I have a 1991 Automatic Honda Accord. The only mods are intake and exhaust system. Lately I have had a major problem. When my car starts cold and I step on the gas the car hesitates badly and had died only once. If u try to step on the gas to make it go faster it backfires from the intake. I have had the intake over a year and the problem just started happening. But when the car gets warmed up it runs like a champ. I just had a tune-up, and have done the gas cleaner. I also just put on a new fuel filter. Does anyone have any idea whats going on? And do u have a solution? Can you please help me try and figure out whats going on? Thanks anyone who can help!

 

My first guess is that you are running lean, my second guess on the backfire is that you are running lean, my third guess is that this only happens when cold is that you are running lean, a cold engine needs more fuel to run good, a cold engine that is lean that backfires has higher resistance in the cylinder chamber and the spark in the distributor finds a path of lesser resistance to the next or probably previous cylinder that just fired and it may be on the intake stroke with the intake valve open igniting its fuel air mixture exploding the mixture right out the open intake valve, up through the intake and you hear it from inside the car as a backfire. Timing could be off a bit and you need good parts for the distributor also, cap and rotor, not the Italian brand. Spark will jump to the closest terminal in the cap if out of time or the path of least resistance if proper cylinder has problems with plug wire, plug, lean fuel mix or higher compression in the cylinder than the one next to it (carbon build up).

Lean cold only??? Fuel injector dirty, pull the vacuum hose off of the fuel pressure regulator cold and plug it up to prevent vacuum leak at the hose, does it run better, granted this only adds a little more fuel pressure, NO GOOD. Clamp off the fuel return hose after the fuel rail, DEAD HEAD, very high pressure. I know some techs say dont do this but for DIY it is a good test, do not do it for long, start it up cold after clamping, check for back fireing, unclamp hose. Probably should do the timing test first, check timing the usual way with light.

More theory, cold engine, O2 sensor probably no authority, engine coolant temp sensor has high authority, TPS is a new word for accellerator pump on fuel injected engines but it should be ok since it is ok warm. MAP sensor has high priority also. It sets baro and air density.

Replacement intake could have developed a vacuum leak at the intake gasket and as the engine warms up the metal expands and seals the lean leak.

 

I just wanted to let you know that the air intake was slipping and not catching the air. So i clamped the intake back on correctly and this caused the problem to stop. Thank you so much for your help.

 

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