Okay Ive posted several times reguarding my 91 accord lx A/T stock everything. Ive some great tips and suggestions. So hears my plight the car starts and idles fine, once I put the car into D4 and press the accelerator the car stumbles then dies if I dont let up. If I let up the car will idle fine again.... I had the ignighter replaced about two months ago, last Friday I replaced the coil, now the car is acting up again. I replaced the fuel filter in the engine compartment three months ago, is there another fuel filter on the fuel pump? Also wanteed to know if and how I might be able to check main relay? Ive tried the jiggling of the keys test and nothing happens so is there another test? With the price of gas over $4 a galon I need this little car to run around town and be dependalbe. Any and all help is more then welcome

Thanks for taking the time to read this post

 

Few things to check would be;
• Fuel supply system - Fuel pressure regulator
• EGR system - Valve stuck open
• Idle air control valve - dirty/inoperable

Sounds like it could be a sensor or fuel system issue. Do you own a multimeter so you can do tests on some sensors. As well you should pick up a manual. Save you swapping out parts for no reason. Kind of a waste to just keep replacing parts without actually troubleshooting them first.

 

Is there a way to teat the EGR without a vacuume tester? Trying to avoid bying one.

 

Quick test, if there is vacuum at the EGR valve #16 hose during idle. There is something wrong with the control end and not the valve itself. Also to remove the EGR valve and clean it doesn't require a vacuum tester...

 

If its stuck open, the vac test wont prove much other than the diaphragm holds. You want to make sure it is capable of moving the valve.

I can't recall if on the EGR valve there is room to manually exercise the valve open with your fingers. If you can, do this a few times before you start the car. In the past I've had a few valves get stuck/sticky from soot buildup, simply manually moving it up and down allowed the valve to open/fully open. It may feel a bit rough/crunchy, what you want is it to move freely and make sure that the valve is capable of completely opening.

What you could do, take a vacuum hose(I can't recall if there is a spare port) connect it directly from a direct manifold vacuum port, T in if need be, and connect it straight to the EGR valve. Bypass any controls or solenoids. With a pair of vise grips or other form of locking plies, close the vacuum hose off. Start car, let it warm up, then release the pliers. If the diaphragm is good you should be able to observe the shaft move and the engine should stumble.

 

Also is there a way to test the fuel presure regulator with out a vacuume tester. Thanks agin guys Ill have to try it tomorrow.
Another side note this only happens when the car is warm if that makes any differance.

 

Yes, look up my misfire thread in this forum and I have a link to a cheap harbor freight fuel pressure tester that fits right into the fuel rail test port.
To test the regulator let the engine warm and monitor the gauge, it should read around 33 with the vacuum line on the fpr and 45 with the line disconnected.

 

Not really, well not accurately. For every inHg change there is a given PSI change in fuel pressure. You can test it if the diaphragm is reacting, you can remove the vacuum hose from the regulator and the car will run like crap, but this is not an accurate way to test. You really would want to have a vacuum pump and a pressure gauge to see the change and if it is within spec.
If it's a change from cold to warm, then it may indicate that a sensor that is monitored only in closed loop is faulty, or that a component is faulty that only affects engine operation during closed loop.

 

I don't doubt the logic behind your method of testing fuel pressure regulator, it makes sense, but could you please tell me where you got this information for testing.
The dealer service manual does not outline a procedure like the one you suggested.

 

So I'm an idiot whats considered a closed circit system

 

So this moring I went out to the car and checked for codes.... After I placed the jumper and turned the ignition on the check engine light stayed on for like two seconds and went off. The repair manuel says 0 check ECU and have ECU diagnosed. Now with the issues that I've been having souldnt there be some stored codes? Any other suggestions.

 

So I might be chasing my tail... tonoght I went out to my Accord used a multimeter to check the MAP sensor and the IAT sensor they checked out... I pluged them back in and and checked for codes. This is what I got..

Code 1 Oxygen Content
Code 7 Throttle angle
Code 14 IAC
Code 17 Speed sensor

Now should I run the car again to see if these code come up again or should I start replacing parts????? I've checked for codes the day before and got nothing so I'm wondering if by me checking those sensors it set out is why those codes came to be?

 

This is typical of return type fuel systems with a vacuum controlled regulator.
At WOT manifold vacuum will be either very low or 0inHg, fuel pressure will be high. At idle the vacuum will be high 18-22 inHg, fuel pressure is lower.
Typically for ever inHg drop of vacuum from idle to WOT, the fuel pressure will rise one pound.
I would not be surprised. Some makes have a given psi/inHg change, others simply may want a verification that the FPR is not leaking and does change fuel pressure with vacuum change. Some times its not all that specific.
Do you mean 'Closed Loop'?
Closed loop is when the engine is fully warmed up and all the parameters are met. The engine management will control the A/F mixture by monitoring the various input sensors such as the O2 sensor.
Open loop is when the engine is cold, just started, or at WOT. The ECU typically ignores the input of the engine sensors until they reach operating temperature. The A/F mixture is pulled from a pre-programmed table in the ECU.
Don't just start replacing parts. The codes are being set for a reason, which does not neceearily mean the component itself has failed. With that many codes showing up it would more likely be due to a shared issue.
If you checked these sensors with the car on, yes. The ECU will have noted the circuit being opened and registered it. If the engine was running at the time and you pulled the connector for a given sensor and then looked at the dash the CEL light would have come on. Once reconnected the CEL light would have gone off.

 

Thanks Mad-mike for your reply. Since all the sensors checked out what should my next step be? Vacuum test? The car only acts up when warm, when the car is cold it runs great? I'm at a loss with the car. Thanks again for the help any other suggestions are welcome.

 

When it stumbles, if you get a feeling that the engine is being starved for fuel, you might want to check your O2 sensor (Oxygen Sensor). It's supposed to place a code and CEL when it's failing or bad, but over a year ago mine didn't. For weeks I searched for why my Honda was barely drivable and finally discovered it was the O2 causing a rich/lean condition based on faulty information it was sending to the ECU and in turn to the IACV. I I had immediate and permanent resolution upon replacing the O2 sensor, which by the way was the original part on the car.

 

Is there any kind of diagnostics I can do on o2 before replacing it? Like you said I can start the car but when warm I put it in gear press the gas pedal and it totally craps out unless I let off the pedal?

 

The problem with over the internet diagnosing is nobody can see the car operate. So outside of checking temp sensors, plugs, wires, cap, rotor, vacuum, compression, map sensor, tps, checking/cleaning grounds etc it's kind of hard to armchair quareterback.

Disconnecting sensors and seeing if the engine runs better is not the best way to diagnose anything either. If a closed loop sensor is unhooked the ECU will simply go into Open Loop or Limp mode, and use pre programed tables.

Do you have a voltmeter? You can back probe sensors to check for correct voltage outputs with the engine running.

The stumble could be from something as simple as a failing spark plug wire to a bad cylinder. Is it really a closed loop issue, or a heat related issue.

IOTW, when the car is hot, can you turn it off, and restart it a couple of minutes later and while it is still in open loop does the car run fine, or does it stumble?

 

Thanks Mad-Mike I appreciate your honesty about all it. The car will rotate several time but it will start sometimes with a light odor of gas.

 

To answer your question more direct mad-mike yes the car will start after it is at operating temp and still stumbles.....

 

Another symptom mine showed after one of the stumbling drives is when I would turn off the ignition the crank didn't come to an immediate stop like it's supposed to. Instead there was this last little chug it would do as it tried to blow the last bit of the bad mix out of the combustion chambers. That didn't start happening until weeks into the problem and the O2 was really sending the IACV haywire. That actually was the symptom that let me know my car wasn't "missing" but choking when it would stumble.

You can unplug your o2 and drive a bit with it disconnected. You'll get a CEL, but if the stumbling problem doesn't accompany it, then you've likely found what's causing it. I think you have the O2 location that can be reached from up top. If you try it, be careful to place the loose wire somewhere where it won't get melted.

 

Thanks Ill give just about anything a try at this point....

 

Well breakdrum I did what you suggested with no change, still stumbled I'm really beginning to think its the fuel pressure regulator. The stumbleing only occurs when warm.

 

So Ive got another qusetion. Is there such a thing as a Reverrt B Tip? My borither said he had the same year honda with the same symptoms and took it to a shop and the guy replaced what he called a "Revert B tip" Any Ideas guys.....

 

Sorry the O2 didn't help. If it was easy to unplug, perhaps try it again, but pull the 7amp backup fuse to clear the computer after unplugging it.

"Revert B tip" brings nothing to mind, but I'll bet its called something else now.

One other thing you might check (although they don't fail nearly as often as they're talked about) is the Throttle Position Sensor or TPS. Easy one to meter by backprobing the wire harness. It also has very specific Ohm readings that you watch while pushing the gas pedal. I laid the multimeter on the windshield and watched the ohm flow as I feathered the pedal all the way through the range. Engine doesn't need to be running for that test. My probe pins were too big to insert without damaging the harness or wire so I shoved some T-bar pins into the flow and then clipped the multimeter probes onto them. My TPS was fine. It was just another step that eventually led to finding the bad O2.

 

This probably covers ground you've long since covered, but are your spark plug wires in good shape?