Gas converted, flat spots

[jeffro ra28]

Heya toymodders.

First off im no EFI junkie as you will probly soon find out and i have done a fair bit of searching on the subject to rectify the problem. No luck
Oh and its regarding a Ford motor....eeeek.... Its actually my dads delivery van.


2.3L ford transit van which has been converted to gas. Running on petrol the engine runs fine however when running on gas there is a major flat spot between 3200 and 3600 rpms.

We found a fractured air box that stopped the air filter from sealing properly, i rectified this problem and the flat spot was reduced substantially. Then a K & N pod filter (please no tryhard ricer comments here) was installed in hope to solve the problem completely. Once installed, the flat spot returned.

We have contacted Sprint Gas (the conversion company) and they said that the gas paremeters need to be changed. The mechanic that did the conversion has the correct software to do this but cannot get any sense from the computer. (I am working on reformatting his computer and re-installing the software).

To do this by the books i know we should be using the program to find the problem. But from the symptoms above can anyone suggest where the problem may be in the system?

I was thinking maybe an air flow meter judging from the weird behaviour we got from mucking around with air filters, but then it works fine on petrol???

Or perhaps, the hot air entering the air box when it was cracked? and maybe this would effect gas mixture more then a petrol mixture which would explain why it ran ok on petrol? The POD filter was just a quicky installation but from my point of veiw should still have a fresh draw of air from the front of the car. However it is possible that some hot engine bay air is still going through.


Thanks in advance for help and suggestions

[mrshin]

Where abouts is the gas mixer located?

[stradlater]

I'd be going with one of two things on that 1..

A) Going the old method (no computer) there may be a vacuum balance line of some sort located near or around the air box that has something to do with the air flow to the converters. To begin with, check that all those are sealed. My thoughts are that that may be leaking some air and subsequently causing the mixer to flow the wrong amount of gas.

B) Obviously the gas computer is a seperate computer from the EFI computer (unless it's one of these new dual fuel fords). Therefore, it will handle the inputs from sensors like AFM, TPS or namely the Air temp sensor, which resides sometimes in the air box, differently from the EFI computer. That would explain why the two act differently. To begin with, check that your not messing with any of the electricals around there..

I know it's not entirely related, BUT, in my car (BMW 318) when I pulled the air filter and air box off I also had to dis connect the air temp sensor to put a POD on it.. The thing ran like complete shit because it didn't have the air temp sensor and was running in crap mode to protect itself (It was assuming that the air temp was very hot). Check that one out..

But, ofcourse, get the ECU checked out, maybe it's throwing codes that you can use?

My 2c.. I'd be interested to know what your result is though.

[mrshin]

Hmmm, maybe a photo of the setup would be useful