Edmunds.com | Inside Line | Auto Observer Your Account | Help | Directory
You are here:
![[F]](http://a332.g.akamai.net/f/332/936/12h/www.edmunds.com/media/townhall/webxicons/site.gif){kind=small}
Forums
Hatchbacks Chevrolet Metro/Geo Metro Chevrolet/Geo Metro
1696 messages, Last post on Dec 06, 2009 at 11:26 PM
You are in the Chevrolet Metro/Geo Metro Forum. Your Host is pf_flyer
|
|
|---|---|
|
Replying to: zaken1 (Aug 18, 2009 10:36 am) Fine. At last some logic in the chaos. In looking at the wiring diagram i see the O2, MAP, IAT, TPS are all in fact connected to the CTS. So how is one to correctly troubleshoot these components? AAAARRRGGGHH. Removing the IAT had no effect because (as you pointed out) it had set a fail code when I disconnected the CTS, and was in limp mode. (BTW) I've found that an easy way to clear the codes is to first disconnect the negative battery cable, then ground the positive cable to the chassis for a few seconds, thus draining the various capacitors- including those pesky ones in the airbag system. Beats a trip to O'Reilly to borrow their OBDII reader. (Personally, I think they should be built in with readouts available in real time) Back at it tomorrow, with a new TPS which seems to have a much better and smoother resistance curve than the last two. Got my fingers crossed. Again. Thanks Zaken! I thought I was witnessing a miracle gone horribly wrong.... |
|
|
Replying to: shaggyman1 (Aug 18, 2009 2:01 pm) Now, back to today's problem; if I were working on a vehicle that acted the way you describe, I would begin with the simple and direct approach: The symptoms you described sound just like what happens whan a TPS is adjusted too lean (set too far counterclockwise). So, before doing anything else, I would loosen the two mounting screws; and turn the damn thing clockwise until there was a noticeable improvement in the running. Forget the adustment specs; those specs are only valid when the engine is all new and stock. As soon as the compression changes, or any of 1,000 other factors changes; the TPS setting goes off. I have had to reset mine all over the range, after changing other things on the motor. And it ran great in all sorts of different settings, when they were appropriate. It would only be if resetting the TPS as far as possible did not correct the problem, that I would start thinking about defective sensors or other exotic issues. If you set the TPS too rich; the consequence will be that the fuel cut does not come in during decelleration. And that is fairly obvious, as you slow to a stop in gear. Normally, the fuel should come back on as you get down below about 10 mph; and the car will feel different when that happens. But the other consequence of too rich a TPS setting is that the fuel mileage drops severely; and the exhaust pipe becomes wet and sooty. One owner wrote in here some time ago; complaining that his exhaust pipe always looked rich. So I finally helped him to overcome his fears about disturbing the TPS setting; and explained that it has to be done by the "seat of the pants." A few weeks later, he wrote in to thank me for going against what everybody else had said, and reported that it took a series of tries and road tests before he finally got it right; but his car now is peppier than ever, the pipe is brown and clean, and the fuel economy is great.
|
|
|
|
|
Replying to: zaken1 (Aug 18, 2009 6:05 pm) I connected a known good CTS and immersed it in boiling water, thinking to imitate a warm engine and started it. Died as soon as I opened the throttle. So the coolant temerature sensor or it's circuit is not the culprit. Okay, what else is temperature sensitive? What about the Early Fuel Evap Heater (EFE) in the plate under the Throttle Body? Fuel system component, temperature related, has a 30A fuse and a relay..... It's on the car, in the wiring digram, and utterly without mention in Chilton or Haynes. AllData says it preheats the Fuel/Air and reduces the time in open loop, until engine reaches operating temperature when it is deenergized by the ECM. Resistance should be 0.5 to 3.0 Ohms. (seems low for a heater) Checks at 2.6 Ohms across the leads, and open from either lead to battery ground. Connect unit and measure voltage: Voltage coming in while running is 13.4V with a drop to 1.2V on the ground side. (12V drop) Tht's a heckuva drop for 3 Ohms. Sounds reasonable that it might be the culprit.
|
|
|
Replying to: shaggyman1 (Aug 20, 2009 6:46 am) I hope you can see from this that the voltage drop across a 3 ohm load has NOTHING to do with the amount of resistance of that load. It is solely determined by how much ADDITIONAL resistance is in series in that circuit. If the 3 ohm heater is the only resistance in that circuit (which is what I would expect in a heating circuit) then the entire 12 volt supply (minus what is dropped across the plugs and wiring harness) will be dropped across that 3 ohm resistance. Applying Ohm's Law (Current = Voltage divided by Resistance); 12 volts / 3 ohms = 4 amps. 4 amps current at 12 volts is 48 watts of power (Power = Voltage X Current). 48 watts of power is about what a single 12 volt headlight draws. That is not at all unreasonable for a heater that has to bring a steady stream of fuel and air up to a temperature high enough to vaporize the fuel. It probably sounds high to you because most other current draws in automotive electronics are much smaller than that. But I expect the rear window defroster grid draws at least that much. And the starter motor draws 20 to 30 times that much!!! So your test of the EFE heater tells me that it is working right. I appreciate your perception that this appears to be a temperature sensitive problem; but I assure you that the root cause will turn out not to be someting directly related to temperature, and will instead turn out to be related to excess leanness, or sudden changes in air/fuel ratio when the throttle is opened. I'm glad you tested the TPS and eliminated that as a potential cause. I can accept that; and this information helps narrow down the focus. What it now sounds like to me is that the EGR valve is opening too soon, or too suddenly, when the throttle is opened. This would happen if one or more of the EGR vacuum control devices were bypassed or missing. (there should be an exhaust back pressure tradsducer and an electrical vacuum switching solenoid in the vacuum lines to the EGR valve). It would also happen if the ignition timing had been adjusted without first disabling the electronic advance by shorting the check connector wires. |
|
|
Replying to: shaggyman1 (Aug 20, 2009 6:46 am) 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. |
|
|
|
|
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.
|
|
|
Replying to: shaggyman1 (Sep 17, 2009 2:07 pm) |
|
|
Replying to: shaggyman1 (Sep 17, 2009 2:07 pm) 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. |
|
|
|
|
96 1.0/5 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?
|
|
|
Replying to: shaggyman1 (Sep 25, 2009 10:31 am) 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).
|
|
You are here:
Forums
Hatchbacks Chevrolet Metro/Geo Metro Chevrolet/Geo Metro
New? Join Now!
Forum Tools
Search Forums
Browse by Vehicle
1997 Geo Metro
2001 Chevrolet Metro
Browse by Board
Browse by Topic
Today's Chats
