Lean condition

[jdt9919]

I have a low-mileage '86 Omni GLHS. Installed a Stage 2 logic module and car was running great. Decided to install a 3" swing valve and bigger exhaust (with test pipe instead of the catalytic converter.) Now the engine is sputtering/stalling. Seems to be happening around 2500 but it may just be when the engine is transitioning from vacuum to boost. The problem resolves if I give it more throttle.

I've done the swing valve and exhaust pipe on other Turbo 2 cars and never had any issues, but I'd always left the catalytic converter on in those cases. This is the first time I've removed a converter, so I'm wondering if the exhaust mod is creating a lean condition, and if bigger injectors or an adjustable fuel pressure regulator is called for.

The only other mod I made was disconnecting the EGR valve. I don't think that's causing the problem, but maybe I should have plugged or not plugged a hose somewhere?

Grateful for any suggestions.

[tryingbe]

Put on a wideband o2 sensor so you know what's really going on.

[NAJ]

As stated above without a Wideband you have no idea if you are rich or lean however you can determine if all of your basics are correct.
1)Fault codes set in memory?
2)Fuel Pressure is correct and verified correct when problem is present?
(Need rail pressure reading and manifold vacuum/pressure)
3)Map output voltage is correct when the problem occurs?
4)Plugs are not fouled and are gapped propely?
5)Ignition Timing is correct?

[jdt9919]

Thanks fellas. Turned out I hadn't disconnected the EGR correctly. Everything's plugged now and the GLHS is running strong n smooth. Happy Thanksgiving

[The Pope]

BTW, other than "problems" the MP Shelby stage 2 runs really lean for power. You just made a big change in flow. I did 3" exhaust and mild porting and the car required +20s or FFVs just to not detonate. Of course a new fuel filter and maybe a new fuel pump. Then getting the injectors cleaned by mister injector is good too. Also the fueling is for a 32 lb GLHS injector not a 34.5 lb T2 / 2.5 injector. So those are an upgrade to a little more fuel. The stage 2 also doesn't like bad fuel, Chevron 92 is a must or Sunco 100.

Also my car always had a real problem with timing and sputtered. I ran my timing to 14 instead of 12 with the water temp pulled and the car was very happy. I also didn't add dielectric grease to the connectors when adding the new computer and the thing sputtered and would die when GLHNSLHT2 here would hit the computer with his foot lol.

I love the stage 2 for what it is, but it has no tolerance for any problems. The stage 2 will melt pistons or just not let the car run sometimes. So you can't have any issues. That means every sensor cleaned and greased and working right. Clean injectors and a new filter and pump. The right timing or a hair more and 92 fuel. Any one of those 3 out of place and your asking for damage, but all 3 in place and woohoo fast though with low boost lol.

[jdt9919]

Thanks, Pope. GLHS is now running well (dang EGR), but I agree, the +20 injectors (on order) are called for with this computer and exhaust. Also on my list is a wideband oxy sensor so I stop tuning these cars by trial and error. Great suggestions! Happy Thanksgiving

[The Pope]

BTW on my brothers CSX it ran great with the stage 2 but too much on edge. So when he went with a +20 he also ran the stage 5 with a 3 bar. The car hold 18 PSI and actually runs a lot safer and has more power. The key has been leave it near stock and run computer controled boost to keep the engine alive.

Stage 2 with +20s works best with a 3" exhaust like mentioned but also a ported manifolds and a mild ported 782.

Check out the stage 1 / 20 PSI thread too.

[jdt9919]

Quote:

Originally Posted by The Pope BTW on my brothers CSX it ran great with the stage 2 but too much on edge. So when he went with a +20 he also ran the stage 5 with a 3 bar. The car hold 18 PSI and actually runs a lot safer and has more power. The key has been leave it near stock and run computer controled boost to keep the engine alive. Stage 2 with +20s works best with a 3" exhaust like mentioned but also a ported manifolds and a mild ported 782. Check out the stage 1 / 20 PSI thread too.

Yep, my T2 Scamp (Rampage) runs a Stage 2, +20s, 3" exhaust (with cat), ported head and intake, and it's a stronger runner than this GLHS. I'm probably not going to do much more to the GLHS after I add the +20s since the car only has 1500 miles on it, and I'm trying to keep it (more or less) original. What messed me up was that factory EGR valve - I'd never encountered one before on a T2. Thanks again