I have a 1995 Honda Prelude with a V-tec engine and over 300,000 miles. Recently the check engine light started coming on and the engine will start to run rough. at times it runs fine but then it will start to feel like I am dragging an anchor. There are times when it feels like it is stalling like it is running out of gas even with a full tank. I have used seafoam gas stabilizer to try to clean up the fuel pump and stabilize any bad fuel that may have been in the tank. The code on the check engine light indicates that it may be the fuel pump or the o2 sensor. I have had a bad o2 sensor replaced in the past 4 years but the issues are nothing like this.also the VTEC engine does not seem to engage like it used to. When I first had the car if I was in a tight spot and really hit the accelerator it would slip into this VTec mode and it was like I had just hung a low. Now nothing really seems to happen. There are also times when it feels like the gears are slipping like I have mishandled the clutch and the gearis not engaging. my mechanic did a fuel pressure test and found nothing out of the ordinary. I do a really good job of making sure the oil is changed regularly and having regular maintenance done. I have also noticed that I am losing a lot more oil lately. My mechanic did a pressure test and said there is relatively little leakage and he believes that it is burning off.Any thoughts?
Might just be a tired engine. Compression test?
When was your last oil change? How long before the problems started to happen was the oil change?
I’m confused about your code. On your vehicle code 1 would be an oxygen sensor and code 43 would be fuel supply. There is no one “oxygen sensor or fuel delivery” code. What is the exact code or codes that blink when you jump the diagnostic connector?
Things I would investigate:
Oil level. Low oil can cause VTEC issues because VTEC is operated via oil pressure. Insufficient pressure = no VTEC.
Fuel injectors. Sticky injectors can cause fuel delivery problems.
Fuel pressure. Bad fuel pumps and improper tank venting can cause fuel delivery problems.
Clutch wear. Old clutches wear out and slip. Put the car in 5th gear while going up hill at 25mph and floor it. Does the engine rev without corresponding acceleration? If yes, new clutch time.
“Might just be a tired engine. Compression test?”
Bingo!
Late Model? How Old Is An Early Model?
I read the Headline thinking it was maybe a 2011 Honda mystery or something. This trusty old friend is 20+ model-years old, a senior citizen of cars.
As others have commented, it’s entirely possible to be near the end of useful life without considering a rebuild of some kind. It doesn’t owe you anything.
I’m very quite cheap thrifty myself and I admire anybody who wrings out maximum life from a machine, but before putting too much money into it, I would check compression and blow-by, etcetera.
How’s the rest of this car, solid?
CSA
How about giving us the actual mystery code that was thrown on this car.
What engine is in this.
Have you replaced the fuel filter?
Was a compression test done to see where this engine is…in regard to engine efficiency for 300K. If yes, what were the numbers.
Yosemite
Compression test: yes!
Every few years I have measured and then adjusted the valve clearances on my 1999 Honda Civic EX with V-Tec engine. Each time some valves had gone out of spec. If your compression figures are off, before condemning the engine get the valves adjusted to spec, if possible, then see how it runs.
If the compression checks out ok, ask your shop to check for a clogged exhaust system. Especially true if the symptom occurs after driving at a fairly high speed for an extended time, or when the engine gets hotter than normal, like after an extending idling event and the radiator fans are spinning like a banshee.
It doesn't owe you anything.
Considering I have two 20+ year old cars, this is perhaps a biased statement, but I’d have trouble parting with that car myself. That generation of Prelude looked fantastic and drove beautifully.
Engine swap time! 
(assuming it’s not something simple, of course) ((which is a big assumption - I know a few people with 400+k on their 90’s Hondas))
Your issue is your DISTRIBUTOR…More accurately its the ignitor inside the Distributor. This is an extremely common failure mode… I’ve owned 5 Preludes in my time…ALL have had this issue at one point or another.
Most people simply replace the entire distributor because they arent sure if its the coil…the pickup, the ignitor or which. This is when the distributor has an internal coil…not the external coil setups…
If you havent replaced the coil or distributor on this vehicle yet…you will soon. Your symptoms are textbook ignitor failure…it will do what you described for a while…then it wont run at all.
If you have the type of system with an internal coil inside the distributor its all in one… You cannot separate the coil from the setup. They used two types of systems Internal or External coil.
Right now you are in the early stages of failure…it will SOON strand you.
Start looking for replacement distributors…OR just the ignitor… In your case with so many miles…a new distributor will cover everything. Especially if its an internal coil type. The internal coil type of Distrib can be had on Ebay for a very reasonable price. I actually have the one you need on my shelf in the garage…this is because Ive owned Hondas of ALL types for many years.
The codes are just a symptom of the ignition system acting up… You need to sort of read between the lines with these codes.
Blackbird
Your issue is your DISTRIBUTOR
We cannot make a firm diagnosis like that at this point. I’ll tell you a story: Years ago I had an 88 CRX. I had the same problems OP had. I posted on the (now defunct) national CRX owners forum. Got exactly the same response. It’s the distributor, guaranteed, can’t be anything else.
Well, 2 coils, 2 ignitors, and 2 distributors later and I was still having the problem. Finally traced it back to a bad injector, which on a DPFI system is essentially pinching off half the fuel flow. But not before I listened to a bunch of guys who with the best intentions pre-diagnosed my car before we had run any tests on it (and at the time I was too much of a rookie to know any better).
OP has not clarified what code(s) are firing, and has provided us with no firm test results, so all we can do is present hypotheses and ask OP to test them for us.
This is true… I shouldnt have stated it thata way… Hows about… You might want to suspect that Distributor? Yeah…thats it… Im going with THAT… LOL
This is why I always have a new or known good Honda Distributor on hand… I can swap it in easily and see if that was the cause.
But in this persons case…he needs to work with the codes and basically do some troubleshooting. It would be nice if he could swap in a known good distributor tho… would save him A LOT of trouble to get that out of the way.
Blackbird
You guys are awesome! Thanks for all the comments. The code was 43 and my mechanic convinced me it was the O2 sensor. I replaced that and it is running a lot better. Compression is adequate for a car this age. I also constantly check/add oil.
Love this car and will keep it alive until it is an unrecognizable smoldering heap or until it is passed on to a worthy heir when I am an unrecognizable smoldering heap.
Good news! Thank you for letting us know how it turned out.