94eg!

iTrader: (2)

I've been searching, but nothing seems to fit my situation...

I drive 29 miles to work every day. My 89 CRX drives fine all the way there in the morning, and 80% of the way home (70mph on the freeway). But since it's gotten really hot here in Vegas (105+), the car has developed a slight miss at light to medium throttle. The odd thing is it only happens during the final 20% leg of my trip home every day (*edit: now includes other random intervals). I come to the freeway interchange & wait to turn. Then after I do, the car has little hiccups the rest of the way home.

Here is a list of services I've done before it started:
- New Timing Belt & tensioner (proper setup)
- New Water Pump
- Valve Adjustment (proper lash)
- New NGK V-Power Spark Plugs (proper gap)

Everything was great (45mpg freeway), until it got really hot out, so I feared the red dust in my distributor was finally catching up with. I then replaced the distributor w/ a new one, but that had no effect. I'm also pretty sure the 4-5yr old NGK 7mm wires are still good (resistance is well within spec). I've even ruled out the A/C system by switching it on and off during the problem. Talk about HOT!!!

- No overheating
- No odd sound when missing occurs
- No check engine lights
- I'm stumped!!!

Any help would be greatly appreciated!

***EDIT: 06-22-2017 SOURCE OF PROBLEM FOUND!!!
Well after all these years (probably 15 years since the 1st time I remember it happening), replacing a bunch of sensors, and even rebuilding the entire top-end of the motor.....I've found the source of the issue!!!! Turns out it has to do with the EVAP system. I haven't had time to test all the components of the system yet, but somehow excess pressure is building up in the tank. This pressure is causing some sort of hesitation or misfire. As an experiment, I simply loosened the gas cap and when for a drive. It was 113*f outside and the car drove PERFECTLY for 20 miles with AC on full blast. I still cant believe it.

Of course this is not a permanent fix since fumes are surrounding the vehicle and fuel even spilled out a bit onto the body while cornering onto the freeway. Just have to identify where the problem is:
- Bad EVAP solenoid or wiring
- Clogged or Faulty Charcoal Canister
- Clogged or faulty 2-way valve
- Clogged vent line or hose
- Bad vacuum hose

Looks like all those years of topping off my fuel tank have caught up with me. Till now I always filled the car till the pump shuts off twice. I will never do that again!

moco_machine

Does your car start up right away when its hot outside? Check your main relay. Open it up and check the soldering if any are cracked.

94eg!

iTrader: (2)

Fires up first time, every time. Is the main relay in the under-hood fuse box or the under-dash fuse box? It's definitely worth checkin'.

moco_machine

under the dash bolted up on the left hand side. A little brown box. Open it up and check the solder to see if its cracked.

94eg!

iTrader: (2)

Well I checked the main fuel relay and it was in perfect condition. Now that it's hot again, the symptoms are getting worse. I think I've ruled out changing altitude as it's doing it at different intervals now.

I'm pretty much convinced it's completely heat related. Anybody else have any suggestions or insight?

atmdc

Id also like to know what causes this. is your air filter clean?

4gen5thtime

Find a friend with a 88-91 civic/crx and borrow their main relay, could also be the ignitor. I'm guessing one of the two. Have you changed your fuel filter?

94eg!

iTrader: (2)

The fuel filter is probably 20k miles old, and the air-filter is less than 10k. I'll give the fuel filter a swap though and see. I just can't imagine this only causing a problem in the heat of the day. When I drive at night, it's fine...

The ignitor was changed when I swapped to a new distributor (with no change to the problem), so I'm pretty sure that's not the issue. I took apart the main relay and it looked perfect. From what I've read, they only fail when the solder is cracked...

sbarmann

It could be a fuel problem, either the fuel pump or the fuel pressure regulator. Does it always happen when the engine is warm? I know when I first got my CRX it would have a problem when there was less than a 1/4 tank of gas and it would start to hesitate and act like it was going to shut off, even more noticeably around turns. The fuel pump was on it's way out and was not constantly delivering fuel. Also, recently my fuel pressure regulator was on it's way out but this was causing more problems during start up and idling more so than anything. I was thinking that maybe when the engine is warmed up it's affecting the diaphragm or spring inside the regulator causing your issue. Can you describe in greater detail what it does when this problem occurs? Hope some of this helps.

94eg!

iTrader: (2)

That sounds like something...

At the moment, the car starts hiccuping during the heat of the day after driving some distance. The funny thing now is seems to be doing this the next morning (only after doing it on it's way home).

The morning hiccups only happen after I first start it up and drive down my street. It also only happens when I first let out the clutch in any gear and start getting into the throttle. Once it settles it drives fine until I shift. It goes away before I make it half a block. It doesn't return until the heat of the day on the way home...

94eg!

iTrader: (2)

Long time since last post.

Car still does this occasionally, but only in the summer time. Well recently I realized it only happens in very specific spots during my afternoon commute. This is leading me to believe it's actually caused by an outside influence. I'm finding it happens at spots where I pass underneath high-voltage transmission lines (69kv or greater). Is it possible there is increased electromagnetic interference (EMI) from the power lines due to the high load of summer air conditioners here in the desert? If so how could you even go about testing for this?

94eg!

iTrader: (2)

SOURCE OF PROBLEM FOUND!!!

Well after all these years (probably 15 years since the 1st time I remember it happening), replacing a bunch of sensors, and even rebuilding the entire top-end of the motor.....I've found the source of the issue!!!! Turns out it has to do with the EVAP system. I haven't had time to test all the components of the system yet, but somehow excess pressure is building up in the tank. This pressure is causing some sort of hesitation or misfire. As an experiment, I simply loosened the gas cap and when for a drive. It was 113*f outside and the car drove PERFECTLY for 20 miles with AC on full blast. I still cant believe it.

Of course this is not a permanent fix since fumes are surrounding the vehicle and fuel even spilled out a bit onto the body while cornering onto the freeway. Just have to identify where the problem is:
- Bad EVAP solenoid or wiring
- Clogged or Faulty Charcoal Canister
- Clogged or faulty 2-way valve
- Clogged vent line or hose
- Bad vacuum hose

Looks like all those years of topping off my fuel tank have caught up with me. Till now I always filled the car till the pump shuts off twice. I will never do that again!

94eg!

iTrader: (2)

Update: So after complete inspection of the entire EVAP system, the culprit appears to be the 2-way valve at the fuel tank. When I initally disconnected it from the hose to the fuel tank, there was a HUGE vent of fumes and I could actually hear the tank popping and creaking as it's swelling went down. I cleaned the ports out with some chlorinated brake cleaner and blew them out with my mouth. I also disconnected the charcoal canister from the vent line running the length of the car (at both ends) and pumped a bunch of brake cleaner through it. Then I followed that up with some compressed air to dry it out. After hooking everything back up, the car is now driving like normal.

Today I had a 20 mile drive w/ AC full blast in 107* weather with the fuel cap tight. Car drove perfectly without a single hiccup.

If the problem returns, I will probably have to replace the valve completely. Unfortunately it's no longer available from Honda (of course), so I'm guessing I will have to adapt the newer style valve from the OBD1 cars.

Again people....DON'T TOP OFF YOUR FUEL TANK!

1991_crxsi

iTrader: (1)

Wow. Thanks for posting this update after so man years. I'm glad you got it all figured out . . . would have never guessed that was your problem!

94eg!

iTrader: (2)

Drove home yesterday in 114* weather. Ran fine till I was just about home. Issue started up again though very minor where I could barely feel it. Undoing the fuel cap and re-tightening had little effect, pressure came back almost immediately. Had to drive with the gas cap loose to make the issue go away completely. I'm wondering if the fuel pump is just old & weak, and can't handle the heat/pressure. A new Denso brand pump would be nice, but unfortunately I have no time to try replacing it.

Also my AC compressor clutch coil shorted out completely.

1991_crxsi

iTrader: (1)

This is going to sound stupid but have you replaced your PCV valve/ made sure it is properly seated? I had a similar issue with that in the past. Please tell me that you don't have a breather on your valve cover. Have you made sure that all your vacuum lines are good? It could also be a leak in your intake manifold somewhere along a sensor's gasket/TB/ or actual intake manifold gasket. How is your air filter?

I also had a similar issue when my distributor was going bad. It could be an ignition issue like that. You can get a whole new distributor and replace wires and plugs for cheap. Oh yea, one more thing. As strange as it sounds I had a TINY (almost visually impossible to detect) bit of water get under one of my spark plug wires on the head side and it caused a similar issue. It happened after an automated car wash. I just took it apart, let it dry out for a few hours and plugged everything back in.

94eg!

iTrader: (2)

Car is 100% stock (no breather modifications)

Replaced distributor, wires, plugs & relay. Idle & ignition timing set perfectly per manual.

I also replaced the entire pcv system when I completely rebuilt the top end of the motor. Intake manifold was cleaned and ALL gaskets replaced. All hoses and sealing areas checked for vacuum leaks (except throttle shaft).

I'm not sure if you read the entire thread, but I have concluded the issue has to do with fuel tank pressure. What exactly the tank pressure is doing to cause the hesitation is still under investigation. Main suspects are either fuel pressure problems or over abundance of fumes into the intake (from the charcoal canister). I have an idea of how to check for the later.