1987 Honda Prelude losing power once warm

I have a 1987 Honda Prelude 2.0 SI. It's the fuel-injected model. If the car is cold, it will start up immediately and runs great - i can lay a patch of rubber. It will run perfectly immediately following a
cold start. Once the car has traveled a few miles, however it starts to lose power quite dramatically as I attempt to rev it up past about 2000 RPM as though it were starving for fuel or air or something. The problem will happen in any gear but seems a teeny bit more pronounced in the higher gears. Around this time, the PGM-FI light comes on on the dash.
I've been looking at this problem for some time now and I have had some repairs done: * rebuilt/replaced fuel injectors * new fuel pump * new air/fuel/oil filters * replaced EGR valve * checked main relay for broken solder - it seems fine
After posting here previously someone told me to check the ECU codes. The ECU code that is blinking is code #12 which for my car means a problem with the EGR system. When I took the car in for repairs last January to a small shop, the mechanic claims he replaced the EGR valve so I'm inclined to rule that out.
Any hints on what it could be? Would a clogged oxygen sensor result in the ECU sending code 12? Any advice would be much appreciated! I MUST fix this problem and simply cannot afford expensive repairs.
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zardozrocks wrote:

Hi, Manifold vaqcuum leak?
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Which manifold? How does one test it? Also, sounds expensive.
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zardozrocks wrote:

Hi, Intake. You can hook up vacuum gauge.
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Thanks for the response!
Wouldn't that problem be evident even when the car is cold? Any links or advice on how to test or where to buy a vacuum gauge?
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zardozrocks wrote:

Hi, Heat/cold expand/shrink things. You already done quite a few rmedial tries. Checking vacuum for proper level won't hurt. Also checking all the ground point like fuel pump ground joint is good idea.
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OK I'll buy the heat expansion/contraction, but I'm also wondering if that will solve the car complaining about the EGR problem (code 12 on the ECU).
Most importantly, HOW do I check for a vacuum level on the intake manifold? Got any links or suggestions?
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zardozrocks wrote:

Hi, Take a minute and think about how EGR valve operates. Manifold vacuum does many things. One example is helping brake master cylinder. Usually there is a test port for vacuum connection with little rubber nipple cap on it, or you have to find where you can tap into vacuum line using a T fitting. Vacuum level is highest when idling. If it fluctuates wild or unsteady moving up and down, etc. Bad sign. I am not pretending an expert but this is very basic stuff. DTC code is a starting point for trouble-shooting a problem. It does not mean pointed part is bad. Old cars often have cracked vacuum hose causing leak as well.
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Tony Hwang wrote:

I'm wondering, does it also operate the EGR valve, like it does in my carb'd '87 Accord, via a vacuum diaphragm? There could be a leak in that vacuum line or even the diaphragm itself, and the leak is only presenting itself once the car warms up enough to activate the EGR.
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Harbor Freight has vac gauges at "low cost".
How many miles on the car? O2 sensors last about 60-100K miles. OEM are the best.
--
Jim Yanik
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zardozrocks wrote:

--------------------------
If it's a problem when it warms up, what's your TEMP gauge showing, and how full is your rad and reservoir? Your engine can run like crap if the computer is getting wrong info from the coolant sensor(s) because they aren't immersed.
'Curly'
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When I say 'warms up' I didn't mean to imply anything at all about the temperature. I was only trying to imply that the problem happens once the car has been running awhile...like after 20 minutes/5 miles or so. The temp gauge appears to be fine...it definitely doesn't appear to be running hot or anything. I'll check the radiator but I'm fairly certain radiator levels are fine. The car doesn't leave any leak spots at all on the driveway.
Thanks for the response.
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zardozrocks wrote:

It looks more like a clogging fuel filter...
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Admittedly one does not want to replace things willy-nilly at this point. And you say the Code 12 continues. (I also confirmed Code 12 is symptomatic of a "problem" with the EGR system.) Using the manuals at the sites below, I would be checking the EGR's electrical connections first. Yes, it's new, so this suggests that, if it's not working, it's more likely that the connections were not made correctly.
For troubleshooting codes yada for your Prelude: http://www.autozone.com/az/cds/en_us/0900823d/80/0c/fb/59/0900823d800cfb59/repairInfoPages.htm
Your Prelude's factory service manual: http://www.honda.co.uk/car/owner/workshop.html
Next I would do what Motsco said. One must take seriously purging air from the coolant system. If any repairs you had done recently involved the coolant system in any way, I'd do a purge, per the manual. It may take 50 minutes or so for your car to warm up during the purge, so be patient. The level appearing to be fine is not enough to indicate air is fully purged.
If this Prelude is on its original, OEM oxygen sensor, nonetheless I would consider replacing it. Your symptoms do suggest a failing O2 sensor. Particularly the symptom that it starts going amiss after warmup. If it is the original O2 sensor, then it is in fact quite old. A code will not necessarily be thrown for its malfunction. You can get an OEM O2 sensor from www.automedicsupply.com for under $40 total (= about $32 + shipping). In 2004, I used this online store for a new O2 sensor for my 91 Civic (the Denso one). Great service. No problems with the new O2 sensor.
Based only on reading here and a bit of googling, I'd also investigate whether the catalytic converter was partly plugged. Google on same for more info. Of course, then the big question is how it got plugged. Related to the EGR system?
Keep checking back. Others with more expertise will post.
Elle Original owner and now sole mantainer, 1991 Civic
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If the cat was restricting,it would affect running ALL the time,not just after warmup.
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I think I understand what you're saying, ("If it's plugged, it's plugged! Even partly plugged... ), but from my reading, the symptoms of a partly plugged cat converter become more manifest with, say, acceleration and warmup.
http://www.aa1car.com/library/converter.htm , among other sites, has some stuff on how temperatures yada affect cat converter operation.
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P.S. for the record, when were ignition wires and plugs last replaced and timing checked? Distributor cap and rotor? Were OEM parts used?
It's amazing sometimes how often it's just old ignition parts.
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zardozrocks wrote:

You left out the mileage on this vehicle. How many miles on it?
JT
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