Hello - I'm new to this forum (well, I've browsed several times but never posted...).

Now, I know there's been a thousand posts on here already about bogging/hesitating Hondas, and I've searched thoroughly and not found a solution to my problem....


I've got a '96 (2-Door) manual tranny, with ~150K miles. I've had it for ~a year, and use it for commuting (I've got a 60mile one-way trip to work everyday...). I've put a-ton of miles on this car already, and up until recently never had any mentionable problems. However, prolly about 2 months ago, it started to bog down/hesitate on acceleration - this occurs at all road and engine speeds - but would only occur rarely. As time went on, it has become increasingly worse, and is so bad now that it is becoming a safety hazard.

So, more specifically - engine bogs down big-time, so much so that acceleration ceases and sometimes even slows the car down. Now, this only happens with the engine loaded - the more loaded the worse it is.

I've seen the responses to many posts such as this, but the big difference here is that this ONLY happens when it is hot outside (95 degrees or more - I live in Phoenix, so this is often). My drive to work everyday is a joy because the car runs great, no matter how hard I load the motor up. But, on my drive home (it's been ~105deg) it gives me fits the whole way home...

Before we start: No, I have had no CEL come on - until of-course, I unplugged my IACV to see what it would do... I put her on a scanner, and only that IACV code was stored...

Now, for the things I've done up to this point:

1) Replaced: IACV, Plugs, Wires, Cap, Rotor, Coil. (Ignition parts seemed to make things worse actually - and all my old stuff tested good - have since returned most components to recover $$).

2) Done: Ran w/out airfilter one day to negate this. Unplugged intake air temp sensor to see if any effect (none). Cleaned/inspected Throttle Body, and tested TPS (no discontinuity in resistance across throttle sweep). Checked timing - good to go. And today, unplugged and capped vaccum lines running to PCV and charcoal-cannister - to rule them out (I'll see soon whether that had any effect).

Now, the fuel filter and timing belt were both replaced by the previous owner within the last couple years. I have not yet checked fuel pressure, but my reasoning is this - car runs strong and smooth all the way through RPM range and at all loadings and throttle openings - when it is not hot outside, which tells me that my fuel system is solid.

I'm running out of ideas here - but this is definitely heat-related, and it should be noted that the engine temp is not much or any hotter during the hot afternoon than it is in the morning - at-least my temp guage tells me so. So, somehow the ambient temp is affecting this - which makes very little sense to me... I'm a pretty seasoned mechanic, but am drawing some blanks here, and am getting frustrated.

Any help here would be greatly appreciated!

 

BTW - Car always starts and idles fine. Idle does occasionally 'hunt' between 800 and 1000 RPM, but seems to be a natural cycle for the EFI. Also, it revs fine in neutral - even while bogging problem is present.

This feels like a fuel delivery problem, as I cant detect any missing (car is quiet, so it's hard), but the motor does shake around quite a-bit as it is bogging which can last for quite some time - at which point it seems to just 'snap out of it' and rev right up with full power - which is what makes me think this is electrical/sensor/computer related - as it is very intermittant...

 

1) Remove the ICM inside the distributor and have it tested at an auto parts store.

2) Measure the fuel pressure on a 105-degree day. When you do so, compare the pressure with and without the vacuum hose for the fuel pressure regulator connected. In addition, just replace the fuel filter. It will only cost $15-$20 for a new one.

 

The fuel filter is a prime suspect. Yours is years old. The life of a fuel filter depends on how much dirt it encounters, not a number of years or miles.

 

Allright - it's fixed!

I was intending on picking up a new ICm from Autozone on my way home yesterday, but didnt end up needing to...

On my drive home, as the car was bogging and bucking as usual, I decided to stop and unplug my primary O2 sensor - as I'd caught a thread on here somewhere about a non-failed but malfunctioning O2 sensor causing the FI to way over-richen or way over-lean the incoming mixture - thereby causing bogging issues. I didnt think much of it since I was getting no CEL, and I've had several vehicles (5.0L Mustang, Jeep and VW GTI) that ran just fine without operable O2 sensors. I didnt realize it could/would cause so much trouble...

So, in my case, it's a non-failed (no CEL) but malfunctioning O2 sensor. I'll just leave it as-is until I've got to get through emissions again...

Thanks for the help RonJ and mk378...