I have a 93' EX 2dr.
My problem: Bad gas mileage, CEL comes on after about 5-10 min of driving (codes don't make sense-comparing to Haynes Book). When cold, it starts and drives good; but when CEL comes on I can feel car sputter/hesitates when I press gas pedal, and when I stop at a light the RPMs lower (feels like it's about to shut off). When I'm on freeway it rides good.
When weather is hot or after a 45min drive, and I go to restart it cranks but won't turn over. Then I wait 10 minutes and when it turns over it's like it is not getting enough gas then starts right up. **So, the "3" main issues I noticed -- 1) MPG, 2) Start/Fuel/RPM issue, 3) CEL. I'm new to Honda but not scared to get dirty... Please help.

Oh, Main relay seems to click, and I have not changed the IAC or O2 sensor sinced purchased 2 months ago.

Did change: MAP sensor, timing belt, Water pump, spark plug & wires, all Fluids, Valve Assy PCV.

IS is the IAC?

I NEED HELP:confused:

CEL coming on, after it's out of "open loop mode," and poor gas mileage sounds like the oxygen sensor is bad. Replace the oxygen sensor, reset the ECM, by pulling the BACKUP Fuse for 10 seconds, and the problem should go away.

15 years old.. could be anything ;)

(and its been a while since i have done this stuff ;) lol.. so PLEASE correct me if I am wrong)


The O2 sensor is a good place to start. Old ones get clogged with "crap". Once clogged they respond slowly. ALso, old ones can not put out the same voltage, which can fool the car into thinking its leaner than it actually is... etc. basically this can cause issues :)

BUT, I don't remember if this can cause the hot start/hesitation. The O2 can cause the drop in mpg though

Could be bad fuel pump? Clogged fuel filter? What are the codes? (post them anyway)

OK, will give that a try (O2 sensor). Looks like it needs to be replaced anyway. But when I unplugged it the car still ran, and when I did the same to the IAC I got similar problem... just trying to troubleshoot. I'll try your IAC cleaning post "TX" and the O2 sensor.

Static, it seems like more than O2 to me as well, but I don't know Hondas and TX might have a point. I change the fuel filter, but not fuel pump. Seems to me as if I can drive once started (normally 45-60 minutes home) that the pump should be in working order.

Thanks for the rapid responses from you both. I will get on this as soon as I get home.
I'm in Florida preping for possible hurricane, but I need to get the car right... bought it to commute to and from work and save on gas...

Thanks again and I will post my findings.

C1

On these older Hondas, it's important to replace the ICM and coil:

https://www.askmehelpdesk.com/cars-t...tml#post265896

While your are at it, I would also replace the rotor and distributor cap.

Hi, I have a similar problem with my 93 vtec... I'm an appretice tech and it's mildy embarrassing. I recently swapped the engine from the dx 3000km ago. It's never liked starting when it's hot, even when I first bought the car with the old engine 5 years ago. I'd accidentally stall it (learning the clutch) and I'd be the bane of all traffic behind me as the car wouldn't start back up. After a few minutes it'd come back to life. Sometimes I'd just have to open the hood for 5 minutes and it'd start.
It seems lately in the saskatchewan summers it's just too hot for it and whatever used to struggle might be starting to die. Lately if I park the car at night and don't start it till about 5 or 6 pm she won't start. She cranks steadily but won't start. I just tried today around 6pm and got the same result, but after finding this site I went back out a few minutes ago to test a few things and she started right up no problem.
A friend said she's missing a bit (I don't know what to listen for when it comes to misses) and it might be the spark plug wires. I checked all the spark plugs (with 3000Km on them) and they all look the same with a whitish grey tip and black around the threads, except for one that has a thin coat of oil on the bottom by the washer. It does idle irregularly, the rpms will drop like it might stall then come back in 5-10 second intervals, but then sometimes it runs smoothly. The power has also dropped off a bit since the engine's been installed.
I am considering replacing the cap and rotor and spark plug wires just because they're all fairly old parts. The engine came from japan with allegedly 90,000km on it, I don't know if any of the parts that came with it are original. I don't want to go buying tons of new parts and still have a car that won't start. When I can figure out what wires the vtec needs I'll order those and pick up a new cap and rotor. I changed the fuel filter, plugs, iac, and computer during the engine swap. The charcoal canister had to be partially bypassed since japanese engines don't have emission control systems. There was a fuel leak throwing a low fuel pressure fault code, but I stopped filling it to the top and I haven't had another problem.
Is there just too many ghosts under the hood? I'll do more diagnosing tomorrow when it's hot and she probably won't start, but I'd really appreciate some help/ideas of what to focus on. I've baffled most of my neighbours and gotten 20 different suggestions from my fellow GM techs, so I need some honda specific help.
Thank you!

Darkwingchick, replace the Ignition Control Module, coil, and main relay. That will likely take care of the hard starting issue. It's a good idea, however, to replace the rotor, distributor cap, spark plugs, and spark plug wires.

Here's how to replace the ICM and coil:

https://www.askmehelpdesk.com/cars-t...tml#post265896

Ok, thanks! I'll give that a try and let you know how it goes. I might try a piece at a time to see what does it.

Since you had trouble starting the car in hot weather with the old engine, replace the main relay first (since it is a constant). Cold solder joints may have developed on the main relay's printed circuit board.

TX, have to take car to the shop... the O2 sensor looks like it has been there for a while (won't come of with PB Blaster)... might need heat and rethreading (I have no torch experience).

Also, looks like the Main Relay is bad... Had the starting issue again and turn the ignition switch while thumping Main Relay :) and it started (reluctantly)... so I need to get one of those. I'll check for the ICM, coil, rotor, and cap.

Any suggestions on where to buy parts?

Channo1, shop for price and warranty. I got the best price on a coil at RockAuto.com--the TEC coil is OEM and the exact one that Honda used on my 1993 Civic DX. I got the best price and lifetime warranty on a new ICM at Advance Auto Parts. Things change, of course--just shop around to get the best deal.

See if the link below helps with replacing your oxygen sensor:

https://www.askmehelpdesk.com/cars-t...tml#post223376

TX, may be silly but need guidance on Main relay name: is it PGM/FI, or will a Niehoff Ignition Relay - Multi-Use (from Advance Auto Parts - Part #RL39571) work?

Thanks for the Rock Auto.

PGM-FI Main Relay is what you want.

Here's AutoZone's offering:

AutoZone.com | Shopping | Parts | Product Detail - Relay - EFI Main

They normally have a 7-pin connector.

Before you buy, it's always best to compare what you have, in all particulars, with the replacement. Therefore, remove the old PGM-FI Main Relay first and take it with you for comparison.

Changed the relay (drilled holes for venting); worked like a charm. Drove around 15mins, stopped and had same start issue. Now it idles high (1500rpm) for a minute or two then normal. Start issue still there and CEL... will take to mechanic this weekend for O2 sensor replacement (original seized). Still have in morning only: high rpm, doesn't shift into next gear for about 2 minutes.. then all is well for rest of day. Will replace distro/rotor and ICM 9only thing after that I haven't changed will be IACV and ECU..

Saw this site on cabelas forum Get an estimate for a service or repair on your car : RepairPal Put in your info and get parts and labor estimate for replacing the oxygen sensor, also has a list of nrepair shops in your area. Hope this helps

Hey, I replaced my cheapy parts (plugs wires rotor) but haven't replaced the other stuff yet because of $$. It hasn't been warm enuf to notice the hard start issue lately. I am more concerned about getting a CEL with code 43.
Channo1: what code are you getting? I'll bet it's the same. Sounds pretty close to my performance.
I'll drive for about 5 minutes then the light comes on. Sometimes idling at a stop the rpms dip up and down, sometimes they dip so low I get nervous and tap the gas to bring them back up. There's tons of heistation at acceleration and at the worst moment it felt like I had to give her a bit more gas to keep her going constistantly.
From my online digging I've narrowed it down to the O2 sensor or the fuel pump. A third cause is commonly the fuel filter but I just replaced it so I doubt it. With the drivabilty issues, it's more likely the pump, but the idling makes me think the O2 sensor could also be bad, since it's always idled up and down since the engine swap. Some journeymen from the shop are going to look at it for me tomorrow so I'll try and keep you posted.
Poor little d15B.
PS having to figure out which parts match a japanese half this engine half that engine is no fun. :P