I have a 1990 auto GXL / T2 5 speed swap that I've been working on all summer. I just can't get the rpms to smooth out. Its always speeding up and slowing back down, with +/- 250 rpm. Its not just at idle either. If I try to hold the rpms at say 3000, it will vary between 2750 and 3250 over and over. It never changes.
Anyway, I plan on pulling the engine this week and taking a peek inside. I figure the apex seals might need replaced since I only have about 90-95 psi compression.
Which seals are the most popular right now? I used the RA Super seals on the last rebuild and I didn't have any trouble with them.
So, its time to gather some parts. Recommendations?

ash

 

Is it smooth and rhythmic or is it stumbling? If it's smooth, try adjusting the idle screws on your throttle body.

You seem to have quite a bit of rotary experience and I was just working on something similar recently. The throttle body adjustments seem often overlooked.

 

I have a T2. The only adjustments are idle speed and the tps. The engine is emissions free.
A lot of the guys have helped with this thing since last Dec.

I've changed: ECU 3 times, OMP 3 times (now it is an S4 OMP), TPS 3 different one, 3 different CAS, replaced all the vac hoses, replaced all of the intake manifold gaskets, switched to a Rtek 1.8 with OMP bypass, new fuel pump, new fuel rails, new spark plug wires and plugs, swapped out the throttle body assembly, swapped the fuel pressure regulator and more.

 

Its not just something daft like a vac leak?

 

if your compression is that good, I seriously doubt that your problem lies with the apex seals. blown motor = no/very low compression. simple as that.

Not to get on a soapbox or anything but... just replacing things isn't usually a good way of trouble shooting a problem. even with 10 TPS replacements that could still be your problem if it isnt adjusted right. and let me tell you.. I've taken my car to the shop out of frustration with a crappy idle after adjusting the TPS to within spec like 6 times. want to know what the problem was? the TPS wasn't PERFECTLY aligned. even though it was within spec it was still causing problems. It's all about actually checking for problems rather than simply swapping everything, especially if you're swapping to more used parts. If my experiences are anything to go by (this also comes from a guy with 3 logicons, and I still can't get my heater fan to work properly) I'd suggest just going through it all again with the FSM in one hand and a beer in the other.

 

I can't find a vac leak. I replaced all of the vacuum hoses and all of the intake gaskets. I bypasses the front IC to be sure it wasn't leaking there. I tried starting fluid and propane to help pinpoint a leak.

 

I didn't just blindly replace parts. I've been trying to get this 7 to run since last Nov. I replaced parts where diagnosis pointed. Its tough using used parts as replacements because some people will sell parts they know to be bad. I've had it happen twice on this 7.

I just pulled the engine. Well, not alone.

Once I get it apart I'll let everybody know what I found. If I find nothing, great. I'll just replace the apex seals and button it back up.

ashley

 

I can not find the nuts to bolt the engine to the stand, so I'll have to run to the parts store.

I did remove the turbo and the apex seals all appear to be OK. Nothing missing and they pop back after being pushed in.
That's good. Maybe I'll be able to get away with reusing the rotors and housings.

ash

 

Several guys pointed to a vacuum leak and I did only have 10 psi on the vacuum but I just could not find a leak.
Somebody said it might be an internal vacuum leak. He didn't say what he meant.

 

i love my ASL seals

 

Best way to check for leaks would be to pressurize the entire engine and listen for leaks. I found many leaks on my engine from this method. I bought my coupler from a 3000/stealth site, forgot the name at the moment.

 

Seems a bit redundant to do a rebuild when u can't fix your rpm issue.

 

I disassembled my engine. I didn't find anything major but I did find that 1 corner seal was missing, the previous builder for some reason only used the long apex seal springs ( not 1 short spring was found), the apex seals are in very newish condition. It was ported, intakes for sure but I don't have a housing to compare the exhaust ports to so I'm not sure if they are ported. One oil seal was twisted but it didn't seem to use much oil. The apex seals are like new but but a couple of weeks ago I dropped the oil pan and there was sludge in the oil pan and the oil that I removed was really dirty but only had maybe 2 hours on it at idle.

I have pics. Comments please.
https://www.rx7club.com/attachment.p...1&d=1314292216
https://www.rx7club.com/attachment.p...1&d=1314292216
https://www.rx7club.com/attachment.p...1&d=1314292216
https://www.rx7club.com/attachment.p...1&d=1314292216

 

A couple more:

https://www.rx7club.com/attachhttps:...1&d=1314292311

 

a corner seal was missing?

doubtful, it probably fell out during disassembly or your motor would be trash.

if they're 3mm apex seals then a single long spring is common.

the porting could also use a bit of cleaning up, messy.

 

I can not find the seal anywhere. I don't think it came out after assembly I think the builder must have left it out. The apex seals are the 2mm stock ones. The side seals are a little below spec so they will have to be replaced.
This engine was supposed to have been professional built.

 

i have a few comments, so bear with me.

1. at first, i was disappointed that you went ahead and disassembled the engine, but after seeing the port-work, i think you may have made the right decision. i think you could have done a few more things to troubleshoot your idle problem (TPS, vacuum, etc.) and find the cause of your problem because with the compression you posted, i feel fairly confident saying it was not your apex seals.

2. i find it hard to believe a corner seal was missing altogether because of your compression, but freakish things do happen wth cars, so i won't second-guess you on that. you pulled it, and if you say it was missing, then so be it.

3. the exhausts were ported - at least an attempt was made.

4. you need to get that engine re-ported (if it can be) by someone that knows what they're doing. i don't usually critique finishes (because, to each, their own) but these are totally inconsistent - and quite frankly - i think they suck!

those are my thoughts. we can discuss if you want.

 

1) I tried everything/anything anybody even mentioned for 8 months. The engine was emissions free so there weren't very many vacuum hoses and the ones that were left were new. I set and re-set the tps. I used the twin led method. Then I used the 1k ohm method and then I used the 1 volt method. I tried the 2 tps' that I had and I bought a low mileage one on the forum and I tried that. I had just run out of things to try.

2) You are correct. I did find the corner seal. It had fallen out on dis-assembly and was hiding.

4) I agree, not that I know much about porting but just by comparing mine to pics of professional porting. Do you have any suggestions? Would I be able to get satisfactory results by using the Mazdatrix templates?

I've been wanting to tear it down for several months but I thought if I plugged away at it long enough a solution would become apparent. This is not my first 7 but it is the first one that I could not make run correctly. I've done 3 full rebuilds.

I was told that the engine had been rebuilt by a professional shop but I doubt that. Just the porting job out rules the pro shop but I don't think a pro shop would only use 1 apex seal spring or that they would use the little stock corner seal wire springs instead of the newer FD spring.

 

i figured, i just can't forsee a motor holding together with a missing corner seal. pieces would work out of the side seal grooves and start a gross chain of events.

wire corner seal springs? i don't think i've seen a rebuilder yet still use those.

 

I have not posted in here in a while and this might not help the OP but what the f!@#$% happened 2 those irons?and the exhaust ports.........oh my good.The port goes right into the oil seal track i see no bevel for the side seals....TOTAL JUNK.Get a nice big streetport template and see if they can be fix brother.Good luck.

 

It does happen

I disassembled my engine 2 months ago and according to the last owner, it was a rebuild unit from the owner before him. has about 30K miles on it since rebuild. it's still using the old version of corner seal springs (the wire type)

so either the rebuilder is a moron, or someone is lying.

Another issue was that the engine was using the Black-type o-ring that Mazda said don't use it, use Green ones instead. I was getting massive oil leak on this engine and when I pick the oil control ring up, the rubber inside is pretty much all hard and cracked already one little tab the pieces just fell off. Rebuilding it with Green ones.

Corner seal rubber was missing. and lots of other crap.



bad builder does exist I guess.

 

That port job looks so funny lol.

 

The shape of the ports look fine. I'd make paper templates and compare them to make sure they're symmetric. I'd also use a dremel with sanding drums to blend the grinder marks. Can't see if the opening is back-cut or if the tunnel was lowered and blended.

What was the clearances between the side seals and corner seals?

 

The better 93-95 springs are even cheaper on the Mazdatrix site.

 

I didn't measure the gap but the gap was really small, well within specs.

The builder did leave out the primary plastic diffusers that go under the injectors. Maybe that is why I was having so much trouble with the engine.