timesteals

My car is a 91 NA FC with the following mods:

auto to manual transmission conversion (transmission from TII)
LSD w/ 4:30 gears
full suspension
cross-drilled brake rotors
stainless steel brake/clutch lines
lightweight flywheel
underdrive pulley
Apexi N1 dual exhaust (3" throughout = too big!)
Pacesetter header w/straight pipe
silicone spark plug wires and vacuum tubing
Bonez cold air intake
removed secondary butterfly throttle plates (the set nearest to MAF)
I think that's about it. . .

I've checked about everything I can think of. The car ran fine, then the main drive belt broke one morning when I tried to start it. I picked up a new belt and installed it, but couldn't get the car to start (I think it was probably flooded). Anyway, I ended up leaving the seven in the garage for several months (I was busy with classes) and just recently began working on it again. I had one hell of a time getting it running. I used a little ATF to get it going, and then did a full tune-up:

changed oil/filter
drained fuel tank (refilled with fuel and Lucas fuel treatment)
changed fuel filter
replaced spark plugs
cleaned K&N (cone-style) air filter
filled up radiator
replaced battery

However, there were problems. . . At first, the car wouldn't idle correctly, but this is nothing new for my car. In addition, the car seemed to die quite easily and lacked power throughout the whole RPM band. Throttle response sucked, and there were hesitations throughout the power band (esp. lower RPMs). So. . . I:

checked for vacuum leaks (my first instinct) and found nothing. I sprayed carb cleaner around, listened with vacuum tubing, and performed a thorough visual inspection (everything short of removing the intake manifolds). I recently (about a year ago) removed the intake manifolds, cleaned them, removed the 5th and 6th port sleeves and sent them to Rob for the inserts, replaced all vacuum hose with silicone tubing, and put it all back together with new gaskets. So, I'm sure there could be a vacuum leak or disconnected hose that I can't see, but it seems unlikely to me and I don't want to remove the intake manifolds again unless I have to.
cleaned throttle body
lubed up various mechanical parts
replaced O2 sensor (the wire was cut somehow)
checked resistance of:
coils = OK, BAC = OK
adjusted TPS with test lamps (tried to check resistance, but not sure which pins to test-Haynes manual/FSM seem to describe a different connector than mine?)
adjusted idle (by grounding initial set connector)
added ground from negative battery terminal to car body
added wire from positive terminal to alternator post

At this point, my idle was almost perfect when the car was completely warm (still jumped around slightly, varying about 50 RPM above and below 750 RPM-no biggie). However, the car still wants to die if the RPMs are revved high (3-7k) and the throttle is released. The RPMs drop very quickly, stumble for a split second near idle range, and then the car dies. The car will start right back up, but it will usually take a couple of attempts (this is also the case when the car is cold). The car also seems to backfire quite a bit. It has always backfired some (probably because of the aftermarket exhaust), but it seems excessive now. EGR valve? In addition, the car idles quite roughly in the range of about 800-1000 RPM, but seems fine at any other RPM.

I tried adjusting the throttle plates by tightening the throttle stop screw on the front side of the throttle body, but this just seemed to make the idle more erratic. I'm sure it would prevent the car from dying, but would also waste a lot of fuel.

This is where I've left off. I'm not really sure what to try next. I think maybe I'll remove the BAC and hook it up to 12V to ensure that it's operational. I know I also need to test the TPS resistance if someone could please clarify the procedure for doing this. I should also maybe check the solenoids in the rat's nest to make sure they're working OK. I haven't checked compression yet (would have to use the cheap-hand in front of spark plug hole method), but am hoping that this isn't the problem as the car ran fine before the belt broke. However, the car did sit for several months without being started. . .

If anyone has any ideas they would be much appreciated. I may have left some things off, so please ask if you need any clarification. Thanks!!

P.S. I've been searching the forum and troubleshooting for about a month now. Didn't want anyone to think that I'm too lazy to try and solve the problem myself. I actually hate asking for help, but I realize that it's important to do so sometimes. . . Thanks again!

'87 turbo II

iTrader: (1)

I didn't read all that, but my 7 does the same thing if it isn't wamred up. Blip the throttle at the end of a fast RPM descent.

timesteals

Yeah, I've tried that, but when I'm coming to a stop it dies when I apply the brakes. . .

timesteals

Anyone else? Sorry the thread is so long. . .

timesteals

Come on. . .I know one of you 2nd GENiuses has a good idea as to what might be the problem with my poor little FC. . .

HAILERS, IceMark, Aaron Cake, NZConvertible, etc., etc., etc., . . . please give me something

scrip7

iTrader: (6)

Lots of things to check, but because it is running poorly after sitting for several months, I would stick with the plan of checking compression, ruling that out before exploring other avenues. I have torn apart several rotaries that sat several months, all of them had at least a few stuck side seals on the rotors, reducing compression enough to give them crappy idles and low power. Coolant seal seepage and condensation during those months of storage can cause it.

timesteals

Thanks for the info. So, do ya think there's any way to revive it? Should I let some ATF soak in the rotor housings for a few day to lube up the seals, or is there no hope? Thanks again.

scrip7

iTrader: (6)

I don't advocate the use of ATF in the chambers. Some have had success, only to have problems later. The atf tends to soften and eat the oil control o-rings.

NoDOHC

Did you check your timing (I may have missed in the listing.)

My car did the same thing (only cold, not hot) and it was a combination of bad AFM adjustment (by previous owner) and 15 degree retarded timing (preignition would not have been a problem on 68 octane.)

The ECU mostly ignores the AFM while driving down the highway in closed loop, but it needs it for hard acceleration, idling and running while cold.

87Rx78488

Go to the passanger sid of the car. Look down and you should see a silver like plug. If the wire is still connected to it I can't help you buddy. but if the wire is off it connects to the cback of the intake manifold. it is a tight fit, but feel around you'll find it.

timesteals

No, I haven't checked the timing, but was actually just searching the forum in attempt to find a How-to on it. What is the best way to go about checking the timing? I have the check lamps (same ones used to adjust TPS). I thought I'd read somewhere that they can also be used to check timing. . . Is this correct? Thanks!

timesteals

When you say "silver plug" are you referring to the O2 sensor? My O2 sensor was actually found to be disconnected when I first popped the hood to try and get the car running. I bought a new O2 sensor and spliced it into the severed wire, so it should be fine now. However, mine doesn't connect to the back of the intake manifold, but rather near the front of the engine somewhere (can't remember exactly off the top of my head). Thanks for the suggestions.

Anyone else have any ideas or know how to go about checking/adjusting the timing?

shrek

Could be caused by the throttle body mod. I modded my throttle body and also had idle problems. I don't suggest the modification. Try installing a stock TB or buying a new one.

scrip7

iTrader: (6)

You said the car was running fine, then a belt broke one morning. You fixed that, but still wouldn't start. You let it sit for months, which is a bad enemy to rotaries unless you followed proper storage methods.Vacuum leaks didn't suddenly appear, and the timing didn't change on it's own. My bet is reduced compression from stuck side seals. Have you done a compression test yet?

timesteals

Shrek:

Yeah, I agree that the TB mod probably wasn't a great idea, but I've had it done for years. My car never really had a great idle, but the bigger problem is/was it dying as the RPMs drop. I'm gonna check the grounds this weekend. . .

Scrip7:

You may be right, but I'm hoping not. I'll try and check the compression this weekend.

Sorry it took so long to respond. I haven't been able to get on the forum for the past few days. Was there a problem with it?

Thanks for your help everyone!