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Discussion Starter · #1 ·
Hey everyone. I bought this '99 prelude base auto a little over a month ago. The previous owner expressed there was a rough start occasionally and that his mechanic said it was likely the primary O2. No service/cel lights on though, not since I bought it. He gave me a list of odds and ends that he had repaired and said the motor was fresh and gone through thoroughly. Replaced seals, o-rings, etc.. All compression nearly stock numbers. The motor does indeed look super clean.

Here's my problem. I recently replaced the O2 sensor and changed the oil (3 days ago). Nothing has changed. It still starts rough on cold and in fact seems like it starts rough a lot more often now after the car has been driven for a while. I usually have to pump the gas pedal to get it passed the rough bogging start. Inspecting the oil when changed it had a pretty bad smell of gas in it. More than I think it should. The O2 sensor wasn't too bad looking but I swapped it out anyways since I had a new one. My cat is needing replaced too due to it sounding like its' internals are in pieces. I don't know if that has anything to do with my issue though. There is a lot of black soot on the muffler tip and tends to get on the back bumper as well.

All this is leaning me to think it's running super rich. Like more rich than it should be cus I know these cars tend to run rich and use oil anyways. But I think it's trying to dump too much gas on start up. There is a fuel pressure gauge in-line under the hood. But no regulator on the fuel rail. It's a factory fuel rail anyways. Only reasons I can think of a previous owner adding the gauge is if this issue has been ongoing and they wanted to monitor the pressure, monitor pressure if the fuel trim was bumped up for some reason, or they were running NOS (no indication anywhere else to confirm).

So I guess my questions is, where do I need to start to solve this issue? It's not throwing any lights on (I should probably still check for codes) and it runs and idles fine once started (gets 25ish mpg). What should the pressure gauge be reading at stock, wot and idle? Possible injector(s) toast? Fuel pump issue?
 

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Hey everyone. I bought this '99 prelude base auto a little over a month ago. The previous owner expressed there was a rough start occasionally and that his mechanic said it was likely the primary O2. No service/cel lights on though, not since I bought it. He gave me a list of odds and ends that he had repaired and said the motor was fresh and gone through thoroughly. Replaced seals, o-rings, etc.. All compression nearly stock numbers. The motor does indeed look super clean.

Here's my problem. I recently replaced the O2 sensor and changed the oil (3 days ago). Nothing has changed. It still starts rough on cold and in fact seems like it starts rough a lot more often now after the car has been driven for a while. I usually have to pump the gas pedal to get it passed the rough bogging start. Inspecting the oil when changed it had a pretty bad smell of gas in it. More than I think it should. The O2 sensor wasn't too bad looking but I swapped it out anyways since I had a new one. My cat is needing replaced too due to it sounding like its' internals are in pieces. I don't know if that has anything to do with my issue though. There is a lot of black soot on the muffler tip and tends to get on the back bumper as well.

All this is leaning me to think it's running super rich. Like more rich than it should be cus I know these cars tend to run rich and use oil anyways. But I think it's trying to dump too much gas on start up. There is a fuel pressure gauge in-line under the hood. But no regulator on the fuel rail. It's a factory fuel rail anyways. Only reasons I can think of a previous owner adding the gauge is if this issue has been ongoing and they wanted to monitor the pressure, monitor pressure if the fuel trim was bumped up for some reason, or they were running NOS (no indication anywhere else to confirm).

So I guess my questions is, where do I need to start to solve this issue? It's not throwing any lights on (I should probably still check for codes) and it runs and idles fine once started (gets 25ish mpg). What should the pressure gauge be reading at stock, wot and idle? Possible injector(s) toast? Fuel pump issue?
I'd start by making sure the fuel pressure hasn't been messed with. It's not really something you would be able to do with out an adjustable FPR, and I'm assuming the stock regulator is there.

If you're not throwing any codes, and nothing else looks amiss, It might be time to send those injectors off to be cleaned. If one of them is stuck open you'd have flooding issues.
 

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How many miles are on the car?
Does it have a Check Engine light on?
Have you done a compression test yet?
What service items have been done? (Fuel filter, spark plugs, etc.)

I would start with a compression test first and foremost. That will tell you the state of health with the engine before you dump any parts into it. If it's low on compression, that would explain your rich condition as well as all the soot.
 

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Discussion Starter · #4 ·
I'd start by making sure the fuel pressure hasn't been messed with. It's not really something you would be able to do with out an adjustable FPR, and I'm assuming the stock regulator is there.

If you're not throwing any codes, and nothing else looks amiss, It might be time to send those injectors off to be cleaned. If one of them is stuck open you'd have flooding issues.

I have no lights on but I do need to check for codes. It might be time for injectors, I don't recall the previous owner discussing replacing/cleaning them.

How many miles are on the car?
Does it have a Check Engine light on?
Have you done a compression test yet?
What service items have been done? (Fuel filter, spark plugs, etc.)

I would start with a compression test first and foremost. That will tell you the state of health with the engine before you dump any parts into it. If it's low on compression, that would explain your rich condition as well as all the soot.
Has around 134k on it.
No check engine light or other trouble lights for that matter. Doesn't mean a bulb wasn't pulled. Like I said, I haven't had it checked for codes.

The previous owner stated the motor was gone through to replace seals, o-rings, etc... Compression was checked at this time and psi was stock on all cylinders. I know it has new plugs and wires. Don't know about fuel filter or pump and don't remember him saying anything about the injectors.



I just checked idle fuel pressure. I'm at work so can't go WOT and make all that racket. Anyways, it was right at 48.

This is the line it's on...





The only aftermarket items on the motor are that fpg and a K&N FIPK.

 

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Discussion Starter · #5 · (Edited)
Got checked for codes and came back with a few. Doing a little research now.

P0420 - probably due to crapped out cat. Maybe secondary O2 is toast as well.
P0430 - likely same as above.
P1457 - this might be what is causing my rough start and running rich. One of the most trickiest codes to diagnose :(

Checked some of the service records I had from previous owner. Fuel filter changed around 132k. Valve cover gasket replaced, distributer o-ring and most the sending units o-rings replaced due to leaking oil.

Compression tested around 130k as followed:
Cyl #1: 200psi
Cyl #2: 200psi
Cyl #3: 187psi
cyl #4: 197psi
 

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That compression test is within spec... barely.

If you know you have a bad catalytic converter, replace it immediately. That's more likely than not the cause of all of this- your exhaust has no where to go, it builds up pressure on the exhaust side of combustion, and causes contamination. I had the same exact thing happen to me with an Accord once, and the symptoms sounded almost exactly the same (minus the soot on the bumper).

Here's what you're up against with a clogged/loose cat. You're trying to force all the exhaust gasses through something like this:


To get an idea of what that's like, try breathing through a straw and going for a jog.
 

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Got checked for codes and came back with a few. Doing a little research now.

P0420 - probably due to crapped out cat. Maybe secondary O2 is toast as well.
P0430 - likely same as above.
P1457 - this might be what is causing my rough start and running rich. One of the most trickiest codes to diagnose :(

Checked some of the service records I had from previous owner. Fuel filter changed around 132k. Valve cover gasket replaced, distributer o-ring and most the sending units o-rings replaced due to leaking oil.

Compression tested around 130k as followed:
Cyl #1: 200psi
Cyl #2: 200psi
Cyl #3: 187psi
cyl #4: 197psi
If your CEL wasn't on, how did you get those codes?
Was your CEL bulb pulled/wasn't working?

25ishmpg is great in an Auto, I'm lucky to get 21, but that's all city driving.
 

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Discussion Starter · #8 ·
That compression test is within spec... barely.

If you know you have a bad catalytic converter, replace it immediately. That's more likely than not the cause of all of this- your exhaust has no where to go, it builds up pressure on the exhaust side of combustion, and causes contamination. I had the same exact thing happen to me with an Accord once, and the symptoms sounded almost exactly the same (minus the soot on the bumper).
I don't know for sure that my current cat is toast beyond use but I'm willing to bet that it is causing some issues. Purely due to the fact that on start up I can hear it rattle pretty good. I got a cat that just came in today. Will be my weekend project to replace it. It's a slightly used Random Technology cat. Might have to do some kind of simulator for secondary O2 sensor.

If your CEL wasn't on, how did you get those codes?
Was your CEL bulb pulled/wasn't working?

25ishmpg is great in an Auto, I'm lucky to get 21, but that's all city driving.
That's what has me scratching my head. I think either the bulb was pulled or it has been off/on so many times over the years it's burnt out. Will definitely look into replacing the bulb so I know when I have an issue. As far as the mpg, I range around 23-25. Saw 21 a couple times when I first got it but I was dogging it a lot lol. I'm about 40/60 - city/highway but it's still a lot of stop and go due to traffic to and from work.
 

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I don't know for sure that my current cat is toast beyond use but I'm willing to bet that it is causing some issues. Purely due to the fact that on start up I can hear it rattle pretty good. I got a cat that just came in today. Will be my weekend project to replace it. It's a slightly used Random Technology cat. Might have to do some kind of simulator for secondary O2 sensor.



That's what has me scratching my head. I think either the bulb was pulled or it has been off/on so many times over the years it's burnt out. Will definitely look into replacing the bulb so I know when I have an issue. As far as the mpg, I range around 23-25. Saw 21 a couple times when I first got it but I was dogging it a lot lol. I'm about 40/60 - city/highway but it's still a lot of stop and go due to traffic to and from work.
Quick way to tell if your bulb is burnt/was pulled is at startup, CEL light should come on and then go off. (you probably know that already)
 

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Discussion Starter · #10 ·
Quick way to tell if your bulb is burnt/was pulled is at startup, CEL light should come on and then go off. (you probably know that already)
That's a good point. I'll watch for it next time. I don't think it lights up though.
 
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