Last post on Aug 22, 2012 at 10:55 AM
You are in the Chevrolet Metro/Geo Metro
What is this discussion about?
Geo Metro, Chevrolet Metro, Hatchback
#1667 of 1864 Re: Sensor Voltage Weirdity [shaggyman1]
Aug 20, 2009 (12:08 pm)
In addition to improper EGR valve regulation (the EGR valve essentially acts as a massive timed vacuum leak into the intake manifold), two other vacuum related issues would be a vacuum leak in the hose to the brake booster from the intake manifold, or the use of the wrong model PCV valve, or a PCV valve that was not plugged into its socket. An additional EGR issue could come from using manifold vacuum, or the wrong throttle body vacuum spigot, to supply the EGR circuit (it should come from the spigot on the front of the throttle body which is closest to the passenger side). A purge circuit issue could be caused by using manifold vacuum or the EGR spigot to supply the purge control valve (it should come from the port on the front of the throttle body which is closest to the driver's side).
You can eliminate the EGR valve as a factor by simply disconnecting and plugging its vacuum hose; and seeing if that changes the stalling behavior. However; the EGR valve may also be sticking partly open; and may thus never close fully. And that would continue whether the vacuum hose was connected or plugged. It should be possible to reach underneath the valve actuating diaphragm, and manually raise and release it to see whether the spring returns it all the way down. If you manually raise the valve while the motor is cold and idling; it should make it stall.
And if none of these things work, it is probably time to reset the dreaded idle air bypass.
#1668 of 1864 check engine light flashing
Sep 17, 2009 (3:07 pm)
96 Metro 1.0/5spd
Check engine light flashing occasionally while driving. Flashes for a couple minutes, then reverts to steady on for a while, then starts flashing again.
Does this indicate it is busy setting a code? Is the brainbox freaking out?
I'm currently getting a fairly frequent #1 cylinder misfire code, but I've never seen the light flash while driving before.
Don't find any mention of this in forum archives or in manuals.
Currently have bad compression in #1, and am waiting on parts to arrive to do a ring and valve job. Hopefully I won't have to replace the ECU too.
#1669 of 1864 Re: check engine light flashing [shaggyman1]
Sep 17, 2009 (7:21 pm)
My check engine light has flashed on occasion; when the air/fuel mixture was too lean in one particular load range; but was OK at other loads. What you describe sounds pretty normal; particularly considering the low # 1 cyl compression. I would expect it to go away after the compression is fixed. I seriously doubt that there is a problem with the computer.
#1670 of 1864 Re: check engine light flashing [shaggyman1]
Sep 18, 2009 (9:27 am)
I just wanted to add that when one of these motors reaches the point where it is leaking compression past the pistons; just replacing the rings is often not enough to fix it. The reason for this is that a major part of the leakage takes place from the ring gooves in the piston becoming enlarged by wear. And that leads to compression leakage on the inside edge of the rings, through the ring grooves. In addition, when the ring grooves become worn; the increased clearance erodes the support the grooves normally provide to the rings; which allows the rings to twist and flex. And that raises havoc with the seal between the rings and the cylinder wall. So the right way to fix the problem is to replace both the rings and pistons; once it has been determined that the cylinder bores are still straight enough to support new pistons.
These little motors make much more economy and power for their size than an old Ford flathead or Chevy 6; and as a result they are far more critical and demanding about precision in mechanical tolerances and tuning adjustments.
#1671 of 1864 Same Bug after rebuild.
Sep 25, 2009 (11:31 am)
Valve job, rings, bearings. Compression test shows 200 in all three.
Replaced: MAT, Distributor, Coil, Cap/rotor/wires/plugs, PCV and
Throttle body with TPS, Injector, Fuel Pressure Regulator, ISM.
Thoroughly clead all carbon from pistons and EGR tube in intake manifold.
Set a code for EGR flow after 40 miles- had the vacuum lines reversed on the modulator (the label on mine was gone). Just to be sure, I replaced all the vacuum lines, the modulator, and both the solenoid valves.
Runs great, except for two problems:
1. Cold starts are the same as on the last engine/TB, etc- will not accept ANY throttle without dying until warmed up. ( I now suspect either the TPS, which is a three wire without an idle switch in it) or the fuel vapor purge system, which I find difficult to fathom. I just don't want another burned valve in a couple thousand miles....
2. Air in the cooling system- this one REALLY scares me, as I don't seem to be able to clear it out. It will idle warm with an occasional bubble in the radiator filler neck, but when I race the engine, I get lots of bubbles, with an occasional surge- as if there were a pocket of steam forming somewhere and suddenly venting with the increased flow. The bubbles do not smell like exhaust, and there is no greasy film on top of the water (haven't put antifreeze in yet, as I don't want to waste it).
Could this be a failing water pump, or is it more likely to be a cracked block?
Is there a flow spec for the water pump? Some kind of sniffer for the cooling system?
#1672 of 1864 Re: Same Bug after rebuild. [shaggyman1]
Sep 25, 2009 (1:07 pm)
You say you replaced all those parts; but were they new or used replacements? If they were used; there might be compatability issues. And even if they were new, there still might have been errors in listings or model selection. There were significant changes in the TPS and distributor over the years. I tend to feel that you still don't have the right TPS. Also; the distributor for the 1996 model should not have a vacuum advance. If it is the right type (made for electronic advance, rather than vacuum advance) the timing MUST be set with a strobe while the check connector terminals are shorted to disable the electronic advance. Otherwise your timing will end up too far retarded.
Does your engine have an electrical EGR vacuum switching valve unit in series with the exhaust back pressure transducer? If the VSV is not in the circuit; the EGR valve will get far too much vacuum; which will create all sorts of undesirable leanness. Do you have a vacuum hose routing diagram, so you can be sure the hoses are correctly routed?
Regarding the evap cannister purge; the purge control valve on top of the cannister (at least on the earlier models) is activated by a vacuum signal from the purge port on the throttle body. There is some sort of temperature sensing "wax valve" plumbed into that vacuum line; which bleeds air into the signal line when the engine is cold, to reduce the strength of the vacuum signal to the purge control valve. If that air bleed function is defeated; it would result in the purge valve opening when the engine is cold; which would cause severe hesitation.
On the earlier throttle bodies; there are three vacuum spigots, coming from ports which are all located at slightly different heights. The spigot closest to the distributor is intended for the purge system. The port which supplies that spigot is the highest of the three on the throttle body wall; which means it will be the last one to supply vacuum as the throttle is opened. The spigot furthest from the distributor is used to supply the EGR vacuum signal. It is the lowest (earliest opening) of the three ports. And the spigot in the middle was used to supply vacuum to the distributor advance (on those cars with vacuum advances). That spigot is typically capped on cars with electronic spark advance. If you get vacuum from the wrong spigot; it can really mess up the engine operation, particularly with regard to setting EGR codes.
Have you tried setting the heater temperature valve control to maximum heat; in order to purge all trapped air from the heater core? And do you have a thermostat installed in the cooling system? Running without a thermostat can create weird imbalances in coolant flow. You can check for pressure build up in the cooling system with a radiator pressure tester. Install the tester in the filller neck, and pump up just enough pressure to lift the needle off the peg. Then start the engine while it is cold; and watch the pressure gauge. There should be no significant increase in pressure for at least the first 5 minutes of running (or until the temperature gauge reaches normal and the thermostat opens).
#1673 of 1864 Re: Same Bug after rebuild. [zaken1]
Sep 25, 2009 (2:14 pm)
Most of the RPL parts were used, but bench tested okay.
All of the TPS units (5) are the same- 3 wires, same as my harness.
Input Voltage from ECU, Signal to CPU, and ground. Signal always goes through the potentiometer.
Distributor is correct- with no vacuum advance and the pickiup coil bench tests okay.
EGR is a bit different: Vacuum from TB base goes to a VSV, which goes to the "P" side of the modulator. The "Q" side of the modulator goes to a second VSV, which controls actuating vacuum from another spigot on the TB, which is connected to the
EGR through this second VSV. All connections are true to the diagram on the hood.
The third and lowest spigot goes to the purge system. I think I will try plugging the line to the purge system and see what it does to a cold start.
I have a new thermostat which functions as expected, and have "burped the system from the high point on the back of the TB. Spot on with the pressure check- I hadn't thought about it in that way. If the engine is cold, there should be no increase in pressure until the coolant starts warming up, so an increase would have to come from combustion gasses leaking into it. I sure hope not- I really don't want to tear the whole thing down again. Sigh. At least I have a couple other blocks to start with, and might as well jump on whichever one has cylinders in better shape. (BTW, the piston ring grooves appeared to be undamaged, although I didn't bother to mike them- I was hoping for a quick 'n' dirty rehabilitation, not a perfect remanufacture)
Thanks for the good advice....
#1674 of 1864 vacuum hose routing
Sep 29, 2009 (6:15 am)
I have a 1996 geo metro I am restoring and the vacuum hoses are missing. Its a 1.3 liter. Does anyone have a diagram of these hoses?
#1675 of 1864 95 metro : wont idle will run other wise
Oct 01, 2009 (1:32 pm)
I have 95 metro 1.0 engine with manual 5 speed it starts and runs as long as i give it gas and drives normally. just replaced fuel regulator had head done a few weeks ago ran fine for a week then this O2sensor gave readings of .4- to 1.2 volts seams a little high since most i read say up to 1 volt TPS was smooth resistance from bottom of reading to top dont remember what the readings where exactly idle control motor is working after took it off and cleaned it and surrounding stuff. also the fuel milage has dropped 5-7 mpg since head gasket was done not so much worried about that as the wont idle (dies every time come to stop sign) since i drive 55 miles to work then same home kind of pain driving it this way i am new here so any help would be appreceated()
#1676 of 1864 Re: 95 metro : wont idle will run other wise [leadfoot429]
Oct 01, 2009 (1:33 pm)
sorry i ran everything togther-- still new to forums