fd3s_rx7

iTrader: (13)

Well,
I screw off that check valve...
Compression didn't hold, everytime I crank, the needle will jump to 100 to 95 psi, and drops right back. Crank again, needle will fly right up there or sometime 60 to 70. and drops right back down. But the highest the needle reach was 95 to 100 psi on both rotors on both side, and then the needle will drop right back down. But when I put that check valve back in, compression is right back to 100 psi on both side on both rotors...

r_ed_line53

...so the third time that the engine cranks up - it goes to zero?

follow this site: http://www.rx7turboturbo.com/robrobi...ompression.htm

see ya,

car 53

shawnk

The valve will cause the highest reading for the whole test to be held. That value is worthless as you are really looking for the lowest peak value. That tool is not the right one to do this easily but it is possible to use by watching the needle as it goes. The rotor divides the rotor housing into 3 chambers at all times. The seals are responsible for separating these chambers. You should see something like 100,100,100 etc consistantly. If you loose an apex seal it is still possible to get a good compression reading for one of those chambers since there are still 2 seals that are fine but the other 2 chambers will show low or no compression depending on the damage. In that case you would see something like 100,50,50,100,50,50.

It sounds like you may need to have the test done somewhere if that gauge is not giving you the info you need. Go ahead and pay for it and rule this possibility (blown engine) out and then start troubleshooting the problem.

Shawn

Mr rx-7 tt

iTrader: (5)

You are going to have to get Mazda to do a compression test, your tester is for a piston motor. You are getting the highest reading off of the three faces which does you no good. You need to read EACH rotor face seperatly.
Try this, unplug the ignitor (small silver box with fins on the drivers side, in front of brake booster.) Then pull the fuel pump relay or the fuel pump fuse. Next pull out your lower spark plug on each rotor housing. Have a friend turn over the motor while holding your hand 4-5 inches in front of the removed spark plug. You should feel and hear 3 even puffs off each rotor.

rotoboy661

hey bee

maybe is ur map sensor!!!!


thats wut happened to mine

mike

Fatman0203

Ok he doesnt really HAVE to get the Mazda Compression Tester. This is my cheapo version a bit of trouble but worth the cash you save. Loosen ALL belts to the point where the crank spins with your hand moving it. Set up someone to read the compression while you turn the crank to check each face of the rotors. In this way you check each side without buying the pricey tester.

fd3s_rx7

iTrader: (13)

I know it's not coolant seals, because no white smokes at all. But for a cracked, and broke Apex seals, what are the signs?? does it smoke white, black, or does it even smokes???

fd3s_rx7

iTrader: (13)

will a clogged, or busted Main Cat do this as well??

Fatman0203

A clogged cat should not do those signs. Do the test the way I told you unless you want to spend the spare cash and do it the other way.

M104-AMG

iTrader: (8)

So what was the problem ?

I experienced the same thing.

:-) neil

DaleClark

iTrader: (55)

Had to throw 2 cents in to clear up misinformation -

You do NOT have to remove the check valve on the compression tester. Most cheapie testers have a relief valve on the side, just under the gauge. You can press that valve in and it lets pressure out. Hold it in, and crank the engine - watch the needle on the gauge. If you see 3 even pulses, you're good. If you see high pulse, low pulse, low pulse, high pulse, repeat, you've got a broken apex seal.

You can also let go of the valve so the compression builds up to a reading. This can give you an overall picture of the health of the engine - the higher the reading, the tighter the engine is.

Unfortunately, Neil, your symptoms (and the original poster's symptoms) do point to a blown motor, but you're just peeing in the wind until you do a compression test. $30 for the gauge and about 10 minutes later, and you'll know - it's very easy to do.

Dale

fallenengel

spray some carb cleaner at the lower intake manifold. located at the right of the turbo assembly when looking at the car head on. the original gasket is paper, and if it hasn't been replaced, it is gone. i had this problem, took 20 hours to replace the LIM. If this happens to be it, PM me for tips on changing it.

-hrach


i especially suspect that its the LIM because it happened after a hard run - high boost punctured the gasket.

broken93

Check where your map sensor connects to the UIM; not just at the sensor itself. Also, try another map sensor, and check the plug for breaks in the wiring.

broken93

Did you ever fix the problem?

BoOsTin FD

I'm sorry to bring this thread back up, but was this problem ever fixed. I just got the same exact sympthoms, i will test the compression tomorrow (with Piston engine tester)

Thanks

joeyz87

WHen was your last oil change? Did you have any overweight passengers in the car when this happend?

BobfisH

what is it with you and overweight people joey?! your gonna mention the fat chick again arent you?

sounds like an apex seal has gone to me im afraid sir, symptoms point to a lack of combustion in one of your rotors. Whether this be due to lack of intake due to gasket splitting or apex seal gone i cannot comment as i havent read the whole thread, but a rought "Paint shaker" idle and smooth at higher revs is a symptom of a dead apex seal.

Check using a compression tester for 3 rhythmic bounces of compression when cranking the engine, if you get 2 high 1 low you have a side seal gone, if you get 1 high 2 low then you have an apex seal gone.

Sorry to hear about the engine dude, if it has gone that is...

BoOsTin FD

I'm affraid it's the engine too... the problem is there is only 4k miles on the new ported engine, and when this happend, i was driving it the way i normaly drive. I redlined it in 3rd and after i came to a stop, there comes the paint shaker.

Amel

BoOsTin FD

Ok, I just did a compression test using the piston engine tester. On both rotors i get an even swipe of the needle, which looks good. Also when i put my hand on the spark plug hole to feel it, it feels the same.

Overall compression number on all three sides (using piston tester) I get on the front about 89-95 On the rear 100-105 Give or take.

I checked the map sensor, the spark plugs, The wires (there is one wire that seems to be letting some spark out at the top, but i'll try to fix that soon, doubt that would be it).

I bypassed my MSD, and put it back to stock, still the same, so i put it back with MSD.

I'm running out of the options here. The only thing left to check is fuel injectors, but I highly doubt they could do this kind of crap. ON PFC they are showing 7.1 or so inj duty at idle, which is about right(i think i always had it like that).

It idles like crap, like on one rotor, and vacuum shows 10-12.

The engine has big street port, but it used to idle at 15 in of vacuum and it didn't feel like crap.

Any suggestions guys please.

Thanks

BoOsTin FD

Got new spark plug wires... still the same. Although... i got to say I smell A LOT OF FUEL.. it's like raw fuel, not regular midpipe smell. Could injectors be leaking that bad all of a sudden to make it run like crap?

charliegt

Ok, as far as the compression testers go - if you're using a normal one you DO have to remove the check vale (the one that is in the tip that you screw into the motor). Holding the relief valve lets the compression out and you don't get a full reading. You can use the hold the valve open method to test consistency among the faces but not to get an actual compression reading (since holding the valve open is like putting a hole in the line).

As far as your problem, I don't know anything about aftermarket ECUs, but it sounds like you're running rich. I had a similar problem (although I had a stock ECU), and it turned out to be the water temp thermosensor. Does your ECU let you see what the sensor is saying the engine temp is?

-Charlie

BoOsTin FD

I'll check the ecu and the sensor, as i happen to have the spare.

As far as testing goes, i'm pretty sure i did it right.

Any other suggestions? I can't believe that the engine with 4k miles on it can just go out like that for no apparent reason.

potatochobit

iTrader: (1)

start believing.... not all engine rebuilds and installs are the same. LOL

BoOsTin FD

Well, how do i prove that the sucker is blown? I can feel the compression and i watched the damn needle move, it had all same spikes. I ain't going to the damn dealer here to ge it tested with mazda tester... last time i took my old fc there, they fucked up something else and all i got back from them was "it has low compression". No numbers nothing.

Any other suggestions?

zerrovalve

it seems almost every tests have been focus on the mechanical part... you haven't mention if your M.I.L is on, maybe you may have electrical problem...or does the pettit ecu not have one M.I.L?