rx7_turbo2

I know sometimes posts about blown motors go on for pages so I'll try ant keep it short, any feedback would be appreciated. Before I decide to rip the engine apart or buy a rebuilt one I wouldnt mind seeing what others think.

87 T2 hybrid turbo

3000rpm light throttle not on boost, shifting into 3rd gear. Heard a sharp pop then lost power. Next set of lights car would idle on it's own but really rough. Did a compression test with cold engine 92psi on front rotor 60 on rear. However rear rotor has 3 even 60 psi pulses, and still pulls 12" of vacuum. Car will hold 750rpm idle on its own it's just really rough, and will start and fire up on it's own just fine. The car also seems reluctant to get on boost.

Any ideas at all would be greatly appreciated, I think I know the answer to my ultimate question but if there's anything else I should check first then....

Cheers
Graham

Cameljoe

If you are holding a steady 12" of vacuum at idle, your engine isn't blown. Its just "tired".

bcty

try the ATF trick... that should help bring back some PSI.. try that and then get back to us!

RICE RACING

G, If its pulling "even" 60's on the rear and 90 on the front, you should pull the motor apart at your soonest possible time, It will save you money in the long run.....mark my words !

Because of the big front to rear difference, I doubt that it is excessive carbon that is causing your problem, the engine is just worn out from the sounds of it, I would say on examination you will find the apex seals on the rear rotor are heavily chamfered, which could have been casued by a lean or excessive rich condition on the rear rotor or by having a problem with the OMP (not enough pre mix).

Either way, take your injectors out when you rebuild it and test them, to make sure they flow correctly.

banzaitoyota

Sunds like good advice to me RICE_RACING

rx7_turbo2

Thanks for the info.

I am going to give the ATF trick a try as a last resort, failing that I'll rip it apart and start the rebuild procces.

It's unlikey the rear seals have gotten tired because I did a compression test a month ago and both rotors had 90+ compression so.

Salguod

Wow thats really bizzarre. So now just one month later, you have 60psi on all sides of the rear rotor.

Just a thought, but you know it almost sounds like something metal got sucked into the in through the intake. It didn't take out an apex seal, but instead tore a pretty good groove in the housing, thus leaving you with an even 60psi on all three sides of that rear rotor.

Just a theory...but if I were you I would take a quick look at the throttle body, and see if one of the screw/studs on one of the throttle plates worked its way loose and ended up firing through your engine. From there I would check your turbo to see if it has gone south, and pitched a metal shaving or something through your engine.

Good Luck,

fc3s.org

You could pull off the turbo and manifold, and look inside the housings to see if anything looks out of place. When I threw a piece of apex seal in my project 86 (ran out of gas on the track at 14lbs of boost ) the chunk actually just embedded in the rotor, and my turbo was spared. You could easily see it in the rotor, and where it scored the housing like Salguod mentioned. It's worth a shot just to see what you are starting before you even start.

Good luck man.

rx7_turbo2

Thanks for the feedback everybody.

I did the ATF trick tonight. In the proccess I found a split vacuum line and replaced it.

To say the car smokes after this treatment is the understatement of the century.

Not much has changed, the car still has a lumpy idle all be it at a steady 750rpm. It just doesnt sound right, if you listen carefully to the exhaust note you can hear a very consistant "woomp" in the regular exhuast pulses. I'll run a compression check tomorrow to see if the ATF trick raised compression at all. I havent had a chance to look at the blades if the turbo yet, either intake or exhaust side. I have a feeling however the only way to find out the real answer is to get inside it.

Rotor13B

Man, you have to let that **** sit at least 24 hours, at least. then the atf will have done it's magic then test the compression. a few hours won't cut it.

peejay

If you're going to ATF an engine, let it soak 3 days to a week or longer. Putting it in and starting it up does absolutely nothing, in fact probably does more harm than good because it WILL leave SOME carbon when it burns off.

The detergents in ATF work rather slowly. They need time to do their thing. I did an experiment with a used and well carboned rotor and a pot with a quart of ATF in it. The size of the pot was just large enough for me to put the rotor in it on end, and the ATF level was just high enough to cover both apex seals on the submerged face.

After 12 hours, nothing.
After 24 hours, very little.
After 3 days, noticeable improvement. Lots of black crud on the bottom of the pot.
After a week, very noticeable improvement - all the "soft" carbon was dissolved, all of the "hard" carbon was softened. It cleaned off easily with a soft fingernail brush.

ATF only restores compression OF the reason the compression is low is because the seals are sticking in their grooves due to carbon. If that is not why compression is low, then ATF will do nothing except keep the mosquitoes away from your car for about 15 minutes