Sudden idle problem after hard acceleration
 

Hello guys,

Few days ago, at night after coming back from watching Fast 6 at the cinema with my friend, i start my rx7 and it was fine, turned on the AC and everything was fine, then afterwards before arriving home, i wanted to accelerate abit, switched off the AC then GO!, after a hard acceleration of 400meters, suddenly after arriving home the car started shaking hard and the RPM went too low, below 850rpm, similar to this video on youtube:
I was really depressed, and no one knows about 13B in Oman, i have to send it to UAE-Dubai, which is 500kms away from home.

My friend said it's all about the vacuum lines, although i replaced them with silicons. I checked the vacuum lines without removing the Intake Manifold, the lines were fine, but i don't know yet because i haven't checked under the intake manifold, i also don't know how to remove it :(

Can anyone please help :(

Thanks

...sounds like a vacuum leak. Make sure lines to the map sensor are good and secure. To remove the uim (upper intake manifold), remove the intake elbow. Then disconnect the throttle position sensor, and the five bolts/nuts on the passenger side of the intake manifold. From there you should be able to lift it up enough to disconnect the temp sensor thats mounted on the bottom of the uim.

+1 for checking the map sensor vacuum hose, it's a slip fit and a poor design that always comes loose. i recommend zip tying or super gluing a silicone hose to the map sensor end.

without the map sensor line connected the ECU gives fuel for ambient atmospheric pressure, which is far too rich for idle and far too lean for boost and usually pops off after a WOT run.

Guys, i've edited the video, please see the youtube video i've edited, it's my actual car and actual problem, it seems the RPM went a bit low than usual, but not below 500RPM when the car is hot and idle.

Here's my actual problem: RX7 Engine problem (after hard acceleration) - YouTube

Notice also the ignition is weak too.

Is it really a vacuum line issue?

It could be a few thing but you won't know until you start eliminating possible causes. If you're looking for someone to tell you exactly what the problem is without diagnosing anything first you won't get it here.

Start by checking the vacuum lines
Also check your spark plugs as they could be fouled
You could also clean the throttle body and the Idle Air Control valve.

with your vacuum bouncing like that i personally would start with a compression test.

Blown apex seal , get a compression check :(

:-O are you sure?? Or you only suspect, because the car works normally while driving, but when idle it shackes.
Shouldn't smock be coming out when Apex seals are damanged?

no, there are many varying levels of apex seal damage.

and of course everyone is always in denial and makes every excuse they can to avoid taking 10 minutes to do the test.

YEP!

Hard acceleration followed by lumpy idle and paint shaker engine equals blown engine 99% of the time IF you didn't blow the hose off your map sensor which happens 99% of the time you think you blew your engine LOL.

I never check compression because I never wanna know the truth...like my bank account lol

So my engine is blown? :'(
Btw i also smell strong smell of fuel from the exhaust...

I guess i have to do a compression test!

If it's blown, then why it still runs normal and it also pulls?
Problem is only while on idle, after the car is heated up, rpm goes down to 500rpm and shakes hard.

do the compression test and you will know.

a slightly chipped seal will cause 2 low faces, sometimes as high as 65/65/100+ on a rotor that will idle like shit, accelerate off idle rather smoothly and generate boost just fine and run totally smooth above 3k.

Rebuild
 

:badrebuild:Better rebuild the engine since i don't know when was the last time it got rebuilt, probably never.

I am looking to purchase a Master Rebuild Kit from AtkinsRotary, and that will include:

Gasket Kit
2mm 13B Apex Seals
2mm 13B Apex Seal Springs
Side Seals
Side Seal Springs
2mm Solid Corner Seals
Corner Seal Springs
Oil Control Ring O-Rings
Metal Oil Control Rings
Front & Rear Main Seals
Thermal Pellet
40ml Hylomar Tube
Oil Pump Chain
Needle Thrust Bearings
Oil Filter

Options that i am going to choose:

Apex: Cryo Atkins Apex Seals
Apex size: 3mm
Corner: OEM Corner Seals and Plugs
Side: Stock

What do you think guys? :scratch:

I'd say chipped apex seal.

Hard acceleration then sudden lumpy idle is almost always blown motor, don't listen to the optimists out there. Check the map sensor hose and if still OK I'd put money on a engine issue.

Sorry to hear.. i just been through the same thing and my FD is just about back on the road ready to start the run in period.

I ran some guy off the lights, beat him by about 38 car lengths lol then next set of lights I had lumpy idle... was a chipped apex seal.

Same thing happened to one of ours. One hard run, lasting about 20 minutes, and then when the car slowed down off the highway in traffic, lumpy idle and did not want to keep idling.

PFC, Knightsports twin turbos, exhaust, etc. Injectors went 100% under high boost & full throttle, it leaned out, crackled and detonated, and that did a seal.

Was our own fault. We knew it was maxing out the injectors and running lean. We said we wouldnt drive it hard til we could upgrade the fueling. But one moment of "it'll be fine" idiocy was all it took..

**Edit. Just watched your video. That engine is definitely blown. You can hear it in the idle, and the way it starts and revs. Its a classic sick rotary sound you've got there :(

Remove the spark plug, cut the fuel and crank i. Then listen to the pulses. Bad compression is apparent by sound also.

Yeah any trained ear can hear it with a plug removed. Try the rear first, more often then not the rear goes. You should hear hard fast pulsing PTSCHH sound which all sound identicle. If you can hear difference in the sound of the pulses that aint good. Only sure way to know exactly how much compression you have is with a comp tester.

Check you idle valve ！

Okay guys... Going to rebuild the engine.

I am confused which to take, 3mm Apex seals or 2mm? and why?

Help guys.

Thanks

depends if you want to have your rotors machined to accept the 3mm apex seals.

sorry to hear about your car. i made a thread some time ago about the 2mm and 3mm apex seals. theres some good info in it..

https://www.rx7club.com/3rd-generati...-seals-993109/

I have some good 3mm rotors 450 shipped :)

I see... Thanks