Prelude problems

[texace]

Ok...this is begining to bug me. I own a 1986 Honda Prelude, bought about a year ago for $1,500. (not bad for a can in this good of condition) The "Red Rocket" as I affectionatly call it (but it won't be red for long) has been good to me, but there is one problem that bugs me. (Aside from the speedometer working only if the parking brake light is on)

The car uses a 2.0 liter (Si) fuel injected 4 cylinder. It also uses the new (at the time) PGM-FI programed fuel injection system. In the cockpit, there is a small red light that says "PGM-FI". Since the car has no manual, I assume this means a problem with the system itself.

Ever since I bought the car, this light will come on within five minutes of driving. I've tried everything...cleanign the injector heads...cahnging the spark plugs...changing the fuel filter, and useing a higher octane fuel. While the frequency of the light's illumination have decreased...it still comes on.

What else could be the problem? If it's with the computer, then I'll need to spend money getting it fixed, I bet. I'm trying to avoid that (and the $1,400 air conditioner) If anyone can give me advice...thanks.

[ra]

Some cars have onboard diagnostics.  You can probably find out how to use yours by going to Google and doing a search on 'honda prelude diagnostics'.   The codes may tell you what the problem is.   Almost all cars have fan pages maintained by geeks who live eat and breath the things.  FAQ's on those pages are very valuable sources of information.  The Net ain't just for simming ya know.  

ra

[senna]

Its probably nothing too serious. Under the passangers seat is the computer (it could be under driver or under the area where the passenger places his/her feet underneath the carpet. The computer upon looking at it will have a set of lights on one side, sort of like a modem. The signal patern of those lights in conjunction with the key on and possibly some other prerequisites like disabling a certain engine function will create a series of different light flashes. You read that signal (like morse code but simpler) and compare it to what the fatcory manual says and it will tell you whats wrong with your computer or its systems. PGM-FI light on means you might want to take a look at the diagnostic features just mentioned and that it relates to fuel injection. Most likely you may need a new fuel pump (its in the gas tank removable from the trunk) as the original is now fluctuating. The PGM-FI light is probably being triggered by slightly fluctuatuing fuel pressures (once you drive off engine uses gas, fuel rate goes up).

I've fixed a ton of Hondas and cars as a teanager (was a hobby).

[texace]

Wow...thanks, senna! That might be it...you're a great help. Problem is cost in getting it fixed. I dont' make all that much money, ya know. Any idea how much that will run me?

Now...if I can just get that speedometer fixed...

[senna]

If thats what it is (Im guessing) it could be done in an hour. Cant remember how much fuel pumps cost but there are two types. The ones that are removable from on top (internal like on Japanese cars) the gas tank and looks like a fuel pickup device or an external one like on VWs (located underneath the car and along side of tank)  that are about size of a soda can. I would say 60 to 180 bucks for the fuel pump then the labor. Talk to a mechanic if you dont want to try it yourself and let him know what the problem may be (that way he wont jipp you). Your car will run good though even with this problem until it eventually dies which may be a very long time or possibly not ever konk out. If you notice the light always on and you get sluggish throttle response, then its probably time to really get it fixed. As a teenager I was duped by a dishonest mechanic. Went in for a brake job and next day saw my air conditioner belt roll down the road in my rear view mirror. Didnt realise what it was till I looked at the engine and saw the AC compressor laying on its side, 5 inch bolt missing. Duh, LOL. Then I started to fix stuff myself. I've found that possibly knowing what the problem is helps to prevent getting duped.

[lord dolf vader]

dont know about where you live but alot of shops here will let you use a code reader for free. it might not help (they can be misleading as the part showing bad my not be the actual problem)but then again it might tell you exactly what the problem is. either way its free. and you get to see how a code reader works.

[Vulcan]

Dude... it needs defragging.

[capt. apathy]

could be something as simple as a 'service light'.  just a timmer that says it's time to do all the service that you've said you have already done.  had you had the work done in a shop the would reset the light for you, and it would start counting down like a timer.  if you take it in to a shop and they say it means work needs done that you already did, explain to them that you've already done the work and ask if it could just need reset.  some shops will redo work that doesn't need done if they think you are unaware that some of these lights just need reset.

also if you have a manual for the car (chilton,clymer, whatever) read the section on computer codes, on many cars you can jumper over 2 slots in the diagnostic plug (paper clip works nice) and thelight will flash a sequence that you can look up in the book,  this will save you paying for the use of the code reader

[Kratzer]

Here's the problem:

Originally posted by texace
I own a 1986 Honda Prelude

It's an old car.  If you don't notice anything wrong, nothing is wrong.

[Replicant]

I haven't worked on a Prelude before (I worked on Rover/Sterling 1989-1996 which had Honda engines) but other Honda's often have the diagnostic unit either under the drivers seat, or beneath the passenger foot rest (under the carpet beneath a metal cover).  Often they have a hole in the metal cover so you can see the diagnostic light flashing a code.  Some other Honda's also have a Fuel module (seperate to the Ignition module) either in the same location as the passenger foot rest or situated in the boot behind one of the side covers.  (fuel adjustment will either be on the passenger bit or next to the main fusebox compartment beneath the steering wheel).

Unfortunately the PGMFI uses a 'map' that incorporates many sensors and switches so unless you know the code it could litterally be anything from a faulty coolant sensor, ambient air temp sensor, etc.  It is unlikely to be the injectors tho as I'm sure they're not on the diagnostic ECU.

[Replicant]

Originally posted by senna
If thats what it is (Im guessing) it could be done in an hour. Cant remember how much fuel pumps cost but there are two types. The ones that are removable from on top (internal like on Japanese cars) the gas tank and looks like a fuel pickup device or an external one like on VWs (located underneath the car and along side of tank)  that are about size of a soda can. I would say 60 to 180 bucks for the fuel pump then the labor.

Not sure on early Preludes, but again some Honda's you can access the top of the fuel tank without removing the fuel tank itself.  Have a look under the floor carpet in the boot and you might be lucky enough to see two inspection panels.  One is for the fuel gauge sender and the other is for the fuel pump.  Well, that's how it is on the Rover 600, which was based on the Prelude, 94>.

[myelo]

Originally posted by texace
I've tried everything...cleanign the injector heads...cahnging the spark plugs...changing the fuel filter, and useing a higher octane fuel. While the frequency of the light's illumination have decreased...it still comes on.

Have you tried black electrical tape to cover the light?

[loser]

texace this is a long shot, but try it

sometimes those lights come on for no real reason.  I have seen this quite often in the shop i work at.

If you disconnect the negative battery terminal it should reset the light if it was just on to fool with you.

If it stays on, then there might be a real problem.  Most likely the sensor that is related to the function of the gauge  eg. mass air flow sensor, throttle position sensor, oxygen sensor.....the list goes on.

If your car runs fine and the light that says "your car has just exploded" doesnt come on...you should be alright.

[senna]

If its time for routine maintenence, the engine icon light will go on. I thought it might be the fuel pump since the Honda is rather old now. Fuel pumps are common issues for Japanese cars as they age. The electrics in Japanese cars tend to be pretty solid. However a working but slowly dying fuel pump would trigger a sensor in this way.

However if you do simply have a bad FI sensor, checking the puters error codes would show the problem since a bad sensor has zero current and zero resistance on its curcuit. A sensor showing a problem would have some resistance past tolerance thus triggering the computer.

[john9001]

just a longshot guess....
bad ground on the speedometer circuit