1990 Integra, engine is missing under load. It's down on power when missing, but will eventually run smoothly, usually once the revs pick up, but doesn't seem to want to rev over 5,000rpm, it just sort of run rough and seems to top out. It runs pretty normally when not under load. it doesn't seem to really do it until the engine is good and hot, after like 20 minutes of driving.

I'm not getting any codes, you would think with it running this rough the computer would sense something is wrong and throw a code, but nothing. btw, I was getting a code, but replaced the fan switch and it went away.

I'm wondering about dirty injectors or faulty fuel regulator, but again would expect a code, especially since the engine seems to be running rich (just a guess from fuel consumption).

I've considered fuel pump, but it can keep up sometimes when reving, just not under load.

Has anyone ever had these symptoms from faulty main fuel relay? I've replaced mine once (with a used one) and soldered all the joins and it isn't effected by heat and doesn't have a starting problem, which are the normal cause and symptom for this, so I haven't suspected it.

Any suggestions?

Thanks!

 

Is your engine missing? Maybe you should find it first. Then after that....maybe check the condition of spark plugs and other ignition components.

An OBD1 or OBD0 car really only throws a code if a sensor sire has an open or short circuit. It doesn't know or care how the car is running.

 

My 1990 Civic had the exact same symptoms and no codes, and i fixed it with a new cap and rotor and new plugs. Runs perfect now.

 

Badabing.

Plugs are not that old and look good. Rotor was replaced, cap could maybe be replaced.

Thanks for the info on the codes.

Thanks DA9, I'll try that.

 

Just checked, distributor was only held on with two of the three bolts. Here's a shot of it, does this look like it needs replacing?

Also, could the problem be the coil? When I had the cap off I noticed that it has the marking from a wrecking yard, so it was replaced with a used one at some point.

Thanks.

 

Id say replace the cap just so you know you have a good seal, and throw on a different coil. Then if you're still having problems check and replace the plug wires. Just start with the cheapest, easiest fixes first!

 

had the same problem with my teg turned out the cat had melted inside and was clogged.

 

"Was throwing a code"? Pull the code as replacing a fan switch won't fix a code or won't throw a code for fan switch.

 

A dying coil pack will cause this as well until it dies completely.

 

Does your motor seem to run hotter than normal?

That cap does look a bit worn out, I'd pick up a new OEM cap and rotor.

On an older motor, it usually tends to be more than one thing thats contributing to missing under load, and/or lower power overall, especially after the motor warms up.

I would take off your cat converter and look through it to see how clogged up it is. the bolts are prob fused together by now, I'd just cut them off with a dremel or angle grinder and get new ones. Let it soak in a bath of citric acid, check this out:
( (All Years) Catalytic Converter Citric Acid Bath P0420 - Subaru Forester Owners Forum )

when was the last time your coolant was flushed? how old is your thermostat? sounds like the cooling system can't keep up, especially if your cat is clogged, too which prevents some of the excess heat from blowing out the exhaust. as it warms up, the heat starts to soak into the motor, instead of properly going through the radiator and through the exhaust along with the gases. which will make the motor start to miss and ping, because the gas is igniting before the spark plug lights it. no good. i'd run some coolant system cleaner ( http://shop.advanceautoparts.com/p/p...l.-oz.-pkf0ae/ ), and flush everything out with a flush kit ( http://shop.advanceautoparts.com/p/p...ll-kit-pkf0aa/ )

try the cheap stuff first. at the very least, both of these things will help out quite a bit, even if it does turn out to be something in the ignition.

 

Thanks for the suggestions. I put in a new dist cap, same issue, so ordered a new coil, haven't got it yet. It could possibly be the cause as the coils inside the distributors heat up and degrade, so would tie in with the issue happening once everything is good a warm, although the engine is not running hot (and thermostat is only a couple of years old). I'll post once the new coil's in.

The switch was to the radiator fan, I checked it with an ohm meter and it was broken, installed a new one the computer stopped throwing a code.

Thanks again.