The car

1988 TII
Newly rebuilt massive streetport
Rebuilt stock turbo
2.5" Racing Beat downpipe, 2.5" midpipe to single SS muffler
CAI
Turbo XS BOV
3 row Koyo radiator
FD 120 amp alternator w/ dual-belt pulley
HKS Type 0 Turbo Timer
No air pump or accessories
No rat's nest
sub-zero system removed
BAC was disconnected and blocked off except for the air pipe in front of the turbo
fuel cut defenser

Starting up, she doesn't idle...will not. I have to get her up to about 100* before she'll even try to hold an idle on her own. I set the idle to 1100rpm...that helped.

When you're driving, there's periodic stumbles at gradual accelleration and and steady driving.

Going to WOT results in a bog then a slow climb in rpm...at about 4000rpm or so it smooths out but it's nowhere near as fast to rev as my experience tells me RX-7's should.

I've checked for vacuum leaks, didn't find any. I do know that my injectors leak...there's caked grime around the injectors themselves and after the car has warmed up and shut down, you either have to do the deflood proceedure or wait for her to cool off.

Any suggestions?

 

Bad BOV. Tighten down the adjustment screw.

 

the adjustment screw on the BOV? How do I test the BOV to see if it's malfunctioing?

edit~ I don't see an adjustment screw on my BOV. Where should it be?


Who makes "Turbo XS" BOV's anyway?

 

okay...did a search and these are supposed to be fully adjustable via packer washers...can anyone tell me more about this?

 

anyone?

 

from the couple people ive seen with turbo xs bov's they seem to have some problems with em, maybe you should look into a different one? Im in no way sayingthey are bad (ive never owned one). Sorry i cant help with the adjusting, but at least its a start?

 

sounds like a vac. leak (at least partially). I assume you checked by spraying carb cleaner around the motor?

Have you checked your TPS?

Compression? (might as well)

I know that disconnecting the thermowax/emissions stuff makes it hard to start cold (i.e. give it gas for a while)...

Since you say it starts 'smoothing' out at about 4k, maybe your primary injectors are gummed up or something (wheras your secondaries are fine....?)

Is your twin-scroll hooked up correctly? (this will cause slow boost response in s4's).

Re-reading, those "slight stumbles" at partial throttle (like a jerky/boggy feeling) are likely due to a TPS on it's last legs...

 

Tried carb cleaner and water mist all over the intake assembly. No leaks that I can find.

Have not, yet. I don't have a volt-meter (not sure where it went).

Doing in the AM.

I've always gutted the emmissions and never had this kind of problem but I've never messed with the "thermowax"...what the hell is that?(searching)

Hoping to test soon...got another set of injectors coming my way.

Twin scroll? I build boost like a ************...

I'll be sure ot check the TPS out as soon as possible...I didn't think that it could cause such problems.

Is the S4 NA and TII TPS the same? I have several S4 TPS's (or is it's TPI for plural?...I'm a dork)...

 

About the twin-scroll; on a s4 turbo, half of the exaust is 'blocked' by a little door that opens at like 2800 RPM's (I think). It's controlled by an actuator ran off of vac pressure. If the twin-scroll ISN'T hooked up the car will be a little lazy until the boost finally builds... If you're not sure if it's hooked up etc. it's definitely worth looking into. When it's hooked up correctly, the low-end response is a lot better.

 

I'm sure it's gone but I'm not quite sure I know what you're talking about. Lazy to boost would just be slow throttle response, basically...this is violent thrittle response. Jerky and lethargic the whole way. She builds boost like nothing else...full and holding just oer 3000rpm, and instant to build if I touch the throttle.

 

Ya', jerky would be a bad TPS.

On the s4 turbo's, one of the exhaust 'runners' is smaller than the other. This is covered by a small 'flapper door' (to help spool-up). At a certain RPM/vac. pressure the door is opened by a little actuator (like the WG).

If the 'runner' isn't ported out (to match, for example the s5 turbo), you won't be getting full spoolup as early (although max boost etc. is uneffected).

I'd compare it to having your 5th and 6th ports disconnected on an N/A.

 

alright...I'm going to wire me up a couple of LED's when I get home and set the TPS. I haven't found a good diagram of the plug and terminals I'm supposed to use...any help with that?

 

check the leading coil my car did the same thing when that went, almost felt like a blown motor. If not that maybe AFM oh and like what was said above, check twin scroll

 

TPS is set. No change.

Any other suggestions?

75lbs of compression at WOT...plus ambient atmosphere is 90~ish lbs.

 

Those are terrible compression numbers even for a fresh rebuild with a "massive" port.
It should increase some with a proper break-in but you will be lucky to see 90-95 which is still weak.

It sounds like you need to check a few different things.
Water thermosensor - green sensor on the back of the water pump housing- if it is running rich
AFM (common failure item) & turbo inlet duct- for cracks, also very common failure area
Intake air temp sensor can also cause it to start very hard and have a bad idle.

 

The manual says 85lbs is spec on compression. The motor should already be "broken in".

I've checked the intake plumbing for leaks and I don't know how to check the AFM out. I'll look at the thermo sensor, though, and the intake air sensor.

 

did it again...

even 62psi on both rotors at 300rpm. This is by just bolting the guage up and let it pump air to it's max. Levels off between the 50 and 75 marks. Plus the ambient 14.6lbs or whatever....<80psi...

Yes, had it floored.

 

85 lbs is not the spec on a rotary engine, 8.5 bar which equals 125psi is the spec. Below 90psi we tell people to start saving for a rebuild.

 

Who did the rebuild?
What kinda vacuum readings are you seeing at idle?


-Ted

 

Stuff and nonsense. Read the fsm or don't post. humor sort of.

See page 1-11 of the Factory Service Manual, 1987.

That said, the compression sounds very, very low. Buy new rotor housings on your next rebuild.

 

trying to find that out now.

Vac at idle bottoms the guage out...I can't remember what that particular number is but I know it's a good one...

 

Damn i forgot about that, great suggestion!

-Andrew

 

pulling 28lbs at idle (1000rpm or so)


What does that tell me?

Last night I fed her about 16oz of water and then about 12 of barryman's EFI cleaner and she really drove a LOT better, but still nowhere near as powerful as I'd expect a turbo with a large streetport to be. At least now she feels faster than my Bimmer...but not by much.

 

It means the gauge is bad, or you're not reading it correctly.


-Ted

 

yup....you're right...misread AND wrong number

at idle it's pulls right about 13in hg.

What does that tell me?