Hi everyone, I've been searching through the forum but haven't come up with any answers to this one. Hoping someone can help me out.

When driving up to a set of lights and downshifting I go into second gear and push the clutch in just before stopping, the engine idle goes way to low and nearly dies altogether. Listed below is what I know about the engine. Any comments will be greatly apprieciated.
-305 tpi w/5speed
-new IAC installed to correct torque. Tested and works correctly.
-Minimum idle adjusted with IAC closed, but could only get idle down to 500-525 without engine stopping.
-Fuel pressure 42psi ignition on, engine off - 36psi during idle. Responsed up to 42psi during accelleration.
-IAC counts couldn't get any higher than 10 at idle when adjusting throttle plate screw.
- IAC counts always go to zero approaching lights and when rpm drops to 450 it opens up and only just keeps engine alive.
-TPS sensor 0.57v at idle.
-52mm throttle body and larger runners.
-O2 xcounts are counting up normally.

Has anybody got any ideas??
Thanks, Richard

 

Hi.

I would guess your EGR may have a problem.
Also there may be too much carbon buildup in the throttle body, restricting air flow and when's the last time your air filter has been swapped?

 

The air filter and throttle body are all good, nice and clean. I'll check out the EGR though.
I'm no mechanic so why do you think it may be EGR related??
Thanks, Richard

 

Ok.
When the EGR is sticking, you will get all sorts of troubles regarding engine air flow.
The EGR is responsible for "recycling" some of the exhaust gases, so it makes a connection between the intake and exhaust manifolds and opens/closes this passage depending on... pressure I guess. I'm not sure.
So if it sticks in an open position, you're having too much exhaust gas in your intake and not enough proper air. If it sticks shut... well the engine is expecting a bit of extra "air" coming from there and calculates with it.
At least this is my non-pro explanation.
My only own experience of this kind was with a different car some years back. The EGR died and the engine kept shutting off in a jerky manner until the EGR was replaced with a new part.

 

I had this exact same problem with TPI 5 speed - while braking and downshifting into second the engine would either slow down to a really rough idle or even stall. While running rough, if the brakes were released before stalling, the engine would smooth out. If the engine stalled, it would restart immedialety and idle smoothly 100% of the time.

The problem turned out to be the exciter ring on the distrubutor shaft. Some of the teeth on the ring were rusted and cracked, so the pickup wasn't able to get a good signal as it was spinning inside the reluctor. It worked most of the time, but under hard braking, there was just enough movement to stop the signal and kill the ignition. Remove the ignition cap & rotor as well as the brass shield and take a look at those teeth. I replaced the parts, reset the timing, and now it's all good.

Distributor shaft with exciter ring is available as a seperate piece. While I was in there I also changed the reluctor and pickup coil since they were very inexpensive. Any parts store should be able to either get these parts or cross them:

Standard Motor Products:

shaft - DG43
reluctor - LX372
pickup coil - LX342

Good luck!