Poor Revings, withe smoke and backfire
 

Hi there everybody :)

its been a while ive been on the website

i have bad news! :(

A guy came to seek help with his rx7, he knew i had a 3rd gen one and came to ask me help, he wants me to check his rx7...

The problem is that he have a 1st Gen with a second gen engine(im not sure i dont have alot of information right now) and I personnaly dont know much about 1st gens and second, ive only worked on my 3rd gen (i guess its similar)

i wanted to take some advices 1st, before going and diagnose the car(if anybody already had this issue)

OK heres the symptoms:

Bad reving:
huge backfires when reving
looks like chooking or bucking when reving
seems to have withe smoke coming out exhaust(not sure it was little bit cold outside)
all of the above happens bellow 5000RPM

The cars was parked a little while without being started
mods: he have a ful cutdevice (not sure how it works) and he has no O2 sensor... thats wat he said

Ive been very busy and did not have time to test drive it and take a look at it
i will try to do it this week
I am conscient that i need more clear info.. will do

ill will post on the same thread some news.

any ideas were to go check 1st? Please and Thank you very much

Vlad

Compression test and check the timing.

White smoke coming out of the exhaust is an indication of blown coolant seals, which could explain the rough running. Here's a link to a thread I wrote on how I dealt with this issue. It involves the use of a radiator sealant called Alumaseal. I've got over 20k miles on that motor now and its still going strong.

https://www.rx7club.com/1st-gen-archive-71/engine-coolant-seal-repair-maybe-750774/




.

I know that withe smoke indicate coolent being burned
but i heard some things like a vacuum hose or line can be poped out
or cracked vacuum hose can cause these kind of things

Anyway thanks alot for the help!
ill keep these things in mind

If you think it's a vacuum leak, spray some carb cleaner over the questionably vacuum line and listen for a change in the revs. Vacuum leak wont cause white smoke though.

Do a search for champagne bubbles. If you see small bubbles in the radiator will running, then there is a water seal bad somewhere. You'll also notice the water level will go down after it has been running for a few minutes. The temp might also creep up.

I finaly had time to check his car im am very busy over here its hell..

I had time to visually inspect all the vacuum hoses of the turbo
reslults are that i saw alot of them not in place, poped out.. i put them back into place, the thing with this car is that there is so many people who checked it and played in the engine that there alot of things missing.. its a mess

theres is some hoses missing around the intake manifold.... i will have to get a vacum diagram and check wat they serve for.(if anyone have one 2nd Gen engine)

i also had time to perform a compression test and i found the spec :

Compression :85 psi(589KPA)

difference between: 21psi(147KPA)

Results:

Compression: both(front and rear rotor) have 60 psi with pressing the relief pressure button on the compression gauge and checking the compression of the 3 faces of rotor

and both have 70 psi when just cranking the engine over 5 second and watchin the gauge without thouching the gauge

all this was performed with engine a little bit under normal operating temperature with gas pedal fully pressed to the floor.

Do my results make sens?

For the timing, Can you check the timing? I thought the timing was adjusting it self by the computer(the computer is adjusting the timing).

Thx

Oh and for the smoke, its strange, it looks grey or white when you are flooring it and you look back in the mirrors. Im not sure but it seems to smell burned oil

My friend said that his coolent level is not dropping(one thing i have to check and be sure about). There is no bad inner coolent seal symptoms

there is no smoke at starting only one mini black rich puff(looks normal for a rx7)

one important thing is when he drives around and turn the car off and start it back real quick, all of a sudden the car works normally just after couple of second(30 second) the bad reving chooking bucking comes back.
What does that mean? any idea?

Thx

If he is running an FC engine, you may have better luck in the 2nd gen section. If it is a 12a, sounds like the choke is stuck :)

Can be many things if its a 12a. Just cross yur fingers its not the seal!