chris1234p

Hey, I was just wondering a few things. I just got a rebuilt engine about a month ago and it has ~2300 miles on it. The wastegate has been wired open and has never seen boost above maybe ~3 psi. I am currently on the stock fuel system, with new injectors but stock size cause my old ones were like destroyed.

My first problem is this, sometimes if im following a slow car going like 40 and cant pass, i will have to have my foot barely on the gas, and the car will buck and go haywire like it wants to stall untill I let off the gas or hit the gas more, there is like a certain point on the gas pedal where if i leave it there that is what happens. Now I was just browsing through some other stuff (https://www.rx7club.com/forum/showth...threadid=71651) and they said that can happen if your fuel pump has trouble switching the voltage from idle voltage to WOT. Does this sound like what is happening to my car? I have a walboro 255 on the way and I am going to install that over my long weekend. Should this fix my problem? or should rewire the walboro as explained on http://www.1300cc.com/howto/how2/rewire.htm

any help/comments would be appreciated.

chris1234p

going to class and no one has responded.... bump

Cameljoe

Try rewiring the pump first. Btw why do you have your wastegate wired open?

chris1234p

Because you arent supposed to have any boost during engine break in. I really want to close it up and get my old boost back, so im impatiently awaiting my walboro...

chris1234p

ok, i dont see why people never respond to my questions, but jump on any other question no matter how dumb it might be.

Cameljoe

Lol. The only reason I asked about the wastegate is because most people just use watch their boost guage and don't cross 0 by varing how much they push down on the gas. No need to get ticked because you went down a different road. But back to hesitation issue, you can check to see if the pump is seeing correct voltage by hooking up a voltmeter to it and going for a ride. You might want to check the TPS too. As I have a feeling the problem might be a result from both.

chris1234p

Well I have a walboro on the way, and next weekend I am going to install that, ground some stuff, and hopefully close my wastegate back down if I can find a friend with some jacks/jackstands. If that doesnt fix my hesitation then I dont know. I also heard that my home made BOV could cause a lot of problems. Anyone have any wisdom to share?

NZConvertible

It's got nothing to do with the fuel pump voltage. That doesn't change until you'll well into boost, not at light throttle.

It sounds much more like a TPS out of adjustment. The ECU turns the injectors off when the throttle is closed, and if the TPS isn't set right they turn on and off with the throttle further open than it should be, hence the lurching.

Ryde _Or_Die

What is the downlow on your ignitiom system? How old are your plugs wires? None crossed?

chris1234p

Thanks NZ, I think that may be my problem. How do you adjust/set the TPS? My wires are new 8mm, none crossed. The plugs were new 3000 miles ago, should probably replace them.

HAILERS

tps. better late than never.

Fully warm/heat the engine up. Get a digital volt meter. With the engine running at idle, fully hot, get a loooooong screwdriver and adjust the tps adjust screw until the output wire on the tps reads one volt give or take .o5 or there abouts. Access to the output wire from the tps to the ECU can be had at the ECU. The middle plug, green/red wire, top row, fourth from the right. Shove the meters positive lead in the back of the wire with the connector still on the ECU. Might have to use a piece of saftey wire to shove in the back and put your meter on that piece of wire.

Or use the two LED'S method using the green check connector.

Or use the resistance method as described in the online manual.

Or use the first method mentioned above, except.......remove the intercooler and throw it to the side. Buy some PVC tubing and elbows from Home Depot for a cost of about three bucks. Install the pvc b/t thte turbo outlet and the turbo inlet. Start the engine and let the engine get fully HOT. With the pvc in place, you now have plenty of room to access the tps connector and shove a positive lead of your digital meter in the back of the green/red wire. Put the negative lead on a good ground. Adjust the tps screw til the meter reads one volt give or take a smidge.

With the pvc in place you can now adjust those little screws that you always wondered about. Hope you can get back to square one when finished fiddeling around.

NZConvertible

Hailers, the IC bypass pipe isn't required to set the TPS, since you only need the ignition on, not the engine running.

They're a damn good idea though. It makes setting the idle screws sooo much easier.

RX7-RICE EATER

i think i had a similar problem and if it is, its related to the fuel pump, as soon as i hit about 3500 rpm the car will lean out and start bogging, as soon as my walbro 255lph pump got 12 volts, it would start failing. i tried wiring the pump directly to a 12 volt source thinking it was not getting enough voltage and my car wouldnt even start. as soon as i ripped out the pump the car was fine.
in my opinion the walbro suck's. im going to buy a real pump once i get my ems and injectors

RX7-RICE EATER

my bad, i thought you already had the walbro, have u tried testing the voltage to the pump at wot.
by the way i would perform the 12 volt rewire if your getting the walbro 255, jut my 0.02 $

ThE R

i some times have that problem too but when it happens it means im runnin out of gas(fuel gauge dont work)heheehee sorry couldnt be more helpful.

HAILERS

****Hailers, the IC bypass pipe isn't required to set the TPS, since you only need the ignition on, not the engine running.*****

Yes/no. Personal preference on my part. I find that the tps setting is more stable if the engine is fully warmed up and kept that way as the tps is set. Say a person warms the car up...turns it off.....pulls the intercooler off...then adjusts the tps. If he fiddles around too long, the thermowax will start to retract and throw the setting off a touch later when he puts everything back together and starts the engine. Not much...but some. And yes, he could just use a very long screwdriver to set the tps instead of pulling off the intercooler. I just prefer having the engine idling and fully HOT when setting the tps. Nope. Not to the fsm, I agree on that.

Anyway.....take heed of using a section of pvc to replace the intercooler when doing adjustments on the throttle body. As NZ hinted, its very helpful.

NZConvertible

Good point, but when you've done it as many times as I have, the job's done before the thermowax can even think about retracting.