Hexa-dB

I know idle problems have been done to death but I still can't find anything the same as the problem I have.

When I start from cold, idle is fine at around 1500rpm
When the engine is fully hot, idle is fine at around 750rpm

The problem is in between. Before it gets up to full temp I get hunting from 500 to 1500rpm, more of a regular surging than hunting. Sometimes (like at junctions/traffic lights) it will drop low enough to stall.

Things that have been done:
New distributor, HT leads, plugs
New O2 sensor
I removed the FITV and gave it a good clean, but must have failed to screw the white plastic bit back in properly as I had a 3,000rpm idle when I refitted it. I swapped the whole FITV for another known-good one which fixed that.
The EACV has been cleaned with carb cleaner (mesh screens are nice & clean now)
Coolant has been bled and bled and bled.

Current thinking is possibly thermostat (takes a little while to heat up, temp guage never gets above just-below-halfway), water pump not circulating the coolant properly (but I don't get any overheating), bad EACV.

Anyone have any ideas?

mmafighter130

hey man ive had that same problem several times.
heres what i would try: its pretty common problem among honda and people generally overlook it cuz they think it is hard to do. Try adjusting your tps. Many tps sensors are secured with tork head fasteners and some are riveted. if it is riveted you will need to drill the rivets out and put some type of threaded fasteners in. The tps should have 3 wires running to the plug. You should be looking for the red wire. Probe into this wire with a multimeter (red lead) and fround the black lead. Turn the igniton on and make sure the tps is plugged in with the wire back probed, When the throttle is fully closed the reading should be anywhere from .4 to .5V. When fully opened it should read 4.5 V. So if the closed reading is not at or around the right range, loosen the tps fasteners and actually turn it until you get the desired reading. I believe this may be your problem

B16B_coupe

clean your iacv?

fitv out of adjustment?

engine light?

Hexa-dB

Hi,

I've got a VAFC fitted, which is just hooked up as a gauge (none of the outputs connected) and that can show TPS voltage - everything looks ok but I'll double check. Thinking about it maybe I should rip out the VAFC just in case it's causing probs..

B16B_coupe - yep EACV has been cleaned, FITV should be ok as it was a straight swap from a car with no probs, no engine lights at all.

Hexa-dB

Checked the voltage from the TPS on the VAFC and it was in range - around 0.44v with throttle closed and 4.45 or so when fully open. This with ignition on but engine not running.

I keep thinking it FITV because it's ok when fully hot (but also ok when started from cold, just while it's warming that there's a prob) but the FITV has been swapped for a completely different one

Any other ideas

92d16z6boy

you could try and bleed the coolant system. i had this problem on my gsr swap into my eg 92 . kept fine at idle and when i drove it it hopped up and down. my tps had a pin loose and that unplugged did the same thing.. if the idling doesn't get fixed by the coolant bleed, then unplug each sensor and if the engine acts differently when you unplug one lets say u unplug the tps and it doesn't do anything then most likely its a bad tps sensor or loose connections. but if the engine changes rpms or idle tendencies then look futher into the plugs that had no response. try and reset the computer. unplug the positive and negative for about 5 minutes and try again if that doesnt work u can unplg again and touch both UNPLUGGED cables to each toehr for a few seconds and this will reset the computer in most instances. that helped me when i had a fouled 02 sensor and codes kept poppin you can fork out 75$ at most garages.. they will do a scan test for you for that much most of the time unless they are sh** heads

92d16z6boy

did u check your egr valve. clan it check connections and tourqe on the bolts a slight space where air can get in will cause jump in idle. also, iac will do the same thing.

92d16z6boy

first check the iac most of all thats the problem. my boosted 97 d16z6 had a bad iac and would do the same thing you are explaining.
good luck

Hexa-dB

Thanks for the suggestions - I'll try pulling the sensors - I haven't tried that yet.

When you say egr valve, do you mean the EACV? If so, I've taken that off and cleaned the mesh screens.

I've swapped the FITV already for another one and it seems to be working as the idle does drop the right level when up to temp. Don't get any engine check codes, the TPS voltages look ok, and I've bled the coolant a few times (for ages).

I'll check the torque on all the bolts too, just in case. I guess that could explain it as things will expand when hot - maybe enough to seal up any leak.

I think my current plan is - check torque on FITV, EACV and TB bolts, take the intake off and see if I get air sucking in from the FITV/EACV holes when warm, try removing sensor plugs to see if I can find anything weird.

Thanks

icantdrive

have you checked your Sparkplug wire lately?

Hexa-dB

Plug wires should be ok, I changed the plugs not too long ago and they seemed ok then (I fitted Magnecor Competition wires sometime last year)

Current theory is possible air leak from the TB/IM bolts not being tightened enough. A friend suggested that maybe when the engine is hot the metal could expand and seal any gap. That would explain it - when the engine's cold the revs are around 1500rpm and it's fine, when it starts getting warm and the revs drop (as the FITV closes) the ir leak may confuse the ECU causing the hunting, and then when it's properly hot it's expanded enough to close the gap.

It's dark by the time I finish work at the moment so I'll have to take a proper look at the weekend.

92d16z6boy

another problems i ahve been running into latley was the spark plug gap.. i got 4 sparkplugs last month and they were all gaped rediculously far apart from one another.. it was rediculous! egr valve teh thing behind the intake mani attatched with two bolts and a sensor on it.. between mani and firewall. try your pvc valve.. these newer motors could all have one little tarded thing wrong can mess up a whole engine