum line to the C4 as it sometimes wants to start out in 2nd gear.

 

[Viperwolf1]

It might be the vacuum line to the C4 as it sometimes wants to start out in 2nd gear.

Not likely. Loss of vacuum there would make it want to stay in a lower gear. More likely a problem with the governor.

 

[tatersalad]

Hey Viperwolf1, I moved the timing back to the spot that my engine builder had marked on the dampner and it started running good again. I didn't drive it but it sound good. i think that my engine builder might of remarked the timing marks for some reason. Yhanks for all the help dude, maybe someday I can return the favor.