virgilr

First off- WOW to this entire forum and everyone here. This is fantastic, and I'm so happy to have found such a fantastic source for information on my new/used accord!

I recently purchase a 1996 Accord EX-R, A/T, Canadian model, with around 172k. Many things had been replaced by the guy who I bought it from, and I'll list those first:

New radiator, thermostat and water pump.
New AC condenser and system charge.
New plugs, wires, dist. cap and rotor.
Transmission service (flush and refill).
New front exhaust pipe and cat. converter. (new to the muffler).
New rotors and pads all the way around.
Timing belt/tensioner belt changed.
Exhaust manifold was welded.

Ok, my problems are these:

When driving in D4, at around 25 mph (40 km/h), the car will start to shudder, almost as if it's trying to shift. The Tach reads around 1500 rpm. If I shift into D3, this problem goes away. I also notice this at times when decelerating from low highway speeds in D4 (from 45-55 mph), but again, if I drop it into D3, this goes away.

I also notice that when driving, if the Tach is reading above 1500 rpm, and I let off the accelerator without braking quickly, the tach drops to about 1100 rpm, then bounces back up to 1500 rpm and holds steady. This is variable- it does happen at about any speed I'm driving at, as long as the tach is above 1500, but if I use the brake, it doesn't seem as prevalent, just when I let off the accelerator.

The car accelerates smoothly, runs great except for these very specific conditions. It is also doing very well in terms of fuel economy (around 23 mpg in mostly city driving).

It also tends to idle a bit rough with no load, but this does smooth out after a few minutes.

This is what I've had done so far:

Oil/filter change (synthetic oil- that is what the previous owner was using, and it doesn't burn a drop!).

Had to have the master cylinder replaced, as well as a leaking rear brake line (had this performed at a local garage).

Work I've performed:

Removed/cleaned IAC valve.
Removed/checked/cleaned the FITV- seal was tight, I just de-gunked around it a bit with some carb cleaner and a toothbrush.
Cleaned throttle body in car with carb cleaner and toothbrush.
Cleaned throttle body in car (didn't remove it) with some Canadian Tire throttle body cleaner (sprayed liberally inside while running, as per the instructions on the cleaner, while working the butterfly).
Removed and cleaned the base idle screw port with a pipe cleaner.
Reset base idle to 500 rpm as per the instructions I found on this site (warmed up engine, jumpered ECM, disconnected IAC valve, set idle to ~500 rpm using the dash tach, shut off engine, reconnected IAC connector, reset ECM).

I must say that the warm-up idle is working fine- no hunting as the car warms up, and she holds steady once it's warm.

I'm wondering if a cleanup of the EGR ports will help this problem. I'm waiting for a code (hopefully!). Any other advice would be greatly appreciated- maybe I need to replace the IAC valve? Or, perhaps check the timing?

Thanks to all!

2canoe

Check that rad cap is maintaining the right level of coolant in Rad. If it is low it effects the idle info sent to the ECU. might not fix the shifting but the rpm problem might go away and it is cheap to fix. worth a try, top up your coolant first, if it solves the problem then if it re-occurs check rad cap , or head gasket.

gulfview

Yes, it could be the IAC valve or the throttle position sensor or the MAP sensor or an air leak by a gasket somewhere in the intake manifold area.

You can unplug these valves and sensors one by one and see what happens. For the air leak, carefully use an unlit propane torch around the intake manifold area. If the running engine speeds up, you have found the leak.

virgilr

What about bleeding the coolant system? I checked around the thermostat housing, but I didn't see any bleed screw that was obvious. I can't find anything on how to perform this procedure.

I'd love to test the throttle position sensor, but without a test harness, good luck! Terrible location (right next to the firewall), and you can't test on the backside of the connector with those rubber boots- and I DON'T feel like exposing wire and re-taping for testing purposes.

virgilr

Update: something interesting happened when I went to pick up my wife.

Drove the car for about 25 minutes, and when I got to my destination, left it idle with no load. It was running very rough. So, I tapped on the accelerator, and lo and behold, the idle didn't drop down immediately- it started revving up and down a bit, hunting around, until it finally settled down and was running rough again. Same thing happened when I got home.

I didn't have time to test (need to nurse the sick wife!) but I'm going to try and reproduce this, then pull the elec. connector of the IACV. If it continues to rev around at idle, I may have a bad FITV, but if it doesn't, then I don't know what is sending mixed signals to the IACV. Could it be the throttle position sensor? That would explain the weird bouncing when I'm driving (I can't repro the bouncing RPM when idling, btw- only when I'm driving it).