Engine Surges - Chevy Metro

[kimokalihi]

A couple weeks ago I noticed the engine cut out a few times when I accelerated from a stop sign. It did it in 1st and 2nd gear and then it was fine in 3rd and up. Didn't think much of it since it's been doing this for years when it's really cold outside and the engine isn't warmed up. If you give it too much gas in 1st gear it will fall on it's face for a second and jerk the whole car like it's not getting fuel.

Now two weeks later it's gotten way way worse. There's also a code stored in my ECU for the EGR system. The exhaust has gotten much louder and sounds like there's a hole in the pipe or muffler towards the rear. The car now jerks in all 5 gears violently if you try to accelerate. It's fine on cruising and once the engine is fully warmed up it goes away completely. It's quite dangerous if you forget about it because you won't be able to accelerate and merge into traffic at a fast enough pace.

Any idea where to start here? I haven't had time to check it out yet but I did push the EGR plunger open by hand a little bit and the rpms went down immediately which I read on another forum indicates the EGR passage is not clogged?

What do you think the relationship with the temperature of the engine is with this intermittent problem?

I miss the legacy.

[kimokalihi]

I replaced the EGR probably over 3 years ago with a brand new one just for the heck of it during a routine tuneup. I think it could also be related to he the MAP sensor because I read that the MAP sensor is what controls the EGR valve.

[PhyrraM]

Do you have an OBDII code scanner? Most of the 'one step above basic' ones can read the sensors straight from the ECU. Look for anything that doesn't behave as expected.

Fuel pump/filter? Sticky EGR? Leak in vaccuum/EGR lines?

[kimokalihi]

I do not. I have the scangauge 2 which is how I knew there was a code. After it started acting up I used it to scan the ECU and it came up with the EGR code. The check engine light has never come on.

[mike-tracy]

Have you tried some seafoam through it yet? My old 91 Toyota 4Runner (California model) had the code for EGR and I seafoamed it twice, and the code went away. A knocking noise at startup went away as well.

[kimokalihi]

I think I seafoamed it back in the day. Probably 4 years ago. I guess I just don't understand how the EGR is causing this. Where does the EGR gas come from exactly? The head or the exhaust manifold?

[PhyrraM]

I think I seafoamed it back in the day. Probably 4 years ago. I guess I just don't understand how the EGR is causing this. Where does the EGR gas come from exactly? The head or the exhaust manifold?

EGR dilutes the oyxgen content. If the amount of EGR being introduced doesn't closely match what the ECU is expecting then the ECU cannot make proper descions. This is why some cars monitor the EGR sensor or EGR line pressures directly, while other ECUs just assume that everything is working withut any real doublechecks. It's primary use is to reduce combustion temperatures to slow the formation of NOx in the exhaust. Most ECUs modify both timing and fuel injected to compensate for the O2 diluted effects of the EGR.

Every manufacture does it differently, some grab it from the exhaust manifold, some from the head directly. My old Mazda grabbed it from the exhaust manifold, used a pipe to deliver it to the EGR valve on the back of the head, through a passage in the head to the base of the intake manifold, and finally through a passage in the intake manifold that discharged into the intake stream behind the throttlebody. Horrid, but cheap to produce.

Either way I still say to start with all the sensors. Check that all are operating within expected ranges and don't have 'dead' zones.

[kimokalihi]

Alright. I hate this sort of problem. Luckily I have the FSM from Chevy for this car and this exact year, just like I have for the legacy. I'll have to look into that. I also ordered some new multimeter probes because mine broke. Hoping they fit because I couldn't find any craftsman specific probes.

I wonder what the relationship is with the exhaust being much louder? It almost sounds like there's a hole in the muffler which occured at the same time this problem happened. Odd.