I’ve been searching this site for a couple hours looking for an answer, but I think this is a somewhat unique situation. I’m going to get a little detailed here, in case something I think is a coincidence is actually relevant, and to answer any initial questions you may have for me before giving an opinion.
I picked up a 92 GS-R a couple weeks ago. Rough paint and interior, 195,000 miles, but everything electric works, and the motor seems to be in excellent shape. Everything appears 100% stock. Even the intake and heat shield. I feel like it should be faster than it is, but I’d never driven a GS-R. However, I do “feel” that my 91 GS pulls harder (this is based on no evidence whatsoever, other than my internal G-meter. Ha).
The GS-R had been sitting for at least 9 months, so after running through most of the gas that came with the car, I filled up (10 gallons, so not totally empty) with premium and added a can of 44K (fuel system cleaner).
After that tank ran through and I refilled it again, the car was taking 3-4 minutes of cranking to start, but only on the first start of the day (I deliver pizza so it gets started many times per day). Every other start feels normal. There’s no hesitation, no sputtering, no jumpy idle, no check engine light. Ever.
Checked the cap/rotor/wires. All seem fine.
Replaced the spark plugs with the exact part number on the sticker under the hood, gapped to 1.3mm.
Problem unchanged.
Fast forward a week, and the car is taking less and less cranks to fire up every day. The last 2 days it only took 10-20 seconds (vs 3-4 minutes).
Figuring a fuel filter was the next step, I had that replaced today, along with the power steering high pressure line, and the exhaust return line (not sure what it’s called exactly, the tube that runs from the top of the valve cover back into the intake). The mechanic commented that he thought the old fuel filter he replaced was on backward. Then thought maybe it was just a different design than the new one. Seemed a little unsure.
As I was waiting for them to pull the car around after the work was completed, they came into the lobby to tell me the check engine light is now on. It’s throwing code 5: MAP sensor.
The mechanic said that when he first started it up after the maintenance, one of the vacuum lines wasn’t attached, so he attached it, reset the computer and restarted the car. Code comes back within 2 seconds of startup. He felt bad so he stayed almost 2 hours off the clock after the shop closed to try to figure it out. We reset the computer half a dozen times, after he checked all the vacuum lines, checked the MAP sensor itself, and even replaced the sensor with one from a 93 Prelude they had lying around (he said it’s the same?). No change.
The car runs and drives exactly as before, no hesitation or weird idle, it’s just that this damn light is on.
SO. I think that’s everything. Any help would be MUCH appreciated. I’m not really sure where to go from here.
