1985 Fiero 4 cyl/ auto. car ran Great for Years, past 6 months it been stalling at a light, replaced : Injector, IAC, MAP, O2 sensor,and Temp sensor at fill neck. today, ran perfect, went to fill it up with premium gas (has always run better on premium for some reason), anyway, I get 500 feet from my drive way, still running perfect, and the engine light comes on ! Code 45, O2 reading Rich ! This is getting Old. WHY ?????
My neighbor had a fuel trim exception rich code on her Hyundai, I opened up the air box and dug out a chipmunk nest and about a thousand acorns. Not to say your problem matches this, but anytime a code indicates rich mixture, I check all air intake parts for obstruction.
unplug tran's TCC plug in/on front of trans. make sure the wire/plug won't hit the exhaust. If stops stalling at stop lights/signs then TCC solenoid is bad or fluid is old and dirty faking same problem. But Dumping 2-4 quarts oil in the pan and filter often isn't enough. You want max oil change w/o draining the TC itself... See my Cave, Automatic I don't trust "transmission flush" from anyone for many reason. Many just rip you off to Can wreck the trans.
Leave it unplug until you fix whatever else.
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"Presently", the car is NOT Stalling anymore, runs pretty good, it's just" lighting the SES light" and "throwing code 45". Has New air filter, new injector, no clogs. I don't think there is ANYTHING that I have NOT replaced, What could be Left ?
this '85 2.5 has always STARTED better and "Idled" better on premium, driving down the road you can't tell any difference. have no idea Why, it's all a bone stock 1985 flat tappet 2.5.
Sounds like the problem is probably still there, so: Check for vacuum leaks and also check the condition of the wiring and connectors. Any broken connector clips that might be intermittent? Frayed wiring?
The ECM calculates how much fuel it thinks the engine should need based on the various sensors. Major inputs include engine RPM, the coolant temperature and the manifold air pressure. The O2 sensor reports a voltage between 0.0V (lean) and 1.0V (rich). The ECM tries to control the fuel so that it keeps switching above and below 0.45V. If it's above 0.45V, then the ECM starts trimming fuel until it goes below 0.45V. Then it does the opposite, and so on. There are limits to how far it can trim or add fuel. If the O2 sensor reading stays above 0.45V for too long, and the ECM cannot trim the fuel any further (due to it's programmed limits), then it sets the "rich exhaust" code.
So if you get a rich exhaust code, if means either a bad O2 sensor, maybe a bad connection to it, a leaking fuel injector, or a completely different problem that has confused the ECM so that it grossly miscalculates the fuel mixture. If the calculation is bad enough, it won't be able to trim enough fuel to compensate and so the "rich exhaust" code is set.
A vacuum leak could do that, especially if it's local to the MAP sensor (so the sensor sees more air pressure than what's actually in the manifold). So give close attention to the vacuum hose leading to the MAP - take it off and make sure it doesn't have a pinhole leak. Cover the other end and blow in it.
I don't remember the pinout, but one of the wires leading to the MAP sensor should have 5.0V on it. I'm assuming one of the other pins is ground, so you should find 5.0V across those pins with a multimeter. Sorry I don't remember the pinout details, but the point is that if you're not getting the proper 5.0V supply then it could mess with the sensor readings. There might be better info about this test on the forum somewhere.
I think you can measure voltage across a different pair of pins to get the MAP's current pressure reading. But I don't know what voltage you should expect to see at particular conditions. This might be documented somewhere. It's much easier to verify good sensor readings with WinALDL, but lacking that, probing with a multimeter can partially substitute. The difference is that when you probe with a meter, you can't be sure that the ECM is seeing the same thing you are seeing (it won't catch wiring problems, etc).
Engine RPM comes from the same signal that eventually gets to the tach (does your tach work?)
The coolant temperature sensor (CTS) is separate from the sender that drives the dashboard gauge, so a working dash gauge doesn't mean anything. You can test the CTS by unplugging it and measuring the resistance across it's 2 pins. This chart shows how many ohms of resistance there should be for a given temperature. Make sure you're measuring the right sensor (not the dashboard sender).
[This message has been edited by armos (edited 06-10-2018).]
OK, was running great, then it wasn't, then it was and now its not. If you are pulling a rich code then then engine is getting more fuel than the ECM can compensate for. If you replaced all the sensors then the: Fuel Pressure System could go rich if pressure is too high. Check your fuel pressure regulator function by measuring the fuel pressure. Also check for a leaky injector. My guess is that your problem is fuel related.
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well, Here's where it gets Weird. turn the key "on", No fuel pressure. crank it, & it will start up run at 13 psi until shut off, then immediately go to ZERO. turn key on again, goes up to about 6 then drops to ZERO again ! will start and run but NOT hold pressure if shut off, not even for 2 seconds ! So, What Now ???
Well, usually when you turn the key to "On" the fuel pump should run for about 2 seconds and then stop if there is no crank signal from the engine. Likewise after you shut the engine off, the fuel pump should stop and the fuel pressure should dissipate.
WHY would it pull a "RICH Code" if it's running out of Pressure ??
I'm not real familiar with the 4cyl setup, but the pressure loss could be happening somewhere that's feeding excess fuel into the engine. The rich code would be consistent with that. A properly working V6 setup takes a very long time to leak down with the key off. But I don't know how much leakdown is normal on the TBI 4cyl.
I remember checking fuel pressure on a 4cyl something like 20 years ago. With key on, engine off, it went to something like 14psi, and I think it held but I don't remember how long. I certainly don't think it dropped in just a few seconds or it would have been hard to read. You must be leaking fuel somewhere.
I Answered that Too Quickly ! if I turn On the key (not start), it Does Nothing. If I "Crank it", it will start and hold 13 PSI. As soon as the key is "Shut Off", it goes to Zero within 1-2 seconds. ** NO Pressure only turning the key to "On" Position.** Only pressure if it's cranked and running.
I wonder if it is a fuel pump issue, I hear they can become incredibly cryptic and anomalous when they begin to fail. Does the pump make noise with the key at the "on" position?
If I get in the car, (cold start,) turn the key "on", the pump "buzzes" for 3-4 seconds, (No pressure). Then crank it, it will start and hold 13psi. shut it off, it immediately goes to 0. turn they key "On", it will buzz 3-4 seconds, go to about 6 PSI, then immediately drop to 0. the "Pump IS getting Current". HELP ! This is like the 3rd pump in 5 years. IS IT the PUMP ? Regulator ? (of course it has a FULL tank, so if I need to take it out.....! ) LOL
