15 replies to this topic

[fcrizzo]

I have a 1985 crx si 5 speed. Original 1.5 sohc 12 valve.the car runs fine for like 10 min. Then it starts to struggle under load like u have no power even with the gas pedal to the floor, I can even hear the engine struggling to run like its starving for air or fuel. Then if it hits 3000 rpms the engine kicks back in like a rocket, but when u slow down it goes right back to the same struggle. It's pretty scary because I have pulled out a few times and almost got hit had to push clutch and rev it up and pretty much spin tire to go. Now if u keep your foot on the throttle while it's struggling eventually the pgmfi light comes on and the car runs fine until u shut it off again and the light is not on again when I start the car. Start the car again go 5 or 10 min and it does it again. Now I replaced the o2 sensors recently same problem still. Also like 4 years ago I like my ecu got water in it maybe. But the car still runs and starts every time on that ecu....the car has never stalled on me....no surging.... I have tried a lot of different things I'm just pretty sick of this problem PLEASE HELP. I have had this car a long time with this problem...... I also rebuilt the motor about 60000 miles ago and the car had this problem before and still does now..... now I have run into when I change my spark plugs the problems is gone for like 2 or 3 weeks and comes back. Also I have checked the code from the ecus lights and it's the number one light but the o2 doesn't fix it.

[chedda_j]

It can read o2 if its just running really rich, mine did this right before I blew it up lol.

[anjin]

So its fine when cold, and fine above 3000 when hot. And a change of plugs fixes it for a few trips. Sounds like running rich, as Chedda says. Why?
My first suspect that the temperature change from cold to hot is not registering in the ecu so the ecu is piling in the fuel. So check the wiring from the engine temperature plugs. They do corrode and get broken insulation.
After that it will get tricky to solve.

[nwinter81]

It could be a faulty temp sensor, or a bad fuel pressure regulator, or it the main relay, or a bad fuel filter too, maybe the coil is faulty or the distributor, maybe there is a vacuum leak on it where the timing control diaphragm is. my 85 Si did the same thing. Check the map sensor too. couldnt hurt. but it could be a corroded faulty wire, something so simple could cause some crazy issues.

[eec4tuner]

It could be a faulty temp sensor, or a bad fuel pressure regulator, or it the main relay, or a bad fuel filter too, maybe the coil is faulty or the distributor, maybe there is a vacuum leak on it where the timing control diaphragm is. my 85 Si did the same thing. Check the map sensor too. couldnt hurt. but it could be a corroded faulty wire, something so simple could cause some crazy issues.

What he said.

[fcrizzo]

Thank you for your input. I know it's not the fuel filter it has been changed in the past.
Ok i will check the fuel pressure regulator
Where is the map sensor located??
I replaced the main relay sometime ago too.
The car has an msd coil I don't think it's bad but I will check it.
As far as the distributor I will check that too.


Now Eec mentioned vacuum leak on timing diaphragm that's the back plastic round piece with 2 vacuum lines on the distributor right???

One other thing I forgot to mention is it has been running sort of hot.,,,, so I will check temp sensor.

One other thing also is why when the pgmfi light comes on does the car run fine??

[anjin]

The light comes on to say there is a problem. Depending on the problem, there can be virtually no effect on the actual running of the engine to it won't run.
For example, I run a blacktop D16 head and dissy and ecu from a gen 2 crx in a gen 1 crx. When coasting down a hill, the light comes on, because (as far as I can see) under low fuel closed throttle conditions the fuel is effectively cut, and the O2 sensor part of the ecu throws a mixture fault as the data falls outside the programmed limits. Engine runs fine, I haven't bothered doing anything after the first episode and check that its not a problem, and I turn the engine off and on to get rid of the damned check light.

[EuphoricBlue]

Start by checking the temp sensor that goes to the ECU. You'll need a multimeter for this. (Or just replace it) The SI has 2 sensors from what I recall. If memory serves, larger sensor feeds the gauge, smaller one feeds the ECU. IIR they are under/around the distributor/upper rad hose.

Also, make sure the injectors are all clicking. Easy with a stethoscope. The backyard trick is to take a long flathead screwdriver, press the blade firmly against what you want to listen to, and place your ear on the handle.

I'm guessing when you pull the plugs, hey are pitch black? Possibly even moist. You're running rich. There are only so many things that will cause that. So you're on the right track to narrowing it down by just knowing it's a rich fuel issue.

[nwinter81]

also if you buy universal o2 sensors they could cause that issue as well...but it does sound like a faulty sensor telling the ecu a fault.

the map sensor is on the right side of the intake manifold behind the 4th fuel injector, pretty much above the alternator if your looking from the driverside top of the engine.

if there is a leak in the diaphragm on the distributor it will not adv the timing properly its like prehistoric VTEC lol.

[NWClassicHonda]

I just had this same problem and it was the water temp sensor under the distributor. Swapped out out and the car runs great again.

[Bubba]

The car runs better when the PGMFI light comes on because the ECU is no longer controlling the amount of fuel injected based on information from the oxygen sensor and other sensors. This is called closed loop mode.

If there is a bad sensor or suspicious reading from a sensor, the ECU will "realize" there is an issue, go into "open loop" mode and turn on the PGMFI light and then control the timing and fuel injection based on a general "safe/limp mode" fuel map programmed into the ECU. All the info that it needs to run OK in this "safe mode" is engine rpm and a vacuum signals. You will get worse mileage if you keep running it in "safe/limp mode" with the PGMFI light on, but I don't think there would be any long term damage to the engine.

[EuphoricBlue]

Now Eec mentioned vacuum leak on timing diaphragm that's the back plastic round piece with 2 vacuum lines on the distributor right???

Yes, that's the one. The port closest to the distributor is your primary advance pot. You can test it with a vacuum pump... or by simply sucking/blowing on the vacuum line attached to it XD If there are no leaks in the pot you won't be able to blow/suck through it.

Also check the line itself for cracks and such.

Check the upper pot as well, but that one is not very important as it is only used under very cold starting conditions.

[fcrizzo]

Now jdm4drda7 said it was the coolant temp sensor under the dizzy now if I remember that one is a single wire and it's like clipped onto the tip on the sensor I believe that one goes to the gauge right ???? Bubba thank you for explaining the pgmfi light limp mode I get that totally. So it's good my car has is then. Very good explanation. Now the spark plugs pretty much look fine not wet at all. So it's gotta be a sensor issue. I'm pretty sure the last o2 I bought was universal...... I will be getting a direct fit. So. Hopefully soon I can figure this out. I'm gonna buy a new fuel pressure regulator.

[EuphoricBlue]

The single wire goes to the gauge, there should be a 2 wire sensor in the same area (probably a little more buried) that will go to the ECU.

 

Universal O2 sensors are fully compatible. There is really no difference between them and a direct fit from the same brand other than a plug.

Also, your O2 sensor shouldn't be effecting anything at idle, or under most conditions really... The exhaust temps tend to be too low for proper sensor readings on non heated O2 sensors (like on the 1G) Because of this they are really only used under sustained cruise. They also aren't really used under power conditions (IE, WOT) regardless of RPM because the conditions vary too rapidly to make any effective changes.

Combine all this with the fact that you've replaced the O2 and it didn't fix the issue... I'd guess it's not the O2

 

I'd look at the temp sensor and the map sensor since these are really the only 2 the ECU uses under most conditions to calculate your fuel mix.

Beyond that, it only really leaves fuel pressure, injectors, and spark.

[fcrizzo]

Thank you leadfoot I am hoping to be looking into the sensor this weekend hopefully it will fix my problem not having the full power of my crx is really no fun at all , not only is it not safe to drive the way it is but I can't even enjoy driving it.


One other thing I also wanna mention that if I'm driving quickly the problem doesn't really occur above 3000 rpms I obviously get problems when below that and when accelerating from gear to gear. And I can't just sipped every where. So basically around town stop and go driving sucks BAD.!!!

Again everyone thanks for all your replys and support the beast will live again....I'm not giving up.