Tigerx7

Hey all, as the title says, I'm having a severe sputter/loss of power below about 3K rpm (the actual rpm that it stops varies). During the sputter it is running extremely lean 18:1+ AFR. As it nears 3K rpm the AFR starts to drop and by 3.5K its completely normal. It idles a bit rough and is a tad lean at idle (about 14:1 AFR). in neutral it revs normally with very slight throttle, but if I get into it at all it sputters. when driving it sputters and runs lean no matter what unless I can keep it above 3K at which point it runs great whether cruising or full throttle. Makes full boost of 10 psi, and there's no vacuum leaks. It does have an exhaust leak from a crack in the manifold, and the radiator fan switch stopped working a few days after the car started acting up. It used to run at about 1/4 on the temp. meter but now its running at about 1/2 way up. other than that everything is normal.

It started acting up while on the way to a meet, cruising at about 80 on the highway and it was fine, then I got off of the highway and as I was accelerating away from the first light is when it started acting up. At first it was just below about 2k rpm and I kept driving it because I was only a few miles away from the meet. By the time I got there it was acting like it is now. The only thing I changed was that as I left for the meet I filled up on gas and I switched to Benol oil for premix. I've switched back to quicksilver now and it had no effect.

Its an 88 TII with an RB turboback, Rtek 1.7 and 720cc secondaries, OMP deleted, throttle body mods, gotten rid of the e-shaft thermowax, deleted the twin scroll system, all emissions removed, and premixing at 1 oz per gallon with quicksilver. This was all done long before it started acting up.

I did search and didn't find anything like this. Anyone have any ideas? I'm stumped.
thanks in advance

jjcobm

iTrader: (18)

I'll try to help out. It sounds more like and injector issue to me. If it was fine before, there is the possibility an injector is acting up...

How is the idle and WOT?

Tigerx7

Idle is a bit rough and a little lean, the a/f ratio seems to fluctuate between low 13s and low 15s. At WOT it sputters and has almost no power until 3K rpm, same as any other throttle position except very slight throttle. Above 3K at WOT it runs mid 10 to mid 11 AFRs and runs great. I'm trying to find my other rebuilty injectors to swap in and see if thats the issue, but I haven't seen them since I moved, lol.

jjcobm

iTrader: (18)

Now that I think about it, make sure you overlook all your vacuum hoses and make sure no hoses or intake tubing that has been disconnected due to the pressure from the turbo going through the intake. Remember lean is also an indicator of unmetered air going in or not enough fuel mixing with the air....

Besides that it seems like your primary injectors are acting up. Sound like a bit of the 3800 rpm hesitation too so maybe if you have the intake off go over all the grounds if you haven't already....

Natey

iTrader: (19)

^^^agreed.^^^

The old 3000 rpm hesitation is usually a grounding issue. Check the big three for corrosion, and maybe you'll get lucky.

t2Maniac

iTrader: (1)

I have the same problem, everytime I accellerate from a stopped position it sputters/bogs/hesitates for a second or two, then it smooths out once I'm past 2800-3k rpms. Anything after 2800-3k rpms it runs smooth. I just had injectors cleaned, rtek 2.1 1987 turbo 2. Stock everything, just got new tps sensor too. Reads 5 volts to one side. Sprayed everything with carb cleaner even sprayed injector grommets and nothing changed. Any special wires I should look at or any tips would be appreciated. I daily drive it and its getting real annoying...
Also cleaned and replaced all grounds, even added a couple extras,

*Side question, all 2nd gen TPS's the same for turbo and nonturbo? S4 only*

misterstyx69

iTrader: (142)

/\/\..yes the s4 turbo an N/A TPS is the same.
Not so with the S5.

t2Maniac

iTrader: (1)

I know the s5 different cause theres 2 of them for that series, just would like to know if any certain wires can be stripped from anywhere and I should check? I still have the hesitation and its bad.

Tigerx7

I wound up selling the car a long time ago, but I remember speaking to the new owner a while later and he wound up replacing the wiring harness which fixed it. You might try load testing the wiring to the injectors, the tps, and the afm. That was my plan before I ran out of time and money for the car.

RotaryEvolution

iTrader: (30)

was probably a faulty ground strap to the rear rotor housing, which feeds ground to the injectors which gets lazy with higher than normal resistance.

Tigerx7

I replaced all of the engine grounds before selling the car and it had no effect. All of the engine wiring was deteriorating pretty badly on mine though which is part of why I gave up.

t2Maniac

iTrader: (1)

How would I load test? Get power to one side of the harness from the ECU (unplugged) and check for the same voltage on the other end where the TPS, Injectors, and AFM are plugged into it?