I have been having issues with my 1991 Honda Accord EX. I had an old thread a long time ago asking for help, and I never got around to repairing the problem. Now my Honda is back on the road and driveable (for now). Has had a full tune up, timing done, all vacuum lines replaced, fluids flushed and changed, etc.

I am still having a few issues. After the car is warmed up, my RPMs bounce between ~1000 and ~1500. Since I got the car back on the road Saturday, it has once lost all power, RPMs dropped to under 1000 and no matter how much throttle you gave it, it would bog down. Nearly stalled, started sputtering, etc. (This is the reason the car was parked in the first place, but it has only done it once since Saturday). Lastly, my speedometer usually doesn't work and I sometimes get the "S" light flashing on my dash (general consensus is this is the Vehicle Speed Sensor)

I just pulled the codes using the paper clip method. Here is what I got:
17
43

Also, the "S" light flashed 4 times. Not sure what that means, but thought it was worth noting.

Any ideas?

 

The 17 from the check engine (ECU code) and the 4 from the S light (TCU code) both mean there is a problem with the speed sensor circuit. Most likely a bad vehicle speed sensor.

I would fix this before addressing a code 43.

The code 43 is a different beast. I had that code pop up periodically on my 95 and couldn't figure it out, so I can't give you good advice on how to fix it. The best way I can describe the problem is that the engine computer can not get the air/fuel ratio correct. Do some google searches on code 43 honda accord to see what others have written on that code.

 

Does brand matter? The speed sensor seems terribly expensive.

 

Check ebay for a low cost VSS.

Code 43 usually means the O2 sensor has a fault. There is a lengthy diagnostic for this condition. Check Online Manuals post in DIY forum for a manual download. I think there's a 91 Accord manual for download.

good luck

 

Here is a twist:

Decided to check the idle air control valve and two things stood out.
1) If you rev the engine at the throttle body, the revs will go high, go very low, and then return to idle at around 1100. Seems it isn't doing its job.

2) During one of the fits where RPMs bounce rythmically between 1000-1500 I pulled the pigtail on the IACV and the idle settled down to normal.

What do you make of this?

 

I think the base idle is set too high. When you unplug the wiring from the IACV, it's not supposed to drop to a normal operating idle. It's supposed to drop to the "BASE" idle which is about 500-550 rpm.

My experience (admittedly on later years) is that Honda's idle-control system doesn't work well unless the IACV is operating in the sweet spot of it's control range. That's why the "base" idle is a couple hundred rpm lower than the intended operating idle.

If the base idle is set to 750-ish RPM, then the ECU will have to operate the IACV nearly closed in order to hold the 750 rpm operating idle. That creates a very asymmetric control response that the ECU isn't programmed to handle properly - leading to the oscillation.

 

Would it be worth getting an IACV from Pull A Part or is it likely to have the same issue?

 

The issue I'm talking about is incorrect adjustment of base idle.

https://www.hondaaccordforum.com/for...e-speed-38734/

 

jim, for my accord 98, when i pulled out the iacv connector to adjust the base idle speed, i also have a 1000 to 1100 rpm, and i could not make it go lower than that. it stays there, nothing happens when i turn the idle air bypass screw. what do you think maybe my problem?

 

I just got a VSS from Amazon for $18.00 with shipping (it took 3 days) it was $23.00. Most other places I've seen had it for $50- $130. For $18 it is an easy job and is worth trying.