Hi guys,
I am trying to figure out what is wrong with my daughters 91 Accord LX. The car is fairly new to us and it started out with an engine swap from a donor car which I did... it had a bad rod bearing. The car runs great most of the time but it has been giving her grief recently. She says that it starts and runs fine and then when she comes to a stop light and tries to take off, the engine misses and stumbles for a few seconds and then takes off fine as if nothing were wrong. It drives perfectly once moving again and has plenty of power so I am inclined to think that it is getting enough fuel thru the filter which looks pretty new, don't judge a book by its cover comes to mind but I don't think that is it since the problem seems to be off idle related. It got new timing belt kit, plug wires and spark plugs right after the engine swap and I rechecked the engine harness connectors just in case. The distributor cap and rotor looked good and I don't see anything that seems wrong visually on or in the engine compartment.

I am stumped on this one and hope maybe someone here can give me a few ideas on what is causing the intermittent miss. My daughter is worried that she might get into an accident because her car wont get thru an intersection quick enough. I have driven with her in it and you guessed it...it wont act up for Dad. Any ideas?

Regards, Mike

 

Do you still have access to your old engine? Can you swap distributors to see how it does?

Did you re-set ECU?

 

I do still have the old engine and no I didn't re-set the ECU, I am not familiar with that procedure. Are you suggesting that the ignighter may be causing this problem? The engine swap was done back in July and it has been on 2 1000 mile road trips and a whole bunch of around town driving by a teenage girl and has run very well until this miss/stumble started. If there were a problem with the ECU needing to be re-set wouldn't it have needed that right away with a donor engine? The difficult part for me in this is that it only does it occasionally and it wont do it when I am present so it is hard to diagnose. Would EGR issues cause this type of off idle acceleration intermittent problem, there has been no CEL as far as I can tell but I am going to check for codes when I get access to a reader. Thanks for the reply.

Still scratching my head, Mike

 

Is Check Engine Light on at any time? If so, need to extract the code.

Are you sure the ignition base timing is set correctly? I think its 15 degrees BTDC.

If the idle speed is going very low when coming to stop, the engine may hesitate before accelerating. This can be caused by dirty throttle body or dirty/failed idle air control valve.

If idle speed is acceptable when failure to accelerate occurs, an ignition problem; plugs seem most likely, but could be wires also.

good luck

 

Thanks TexasHonda,
The CEL is not on right now and I don't think it has been on before but my daughter drives this car and she may not notice the lights.

Timing was set dead on the white mark when the belts were changed. I must admit I have not put a timing light on it because it runs so good most of the time and gets 29-30 mpg. This miss/stumble is occurring intermittently and seldom, it can goes for days with out any problems.

The idle is smooth and steady and it has new NGK spark plugs and new Napa premium 7mm plug wires.

If I can catch up with my daughter tomorrow I'll go down to Schucks and see if they will scan the ECM for codes, maybe that may shed some light on this. I have an OBDIII scanner for my Dodge Ram diesel but I am not sure if that will work on her car too, it is a scanner/programmer and I don't want to take any chances with it.

 

A 91 Accord is OBD1, so an OBD2 scanner will not work. You have to short a blue two pin connector behind the passenger kick panel with a piece of wire or a thin paperclip and count the check engine light engine codes or the D4 (or S light) flashes for transmission codes. For the check engine light a long flash =10 and short=1. So LLSSS = 23

See: techauto.awardspace.com/dtc.html

I wonder if the EGR ports need cleaned out. That can cause an engine stumble at around 2000 rpm.

See: home.comcast.net/~em-engineering/T2T013.pdf on how to do this on a 91 accord.

 

Thanks PAhonda,
I am over in the FAQ section right now looking thru the PDF for the on board diagnostics right now, I thought I had seen something on OBD in there when I joined the site. Do you think that dirty EGR ports would throw a code?

 

Plugged EGR ports never threw a code on my car.

There is only one EGR code on older accords that deals with egr valve lift. The electronics on older accords have a sensor on the EGR valve to detect if it was lifting to the proper height. The ECU can't tell that if exhaust gas is getting to the intake manifold. There is a code on newer accords (98+ or maybe 03+) for insufficient EGR flow.

 

Okay that is good to know, I don't think that the stumble is at 2000 rpm. The way my daughter described it to me is that is is an off idle acceleration stumble and then it takes off like a rocket.

 

I had cars do stumble upon acceleration and they were due to weak ignition system. So, I thought your case might be the same.

My 93 LX somewhat run better after resetting ECU by unplugging the radio fuse. My car was not throwing any codes before that.

Did you look for intake leak? It sounds like to me that you have over lean condition upon take-off, the moment throttle is opened, then the engine gets proper fuel delivery.

Or, may be injectors need cleaning. I had a good result using Lucas injector cleaner.