Intermitent hesitation

[luckynumberseven]

Hi Guys,
I have a fd3s rx7 it\'s got a knightsport ecu,decated nur spec cat back,intercooler hard pipes,plus a c.a.i.
The car is acting weird it starts perfectly first turn on the key no matter if it is hot or cold,it doesn\'t stall when accelerating but on occasions it will hesitate badly when it starts to boost, the symtoms are it stutters when i put any power on but it doesn\'t do it all the time and it isn\'t temperature related,i can press the accelerator pedal down when it is hesitating and it will pull through and seem to want to pull above 3000rpm and it does pull much better,although not as good as when itdoesn\'t hesitate then it is brilliant.
This has me miffed i have looked at threads on hesitation and i thought that mine sounded similar to someone who had an intermitent problem which turned out to be the fuel pump wireing not getting the correct voltage so today i cut the blue wire to the circuit relay and gave it a new feed straight from the battery, but that hasn\'t helped.
I\'ve replaced the H.T leads pip has put new race plugs in and something else pip did was put a vaac line from the upper inlet manifold to the fpr bypassing the pressure regulator solenoid pip done some misfire runs and it did hesitate he replaced the plugs for the race ones and put some fuel in it.
A few days later when i went to put more fuel in the hesitation came back.I have no idea what is causing this i have ordered a new supra pump.my ecu is a knightsport which is mapped for 1.1bar i put the ecu on because i thought it was that what was causing the hesitation but it wasn\'tthe knightsports ecu has exagerated the problem when it happens now it is more obvious when it happened with the standard ecu it wasn\'t as noticable but i still felt it.
Could it be my fel pump?

[luckynumberseven]

Anyone shed a little light on what i can do next? i want to eiminate things so that pip will know what i\'ve tried.

[cyman]

well it sounds like fuel or spark so the basics would be. fueling: fuel blockage (when was the filter last changed? ) knackered injector not allowing correct fuel levels through (you can take them out get them checked and cleaned if needed) fuel pressure issue frp letting pressure drop to much (although if pip has sorted that i would geuss he put a pressure gauge in the sytem to check for drop off) fuel pump relay (not switching or when it does giving weak voltage) i know you said you put a new cable in but did you actually check voltage drop off after the relay or at the pump?
electrical: leads breaking down, coil pack on its way causing weak spark, positive feed to the coil packs faulty, how are your earths main engine/battery any individual earths for components (use an ohm meter to check resistance) if earths are bad this can cause all sorts of issues.
 
i know these arent very specific but these would be the basic checks i would do to try and fault find this prob.
 
hope this helps
 
si

[pdtaylor18]

As stated above you need to do the basics, check all earths with a fluke and then start checking a few of the sensors.  Just because there are brand new plugs in here dont take that for granted its not them. I have had faulty new NGK plugs before, spent days swopping stuff over and in the end changed the plugs for a new set and hey presto it all worked.
In your case you need to see whats common beween both the ECU\'s, why is the Knightsports making it worse than a standard ECU? could well be an injector if the mapping is totally different but until you start testing the individual items you may never know.

[luckynumberseven]

Has anyone else got any input,i also notice when driving it hard on wot in any gear when i let out the throttle partly not all the way i can feel the hesitation comeing back then if i open the throttle it again clears.
I\'ve replaced the fuel filter about a month ago,my idle is at 1000rpm and it drops to 750 when at a stop light.
I would like itif i could swap out the 02 sensor then the coolant temp sensor then the tps sensor the cas sensor just to illiminate this problem but that would be to expensive,are the sensors easy to check?
I only have a basic knoledge and a volt meter. i know how to test the tps.
It would be good if i knew someone whom i could swap parts untill i fixed my problem.

[neil_jdmr]

Since your in manchester, is it not worth just whipping it round to pip\'s.He\'ll prolly have it fixed in 20mins

[cyman]

after reading your response to the fault finding i think your best bet is to let pip fault find for you. if u are unable to test things yourself and would only swap things out and replace bits one at a time will it wont work out any cheaper for u. better to let someone with a bit more knowledge track it down. better to pay a couple of hours labour and replace one item than replace 5 trying to rule things out

[luckynumberseven]

Today i got my supra pump the number on the pump is 195130-1270 i got it of e bay it is srposed to be a revised version of the 195130-1020 so i was pleased,i have fitted it and it was a perfec fit upon dissasembling the old pump and wiring i couldn\'t fail to notice the thinness of the wire going from the pump v+ v- how punny they look and the worrying thing is the plastic connecter on one of the pins had melted the plastic and turned back and the spade was barely gripping, the plastic connector was also black there must of been high resistance causing some low flow issues.
I did the best icould cleaning the wire i closed the lugs and reattached the wire.
As far as i can tell the hesitation is gon i only driven it 5miles so i have yet to test it some more but the throttle responce is much better there was no hesitation,
I think now i should off done a more certain fix on the wires inside the tank,i think i will cut them 2 pump wires of that connecter and remel 2 hole and put 10 guage wires through.
I think the high resistane off the wire may of damaged the original pump.

[MaLicE]

alot of people re do the wireing with thicker gauge wire and wire it directly to the battery with a relay as the stock wireing is thin and varies the voltage to the pump....

[luckynumberseven]

I have heard that people doing it that way and it was a good way but my battery is in the standard place so i just took the most direct way to the circuit relay.
I may do ththe resistor bypass cut the blue/red wire and run it to the v+.
I am going to ponder the options and take a drive to halfords to buy wiring ad ring connectors.
I am not going to say it is fixed yet untill i have a longer drive but i am going to find out and then i can pat myself on the back for making my first correct diagnosis.