After a tough fight over the past few months trying multiple avenues to revive our T2, it's time for a rebuild....
I appreciate all the advice and pointers but now I may be asking a lot more questions. Engine hoist is built (looking at modifying my engine stand) the hood's off and now it's time to pull the motor to see what's really going on.
Suspected bad seal(s) in the front rotor giving 30-30-90 compression, won't idle, terrible hesitation accelerating (when its running); pretty sure we've done everything we can to identify our issue with the exception of pulling it apart.

We've done a bunch of research on the process so now it's time to pull the trigger. Everyone is saying to wait until we have the motor apart to order seals but I can't help but assume that I'm going to be replacing most if not all of them once we have it apart seeing how I'm probably not going to want to do this again any time soon.
I've been in contact with Dan at Atkins but I've also been looking at Racingbeat for seal kits, does anyone have any advice on where to purchase from? Atkins has the Cryo seals, are they really any better? Any pointers that would make this as smooth as possible would be great!

Thanks!

 

I also strongly endorse waiting until it is apart, inspected, and understood what has happened with the failure. Fingers crossed that your housings and plates are within spec and reusable. You also might save some serious money if the oil control rings are in spec and don't need to be replaced. Those can get pretty expensive.

As far as seals go, unless you're going for a power build, I tend to always lean on OEM. The quality and consistency are there, and there's no second guessing. Be aware that even some of the Atkins kits will substitute their own seals out for OEM, usually the water seals.

 

+1 on waiting until you get it apart. you never quite know what you're going to find in there, so its helpful to wait.
i'd also look at places like Amayama and Blackhawk Japan, some stuff is a lot cheaper from Japan.

 

Thank you, I'll definitely keep that in mind!

 

I've had good luck with rebuild parts from Mazdatrix as well.

 

I ordered my rebuild kit from Racing Beat. This was a few years ago, but I remember it being very competitive from a price standpoint and they were able to swap out FD corner seal springs with no issues for me. This was the best option at the time to stick with all OEM parts for me.

 

Okay,
Well after a piecemealing the past hand full of weekends and cold nights, we've completed the rebuild and have a running 13b! Definitely some stressful moments here and there but after lots of reading, research and YouTube videos it's done. We had some trouble with the Timing; I initially thought maybe somehow the rotors were out of phase, but we were able to finally find TDC on the rear rotor then the front rotor and now we're dialed in. However, we're having a issue with the idle...
Cold starts seem to be ok, but once she warms up and the idle drops - she dies out... It starts back up ok but doesn't want to keep running on her own. Not without help, I've had to adjust the throttle cable to increase the idle to around 1100-1200 to keep it running after its warmed up.

Things I'm thinking:
The compression is ~60 psi across the front and rear rotor (using a piston compression tester/ I did see higher numbers on the initial test before we had it running) But I've also read that it takes a little time and heat to seat the seals to build compression.
We have new plugs/wires and we're getting plenty of spark
I don't think we have any vacuum leaks, but I've built a smoke tester to confirm this (I do know the plastic inlet pipe to the turbo has a few cracks, but would that cause it to idle out?)
We have new 550cc injectors and we cleaned the whole fuel system including the tank - so I'm pretty sure we're getting fuel
We did a street port... intake and exhaust with the racing beat templates
We did the emissions delete prior to the rebuild (maybe the vacuum lines are incorrect? But I'm pretty sure we have them where they need to be)
Maybe the UITM and throttle body adjustments are out of whack?
Could any of the sensors cause this? (I had to solder a leg onto the air intake temp sensor to reestablish a connection there, bought a new one on Facebook, just waiting for it to arrive) The connection at the oil pan sensor has boke off, the sensor next to the oil level sensor - I think it's the oil temp sensor? (could that cause our issue?)
I have a fuel pump switch installed to prevent flooding.

This is where I'm at.... I feel like we're close and I'm trying to rule everything out before the inevitable.....
I can upload video clips or images if that would help.
Thank you!

 

Without being there and seeing where everything is I cant help much.. what I CAN say is that they get a little cold natured when you start deleting rats-nest shenanigans and coolant passages (fyi). 60psi is a little low.. BUT.. I'll stay on the glass half full side and hope things are still seating to each other. Get a can of starting fluid.. that's a decent "quick and dirty" way to test for vacuum leaks. Start there.

 

Thanks, I have used starting fluid to detect leaks - that's how I found the cracks around the turbo inlet piping. Until we figure this out and go to stand alone I'll need to use the stock plastic pipe, but I found one on eBay that's in better condition. Hopefully that will help, but something tells me that's not the only culprit.

Thank you for the reply!

 

I think this is the best mod for any OE RX7.

 

So, I found some info regarding the set coupler and Bypass Air Control Valve to dial in the idle. Basic instructions are jumper wire the driver side up front green plug (2 prong) to disengage the ECU, start the engine and with the throttle cable secured adjust the BACV to an appropriate idle (700-850) ours however will die out if below 1000 and pull the jumper wire to reset the ECU. The process makes sense, but we still need to adjust the BACV a little to keep the idle from creeping up. Might need to add a bracket or two to the throttle cable to keep it from wobbling.
Has anyone played with this process to dial in the idle? I seem to have had more luck with this method rather than bashing my head against the wall trying to figure out the UIM/throttle body adjustments...

 

Hi everyone,

Just a quick recap; my son and I completed our rebuild a couple months ago (87 T2 13b) the car is up and running much better than it was. Turns out we had a broken Seal in the front rotor and a some pretty bad scoring in the housing.
We replaced the rotor and housing got everything back together and installed, fought with the timing for a while until we had to find TDC by measuring the distance from the Seal in the trailing hole to the leading hole and cutting the distance in half on the pulley.
The motor seems much healthier now, compression is better, just seems stronger and smoother now.

Here's the catch, we stuck now with the dreaded 3500 rpm stall....

We did the Racing Beat intake and exhaust street port, we have 3" exhaust from the turbo to the muffler (no cat/silencer), basic modified intake (cone filter on the MAF/stock piping to the turbo). I know these things usually require a stand alone but we're not quite there yet financially so we're trying to stay within the limits of the stock set up. Current research I've done led me to porting the wastegate to prevent boost creep; we ported the wastegate out to about 25mm and welded a washer onto the existing flapper door. We have new injectors (550cc), rebuild fuel system and have scoured the bay multiple times looking for bad grounds and vacuum leaks (found one open port on the intake piping below the BOV) The latest thing we've added is the HKS FCD. I know there's all kinds of mixed reviews on this bad boy, but we're trying to build a drivable (fun) car until we can go stand alone.
I added a picture of how we've got the FCD wired in at the ECU, I have the signal wire from the FCD wired in at pin B2 (MAP sensor) based on what I found on this forum, power tapped in at the cigarette lighter, and grounded to the chassis. But we're still stalling at 35-3800 rpm. I'm out of ideas as to why. I need y'all's help, please.
I tried adding a video but it was too large maybe I can add it to my youtube and add the link... If we ease the throttle up it'll got through 3k and into 4 no problem, but if we give it some beans it hesitates starting at 3500k. Has to be fuel right? Maybe I don't have the FCD spliced in correctly? The instructions were bunz but I found what I thought was good info on here. We did pick up a new boost gauge to get a more accurate reading and it seems to be stalling out around 6 psi.
Am I missing something? Between the wastegate porting and the FCD it should solve our boost creep and ECU fuel cut right? Timing?
I could really use some advice, pointers, help, anything. This emotional roller coast is taking it's toll on my 16yr old son, to the point where he's giving up and I don't want that.
I can post pics and figure out videos if that would help, I just need to know what the possibilities are.

Thanks everyone!

 

A few developments;
It seems like our wastegate isn't opening. I hooked it up to compressor and forced some air into the line and the actuator arm does move (around 10 psi). But the engine hesitates around 3500 (free reving) and no movement from the actuator. Could we have a leak not allowing the needed psi to open the actuator? I think it should start to open around 2 psi - I would think we're making at least 2 psi at 3500. I think the other option is that our Secondary injectors just aren't getting signal to fire. So today I'm going to pick up a Noid Light set and see if we're getting signal to the Secondaries.

I'm pretty sure the turbo isn't bad, seems to sound fine under load and free reving, and when I had it apart during the wastegate porting it seemed to spin freely...
Thouhghts?

 

i would either boost a pressure gauge on the fuel pressure regulator, or just look at fuel pressure. its easy to mix up the FPR vacuum hose, and then it won't raise pressure in boost, and car basically stops running

 

Still working through this 35-3,800 rpm hesitation.. I've added some images of a spare UIM & LIM for reference.
After our emissions delete, we followed the Vac diagram below where you can see that the FPR hose goes from the regulator to the center nipple on the LIM (center runners) circled in red. That's where we currently have the vac line, but we're also getting sub-optimal fuel pressure. I've recently read that the FPR vac line needs to go on the UIM where there's a better source of vacuum. On the rear of the UIM, the bottom nipple goes directly into the chamber (circled in blue). Would this be a better option for the FPR vac line? And please feel free to add any other comments about these nipples and which lines should be hooked up to them or capped. I'm starting to think that maybe we have vacuum lines mixed or in poor locations for the vacuum we need.

*quick and dirty recap:
experiencing hesitation at ~3500 rpm
Fuel pressure is a little
I don't think we're getting enough boost to open the waste gate (should start to crack open around 2 psi, right?) free revving up to the hesitation point there is no movement from the water gate actuator arm.
We have 3" exhaust from the turbo back
New injectors (prior to the rebuild)
New Walbro fuel pump GSS341 255LPH
Ported the waste gate to ~25mm, welded on a new door
We have the HKS FCD but took it out to troubleshoot
Cleaned the fuel tank and ran new lines
New fuel filer

I'd like to tackle this on my own, I feel like we're getting close by process of elimination.

 

If I may provide my $0.02, I think there may be multiple things going on that need sorted through.

First question, have you measured the fuel pressure during operation? I think this is a lower probability issue, because it only hesitates under certain conditions. There is a procedure in the manual that describes how to test, and what pressures you should be expecting. If your injectors are clean and working and your fuel pressure is acceptable, fuel's not the issue.

From the description, it sounds that there may be a couple of different problems that may be present. Most likely there is an air problem of some sort, vac or boost leak, or incorrect vac routing. The second problem could be that there is a sensor problem of some sort that is measuring incorrect airflow. Both will need to be checked.

As far as vacuum lines are concerned, you want your fuel pressure regulator to remain hooked up to the lower vacuum port (red circle). This vacuum reference is connected to your primary intake runners, as regulated by the primary throttle plate. Anytime the accelerator is pushed, the primary throttle plate opens, changing the vacuum here. Any time the primary plate opens, the air will return to atmospheric pressure (or higher under boost), and will be when extra fuel pressure is in demand. When the acclerator is released, the throttle plate closes, and vacuum builds in the intake runner. This lowers the throttle pressure by pulling the regulator back further so more fuel can bypass. This is the vacuum reference you want for your pressure regulator.

The lowest vacuum nipple on the back side of the upper intake (blue circle) serves a different purpose. Its purpose is to provide a vacuum source to the thermowax air valve attached to the throttle body. This in turn pulls on the vacuum actuator attached to the extra secondary throttle plates. The purpose of this system is that, while the engine is warming up, that additional air isn't allowed through the secondary throttle bores until the intake air sensor at the throttle body is at operating temperature. It does this because at cold startup, or during the warm up, the sensor cannot provide correct readings, so the system limits itself until operating temp is achieved. Once this happens, the thermowax valve closes off this vacuum port and allows the actuator to release and allow full use of the throttle body. The vacuum logic of this system is that this vacuum source remains under vacuum as long as the secondary throttle plates can't open. It encounters vacuum changes differently than the port on the lim you previously mentioned.

As far as checking for air leaks on turbo cars, I am not an advocate for the starting fluid method. For NA I think its just fine, but use on turbo systems has limited applicability. The reason being is that not all of the system experiences vacuum, or does so at the same time. At idle, anything connected in the vacuum system to the manifolds behind the throttle plates should be under vacuum. Pretty easy, a leak here would likely suck in starting fluid. For anything connected to the nipples right behind the throttle body, clear up to the MAF, the air pressure is different. The nipples that run to your primary and secondary injector air bleeds, as well as your oil injectors (keep these hooked up!), are routed so that they draw air from in front of the throttle plates. They are flowing air from near atmospheric pressure before the throttle body to the vacuum conditions encountered in the injector ports. These are flowing air constantly and significantly affect idle if disconnected or capped. Everything before your throttle plates, intercooler, turbo piping, turbo, intake elbows, all of those are pretty close to atmospheric pressure and can't really injest air unless its a big leak.

The way I check for leaks is with an air compressor. First, I disconnect the MAP sensor vacuum line so I don't damage it in the process. Then I use that port on the manifold to inject ~10-12psi into the manifolds to check for leaks. I do this in two stages, starting with just the lim, uim, and throttle body with the throttle body and air bleeds capped off. This will limit the places where a leak can occur. Then, connect the air bleeds, intercooler, and turbo, and cap the turbo inlet and repeat the test. This will allow you to test all the connections pre-throttle, having already tested the post-throttle area. This is where you will often find leaks around the intercooler elbows, or with a cracked air hose that isn't found under normal conditions. You had mentioned only getting a couple psi to your wastegate and it not opening. Under idle, or stationary conditions, there isn't enough load on the engine to spool the turbo enough to make that kind of pressure. It really only works if you are on a dyno or on the road. If you have all your leaks plugged, at this stage in the pressure test, the wastegate should actuate. If it does, one more thing to cross off. From here you should be able to connect your turbo inlet elbows and your MAP sensor back up, and should be good to go there.

Lastly, you will need to check your sensors. Grounds are a big deal because that provides the reference point so the sensors can make correct readings. If the boost/vac leak testing didn't remedy the situation, going through your sensors would be the next step. Check and see that they are in the correct ranges. Also, if someone has messed with the throttle stop screw for the primary throttle plate, you may have to reset the throttle position and readjust the throttle position sensor because it will be way out of position.

Its tedious, but start from the block and work your way out. Good luck, hope it helps

 

I can't express how much I appreciate you taking the time to respond. You've given us some excellent info and some solid leads to chase down. Thank you.
One question I have before we dive back in:
You referenced the lowest nipple on the rear of the UIM and its relevance to the thermowax system; it's kind of funny because I was investigating the thermowax right before your response popped up. During the emissions delete, my son capped the lower UIM nipple along with the nipple on the thermowax unit. The remaining hose (pictured) runs to the diaphragm on the other side of the TB which is supposed to assist in opening the secondary plates at a higher rpm. Should he not have capped these two nipples, should I reattach this vacuum line and check valve?

 

I can't express how much I appreciate you taking the time to respond. You've given us some excellent info and some solid leads to chase down. Thank you.
One question I have before we dive back in:
You referenced the lowest nipple on the rear of the UIM and its relevance to the thermowax system; it's kind of funny because I was investigating the thermowax right before your response popped up. During the emissions delete, my son capped the lower UIM nipple along with the nipple on the thermowax unit. The remaining hose (pictured) runs to the diaphragm on the other side of the TB which is supposed to assist in opening the secondary plates at a higher rpm. Should he not have capped these two nipples, should I reattach this vacuum line and check valve?



Yea, hooking up the capped vacuum port of the thermowax and the bottom rear nipple didn't change anything. Time to start leak testing!

 

I would recommend reattaching that valve system to the lower nipple. The entire purpose of this thermowax valve is to limit the throttle until the air temp sensor at the throttle body is at operating temperature. It doesn't add or subtract power and also differs in function independently from the thermowax actuator also attached to the throttle body that raises the idle. There is one primary throttle plate that opens and closes with the accelerator. There is a mechanical linkage that connects this primary plate to the downstream (closest to engine) secondary throttle plates. These always move together no matter what. If air is flowing through the primary and both secondary throttle bores, that is wide open throttle. There is also an upstream set of secondary throttle plates that are linked to the other secondary valves, but with a twist, explained in a bit.
The ECU relies on incoming air temp to accurately manage the fuel delivery. For the incoming air temp to be measured correctly, the sensor must be at correct operating temperature. The air intake sensor works by passing intake air over a thermistor sensor, changing its temperature and creating a signal voltage. The reference point for the sensor is measured when the sensor is at a fixed temperature. This temperature would be that of the coolant when hot, just shy of boiling. There are two coolant hoses that run up to heat the throttle body to this reference temperature. They provide heat to warm the sensor and also actuate the thermowax valve and thermowax actuator. The objective of these systems is to provide a stable reference at the throttle body for the intake sensors and to prevent high load conditions on the engine until it gets to temperature. There is an insulator plate that goes between the throttle body and UIM that is a thermal barrier so the throttle body warms to the coolant temp, and not from heat soak from the UIM. It isolates it relatively speaking.
The thermowax valve and its associated vacuum diaphragm keep the upstream secondary throttle plates from opening when starting cold. This ensures that any load on the engine is kept low by only allowing air through the primary throttle bores until the coolant can warm up the throttle body for proper intake air sensor function. Once it is warmed up, the thermowax valve closes off the vacuum hose to the UIM, and opens up an air bleed to release the vacuum on the diaphragm. Once it has done so, the upstream throttle plates are allowed to move along with the primary and downstream secondary plates, allowing for wide open throttle.

TLDR, its there to mechanically limit the engine until the ECU can go full throttle.

 

Thanks! I did pick up some vac hose and a check valve to reattach this vacuum line to the thermoswax assy.
While taking off the UIM I remembered that there are two (2) valves(?) on the manifold that I have never been able to correctly hook up. I've attached images below of the valves/solenoids and connectors. One feeds the intercooler and the second is on the bottom firewall side of the UIM. I'm sure they serve a purpose, I wasn't involved in the emissions delete so I'm not sure if they're supposed to be removed or not; but they both have the same shape wire plug and I'm not sure which one goes where.
One connector has 3 wires; 1 green w/black stripe and 2 black w/white stripe (the 2 Black w/white stripe wires go into one of the two connector pins, this plug is also much linger then the second plug. The second plug has 2 wires, Brown w/yellow stripe and a Black w/white stripe.
I assume the black / white striped wires are a ground... I'm just not sure which plug goes to what valve, I've switched them around a few times but it never seems to make any difference. Maybe someone knows where they're supposed to go?

 

The black plastic solenoid on top of the UIM is your Air Bypass Solenoid, pictured in the FSM 4b-3. Its purpose is to assist the BAC with supplying air, especially during cold start, per FSM 4b-6. The wires that plug into it are colored B/W and Br/Y, as shown in the wiring diagram p 25-26. I need to double check one of these days, but I also think it helps idle if you have your AC on.

The solenoid on the back of the UIM is your Air Supply Valve. This kicks on to help the engine keep from stalling when using power steering at idle. Its plug has the colors B/W and Lg/B. Same pages apply for this solenoid.

 

thank you!