93 Accord.EX Intake Backfire / Fuel Starvation, HELP!!!
 

Hello, this is my first post on this board, but by all means I am not a nOOb. Just a mechanic that needs a second opinion before I throw more money at the car. Unfortunetly I dont have access to service manuals or special tools anymore, so hopefully you guys can help!!!

Okay a quick bio before I ask some questions:
Purchased a 1993 Accord EX, 5 Speed, dirt cheap with severely overheated (blown) engine, wouldn't start so I never heard it running.

Purchased 1991 Accord motor (Automatic flexplate, and assuming its an EX because of the dual exhaust Manifold that was on it,) that I never heard running (Also, DIRT cheap).

I changed the complete intake manifold with all sensors, original wire harness and distributor from the 93 motor and put it all on the 91 motor. Also changed over flywheel and installed new clutch.

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Okay, now onto the problem. The car starts and idles perfectly. No valve train noise, compression is even, etc.. the motor sounds good. Once you step on the gas it bogs down and you can hear the intake sucking. If you hold your foot down, it will backfire (pop) a few times through the intake and then it revs normally. If you touch the pedal VERY lightly it will rev normally. When coming to a hard stop the motor will stall.

To drive it you have to pump the gas pedal until it reaches 3000 RPM then you can launch it. As long as you keep it over 3K it drives perfectly, with plenty of power... If you drive it long enough (15 minutes), the check engine light will come on with code 43 (fuel supply problem).

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I have checked/replaced the following in this order:

1.) Tune up -- Cap, Rotor, Wires and Plugs
2.) Timing (belt) Checked, then checked again.. Its dead on, Im sure of it, all marks line up.
3.) Changed O2 Sensor with known good one
4.) Re-soldered PCB in the main relay
5.) Changed Fuel injectors with the whole rail (regulator, etc)
6.) Fuel Filter
7.) (last resort) Loosened all intake valves 1/2 screw turn (only made the valvetrain noisy)

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Common logic says that its a problem with the fuel supply or the intake valves.

1.) If its a fuel supply issue, why does it have power over 3000RPM?
2.) If its a valve issue, then why is the compression even?
3.) Could it be a TPS sensor, even if Im not getting a code for it?
4.) Main question: is the 93 ex intake manifold compatible with the 91 head??
5.) Has anyone ever seen a fuel pump go on an accord (I don't have a fitting for the fuel pressure gauge)?

Thanks,
Matt Wallace
91 Legend LS Coupe black/black

Re: 93 Accord.EX Intake Backfire / Fuel Starvation, HELP!!! (LegendLScoupe)
 

Have you checked the EGR ports?

http://home.comcast.net/~em-engineering/T2T013.pdf

Re: 93 Accord.EX Intake Backfire / Fuel Starvation, HELP!!! (tech8)
 

Yes, I've considered the EGR system. When I had the intake off, I cleaned out the port in the head. If I manually activate the EGR valve with the car at idle it skips, stalls and runs worse.

Re: 93 Accord.EX Intake Backfire / Fuel Starvation, HELP!!! (LegendLScoupe)
 

^^^Bump

Could someone please move this post to the tech section? I did not notice that there was a separate section for technical questions. Any help would be greatly appreciated, I'm stumped.

Matt

Re: 93 Accord.EX Intake Backfire / Fuel Starvation, HELP!!! (LegendLScoupe)
 

P.S. Last night I double checked the EGR system and the firing order. Everything looks dead on...

Re: 93 Accord.EX Intake Backfire / Fuel Starvation, HELP!!! (LegendLScoupe)
 

Bringing this back from the dead for a resolution. I'm experiencing the EXACT same symptoms with a 98 Accord 5-spd.

Re: 93 Accord.EX Intake Backfire / Fuel Starvation, HELP!!!
 

same thing here i have a 96 accord lx 5speed revs to 3.5-5rpms and bogs down and back fires out the intake. i cleaned the egr ports and still same thing

Re: 93 Accord.EX Intake Backfire / Fuel Starvation, HELP!!!
 

Your exhaust cat could be clogged up. You can disconnect the exhaust pipe b from the catalytic converter and see if it runs fine.

Also, and maybe this is the first to check, your ignition timing could be off. Remember to short the blue connector before setting the timing.

Re: 93 Accord.EX Intake Backfire / Fuel Starvation, HELP!!!
 

I had the same exact problem with my 1991 Honda Accord. Pinch off the fuel line that goes from the fuel pressure regulator back to the gas tank. If it runs better you need a new fuel pressure regulator.http://www.autopartswarehouse.com/im...-1580310-1.jpg

Re: 93 Accord.EX Intake Backfire / Fuel Starvation, HELP!!!
 

i know it aint the cat cause the exhuast from the tail pipe has strong pressure coming out of it. and the timing is good cause it runs fine untill it starts happening. but ill try the pinch line thing here real quick and let yas know.

Re: 93 Accord.EX Intake Backfire / Fuel Starvation, HELP!!!
 

The original post stated the problem began after swapping the engine. I would assume the TPS and MAP sensor connectors were switched. I've seen this literally 25 times in my career.

The sensor values arent far enough out of range to set a DTC but will keep the car from running properly or even cause the car to die completely.

Re: 93 Accord.EX Intake Backfire / Fuel Starvation, HELP!!!
 

curtie that wasnt the problem, im going to try the filter ill let yas know.

Re: 93 Accord.EX Intake Backfire / Fuel Starvation, HELP!!!
 

My 91 accord wagon does the sane thing any one fix this yet

Re: 93 Accord.EX Intake Backfire / Fuel Starvation, HELP!!!
 

When mine was doing the bogging, backfiring, chugging, barely-drivable thing, I mistook it for a miss and checked ignition system for days. Finally determined the O2 sensor was bad. It had failed without setting a code in the computer so there was no CEL.

Re: 93 Accord.EX Intake Backfire / Fuel Starvation, HELP!!!
 

For something like this I would use a vacuum gauge to check for a clogged exhaust. They sell a 40 dollar mittyvac at oreilly and harbor freight. The manual that comes with it gives great instructions.

I gave up looking for a fuel pressure gauge on ebay and just bought one from hondapartscheap for 50 bucks. If you're on the east coast u can use hondaautomotiveparts to check for proper fuel pressure.