I own a 93 civic ex 4dr (all stock) and have had a check engine light problem with my vehicle ever since I got it back from the mechanic. The original problem was the main relay which I had figured and resoldered but the other problem behind it was the black/yellow cable going from the main relay to the ecu which was out of place in the main relay harness.

Anyway, my new problem may be the reason why my civic feels like a gas guzzler... It gets about 15-17mpg!! It's a 5-speed and I usually let it roll whenever I can to save gas. The problem is that it seems like it's lost a lot of power on the freeway when I try to get to 5th gear. I spoke with a friend and he stated that my ecu was in "limp" mode. Supposedly during this time, it'll produce less power while having the gas run richer. I wouldn't call myself an expert about these things but would it be possible to resolder the ecu? I tried doing the famous paperclip shortening trick but it doesn't seem to work. I've spoken with some others who own the same generation and model of the civics and they have the same issue about not being able to read it on their speedometer.

2nd problem, my entire dash including the AC, fan, speedometer seems to be faulty with no bulbs turning on at night. The MPH gauge does not work at all which is caused by the speed sensor in the tranny from what a mechanic has told me. However, all the bulbs won't work either... This may contribute to the fact that the ecu does not throw codes out for me.

3rd problem, the 7.5V radio and clock fuse under the hood seems to have blown. I tried replacing it with another 7.5V and it sparked right when the two sides touched. I now have a 10V in there and it works fine.

4th problem, the car seems to overheat quite quickly after about 20-50 minutes of driving. The check engine light also usually comes on within 3-10 minutes after starting up.

I'd hate to go back to the mechanic and spend another few hundred to fix such a small problem I was getting around to anyway. Any help you guys may provide would be greatly appreciated.

There are quite a few fuses that control the interior electrical stuff under the dash. See if any one of them has blown. If they're all fine, then you most likely have fried some wires.

Try to fix your dash lights first, and that'll allow you to see if you can get a read out of your codes. Oh, by the way... if your car has an electrical vehicle speed sensor, and if your fuse blew (one on the vehicle speed sensor wire), that would explain why the speedometer doesn't work.

Do you feel the RPMs drop down slightly when the check engine light comes on?

Wait a second... how does the check engine light come on, when no other bulbs work? Does the "hand brake" light comes on when you pull the hand brake? "Trunk" light?

About your overheating... try to replace your thermostat... it might be stuck closed, and your car cannot cool down.

Thanks for the quick reply! :)

Well, this car has been handed down over and over and I'm the 4th or 5th owner... lol...

Thing is, my dad took out the thermostat and told me I didn't need it so it's been like that ever since I've gotten this car.

For the cluster, the bulb which usually light up at night so you can view all your stats are gone. This doesn't include those lights which inclue the SRS, CEL, trunk light, hand brake, etc. It's just the bulbs which light up your cluster so you can see how fast your going at night.

As for the speed sensor, it is electrical. It's been gone ever since I've gotten the vehicle and my bro told me that he used to kick try and kick the side of the tranny to get the speedometer working. I also got it to work for about 5-10 minutes the other time when I went over a speed bump pretty quick.

Yea, this car's been in pretty bad shape ever since I've gotten it.

UPDATE: I went to check the fuses and they were all in good shape. The heat motor fuse may have been blown since it looks kind of bent...
I tried the paperclip trick again but this time I stuck it all the way in there. The results were 9 which appears to be the cylinder sensor. Hrmm how would I fix this problem?

BTW, Thanks crocivic for helping out with other people's problems. You should get an award of some sort.

Another update, just tested the cyl sensor cables and it turns out that there's a short in the system... Seems like a lot of tracing to get it to work correctly... I'll keep you updated.

Yeah, code 9 means your distributor is having problems. You might just have your timing way off. I rebuilt my distributor (had a bearing seize inside) and I messed something up inside (the plate that you can turn a bit in each direction), and that caused me to get error code 8, then when I took it out and turned it the other way, I got a code 4... I couldn't get a code 9, because my car is DPFI, so I don't have that sensor inside the distributor.

Anyway, check your timing - it may be WAY off. Perhaps your timing belt slipped a tooth.

Oh, I just noticed your wires are messed up. Oh well... work on it then ;)

By the way, thanks for the thumbs up ;)

Yea, it might not be my distributor but not completely sure. My mechanic may have retarded or advanced my settings on the distributor by 180° which means that it's out of sequence.

However, as I went through my service manual and did the procedures for the check engine light code 9, it passed with no problems for the distributor sub-assembly section.

So as I went to the next step of testing the ecu harness, I found that there was no resistance between body ground and those points.

I'll try to retard my distributor's timing by 180° once again. I have no clue how to check the timing belt... Service manual shows how but it looks quite complicated.

Problem #3 gives you the answer to all the problems!

Because circuits require more amperage than designed for, the car's electrical system has been monkeyed around with to the point were the whole system has been overloaded.

You might try to remove all the crap that has been added after-market in hopes that no permanent damage has occurred. That's the start!

Yea, this car's been tampered with before I got it... I didn't think the larger fuse was a good idea when my friend said that fixed the problem. Might be the reason why my deck seems to overheat a lot... Thanks for the tip.

BTW, both fans that should cool down the engine don't move at all... I've been driving around like this with the fans off... Think the engine might need work. Well, I'll try to fix the shorts in the system first. The wires have been readjusted in such a ghetto way that I need to figure out which ones the mechanic had redone.

I've heard that the check engine light will come on if there is no power to the ECU (that computer that generates the codes and controls the engine).
When this happens, no codes are generated.