So I have a 92jdm mostly stock, I hace hks cai, cat back, and relocated battery. So I have searched for 2 days now and in still lost. Here is my problem..I can drive my car but as soon as I hit boost it cuts out and back fires. When I first start my car up I can rev it all the way up and Im getting full boost. But as soon as I drive my boost cuts out and I can only rev it to 4800-5000rpm. Also when I have it in gear (clutch in) my idle jumps around 100-200rpm. I've tried reseting my ecu and the same thing keeps happening. I've cleaned all my grounds and i have my battery grounded to my shock tower. And I grounded the stock batter lead to the abs frame to the body. So I'm pretty sure my grounds are good. I just changed my plugs about 20 mins ago and it runs smoother but still the same problems I may be able to get 0.1 bar of bost beforenit cuts out. I also can hear my turbo spool up. My boost gauge shows vaccum at an idle its just under 500mm/Hg where it always has been. In gear with clutch in my vacuum goes from 400-300mm/Hg back and forth but as soon as I take it out of gear its fine

 

Also my vacuum settles down to normal when I turn all of the lights off then fan off. It only goes wonky with my heater on and or my head lights also my vacuum lines have been replaced

 

Anyone? My car is my daily driver and where I live its all hills! Need help pleade

 

sounds like you'll be fine as long you dont hit boost. just stay out of boost since thats the only time you have a problem....

 

If your seeing ANY boost, you're not in limp mode. In limp mode, if vacuum is NOT seen at the intake manifold, fuel is cut and timing is retarded...or maybe more accurately, it's not advanced. That means positive pressure (boost) would be impossible. In limp you can rev the engine all day long, as long as you do it slowly and keep some vacuum.

 

Hm well I just drove my car across town and I can't get any boost it just cuts out and shudders and I have to let off the gas, its hard to drive up steep hills with no boost. When I hit my battert breaker off then click it back on I can fire it up and get full boost (not moving) and as soon as I try to move the car I can't get boost, its odd cuz its running awesome and sounds good but then I drive away and its terrible boost wise

 

I hope not. I got an extra set but I want to sell them so I can get enough money for a pfc. How can I check them with out yanking it out? I read that a bad omp can cause this or a bad coil

 

Free-revving it while stationary isnt going to tell you anything conclusive. Under *load* you are having problems. Free revving it in a no-load condition (such as in neutral) is not the same as driving it.

Also, dont keep driving it, looking to see how much boost you can get out of it before it begins backfiring/breaking up. Thats a good way to break something.

If its mostly stock, try seeing what codes its throwing, although re-reading your description of the car, its a JDM, which means that may be harder/different to accomplish compared to the How-To's about code reading in these forums (which are mostly related to USDM cars)
If you had a PFC, I would have said look at the sensor check area and see if any monitored sensors are a problem...

I doubt its a "broken turbo" issue. You say you can make some amount of boost at idle under no load. Thats accomplished by the primary turbo, so we know its working/spinning over at least.

With normal twins (not non-sequential modded) you should see boost before 4800rpm easily, on the primary turbo. The secondary turbo spools and begins to come online around the 4500rpm mark.

Check the fuel pump is ok. These cars richen the AFR as they come into boost on the stock ECU. Maybe your fuel pump is dying, and is able to only supply enough fuel for light load driving, but cant keep up once under boost?
Time to get in there and have a good look around

 

It sounds like its not getting fuel, I got a new fuel filter coming in tomorrow so ill try that and then I'm going to get a new fuel pump if its still doing it. I also forgot to mention that a few days ago I drove it out of my garage and it was all fine then I parked it in my garage and put my new batrery in a few days later then boom problem central, i thought it could be a ground issue because i just did my battery relocate so I went over it 100times moving grounds and cleaning them and adding ground checking my positive, rerouting it and then I checked vacuum lines and made sure everything was plugged in and then changed plugs, and then repeated it all over agin minus the plugs. Its driving me nuts

 

Yes, you're in Limp Mode.

 

I wonder how I got in limp mode

 

Since you have all that awesome JDM goodness but don't have a CEL, do this ---> https://www.rx7club.com/3rd-gen-arch...ut-ecl-238994/
Then check it against this ---> Check Engine Light Codes

My first suspect(s) will be one of the three codes related to the OMP.

 

So I found a huge fuel leal coming from the top of my engine so I'm thinking that could be why I'm not able to boost at all because of to low of fuel pressure. The top of my engine is soaked!!

 

If thats the case, DONT DRIVE IT anymore until you can find & fix the leak. Its a huge fire hazard, and you're lucky something didnt go wrong while you drove it across town..!

If its across the top of the engine, look at the group of three hoses that connect to the rats nest, on the oil filter side of the engine. They are main fuel feed, breather and recirculation of fuel back to the tank. Double check those are all secure and not weeping.

From that point, the hoses turn into hard steel lines that snake across the top of the engine (under the intake manifold and rats nest) to the two fuel rails, which are located roughly underneath the joint between the UIM and the LIM. Check the rails and injectors and fuel pulsation damper (round thing on the end of the rail) for leaks.

You shouldnt have to start it to find the leak. With engine cold, simply turn ignition on, and the fuel pump should pressurize the lines, revealing the leak. Wear safety glasses, because fuel in the eyes bloody hurts (dont ask me how I know this)
And have a fire extinguisher on hand just to be safe, and the wife/GF/someone aware of what you're up to.

Good luck!

 

Well I've fully torn into it now and it looks like my o ring on my fuel rail has sprung a leak so I'm taking this time to re do my fuel lines all of them and all of my orings, and doing a simplified sequential at the same time. Its kinda good it happened cuz ibcan fix everything now that I've been wanting to do. Yeah I'm pretty happy it didn't catch fire because ib had my son with me!!!!! It only seemed tob leak when it was in higher rpm no leak at idle and it wasn't has huge as I thought but a leakb isb still bad no matter how small or big. Ill take some pics in the am when my buddy come over (fellow forum member) and it should be all done tomorrow

 

That might be because the fuel pump ramps up pressure as the rpm/boost rises (richens the AFR) which could explain a few of the symptoms.

Glad you got it sorted with no fire

 

The scary thing is when I parked my car in the garage my house reeked of gas and my engine was hot so I'm glad itn didnt burn dow my house. But that's all going to be fixed today