Andrew777

iTrader: (7)

Well I'm a little bit frustrated, the car is a 87TII and I have a strange bucking lean condition going on,, It happens when im in the throttle maybe 5~15% when i watch my af gauge it's leaning to the lean side and the car jerks/bucks. As soon as i dip into the throttle a bit more it smoothes out, the PITA about it is it happeneds right where the throttle should be to maintain a constant cruising speed so it's pretty undriveable now..

Here's a backgrounder on the car and what I have done to try to remedy the situation.

Fresh motor, maybe 12 miles on it, street port and polished irons, stock exhaust sleeves, 3" single exit exhaust, cone filter, full emmisions delete except the Bac valve and IAC valve (no coolant going to IAC) and a s5 turbo.

I started by cleaning battery grounds, (the 2 on the lower strut tower and at the starter), ecu ground connector under the uim was replaced, body harness ground under the Trailing coils. Added an additional ground to the pressure sensor. New plugs and wires with the rebuild. After that I replaced Tps sensor, set it to 1ohm at ilde, Leading coil - when i had my timing light on #1 leading the spark was all over the map (can't remember if thats normal, it's been a while since ive timed a rotary motor.) Trailing timing is dead on, leading is still jumping around. Replaced fuel filter and injector insulators, replaced all vacuum lines, Pulled out Sending unit to make sure the Pickup sock and tank wasn't full of crap. Did a compression test, 105 front and rear. Did a fuel pressure test while test driving, when the stumble occurs fp is around 38 psi, when it clears it hits 42 and when slightly above atmospheric pressue goes up to around 48. Idle is around 35.

I'm pretty much exhausted at trying to figure this one out.. Feels like a nasty misfire and I haven't experienced anything like this with rotarys before so any help would be great. A couple interesting things i saw was the computer is a N332 the coils are a N326 trailing and N327 leading and the map sensor is a N318. Is this normal for a turbo II? and if not should it still run normally with them? Oh yeah and my engine vac seems kinda high it's at 15 inhg at idle,, thought it should be around 22~24inhg, probablly cause it's running rough. Yeah any suggestions would help,, my parts gun is running out of ammo.

therotorrooter

iTrader: (4)

With all the upgrades, do you have a fuel cut defender? Is it the stock ECU? N332 is for the 87TII and the map sensor is n318 and I think the coil #'s are fine. You may already know this, but it's highly recommended to not take a freshly rebuilt engine over 4000 rpms for a few hundred miles. It's also hard to tell with just 12 miles because everything hasn't properly set in. Check that all the vac lines are connected and free of any holes. Also make sure all the turbo ducting is connected and free of holes and cracks. This can also cause issues with air readings to the computer and throw off air/fuel mixtures and such.

Andrew777

iTrader: (7)

yeah I'm keeping the motor below 4000 and off boost All the vac lines were replaced along with the TID, the old one was cracked right at the trubo and was covered in duct tape,, probablly why the motor blew in the first place and there was a fuel cut defenser in place, it looked home made so I removed it. Oh and Yeah, the Computer is original.

Andrew777

iTrader: (7)

any other suggestions?

Andrew777

iTrader: (7)

update, replaced ect sensor, no luck, same stuff

meteoro

maybe TPS

or try autodiagnosis

Andrew777

iTrader: (7)

Already changed TPS twice, once with a used unit and once with a new unit, what do you mean by autodiagnosis?

HAILERS2

No help from me. No real ideas. Except it does have the charateristics of a lean running engine for sure. The fuel pressures don't seem to be the problem though. Normal enough pressures, give or take some.

Might be a fuel injector problem. Maybe swap both primarys with both secondarys and see what happens. What a pain though. Also check the lower grommets on the fuel injectors for leaks...air leaks.

Make sure the injectors are 550's and not *something else*.

I play a lot with my RTEK2.1 and ethonal and Know what LEAN running feels like. Similar to what you have. But you have no way to enrichen the fuel and are running normal gasoline, so that's why I suspect the PRIMARY fuel injectors and or leaking lower grommets on the injectors. Idle the car and spray starter fluid under the manifold and see if the engine speed gains/falls while doing so. But I really suspect the Primary injectors. Swap them with the secondary ones.

Andrew777

iTrader: (7)

Thanks hailers i was hoping you would tune into the topic,, i'll try the injector swap in the next couple of hours,. when you refer to the injector lower grommets are you talking about the part with the fuel diffuser or the rubber insulator that sits on the injector pintle. And yes it does feel like a lean condition, My a/f gague agrees too.

Andrew777

iTrader: (7)

just pulled the injectors out, when i put the motor back together I put a originally positions secondary in the primary rail so will swap that back to the primary position and see how it goes, if not will try both originally positioned secondaries in the primary rail,, pn # on the injectors is 135500-1307, from what i remember that is the S4 TII injector, Purple with a high center square offset. Correct me if i'm wrong..
Thanks

Andrew

Andrew777

iTrader: (7)

well first swap-over done, both primaries are in their original location, same sputter. I also discovered that it doesn't act up as much when it's cold, only when it warms up and the temp gauge lifts past the 2 notches on the bottom. I'm going to try swapping secondaries to primaries now. See how it goes.

Andrew777

iTrader: (7)

Well just finished the change over from primaries to secondaries and there is a difference, it's better but not completely cured, also noticed that I have a two step ilde, one holds 1200 rpm, when i'm on the brakes, lights on, ps cranked, it drops to 700 and holds even after I turn all acc. off. Wondering if this has somthing to do with it, Had the throttle body all apart and cleaned the crap out of it when i did the rebuild. Going to send the injectors out for cleaning and balancing.

HAILERS2

Yeah, should have been -1370 number on the injector body and the locating tab offset for a series five Turbo.

Ah, sorry, I didn't see you have 1680cc in the secondarys. Sorry 'bout that. I wouldn't have suggested swapping the secondary to the primarys if that's the case. Too much fuel for primarys.

A cold engine runs rich for the first couple of miles til the engine temps reach about 120* and then get leaner. That explains the cold engine running better.

I meant the rubber grommets on the bottom of the injector, not the plastic diffusers.

Next time your idle wants to do the 1200 rpm thing, pull the BAC plug off and see if that isn't what was holding it at 1200rpm.

Once the rpms get just a tad over 1100-1200 rpm, the timing advances and that results in a high idle sometimes. Sounds BAC related. Pull plug off.

Were those 1680's you put in the primarys for a test??????? I'm a little confused on the secondary injector size right now.

Kinda hard to fix that one online.

Andrew777

iTrader: (7)

Hailers2 thats my 89 cosmo vert specs in my sig, completely different car. This car is a close to stock 87TII and is still running with the stock 550 cc injectors. I will play around with the bac valve to try to get a better idle, I already tried unplugging it and seems to want to stay idling high.

Andrew777

iTrader: (7)

interesting new finding, It may not be the injectors. After finding a dashpot keeping my throttle stuck open slightly I attempted to adjust my idle to 1000 rpm smoothly, played around with the idle adjust screw and the BAC, found with the BAC closer to screwed all the way in the car seems to run better, not great, still has the stumble but much less, and with it further out (allowing more air) the car bucks and jerks significantly more. Could this be a bummed out BAC valve? Furthermore when trying to blow air through the valve inbetween the TMIC and BAC valve (I think IAC valve) nothing flows through. Is this abnormal?

ikekrull

Sounds very similar to what was happening to my FC - After discounting a massive vac leak under boost, complete loss of power to the fuel pump and failing coils, i figured it had to be something else.

Turns out theres a line and relay that the ECU triggers - it drops the voltage to the fuel pump from 12V to 9V at idle or possibly at cruise? - i clipped the appropriate wire to disable the circuit, so the fuel pump sees 12V at all times, and the massive hesistation and stuttering disappeared. Oddly the car ran fine until one day the problem just started happening - no rhyme or reason.

Could be worth a look?

Andrew777

iTrader: (7)

New update, while installing a aftermarket blowoff valve I managed to knock the vacuum line off of the boost pressure sensor, without knowing I went for a ride to see how it sounded, and the car ran like a top. I figured the factory one was stuck or somthing,, Sounds like a bummed out pressure sensor??,, when i hooked it back up same problem. Anyone ever heard of this causing that?

rex7tuner

iTrader: (3)

MAN im having the sAME exact problem with my car right noW! its killing me cause i wanna daily drive it but with a little bit of throttle my a/f gauge jumps to lean and my car bogs unless i give it more throttle! i have a medium streetport also on a 8:5:1 Tll motor! exhaust intake and some other little goodies. but verrry close the same, everything that u described with ur problem i'm having the same prob!
any luck with the problem?? thanks!

LikedVtecLoveRotary

I have the exact same problem, any insight please? a PM would be great...

im searching everywhere hopefully can find it. BTW i have a s5 not s4

lastphaseofthis

iTrader: (8)

WORD to this thead, i have the EXACT same problem also, but i'm too stuck up to ask for help.

After much efforts like everyone else's.. i did a fuel pressure test.

Fine while driving, and appearing completely normal(32-34 under light cruise, when it starts to run out of breath)

I hooked the tester directly to the pump and low and behold, 55 PSI MAX, when specs call for 71-92 psi.

i am waiting on the (used 3rd gen)pump now, but in the mean time, im gonna try unplugging the boost sensor.
( would also trick the ecu into not going into closed loop.)

But as far as the problem goes, it feels like it's only during CLOSED LOOP, if that helps with suggestions.



Do any of you three have access to a fuel pressure tester? and can you hook it up with no return to get max fuel pump pressure test?

turboIIrotary

iTrader: (9)

change your pressure sensor i had one go bad and it caused a huge hesitation at low rpms. also the timing can only be adjusted when idle is below 1000 rpm.

lastphaseofthis

iTrader: (8)

Are you saying with a new presssure sensor the problem went away, or with only the old one unplugged, did your pressure guage work with the old sensor, but you still had the hesitation?

LikedVtecLoveRotary

i dont think rpm effects mine so much as using only the 'soft spot' of the pedal (first 15% or so) and it starts bucking around

but if i start to boost my car engages and goes fine.

fuel pump? pressure sensor?

lastphaseofthis

iTrader: (8)

pressure sensor mask's it, i think it's the fuel pump but i want you people with this problem to test test test
i need to know max fuel pump pressure, with the return line blocked, or hooked up with no return.

You need to test your tps... just to be sure, as it doesn't sound exactly the same as what i am calling "the closed loop bug"

LikedVtecLoveRotary

I cleaned my spark plugs and it seems to have reduced the problem...

replacing plugs and wires tomorrow hopefully that cures it.