TII used to have a lumpy idle, now it just runs like crap.
 

When I bought my TII, it had a lumpy idle and it idled around between650-800rpm. It was a little tough to start when the engine was cold, and it didn't like idling on its own when it wasn't warmed up. Now, though it is extremely tough to start when cold, has lots of trouble idling on its own all the time, and also stutters on acceleration. When it's at full throttle, it seems fine, but when I'm accelerating lightly, it bucks from2000-5000rpm (that's as far as I've gone to see where it runs like crap). I'm not too sure what's going on, I think it could just be a vaccum leak that's getting worse somehow? Anyone have any ideas?

Also, it only pulls about 200mmHg of vaccum when it tries to idle on its own, but it will go to about 400mmHg when I put the throttle in a tiny bit.

muh. anyone have any ideas? Doesn't it seem most like a vaccum leak? If it was a TPS adjustment issue, wouldn't the problem not get worse and worse? I'll be taking off the BAC valve, ACV, and I believe the EGR valve, so I guess I should check for vaccum leaks then, and seal everything up nice and tight.

I'd definitely spray around for vac. leaks, check the compression (simply precautionary) and check the specs on the TPS.

That light bucking sounds like it could be related to the TPS (as well as the idle).

It could be a combination of a TPS on it's way out and a decent vac. leak.

It does seem like a combination...I think I'll check both things, I have a spare '86 N/A sitting in my driveway, could I use the TPS off of that car? My car is an S4 TII, so it should work, right?

gotta be a vac leak, or its got too much cum in it.

That's actually disgusting. The 'cum' comment.

Yeah, how would that happen, anyways?

It does seem like it would be more vaccum related, because of the low vaccum it's pulling at idle, but it'll pull more vaccum if I give it a little throttle, are you sure it sounds like a vaccum leak?

TPS will work, just swap the n/a mounting plate with the TII one so it'll fit your TB properly. The actual TPS's are the same.

Also, do all the basic stuff just to eliminate possiblities. Such as, check/set TPS via resistance, and THEN check it via voltage. If voltage is off but resistance is correct, your TPS isn't working the best. In that case set the TPS via voltage rather than resistance since the ECU only cars about the voltage setting.

Spray fluid around (carb cleaner, starter fluid, whatever) to check for vac leaks. Even if you don't think it's one, check anyways.

Check resistance on plug wirse.

Check water thermo sensor if you feel like taking it out, specs are in the FSM.

Check timing and/or restab CAS.

Etc.....

Jeez, so much for having fun this weekend...

Diagnosing is never fun :D

It may not be any of those things, it may be one or two of them, but it's really hard to say. That's why I always suggest just checking everything, it eliminates the possibilities of overlooked parts.

Also, some of those things are like a 2 minute job, wont take long.

You're probably looking at a vacuum leak. I fought idle on my '97 TII for weeks. Replaced all the rubber hoses on top and it was better, but still unstable and never below 1500RPM.
Found that the rubber plenum between the AFM and the turbo inlet had a split in it. Fixed that, clamped it tight, re-adjusted the TPS and now it's *rock* solid at 750RPM for the last 15,000 mi.

I understand from a rotary guru in the Denver area that this is common, so I'd check for tight seals from the AFM through the engine intake before I went to any real trouble.

- k -

I want one...

Alright, now I can't get the damn thing to start. I did a compression test, and it came out to 95psi front, 90psi rear on a cold engine. Do those numbers sound alright? They seem lower than my old car...

those sound alright, good enough to still start and run just fine. check your TID, most common culprit for the T2 to have a vacuum leak as it tends to crack and split from the heat, and also check for vacuum leaks in other areas.

95 front and 90 rear is okay, not great but okay. Generally cold compression is higher than warm in some cases. Others claim it is no different between cold and hot, and even others claim that hot is higher than cold. In my experience with my own car, though, cold has always been higher.

Should last you a while longer, though, and should easily start on that compression.

Hmmm...it has a fabricated metal TID. The BAC valve is removed on this car, but it still has the vaccum spider and ACV and also the EGR valve as well as the OMP. There don't appear to be any vaccum leaks...everything seems to be capped off. Does it sound like it's a timing/TPS issue?

No BAC? What was the previous owner, or you, doing to adjust idle? Just a throttle stop screw or what?

Before we go on guessing, between the time it was started/running and when it wouldn't start at all, what exactly did you do during the troubleshooting/diagnosis?

What I did last night was I took off the UIM, put in new secondary injectors, and checked for open ends on the vaccum spider and plugged up two open ends I found.

Pull EGI fuse, crank a few times (unflooding technique), and try again. In my experience with 4 different rx7's, removing injectors/fuel rails and replacing them the engine decides to flood... I guess it's because when you remove injectors or the rail or whatever fuel pours out and decides to go through the injector holes, maybe? Who knows, but unflooding techniques have always worked for me.

Alright, thanks a bunch, I'm gonna put the BAC valve back on and inspect the throttle body for any modifications, too.