For a while now i've been getting this hesitation and black smoke just after warm up..the car starts to shake and puffs of black smoke would come out...that was the normal stuff i was getting....so this weekend i didnt really use the car...this morning i go start it up...let it warm up...the black smoke came back...so i decide to let it run until it clears itself out...after about 5 mins and the same stuff going on, i attempt to rev it out a bit...the throttle is very staggered and when it revs pasted about 3500 rmps...massive amounts of black smoke came out...really thick clouds of this stuff...now a while back i noticed brown stuff in my coolant...maybe this is the cause?...any suggestions....engine check light has come on reading thermosensor,o2,and egr valve...ive ordered all but the egr..waiting for those but in the meanwhile i would appreciate anyones thoughts... my car has a racing beat downpipe and catback,gutted midpipe,flyuidine radiator,racing beat wires,stock ngk leading and trailing plugs,and ast....please help guys....thank you

 

well, full open exhaust and no computer can lead to a blown motor. Before you jump to this conclusion, check to see if your MAP sensor is unplugged. It is located (i think, someone chime in here and back me up or tell him where it is), i think, by the firewall. It should have a vacuum line running to it.

 

will do thanks..ill let you know

 

Black smoke is too much fuel. Smell your oil, it's probably diluted with gas. MAP (boost) sensor is located on the firewall near the brake booster. One vac line.
I know a bad IAT will cause your symptoms but IIRC cleared up a little on warm up when mine went bad. If ignored too long though, I'm guessing it could also cause an O2 sensor to go bad as well.

 

ok i checked the map sensor and it's all in tact...but im sorry i dont know all the Abbreviations..IAT and IIRC...you see, i know a little about the rotary engine but not all...my cousin does most of the work...he knows it all...i love the thrill of the ride and i want to be able to work on everything myslef...but it takes time and experience..i've owned this 94 for almost a year now...i know it gets a little annoying when dealing with newbies but please be patient with me..im trying to get ideas of what to look into with my cousin....thanks guys!

 

IAT=Intake Air Thermosensor
I assumed when you mentioned "thermosensor" in your first post, that's what you meant, and it fits your symtoms. If you pulled the codes from the check engine light (CEL) it would be a code '11'.

 

ahhhhhh....thanks...i ordered those sensors...maybe the sensor is causing this?

 

Maybe. When mine went bad it made it run VERY rich, black smoke, fuel dilution of the oil, fouled plugs etc. Maybe someone else can chime in, but letting it run that rich for an extended time might have also caused your O2 sensor to fail/foul.
Do you or your cousin have the FACTORY SERVICE MANUAL?
https://www.rx7club.com/3rd-generation-specific-1993-2002-16/94-fsms-available-download-449950/

 

yeah he's got the manual...i hope its the sensors..i just snuck out off work into the garage and start the bad girl up..it started fine then about 2 minutes in ..black smoke..i gotta change those sensors...err...i really appreciate the help..

 

i forgot to mention that i changed the fuel filter and put in a supra tt pump in...

 

whats the benefit of adding a Supra TT pump? This is the fuel pump? Is it just more reliable or does it pump more fuel per sec ... and all that.

 

So you have a full exhaust with a upgraded pump, but no computer? You're asking for a goofy running FD. The full exhaust will give you more boost than you should have, and the comptuer can't compensate for it. Add in a higher flowing pump and you'll get more fuel than you're supposed to, because your injector pulse and your fuel pressure are the same (assuming you didn't change your FPR with the new pump), yet your flow is higher at that pressure because of the bigger, more efficient pump. You should really get a PFC and get that bitch tuned. Replace your sensors and get the computer and get a tune and you'll be sittin pretty.

Oh, and you may want to look into an actual midpipe. A hollowed cat will flow much worse than a midpipe. It's barely an upgrade over the cat because you have a big expansion chamber there and the exhaust will slow down alot, and then have to speed up to get back into the rest of the piping. It's just a bad combination all around. Also, get rid of the stock pre-cat and get a downpipe and save your underhood rubber/plastic/battery.

 

You need to stop being a lazy newb and read the FAQ'S at the top of the FD section. And if you have no clue what he's talking about with the Supra TT pump, you need to get your head out of your *** and start thinking about what the topic is about. We're telling him to check his MAP sensor because he's getting too much fuel. This fact alone should tell you that it's a fuel pump.

 

Or IMO, he could/should take the other road. Replace that Supra fuel pump with OEM, it's adequate even for a mildly modified car. Put on a decent Hi-flow cat, add downpipe if he still has the pre-cat. Then reset the stock ECU to see if he still has codes and replace any sensors if indicated. If no CEL, just new plugs, an oil change and stay with the stock ECU until he learns about the car and can intelligently add mods. It's cheaper and safer for the car, and his cousin can't mess it up.

 

thanks for the feedback...ok pertaining to the fuel pump...i had an earlier problem with fuel...the motor wasn't getting any fuel delivery at all...we tried starting fluid to see if its getting any spark...as the sarting fluid flowed into the intake ..... it ran.... and when starting fluid was not there it shut off...basicly it was runing on starter fluid alone...so we tested the fuel pump for power..there was power going to the fuel pump and the fuel pump wasnt spiting..so we decided to look for a fuel pump...heard that the supra tt pump is the best drop in..got it...after Aggravation of back order from a company i will not speak of...droped the pump in and it worked...then shut it off ..tried to start it again and found that it wont start...eventually we traced the problem to a faulty power supply...so i sold the stock pump and kept the supra tt...im supposed to be getting a haltech e6x around tax return time..so until then i wanted to see what i can do to help my motor..

 

Hey Guys Just Wanted To Share My Progress.... I Had Ordered An O2 Sensor, Air Intake Temp Sensor,coolant Temp Sensor, Fan Thermo Switch. And Replaced Them All....cleaned Out All Intercooler Piping And Cleaned Out Throttle Body...changed Spark Plugs And Wires...

Resulted As An Amazingly Strong Running Fd.....its A Beauty To Drive Now...no Black Smoke No Hesitations...no Problems....what A Beauty!!!

 

Glad it worked out. Enjoy.

 

thanks!

 

Just be careful... Your on the line of too much boost....

 

yea i keep a close eye on it