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'93 Subaru Legacy - Check engine light, hard starting, & trouble codes,

My faithful old Subaru is starting to show its age…It’s got almost 216,000 miles, so I can’t blame it. But then again, I replaced the motor because of a burned valve at 158k. I blame on the DPO, as I bought the thing with 126k, but that’s another story.

The reason I’m posting: The check engine light started coming on awhile back, maybe 3 months ago, and of course I ignored it. But recently I’ve been having some trouble getting the car started, which is a first for this car. I may have put a new engine in it along with some other repairs, but it has never, ever refused to start or let me down anywhere.

It turns over and over and sounds like it’s trying to start, then when it finally doesn it runs rough for a few second and then seems to recover. Then for another minute or so it seems to bog down when I push the accelerator. After that it runs like nothing ever happened. Sometimes it starts fine.

So, being such an old and pretty much worthless vehicle, I prefer to do as much as I can myself find and fix things. I’m half decent with tools, and haven;t found anything yet that I couldnt work my way through.

I understand that it’s not too complicated to get the trouble codes from the car’s computer system.

Thoughts on what may be the cause of the hard starting before I attempt a first-time amateur diagnostic reading?

Get the codes and then proceed. Everything else is a wild guess. CEL do not come on easily in OBD-I cars so it is a large hint and hopefully quite helpful.

Not waiting for the DTC (Diagnostic Trouble Code) is like asking a doctor to operate before looking at the X-rays. It can be done; but, why remove your tonsils when your belly hurts?
Come on, give us a break! We need duh code.

OK OK, take it easy! I figured out how to get da codes, at least the easy ones. I’ll get after it this weekend and see what the old Scoob is complaining about. Better not be hard to fix or expensive…hah. Luckily I commute on the motorcycle and live in the desert…the venerable old Scoob gets to rest most of the time.

OK, after following some misleading and obscure directions, I finally was able to make the CEL blink and divulge it’s valuable information about what’s troubling my car. this site turned out to be the one that helped me the most:

I got 3 codes:
21 - coolant temp sensor
32 - oxygen sensor
35 - purge control solenoid valve

from the behavior the car is exhibiting, I’m inclined to think the one that’s causing this sudden hard starting problem is the purge control solenoid valve. What do you guys think?

I guess I’m not sure whether this means that part is faulty or if it’s just pointing to a problem in that evaporative fuel control system?

Well I went ahead and replaced the 02 sensor. That was the only of the parts indicated by the codes that was available. I had never replaced it and figured it couldn’t hurt…well it did hurt my wallet. $100! grumble-grumble.

Anyway I replaced it. Even though I just passed emissions with flying colors a week ago…

Also cleaned the air filter and rotated the tires for good measure.

Seems to run fine, but this problem has been erratic, so we’ll see. A puzzling thing with the codes: i thought you cleared them y disconnecting the negative battery cable, so I did that, but when I reconnected, I was still getting all 3 codes, including the 32 for the O2 sensor…sigh. cars. can’t live without 'em, can’t set em on fire…

How long did you have the battery disconnected? It should be disconnected a couple of minuets to cause the codes to erase. It it doesn’t, you know the procedure.
The engine computer thinks that the oxygen sensor and the evap. solenoid are inop, and the engine coolant temperature sensor has an abnormal signal. To be inoperative, they could be disconnected, or have poor connections. Disconnect, and reconnect, each electrical plug to the three components. Doing so, may wipe the connector pins and restore the connections.
You need to check for volts to each components, and check the out puts. 12 volts go the the ects. 5 volts to the oxygen sensor. Maybe 12 volts to the solenoid. A repair manual tells you how to do this good stuff. Another source is this site:

I don’t know what size engine, or if it has a carb, or fuel injectors, so I don’t know which wiring diagram applies. You choose some from here:

OK, update time for those of you bored enough to still be tuning in…heh.

Anyway, turns out replacing the 02 sensor, while it couldn’t really hurt anything besides my wallet did nothing whatsoever to help my problem. In fact it has progressed from intermittent to every time I try to start cold.

Symptoms are the same:
Engine turns over and over trying to catch, finally does after about 10-20 seconds.
Barely runs for about 10 seconds, chugging along, then gets going & seems to run normally.
Bogs down or stalls when I push on the gas for another 30 seconds or so and then it runs fine.
Subsequent starts once the car is warm are fine.

A couple other things of note:
When I pull up to a stop I notice that the idle is high for about 10-15 seconds and gradually comes down to normal.
My cooling fans are on all the time, probably from the coolant temp sensor problem indicated by the codes.

I disconnected the battery overnight to be sure the codes are reset & will see what that brings after work today.

So that’s it for now. Any ideas what could be causing this cold starting problem? Could it be that purge control valve on the evap emissions system? I kind of doubt it because I disconnected the vacuum hose that runs from that valve to the throttle body/air intake with the engine running, blocked the hole with my finger, and nothing at all happened.

Another quick update: I reconnected the battery this AM, and it started up just fine! Not sure if that’s a fluke or what. But the CEL is now blinking steadily…? Oh well time to go to work…on the morotcycle.

Check for correct voltage (repair manual info) to the coolant temperature sensor. If the voltage is ok, change the sensor.
Check the purge control solenoid valve using the repair manual instructions.
Clean the MAF (Mass Air Flow) sensor with MAF spray cleaner.
Use throttle body cleaner in the throttle body bore and throttle plate.
Here are some good instructions to help you until you get your repair manual. Just check on the menu items.

OK, I hear you. I have a manual, but need a multi-meter. My questions is: can the purge control valve or coolant temp sensor even cause these kinds of problems? I don;t have the luxury of lots of time to go through everything and want to get to the solutions first…then I can go through and fix the little things…maybe.

All of the things I listed, and some I didn’t list, can be partially, or wholly, the cause of the problems. I can’t make it any more simple than this.

Thank you for all of your help. Cleaning the MAF and throttle body sound like great ideas. FWIW the thing hasn’t had a problem since I left the battery disconnected overnight.

I started it cold for the 3rd time and drove it for the 1ast time since then today. The CEL blinked steadily for about 10 minutes then went back to being steady on. The cooling fans have not come on abnormally since.

Will clean those parts & test those sensors this weekend. Thanks again!

OK, so.

Cleaned the MAF and throttle body as suggested. throttle body was pretty gunky! These things made a very noticeable difference in the throttle response and I feel like it has a little more pep too. Overall it feels like it just runs smoother and snappier. Very good. I think between the new 02 sensor, clean air filter, MAF sensor and throttle body the Scoob is much happier. Poor old beast needed some TLC.

I also checked the codes again after resetting them, and the only one still there is the coolant temp sensor code. Maybe jiggling the purge control valve thing brought it back to life.

I picked up a multimeter and tried checking resistance on the coolant temp sensor, but it is a real mother getting the leads in there. I was able to get intermittent readings. The manual says check when cold and hot, resistance should be high when cold, low when hot. I’ll have to try again when the engine is completely cold, but honestly at this point it seems easier to replace the damn thing than try to get a reading out of it. It’s only $25-$35 after all. I checked the voltage to the sensor and it was good.

So hopefully my stumbly starts are a thing of the past. In nay case it’s running much better now. Thanks for the tips on the MAF & throttle body cleaning!

I’m glad that cleaning the MAF and throttle body helped your problem that much.
Also, I’m glad that you gave us some feedback on the success of our suggestions. Alas, you are one of the few who has. We need more like you.
Yes, I know that it’s hard to do some of the electrical measurements with the standard, large, stiff, test probes on multimeters. As an easier way, I like to use back probes attachments. These needle-thin probes are slid along the wire, at the connector, to make contact with the metal terminals. No wire piercing necessary. The back-probes slip over banana shaped ends of test leads. The banana ended test probes are available from ebay and online tool stores. For the backprbes:
By using the backprobes, you can check the voltage into, and out of, the coolant temperature sensor. On the out terminal, the voltage will be lower the higher the resistance. Your repair manual should give you the voltage values for different coolant temperatures.

You could remove the coolant temperature sensor for testing. Plug the hole, to prevent coolant loss, where you take the cts out. The instructions, and values:

Maybe the problem is related to the check valve in the fuel pump. Many times with a hard starting and rough running condition upon startup this can be traced back to the check valve in the fuel pump.
Fuel pressure bleeds off while the car is at rest and the hard starting/rough running is caused by the air that has to be purged out of the system.
The check valve problem can even be erratic in nature and requires replacement of the pump.

As to the burnt valve you suffered, odds are this was caused by failure to inspect/adjust the valve lash; something that should be done every 30k miles.

Hey, I have the exact same care with the same mileage and the exact same thing happened to me about six months ago. We ignored it for a while, but eventually we needed to do something about it. I couldn’t figure out how to get the codes on my own so I took it in and got it checked. They said it was the temp sensor and possibly the oxygen sensor. For about $50 they replaced the temp sensor and that solved the problem. I guess a bad temp sensor can cause the oxygen sensor code too. Good luck.

i Have exactly the same problems you have here, car very hard to start in the morniing, and when it start it loses its power when we push the accelartor the car just goes slow. after a while it will go normal again. it seems like something stuck in the muffler you have to keep push on and off the GAS pedal to get the power.

been check to 4 mechanic waste alot of $$$ and the problems still remain. here the town i stay no check engine shops that can get the code. how can i get the code of the car?

i check on the website possible might be 2 - knock sensor? or O2 sensor. but i need to make sure this is the problems before i change the parts.

my car is subaru impreza 1993 manual 5 speed.