did you jump the computer before you set timing. If you don't the computer is just gonna fight you. I doubt timing was your problem.

If you properly set your timing. I would warm it up till the fan comes on disconnect the iac valve and set your idle then move from there.

Things to check stuck Iac valve, pcv valve, vacuum hoses, more rare map sensor and the ETC sensor.

 

What are the year and trim (HF, DX, or Si)? Is the engine basically stock or has it been swapped? If not stock what do you know about the engine and ECU?

Check your cam timing. It's common to jump a tooth or two on the timing belt. A common symptom is idles OK but will not make power. Your symptoms don't sound like a perfect match but you want to rule it out anyway.

Do you have symptoms of running rich? Any gas smell at the tail pipe or carbon on the plugs?

Mike

 

Thanks Mike, I was going to check the timing belt next. It's a 1989 Si. I'll get the engine and ECU info later. Seems like it's a little rich. I checked the Catalytic converter and exhaust and it's all flowing really well. the plugs didn't look too fouled but were a little black (not on the electrode) They were also slightly red. Not sure what that means. Other than that, the car is pretty much stock. Idle is definitely ok as well. Only part throttle there's a bog and after a mile down the road, a check engine light and things start getting weird. At moments the power comes back and disappears.

 

Thanks Bschwald! Jumping the computer to set the timing is running a jumper wire across the plug next to the washer bottle correct? If so, I did that.

Seems like when I give it throttle and it goes into the bog before it picks up at idle.. the timing goes retarded before it advances. Is that normal?

 

Yup that's the the plug. For it to suddenly start acting up like this. I think Mike might be onto something.

 

Quick update on this. The engine is a D16A6 and the ECU number is 37820-PM6-L080. I checked the timing belt and it's exactly where it should be so it hasn't skipped. The car is getting worse. It's gone from having 75% power for the first mile then getting a check engine light and doing random things to barely being able to back out of the driveway. Top speed is about 30 mph and nothing happens when you push the gas pedal to the floor... it just gets louder. I gutted the converter so there isn't a backpressure issue. I'll look at the plugs again today. It's developed a misfire but I'm thinking something is causing the plugs to go out. The previous owner seemed to mention that there's a place that rebuilds ECU's. It looks like he's been in and out of there quite a bit so I'm wondering if he had narrowed some problems down to there and doesn't want to admit it was bad or going bad.

Thanks for your help!

 

Is it still giving that one code, and are you reading it correctly? If you're not absolutely certain you can post a video of the ecu blinks.

I had a kind of similar issue with an 88 integra. Car would be fine at light throttle but above 3k rpm (over 25% throttle with my driving) the cel will turn on and the car goes into limp mode, unable to go above 45. Can't remember the code but the distributor was tested bad, got replaced (after avoiding it until the problem was so bad, I couldn't hit 25) and all troubles went away! May or may not be the same for you, but it won't hurt to test it

 

Thanks for the info bairdandrew77. That sounds similar. I know the distributor was replaced by the previous owner. He worked at a Honda dealership in the parts department so I'm assuming he bought genuine Honda replacement parts. Still, it's obvious he's been having problems seeing the cover isn't bolted to the ECU. Is there a way of testing the distributor? I remember a neighbor had a Civic that would run fine than do some really weird stuff. I think it was the igniter. Thought it was strange that it was completely random. Usually those either work or they don't correct?

I'll take videos of the ECU codes and of the car idling and driving this evening.

Thanks!

 

Here's a video of the ECU.

I'll post another video of a test drive in a few minutes. I don't think the car is going into limp mode. It will rev over 3k but just has no power whatsoever. I didn't get the check engine light the other day either.

 

Correct timing for a d16a6 is 16*, not 18*

If the car is throwing an 02 sensor code and you think the wiring is sound, replace the sensor.

If this car is new to you, replace the spark plugs, there $2 each. Replace the fuel filter $10 and pull the distributor cap off and give the cap contact points inside the cap, and the distributor rotor button a close look for wear or signs of old age. Have an extra $20? change both of them anyways. Plug wires dont break the bank @ $30 either. All of these parts can be installed in an hour and would make for a good baseline tuneup upon new used car ownership.

Sounds like the car just needs a little maintenance here to be honest, fouled/aged 02 sensors can surely cause the car to run like a bag, thats why they make replacements, dont hate the car for it.

 

I appreciate the input I have gotten so far and the suggestions have given me a good place to start looking. I'll have a link to a video I made while driving today that shows no acceleration even though my foot is to the floor. The car is not in limp mode because it revs over 3k. It is completely random. Sometimes I'll take the car out and it has 75% of its normal power. When the CEL comes on, it actually gets a little better. Sometimes though, it won't even do 30 mph.

Some points of clarification. The car was meticulously tended to by the previous owner who worked at a Honda dealership. It has, a new distributor, new coil, new igniter, new plugs, new cap, new rotor, wires are in spec with cracks, no arcing, a new O2 sensor that I verified works up to the ECU. I swapped igniter's and the coil and the same problem exists.

The car ran great for 3 weeks... including a drive from North Carolina to Florida. Out of the blue, a check engine light came on and the car immediately lost power. Top speed went from very fast to 55 mph then to 25 mph.

The main areas of concern are the engine is getting very hot. The gauge says it's OK but my hand tells me otherwise. I have a new radiator and thermostat installed and with two fans and the heat blasting away, the engine is getting hot as though the timing was running at Top Dead Center.

Today, I traced every sensor and wire coming from and leading to the ECU. Everything functions properly and is within spec as shown in the Honda Shop Manual. The only problem I noticed was the fast idle solenoid. It is broken but apparently only functions in cold weather and most members mention they don't even have theirs connected. The only sensor I haven't checked is the speed sensor.

I will go through the fuel system tomorrow or next weekend. As for now, I am inclined to believe that the ECU may be the problem.

Thanks to everyone again!

 

Here's the car at full throttle:

 

What symptoms is pointing you to think this is somehow a faulty ecu? I dont see any signs of that at all.

the previous owner who worked at a Honda dealership. It has, a new distributor, new coil, new igniter new cap, new plugs, new rotor

A new distributor, would cover all 4 of the parts you mentioned after as all come preinstalled obviously inside of it. That unit, when available is about $500 from Honda though. Even a Honda mechanic is capable of spending $100 on an aftermarket distributor instead of going with OEM. Either way, just because you think it was replaced at one point, its still worth 2 minutes of your time to pull the distributor cap off and give a good look at the cap contacts and rotor button strip. Both cheap parts and can ruin a cars performance

a new O2 sensor that I verified works up to the ECU. .

Showing voltage to the ecu doesnt rule out the 02 sensor being faulty and causing a large performance loss, they foul and have a service interval for this very reason, our ecu relies heavily on this sensor.

Spark plugs and fuel filter are also high service frequency items, and are so cheap and simple to install yourself its silly not to replace them when buying a new to you used car and encountering a problem like yours, especially without specifics of when they were last changed.

 

I never like it when people they it has a new distributor. A new oem one costs between $500-$700 as mentioned above so 99.9% of the time they use a new aftermarket part. Non oem honda disi's are never as good as oem and break within a couple years. I've dealt with them in my cars enough and found that "rich porter" is the only aftermarket one I'd ever trust now.

As for testing the one you have now, inspect the cap and rotor closely. Testing the sensors inside the disi is important, see if you can find it online or use all data to test from the connector.

Also pull the o2 and take a good look at it. Maybe it's been fouled up pretty bad. I doubt it, but always best to check. How far do you drive? The car has to be driven carefully until the o2 is warmed up enough to operate properly, we don't have those fancy heated ones on these cars.

 

I'll pull the O2 today and take a few pictures and post them later. Otherwise, it reads the correct voltage at the given RPM range. My thinking behind the ECU is.. and correct me if I'm wrong, that it seems to be getting the right information. I don't think it's sending the correct information out like the correct timing and fuel curves. The engine gets really hot really fast with a new radiator and thermostat and two fans and the heat running full blast.. the last time I felt an engine that hot is when it was running at TDC (0 degrees advance). I'll post another video of the timing. I find it interesting that when I give it some throttle, the car goes into a bog and the timing goes what looks like 5 to 10 degrees after TDC before it picks up again.

Additional info, The distributor had 360 ohms of resistance on the sensor on all of the pins and is within spec from what the book mentioned. The guy I bought the car off of worked in parts at the Honda dealership so I'm sure he got genuine Honda at cost. I'm not ruling it out but I want to be sure before I drop down $500 - $700 on parts like this. Also, I talked with the previous owner and it seemed like he was quick to suggest a place that rebuilds ECU's. I found this strange but it makes me think he was having issues and narrowed it down to that. When I set the timing, it looked like it was way too advanced. I'm thinking maybe they over-advanced it to get it running half way decent in order to sell it.

Thanks again to everyone for their help!

 

Update on this... I took out the O2 sensor and it looks good. Like the way a clean burning spark plug should. I found another issue that's fuel related. The fuel pressure regulator looks to be malfunctioning. There's about 25 to 30 PSI of fuel pressure when there should be 35 to 41. If I take off the vacuum line, it goes up. Also if I pinch the return line, it goes up. I took off the vacuum line and blocked it and drove the car and it drove great.

Unfortunately, the underlying cause is still there. It seems like the engine overheats and it throws a check engine light and gives me an O2 sensor code and the engine starts to die. What could cause the engine to overheat so bad? Timing? a blockage? Water pump not flowing enough? Fuel mixture too lean?

If I advance the timing to its limit, the off idle stumble disappears. I'm not hearing any valve knock but the timing is too far advanced by the book. It seems like the engine runs a little cooler then. Is there any way to tell how the ECU is changing the timing curve when driving around? It's usually that first drive onto a state highway where the CEL comes on and the performance goes to crap.

Thanks!

 

A quick update on this. I bought the usual tune-up stuff like cap and rotor, wires, plugs... all of which didn't do much except the fuel filter. When I poured the gas out of the old filter, the outlet side of the fuel was just as bad as in inlet. There was a lot of dissolved rust in the fuel.

The car runs somewhat better though it still has no power, jerks and stutters and bogs at part throttle and strangely when the CEL comes on, it instantly gets a little better (though not much.) Could the rust be clogging the injectors and giving me these problems? I don't think overheating is a problem at this point though the car runs better since a cold front moved through.

 

One thing to remember is the computer will throw a 02 sensor code for several reasons. If it is reading rich or lean and everything else seems fine, the computer has nothing left to do other than to blame the 02 sensor.When you the CEL light is thrown the car will run in open loop mode using the default fuel maps in the ecu. I have a feeling that your car is running lean and that is causing the overheating. I would clean the injectors also make sure you don't have rust in the gas tank. Our cars are not that complex. Good luck keep us updated.

 

Well, I think there's a light at the end of the tunnel. I decided to clamp the fuel return line off to see if a little extra fuel pressure and volume would help and sure enough, all the problems disappeared. No more stuttering or bogging and no check engine light. I'd say it was back to full power.

So I've already changed the fuel filter. I checked the fuel pressure and had 40 psi when the key is first turned on. When the engine runs it seems a little low (around 35 psi though sometimes a little lower like 32 psi) At cruise, it's probably around 37. I checked the volume and it seems like it's where it's supposed to be. I ran the pump for 10 seconds and it filled about a third of a 16.9 fluid oz water bottle. Maybe a little on the low side but seemed like a good volume nonetheless. With the engine running, if I disconnect the vacuum on the pressure regulator, the pressure goes up. As well, it goes up when you pinch the return line though I've tried running the car with the vacuum hose disconnected and it still runs horribly.

Could the regulator be returning too much fuel back to the tank or is the pump just a little too weak to deliver enough volume to the rail?

Is it safe to drive around with a pinched fuel line? I won't do this.. I'm just curious.

At least I was able to check the health of the engine by checking the compression and I have 180 in every cylinder. I adjusted the valves too which were way too tight.

As always, Thanks!