running rich, dying, aaargh!!!

[phattyc75]

So, this weeks problem with my saturn is that it seems to be running extremely rich. The problem started with a slight miss at about 1/2 throttle, but if i backed off on the accelerator, the engine evened out. At full throttle it acted like it wasn't getting full power, but the engine ran great at idle. I automatically suspected spark problems, so i went ahead and changed plugs and wires. This didn't really help, so I swapped out the coils. Again no change. The problem grew progressively worse, with the engine missing at everything but full throttle, and at full throttle the engine made a very peculiar deep growl, which I assume is from running rich. My brand new AC Delco plugs, that have maybe 2 hours worth of running on them are horribly carbon fouled, which again makes me think that the engine is running very rich. My buddy has a Saturn that is running well that I have swapped the MAP sensor and the EGR valve from, but again no change on the problem and it is only getting worse. I can no longer even start the car. The problem started after I pulled the battery out to make it easier to access my tranny dipstick, but simply pulling and reinstalling the battery should not make a difference on the cars running capabilities. Please help! I'm out of ideas beyond swapping injectors, and I simply don't have the money to do that on a whim. I want to get this car running so I can sell it. I am sick of working on it every freaking week.

Thanks for any help or suggestions you can give me,

phattyc75

[mysatilac]

Your problem may be as simple as the ECTS, which has messed up SOO many peoples cars, causing similar problems with the A/F ratio...
might want to check the ECT sensor and the IAT sensor to see if they are giving you a proper resistance for the outside temperture...

The ECTS is located on the block under the radiator hose Black and Yellow wires lead to it

BTW the ECTS is ~$10 from SaturnParts.com + S/H

The IAT is located in the air intake duct, right before the filter box

You can check the condition of the ECTS or IAT by taking the wiring harness off of it and using a multimeter set to OHMs and probe it to see if you get the proper resistances... (see below)
or simulate conditions by taking out the ECTS and placing it in cold water then slowly heating the water to make sure it gives proper resistance throughout the temperture range, or a hairdryer for the IAT

while you have the connectors off probe the harness side with a multimeter set to 20DCV and see if you are getting ~5DCV as a referece voltage with the ignition in the on (not started) position


Here are the resistances for the ECTS or IAT in various tempertures
-20 degrees F________39K-53K OHMs
0 degrees F__________21K-27K OHMs
60 degrees F_________3.9K-4.5K OHMs
120 degrees F________1.0K-1.1K OHMs
160 degrees F________430-480 OHMs
200 degrees F________215-235 OHMs

[mysatilac]

Also, to check for spark instead of just replacing everything

check your battery voltage with a multimeter- if its ok then take a spark plug wire off the plug and hold the boot so the wire is pretty close to the engine block or a convienient ground... Have someone crank the engine over for just 1-2 seconds (so you dont flood the engine) and see if you're getting a proper spark. You should see a bright blue/white spark and It should jump nearly a half inch.

Or you can buy a Fake spark plug type spark tester from AutoZone or a similar store for ~$7 and follow the similar instructions included with it

[phattyc75]

Thanks for the tips mysatillac. Um...one question though. I'm not sure exactly how the coolant temperature would screw with the air/fuel ratio. I believe you and I am definitely going to test both of those sensors as soon as I get off work, but in all seriousness and without sarcasm, I would like to know how it affects the ratio, just for my understanding.

Thanks!

phattyc75

[mysatilac]

No Problem, always glad to help and clear up confusion. Especially a fellow Texan, if you dont sell your car maybe someday you'll be posting answers for me


It adjusts your injectors duration during starting and running conditions to compensate for a cold engine, to warm up the block and fluids. And the IAT adjusts your running and starting air/fuel mixture to compensate for the expansion rates of air at different tempertures

The normal symptom of a bad ECTS is irradic/bouncing or rough idle, although it sometimes doesn't show any of the normal symptoms and can just go bad resulting in hard or no start

Posted by Sierrap615:
"the ECM uses the ECT as the primary input to determine the A/F ratio for cranking"

What other repairs have you done in the last few weeks? Perhaps it was one of these that led to your problem (if not these sensors)

Also what year, model, and milage saturn do you have?

[mysatilac]

Also here is what Sierrap615 said about A similar Hard/No Start condition

Originally Posted by sierrap615

a PCM is commonly a "i don't know whats wrong repair" i have heard as many as 9 out of 10 PCMs returned for warrenty test good. not to say its not possible, but its skeptical to me.

although i am not sure of the exact problem, here are a few things that can give a hard/no start but the car will run(basicly in order of possiblety):

1. bad ECT( the ECM uses the ECT as the primary input to determine the A/F ratio for cranking)
2. sticking IAC
3. sticking EGR
4. carbon build-up in intake(2,3, and 4 all go together, all affect amount of air entering the engine, all are affected by carbon build-up)
5. clogged injectors/low fuel pressure
6. weak battery/ other electrical problem (cables, starter)
7. bad KAM(the PCM's memory if you will, its part of the engine becoming dependent of starter fluid i beleave)
8. spark plugs/wires
9. engine mechanical problem(low compression, internal resistance, ect...)

so that said, here is what i would do: start by replacing the ECT if it has not been done before, buy a can of carb and choke cleaner and clean the throttle body, IAC, and EGR(with removing the EGR, you will also need a new EGR gasket), pull the PCM B fuse for about 15 seconds (this will reset the PCM's KAM). then try to crank at partcial throttle(not WOT, not closed throttle). total investment at this point is about $30. if that doesn't help testing of the fuel, starting, and ignition system will be needed.

[sierrap615]

Originally Posted by phattyc75

I'm not sure exactly how the coolant temperature would screw with the air/fuel ratio.

you know how a carb uses a choke to make the engine run richer when the engine is cold to warm up fast? same concept. the ECT detects the the engine is cold, then the PCM fires the injectors longer to run rich. the orginal Saturn ECT had a design flaw that after time would crack. the sensor was redesigned in 2001-ish with a better brass tip. when they crack they tend to read cold, so even if your engine is up to temp, the PCM won't think it is, and will keep running rich.

start by replacing the ECT, if that doesn't help, your other problems sound like a clogged cat. converter, which can be cause by - you guessed it - running rich.

[mysatilac]

Originally Posted by mysatilac

It adjusts your injectors duration during starting and running conditions to compensate for a cold engine, to warm up the block and fluids.

I mentioned that in all my rambling... but yours is a better explanation, especially if he knows about carbuerated engines

[phattyc75]

Thanks for your help y'all. I have a new ECTS in hand, and am planning on installing it at lunch. I also will be installing new plugs again, since the new ones that I put in are already so carbon fouled. In answer to your question, I've done brakes, ball joints, and struts over about the last 3 months. I partially rebuilt the engine (rings, bearings, rebuit head) myself about 8 months ago, and have replaced the alternator and power steering pump, along with a clutch and the clutch hydraulic system. I think that pretty much covers the major repairs that I have done. The car has 139,000 miles on it, and about 7,000 on the rebuild.

The ECTS does make sense, simply because the problem started only after the car warmed up. I could then attribute the fact that the car does not even want to start now to the carbon fouling on the plugs. Hopefully I'm not grasping at straws though, and I'll be able to drive it home tonight.

Thanks again,

phattyc75

[mysatilac]

No problem, "y'all" I love it.
Ok, just making sure you didn't put in performance injectors or something. Which would obviously make the car run very rich without forced induction, or major intake work...Someone did post this problem a while back...
Hope the ECTS fixes your problem, I'll be watching for it