Issues and Help - Compression Reading, Smoking Exhaust, Weak Boost
 

Quick rundown on where my car started, and where it's at now.

'93 FD Touring, nearly stock AFAIK
One of the PO's had a sound system installed at one point, all that is left is aftermarket headunit and wires under tunnel cover etc.
~111k miles on the chassis
~25k miles on Mazda reman engine

Absolute smoke machine when I got the car. PO told me it was an issue with the turbos. They were cracked and leaking oil, and they just needed to be replaced with a stock pair.
Price was within my range and I wanted to get something as close to stock as possible so I could do all the wrenching myself and learn.

Car arrived at my house in April, wishful thinking and foolishness led me to skip doing a compression check, and I just went ahead with replacing the twins. :withstupi
I finished with all the mods in September, exhaust was not smoking at all.
Mods:
-HKS DP
-Efini Y-pipe
-Koyo N-FLOW Rad

Enjoyed driving the FD around for a while on days with nice weather, the butt dyno felt a bit weak and I suspected that there was lack of boost.
Car wasn't driven since late September / early October. Sat in the garage until about a week ago
I installing the Defi boost and water temp gauges last week. I go to start the car up and go out for some pulls, and she's smoking again. Not nearly as bad as when I first got her, but she's smoking again. The smoke does clear after maybe 30s or so.
After a few pulls, there is definitely a boost issue. I'm getting no more than ~40 kPa max (~5.8 PSI). Not getting the expected 10-8-10 boost pattern or anything closed to it.
Got a compression tester from Autozone on the way home from work the other day, and I did a compression check using Banzai's how-to guide (Banzai Racing Compression Test). I tested using the trailing spark plug hole.

I compiled a quick video with clips of the exhaust before any work was done, after all the work was completed, and then my compression test from the other night.
I would greatly appreciate a second and third opinion on the compression numbers. To me, they look OK. The bounces look even, and 85+ PSI on both rotor housings.


Current issues, most of this is new: :icon_no2:
-After cold start when then RPMs have normalized, the idle seems to oscillate and stutter around 1k rpm
-Rad fans turn on immediately as soon as the car is turned on.
-Gurgling noise coming from passenger's side car (water temps staying at 80 C however)
-Weak pulls, weak boost, ~40 kPa max
-Smoking exhaust, clears after 15-30 seconds, or after driving

I would really appreciate some guidance and ideas on where to go next with debugging. There appears to be some fresh oil residue on the underside of the oil pan, so I'm not sure if there is an oil leak elsewhere, or what. The oil pressure seems to be fine when driving if the stock gauge is to be believed. Really appreciate any insight and guidance on what to do next guys! Thanks, and sorry for the long post. :blush:

bad coolant seals, rebuild time.

replace all the turbo control solenoids during rebuild, as well as replace all the vacuum lines. thoroughly check all the rubber couplers after the turbo while they're off for cracks are tears.

The PO gave me the work receipts from the PO before him. The vacuum lines were all replaced by Cork Sport in '07, among many other things. I figured the vacuum lines should be good still.

https://cimg3.ibsrv.net/gimg/www.rx7...6a04aee8c9.jpg
https://cimg5.ibsrv.net/gimg/www.rx7...2be5e3bc61.jpg

well, double check them and make sure none were pierced during installation, most shops do sloppy work. i didn't know corksport worked on cars, so that sais something.

also check the electric fans, its possible something caused an overheat and caused the seals to let go.

How does the car have 111K on the chassis when the invoice from 10 years ago shows 125K? Look for the blue reman tag on the front cover and see if the serial number matches up.

We have seen many cars where the new owners were given receipts from completely different cars from the previous owners.

Yeah, that was a mistake on my part.
~125k miles on the chassis and ~25k miles on the reman. I got the car at about 151k miles.

Banzai-Racing, not sure if you saw the compression test numbers in the second half of the video, but do they look OK to you? I can't get to the serial number right now, but I don't recall seeing any blue reman badge when I did have most of the components out. I try and get to the serial number once I transport the car to my parent's garage for the winter.
That's really rotten if people are giving fake receipts to people. :icon_tdow :icon_no2:

I know insightful said coolant seals, but apex seals and coolant seals seem to be everyone's favorite diagnostic response: https://www.rx7club.com/3rd-generati...-seal-1078858/
I would like to be completely sure that I have to pull the block and tear down the engine before I jump to that. If it was the coolant seals, why would the car have stopped smoking for a significant amount of time after changing the turbos, and installing the DP etc.?

Both coolant and oil levels are staying full. I haven't driven the car hard or for long periods of time, so maybe it just hasn't had time to burn enough coolant or oil off.
Is it worth doing a coolant system pressure test? What other sources can I check to see what is causing the smoking exhaust?

I will check the turbo solenoids and actuators. Gonna follow Dave's guide and see if that helps me locate any issues: https://www.rx7club.com/3rd-generati...-stuff-802060/

The peak compression seems fine, but compression readings vary based on cranking speed.

Pull the plugs and crank the engine over by hand when it is cold, if coolant comes out of the plug holes you have a coolant seal issue. More than likely a coolant seal retaining wall has collapsed.

If the coolant seals end up being the problem, and youre not planning on breaking it down any time soon, you should drain the coolant completely, start the engine for about 10 or 15 seconds (to sort of dry the combustion chambers), then squirt some oil in the housings through the spark plug holes and turn it over by hand a few times. the idea is to prevent as much rust as possible.

Work has kept me from getting in the garage. Pull the plug and turned the engine over by hand. No coolant or fluids came out. I was getting nice *phooom* sounds as well. I even put my pink near or in the hole while cranking and still didn't feel and fluids coming out. Is there hope that it's not the seals then?

Something weird I noticed when taking out the spark plugs. They were all really loose. All loose enough to remove by just turning with fingers, and one or two even felt like it was already coming out on its own. Could this cause any idling issues?
Also, the wire for the front rotor leading plug was disconnected before I even went to remove the plug. I'm not 100% positive, but I don't remember touching the leading plug wire when doing the compression test.

What would you suggest next?

Thanks a lot for that tip!

After some more searching through the forum today, I found this thread which inspired some more hope.
https://www.rx7club.com/3rd-gen-arch...hut-off-26421/
Although I don't seem to have coolant leak that I know of, there are a number of described similarities across both issues. I have the throttle body off right now, and I can't put it back on until I get a new TB to UIM gasket. Once I get it re-assembled, I will do the bubble test when running the engine cold for further diagnosis.

Start by installing the plugs and wires correctly.

if the leak is small, turning the engine by hand won't tell you if there is coolant being pushed into the engine. you should be seeing either oil or coolant on the plugs by reinstalling them and removing the EGI fuse and cranking the engine for a few seconds then removing them.

The car certainly won't idle well with plugs in halfway and a leading wire not connected. Let us know how she runs once sorted :icon_tup:

is it oil or coolant coming out of the tailpipe at startup?

are you pre-mixing and if so how much?

it is not uncommon for some oil to come out of the tailpipe on startup if you premix as the internal engine temp isn't hot enough to burn the oil.

as Banzai suggests your compression is probably not an issue and the absolute numbers relate directly to cranking RPM.

your 5.8 psi boost relates to the secondary turbo door not opening. it takes events on both sides of the door to open it. no wonder the car seems sluggish.

loose plugs absolutely will effect idle as well as contribute too ignition misfires under load.

did you really look at the video? that is not a normal amount of smoke by any means, even in sub freezing temperatures.

The white smoke is coolant for sure, hate to say it but looks like a rebuild is in order. I remember someone on the forum was able to fix their coolant leak with some sealant that you add into the coolant, I think it was alumaseal, any way I say try that before rebuilding. For the low boost issue, I say redo your entire rats nest starting with the vacuum lines, then the check valves, and finally I would move onto the solenoids.

Do not use block sealer of any kind, it will clog the heater core and radiator

yeah, it's also not an old thrashed FB that someone was working on 10 years ago when you could find them for pennies. as well the magic fixes, if they even work for you, are just temporary.

Will do. I'll report back after.

To me, the smoke looks white, but I can't really determine if the smell is sweet or not. I'm a bad judge of that I guess.

I am not premixing

Going to test the check valves, solenoids, and vacuum lines over the wintertime while it's garaged. I will have to thoroughly check the turbo control arm as well. I will search for some threads on testing these items.

Thanks. I guess I will sort out the entire rats nest over the winter season while it's garaged.

Noted. I'll not use that.

personally i think you should just start pulling the engine out, even the ones who suggested otherwise in this thread already know you have bad coolant seals. this puffy white smoke doesn't appear just from magic.

You're probably right, just want to sus everything out. Mentally prepared for an entire tear-down and rebuild in spring.

Got new NGK wires and BUR9EQP plugs installed along with new gasket between UIM and TB.
Here's a video showing the cold start exhaust and the coolant bubbles. In the first video you can hear the idle is off, but in the second video it seems to be fine.

Took a 12 minute drive to bring the car to my parent's house to garage it for the winter. Low and behold, no more smoke coming from the exhaust. :scratch:
Defi water temp gauge showed that the coolant got up to 93 C (~200 F) even though it's -2.8 C (27 F). Idle is smooth as well. Water dripping from the rear well / fender is due to wet roads.

Bro, it's because your water seals are broken in the combustion area. When the car is off, the water seeps into the rotor housing. When it's running the combustion chamber is pressurized, so it's not letting the coolant in. Pull your engine and stop running it before it's FUBAR.

Well, I guess it's :badrebuild: time. I'll start the teardown and rebuild in spring. Thanks for all the feedback everyone! :icon_tup:

plus the thermal expansion of the rotor housings to the irons when warm tends to close the gap and seal the engine until it cools off, rinse and repeat when starting cold.

Do not allow the engine to sit with coolant in the combustion chambers. It will start rusting very quickly. We get engines shipped to us every spring that have sat all winter waiting for an engine rebuild, just like what you are talking about. Very good chance you have a collapsed coolant seal retaining wall.

https://cimg6.ibsrv.net/gimg/www.rx7...a13a7c205a.jpg


https://cimg5.ibsrv.net/gimg/www.rx7...04a3076e42.jpg

Ouch! That's one seriously rusted rotor. What should I do to prevent the rusting? Drain the coolant and run the engine for a bit to remove any water from the housings? Is there some additive I can run through the system to prevent rust, or should I just plan to start pulling the block now?