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-   -   Big problem, please help (https://www.rx7club.com/2nd-generation-specific-1986-1992-17/big-problem-please-help-93022/)

Drakk0r 07-04-02 05:46 PM

I tried it with the TPS unplugged.. Starts up and idles... But it wont rev over 2500rpms.. It revs, drops, revs, drops, revs, drops.... Like I were pushing the gas and letting off very quickly...

..... Oh yeah.. and the car still hasnt seen boost.

hypntyz7 07-04-02 10:46 PM

No other TPS' to try? Yours m,ust be one that doesnt like to run w/o it...

BlackRx7 07-05-02 04:01 AM

wow thats crazy no tps, I drove with mine unplugged for about 5 miles, seemed fine but bogged out at 4k and barely idled, you might wanna try to pull the main engine fuse to cause a temp lean condition, but prolly won't help, prolly should pull all the emisions off and get rid of that stupid vaccum rail, block off the egr, bac, split air, dunno

HAILERS 07-05-02 07:11 AM

Get a fuel pressure gauge and put it in line to find out what the pressure is. Why waste time guessing?

Fuel pressure regulator bad. I doubt it. Chunk the WALDO for now.

Buy some wire taps and tap into your secondary injectors with a meter. Go driving. If the 12v does not drop significantly when you hit 3500 rpm under full throttle, then you have a ECU problem.

I doubt if its a TPS problem.

Its hard to fuck up a block off plate. Flat piece of metal with some rtv b/t it and the manifold. Leave the half dollar size check valve in place. Put some vaseline on it (check valve) so you can use it again.

If you have a blockoff plate, the split air pipe does nada. Could care less if its blocked off or not.

Chunk the WALDO and put you original pump back in til later. You need to get the pig to run first.

Did you put a orifice in the boost line?

What ECU are you using?

What boost sensor are you using. The n/a's won't cut the mustard.

Have not seen boost. Maybe the turbos bad. Maybe there is too much restriction in the exaust.

What size injectors??? Missed that answer..

Drakk0r 07-05-02 10:56 AM

Yes, I used the oriface for the boost guage line. Using the stock N/A ECU. Using a Greddy boost sensor for the guage, the car still uses the stock n/a pressure sensor. I dont think the turbo is bad... Its trying to boost.. It seems that right when I'm about to get into some boost the car stops it and runs like shit... Otherwise its fine. I can drive around fine as long as I keep a very low load on the engine and the rpms down. As far as exhaust restriction.. I dont think so.. I run a 2.5" DP, MP, to a N1 single catback.. Though I do have some exhaust leaks. And I currently have my stock 460cc injectors in until I get this figured out.. Then the 680cc's go back in.


Originally posted by HAILERS
Get a fuel pressure gauge and put it in line to find out what the pressure is. Why waste time guessing?

Fuel pressure regulator bad. I doubt it. Chunk the WALDO for now.

Buy some wire taps and tap into your secondary injectors with a meter. Go driving. If the 12v does not drop significantly when you hit 3500 rpm under full throttle, then you have a ECU problem.

I doubt if its a TPS problem.

Its hard to fuck up a block off plate. Flat piece of metal with some rtv b/t it and the manifold. Leave the half dollar size check valve in place. Put some vaseline on it (check valve) so you can use it again.

If you have a blockoff plate, the split air pipe does nada. Could care less if its blocked off or not.

Chunk the WALDO and put you original pump back in til later. You need to get the pig to run first.

Did you put a orifice in the boost line?

What ECU are you using?

What boost sensor are you using. The n/a's won't cut the mustard.

Have not seen boost. Maybe the turbos bad. Maybe there is too much restriction in the exaust.

What size injectors??? Missed that answer..


Drakk0r 07-06-02 09:58 AM

Until I get this fixed, I'm gonna keep this thread on top.. I'm gonna go buy a fuel pressure tester today.

VetteKiller 07-06-02 11:07 AM

did you try the timing suggestion? that sounded like a pretty good place to start.

Drakk0r 07-06-02 01:48 PM

Just checked the timing.... Timing is right on the mark and advances the same regardless of whether the pressure sensor is hooked up or not.

Drakk0r 07-06-02 02:14 PM

Ok... just went to go get a fuel pressure tester... $40.... forget that... I'd rather just buy a fuel pressure gauge to mount in the car to monitor at all times.

Drakk0r 07-06-02 03:06 PM

Ok.. So lets recap...

Car wont boost over 0 psi manifold pressure
Car seems to hit a fuel cut or rev limiter at either 4k or 6k rpms (depending on engine load)
When driving in first gear I tried to slowly take up the revs and it started bucking voilently at around 5k rpms
Car was running rich (suspected FPR at fault) when the fuel system was stock
Car is now running a Walbro high pressure 255lph fuel pump
Timing in spec
TPS in spec
Battery charged
Intercooler ducting checked/bypassed/then checked again
I can see the turbo blades spinning freely, and the boost gauge shows its trying to make boost

I'm leaning toward it being a fuel problem. The secondaries seem to be fine. So I think its the fuel pressure. I cant reinstall the stock pump tho as I had cut the wires for the walbro harness. I'm not quite ready to spend a lot of money on somthing thats not a sure thing, so I dont wanna try an expensive FPR and have it not work. Does anyone else have a differing opintion or does it seem to be a problem with the fuel pressure?

P.S. Thanks for all the help so far. I really appriciate it.

Aaron Cake 07-06-02 03:18 PM

There is absolutely no doubt that it is a fuel problem. It is going WAY rich at that point.

I'm thinking that it's the fuel pressure regulator. Perhaps your stock one is not working correctly? Have you tried electronically turning down the fuel (noticed you have an HKS controller)?

HAILERS 07-06-02 05:10 PM

I think your use of the n/a boost sensor is the culprit if not one of the culprits. I'm real tempted to put my na sensor in my turbo to prove it. Probably won't.

I may be way off base here, but a n/a is looking at vacuum and atmospheric pressure. The turbo is looking for vacuum and boost pressure.

Thats not clear is it. How about the n/a car never sees boost pressure does it? Now its seeing what???? Boost pressure. Does not seem right to me. The ECU has to be confused. In my pea brain thats the way I see it.
Just a thought anyway. That coupled with a Waldo that is over whelming the fuel pressure regulator.

Just guesses. Nothing else.

Drakk0r 07-06-02 05:16 PM

I think I'm gonna have to agree with HAILERS here... I just took the turbo outta the intake system and vented it to atmosphere and ran the car NA (with a turbo in the exhaust but not in the intake system) and it revs freely to 8k+ easy like it use to and the turbo blows a fuckload of air and blew the venting duct around. :) So its a problem once I start hitting boost. I just dont get what it could be. The pressure sensor only controls timing right? Well I've tried it with and without the pressure sensor hooked up and get the same results. Must not be the fuel system as it runs fine without the turbo hooked up. In light of new info, anyone have any new thoughts?

Drakk0r 07-06-02 05:19 PM

Another thought... Are the TII and N/A MAF sensors the same? Could mine be topping out? Also... When I was running it N/A, bypassing the turbo... When I revved it up, it hits 0 manifold pressure just like it does when I have the turbo hooked up... Cept when its run N/A it runs fine.

Drakk0r 07-06-02 06:51 PM

Ok... Maybe I was wrong.. I just drove it as an N/A (with the turbo bypassed) and it wont rev higher than 6k when under load.. Like its misfireing. And it makes no power at all over 4k rpms. I think I'll bite the bullet and buy a new FPR.... Now its only a matter of whether I should get a stock replacment, or upgrade my fuel system with an SX adjustable and run my fuel rails in parellel. If its not the FPR...... Well.... I'm gonna cry...

relvinnian 07-07-02 02:50 AM

Get your ass over to my place and pick up my pressure sensor. Try it. Then buy a fuel pressure guage or ask on Cols racing. Remember with FPRs, the regulator that wants THE MOST pressure wins. If your stock one is creating too much fuel pressure, an aftermarket one won't work.

Drakk0r 07-11-02 04:52 PM

Today I installed a new stock FPR(well, used, but working), a TII TPS, and a TII pressure sensor. With all that, it runs much nicer and revs freely to 7k in neutral. So I took it for a drive.... Same fucking thing... As soon as I'm about to pass 0 manifold pressure the car wont rev any higher. I'm starting to run out of ideas here...


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