97 SL1 1.9L Manual trans. I'm having a hard time trying to find the cause of this code. I have replaced the IAT/ECT with brass sensors (due to cracked plastic sensors), I have installed new NGK iridium spark plugs gapped at 0.040, thoroughly cleaned the throttle body, IAC, MAP, EGR, PCV, and TP sensors. I cleaned all the connection points of the coil packs/ICM and replaced the air filter. Whether or not it "needed" all that or not I'll never know but the inside areas of all the sensors were covered in carbon or sludgy residue from the PCV. All wires/connectors are in good condition from what I can see.

The misfire is the worst around mid-throttle but smooths out if I push the pedal further. It sometimes has a hard idle after running for a while, like at a stop sign. The engine is much louder (partly due to a small hole in muffler) when it studders and the misfire seems to get worse when the engine is at operational temperature as well as when going uphill. After I turn the engine off, say at the store, when I get back in to start the car, it won't start unless I turn the ignition back to the lock position and then full start again. If the ouside temp is cooler, it tends to run somewhat better. Temp gauge reads between 1/4-1/2, battery reads 14.3 volts while running.

Just to reiderrate...no CEL once the vehicle is running and it doesn't flash when experiencing misfire but it always stores this code. It is by definition "a loss of power", but only at mid-throttle or occasionally low idle (750-800 RPM). Once in a while it will purr like a kitten and I won't have any issues.

On a side note, the fuel injector for cylinder 4 appears to have an oily residue on it but I can not tell if it is from the slightly seeping valve cover gasket or if it is fuel. Fuel economy is of course affected due to running on 3 legs at times. The hoses running from/to the charcoal canister are somewhat deteriorated and spongy. I also am not entirely sure my radiator fan works, ive never seen/heard it working but I havent had it to that 3/4 temp mark to find out.

So to sum it up, I don't have hundreds of dollars to throw at it. I have a multimeter, some tools and a more than basic understanding of how to replace parts/maintain a vehicle, but not so much the diagnosing part. It seems like every "symptoms off...(bad sensor/parts)" posts I have read all cause the same issues. If yall need some voltage readings I would be happy to post em but I need to know where to check. Thanks in advance for the help!

 

A few things to start:

1) Does it store P0300 or P0300 with a small pd or pending next to it?
2) Does your Service Engine Soon (SES = CEL) light light up during key on dash self test of all dash bulbs (turn key to ON but do not crank)? Does it ever light up under any circumstances?
3) Is the Service Wrench light on?
4) How many miles on the car?
5) What plugs were in it before you changed them out?
6) Is catalytic converter the original?
7) Any other codes showing up?
8) What is the rpm at idle?

A) Fan test: Turn on your A/C. PCM should command FAN RELAY closed and Fan should run continuously until A/C is turned off. If you do not have AC, disconnect wiring connector at fan and SAFELY jumper the fan plug wires across the battery. This is a direct test of the fan motor itself. If fan runs when jumpered but not when A/C is on, FAN RELAY or wiring issue.

NOTE: If A/C is low on refrigerant and has tripped the low pressure cutout switch, the A/C on test will NOT work because the PCM will not enable the A/C relay, which has to occur before the FAN motor is commanded on.

(I never thought about it too much until the first time I had to refill my refrig in my 95 SC2. Every time I briefly jumpered the low pressure switch to get suction of refrig from the can, the A/C clutch would engage AND the fan would briefly come on. It wasn't until I had suctioned enough into the system to get above the low pressure cutout limit that the A/C would stay engaged AND the fan would remain on.)
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B) If an S car is truly misfiring, the SES light will blink. This ignition system with OBDII diagnostics will NOT miss a true misfire. If the SES is not blinking, either the bulb is burned out or it is not a true misfire. It may run like crap and fall on its face, but that does not necessarily equal a misfire.
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C) Loss of power going up hills is more often than not related to a plugged up cat con. Would make idle crappy as well. Too much back pressure.
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D) Plugs: NGK 7755 aka #BKR4ESA-11 . Copper. Use them.
These ignition systems were not designed for platinum, iridium, etc plugs. The engines run best on the OEM NGKs. Many a misfire has been traced to NOT using the stock plugs. Really. I've been driving S cars since 92. Some people seem not to have issues, many have nothing but issues.

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Really need answers to the questions above before proceeding further.

 

I agree with derf. The two points I'd check first are the cat con and the plugs. You CANNOT run iridium plugs in these 1.9 engines. They just don't like them. I'll bet your cat con is coming apart.

 

Thanks for the reply derf. The vehicle has ran like this since I bought it about a month and a half ago. The CEL was on when I got it. The 2 codes I mentioned before were what was stored. After replacing the IAT AND the ETCS, the CEL turned off and hasn't been back since. But with the issues I still have, I had it read again and those 2 still showed up. I had them clear it to see if it might cause the CEL to come on after several drives. It hasn't yet and that was over a month ago and I work 5 days a week, but the P0300 came back with no CEL.

To answer your questions;
1. It isn't showing a pending or pd on the display of the OBDII scanner at Advance.
2.The SES light illuminates with key on engine off but it goes out after I turn the car on. It doesn't come back on at all once the engine is running, no matter how rough it runs.
3.The sercive wrench light goes off after a few seconds of having the ignition switch in any position other than "lock".
4. ~180,400
5.I removed the Autolite copper core plugs due to extensive carbon buildup on node and filiment. The ceramics on the node itself was fouled pretty severly. I replaced with NGK iridium plugs and noticed a considerable difference in torque and low end speed, but it didn't fix the mid-throttle misfire entirely. The plugs look like they should as far as appearance (whitish-brown with no carbon buildup) after driving for 3 weeks.
6. The cat doesn't appear to have been replaced. I know it doesnt glow red hot at night after driving it for 20+ minutes. I have no idea how to check one other than that. There is some black residue that builds up at the end of the pipe but it doesn't appear to be new.
7. No other codes are stored.
8. The vehicle idles between 1000-1100 at first start up, with no missing or hard idle issues. After I drive it a few miles and come to a stop, it drops to 800 where it should be but the misfire is then noticable. It's never stalled and I don't have to pat the gas to keep it idled up.

The A/C doesn't actuate the fan relay and the air doesn't seem to get very cold either. If the fan works with a jumper to the battery, I might just install a dash switch to turn it on if I notice it getting hotter than "normal". I would then remove the A/C all together and run a bypass belt. I ride with my windows down so that doesn't bother me.

 

Thank you. It is refreshing to have someone seeking help actually answer the diag questions asked of them.

a) 180K would be a prime mileage for the original cat to give up the ghost. They make backpressure testers (maybe you can loan a tool at AutoBlows, dunno. Anyway you screw it into the front O2 bung by the exhaust manifold and it will read out the backpressure in your exhaust system. I do not remember the spec for these and other cars, but if you manage to measure yours, I'll at least measure mine for comparison.

b) It may be that the P0300 you are reading is an historical code or it has been there so long it has become a "permanent" code. I've never quite understood permanent codes, other than they are stored in non volatile memory, so the avg autozone level scanner can read them but not erase them. I believe enhanced scanners and factory tools can.

c) If the SES light is confirmed to be working, the SES WILL flash during a true misfire as determined by the ICM and PCM. I believe it measures the resistance of each firing and if one of these is not like the others (one of these just does not belong), then it's pretty good at pegging which cyl the misfire is in. So I think your P0300 may be a permanently stored code.

Again, the SES will ACTIVELY blink during what it interprets to be a misfire. Like the one I got going up a long hill in WV as my vehicle could only hit 45mph, the SES was blinking away, and the engine was none too happy. Turned out I totally dropped a cyl. 0 compression will in fact result in a misfire.

I think your vehicle is bogging down severely -- for reasons yet to be determined -- but all 4 cyls are still firing. Even if the engine is running like crap, it's running like crap on all four cyls.

I know what it feels like to drive on three cylinders in an s car. I drove the above mentioned SC2 for 9 months on 3 cylinders. The car runs quite evenly, it just has one less firing, and the car vibrates like a cheap motel room bed. You state that your performance is inconsistent, so between that and the lack of SES illumination or blinking, I do not think it is a miss.

Additionally, P0341 is often thrown with P0300. Its a camshaft position sensor code -- but there is no cam pos sensor on these engines. P0341 usually means you are dealing with a general ignition issue.

Speaking of other codes, your last post mentioned a second code, but your first post did not (or I am blind). What was the other code.

d) Idle at startup and at operating temp seem to argue against any vacuum leak related issues.

e) I actually have to take my key completely out and put it back in to restart; can't do it with key in position from last shut down. Was this a 97 thing or maybe the interlock is just worn down

f) If the sys is low on refrig, when you engage the AC button and turn on the fan, the AC compressor clutch will not engage. If the AC clutch is not engaging, either the sys pressure is too low or the A/C clutch is defective or both.

If it was just an AC clutch issue, the low pressure cutout switch would not be inhibiting the relay closure so I think the fan would actually turn on in that scenario.

Just jumper the thing.

Also, the AC and FAN relays are identical so you can play swapsies in search of a bad relay.

If you bypass the AC, use a GATES belt.

g) Leaking cam cover gasket.

If the external seal is gone on the valve cover, the individual circular seals around each spark plug hole eventually start letting oil into the spark plug well. If the oil gets high enough, it can get wicked up to the top tip of the plug and cause partial arcing, meaning the spark generated is weaker than it should be. This can lead to intermittent performance issues and also ruins the boots on your plug wires -- which you did not mention replacing.

How much oil is in the spark plug wells (if any)?

h) The carbon buildup on the copper plugs means it is either running overly rich or burning oil or both. I suspect oil burning since a truly awful rich condition does throw a code on the S cars.

Also, as it is new to you, you know the plugs have been changed once (since they were autolites, not NGKs) but not necessarily more than that. So you don't know over what time period that buildup represents.

i) Do a loan a tool for a compression tester at Autozone so we know what we're dealing with. Look up on the web the RIGHT way to do a wet and dry compression test. Don't forget to pull the fuel injector fuse and keep the throttle plate at WOT when cranking.

I'm tired

Gnite

 

I completely agree with Rube and Derf. You probably have a bad cat caused by oil consumption. The honeycomb may have come loose and started to crumble or rotate and completely seal the pipe. I have seen all of these types of failures.
Random misfire codes come when the car has problems running and the computer can NOT identify the offending cylinder or reason. The problem is usually something the computer can't control. Like a plugged cat.
I have just unbolted the headpipe and taken a short drive as a test. Of course your S series is up front so be careful not to melt anything.
A solid check engine light usually indicates a problem that had occured twice.
A flashing check engine light indicates a current problem that the computer is actively responding to, to prevent cat damage. The computer can identify the offending cylinder and has shut off the fuel injector so the cat won't melt down.

 

Hard SES I get.
Blinking SES I get -- I thought -- I have always thought it only applied to misfires....so you are saying it can apply to ANY irregularity that would trigger a code if the PCM is actively trying to correct it?

So CAN you have his situation where there is a stored P code that does not light the SES, is not pending, and is not generally erasable by the dime store code reader?

I could look it up, but you explain things so damn well I'd rather hear you explain it. You must be/have been great when speaking with customers.

 

You made me break out the fsm for the proper wording. I am going to paraphrase the fsm, it is like going back to school since I have been working exclusively on Ford and International products for the last 12.5 years.
I think the term you are referring to is a History Code. Permanent codes that cannot be cleared started with the 2011 model vehicles and they are another story.

Since the MIL is restricted to being illuminated only for emission-related faults, there have been four code types assigned.
A,B,C &D.
Type A will turn on the light at the first occurance of a fail condition.

Type B will turn on the light if a fault occurs on two consecutive ignition cycles.

Type C are non-emission faults that may turn on the light but will stay in memory.

Type D are non-emission and do not turn on the light but are there to aid diagnostics.

Any non cat damaging misfire is a class B code.

So the light will flash if it is a cat damaging misfire but go out when it quits misfiring. If it occurs again on the next ignition cycle the light will stay on after it quits flashing.
According to the fsm disconnecting the battery for at least and maybe sometimes more time will clear both the trouble codes and the freeze frame data. This is true for most cars before 2011.

I use freeze frame data to diagnose when the fault occured on my trucks at work. I have been a mechanic for my entire adult life and now I grab a laptop when I have a driveability issue with one of my trucks at work. If it is a 6.4L and it has quit running I just have it towed. Pretty sad.

 

Thank you, sir.

So I then take away from that, as I did before w improper terminology, that his P0300 with SES light OFF is an historical code stored from when the issues were there with either actual misfiring or something else that forced the system to behave with the same symptoms of a misfire non-traceable to any one cylinder. This would kinda make sense based on the repeated recent clearing of the code.
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How many full drive cycles (not key cycles) have you driven recently?

I'm trying to get a handle on whether it has been driven enough to evaluate other emissions related codes that take a full drive cycle to set (usually about 55 miles of driving will get most of your monitors to a READY STATUS). There is an official protocol but we'll only dig that up if needed). However, some of the longer term tests like catalyst efficiency take the full drive cycle to decide if things are in spec or not.

Many emissions related codes set pretty darn quick; the O2 will set quickly if the heater is dead but I think they take longer to determine if the response is fast enough and in the right range. Tied to the long term catalyst efficiency check in both direct and indirect ways