Engine Surging After Timing Belt Job w/No Codes

[lothian]

2000 Honda Accord v6
J30A1 3.0L USDM SOHC VTEC V6 200hp; KA 4AT
~119k miles

I completed a timing belt replacement job (all three belts & both pulleys, TB auto-tensioner, water pump & front eng. mount–all Honda parts). I quadruple-checked timing marks before and after TB removal and replacement, and I manually turned over the engine a dozen times to seat the belt, check for interference, and TDC at all pulleys–absolutely no problems there. Once finished, I topped off the coolant and purged any air from the system. Then I started the engine…

– Cold engine turns over fine, but idles high at ~1700 (per scanner; engine temp is 61°). After ~5 secs the engine surges cyclically between ~1600 to ~1700;
– I can hold idle steady with the throttle or by shifting into gear, although load idle remains high;
– I held idle at ~2500 for ~5 min, then drove it around my neighborhood for ~2 miles (~10 mins @ <30mph);
- I drove it through each gear: idle is steady (though high) thru 2,3,4, but engine surges in first gear;
- Surging resumes after I shift to park (or neutral); engine temp levels at 174°;
- There is no check engine light, and no codes on the scanner;
- I found no obvious vacuum leaks or loose electrical connections;

Engine surge seems bizarre given the straight-forward job of replacing a timing belt. I followed Eric's TB video frame-for-frame; referenced the procedure in the shop manual, and noted my progress on paper as I worked. There are no loose vacuum lines in the vicinity, nor any loose electrical connectors... yet could I have possibly missed something, or pulled something loose? Could replacing a TB induce the idle surge? ...or is this merely coincidental, unrelated problem.

Any suggestions are eagerly appreciated.

Topic

[college man]

When the timing belt was done did the water pump get done?
To bleed the cooling system you don’t need to worry about the
bleeder valve,its only used for filling. Try the procedure again.
Do you have good heat in the car? Did the cooling fan come on?

http://www.ericthecarguy.com/faq/solving-automotive-idle-problems

[Glenn]

I’d let it run a few minutes to give the PCM time to set a CEL code. If your timing was off, I would think it would show immediately, not a few seconds after being cranked. Hopefully, she”ll throw a bread crumb your way…

[Mike]

Is it possible you tugged on anything when moving the engine around to deal with that stripped bolt hole? What about if anybody else might have touched anything just poking around? That symptom really seems like something electrical, but nothing that’s around the timing belt area. There may have been a ground that was pulled apart, not reconnected, or maybe just corroded enough that disturbing it in a reasonable manner caused it to break most of the wire strands without separating.

[Rereonehundred]

The old mechanic’s adage, “What did I “fix” last?” applies to me. And many others.

Go over your work.

[Jerry Shoup]

Have you checked for a sticky throttlee. Check the cable connection at the throttle-body. Probably would not “surge”,, but might be stuck high and then release. If you tap the accelerator and quickly release it, does the idle condition change?

[lothian]

I find it peculiar that the IAC valve would fail coincidental to replacing the TB–they’re on opposite sides of the engine!

But after stewing on this for a while, the only connection I see between the two is… coolant. Coolant is drained significantly with the removal of the water pump, and the IAC valve uses coolant temp to actuate. That’s the connection!

The thing is, a J30A1 3.0L V6 VTEC doesn’t have a coolant bleeder valve, which explains why there’s no such procedure in the ‘98-00 Accord Service Manual‘–perhaps the engineers designed some integral method to get the air out. I simply topped off the radiator w/coolant and ran the engine at ~2000rpm for ~5mins and added more as necessary. Still the engine surges (hunts, pulses, whatever…).

I’m not getting a P0505 code (or any codes, for that matter) so I don’t suspect a bad IACV. However, I do recognize the possibility that the IACV may be clogged or suffering an air lock within its coolant chamber. And given the fact that the thing is 1) a 15yo part that’s 2) never been serviced and 3) sat for a week without any coolant in it while I waited for the TB parts to arrive, it isn’t beyond reason that my gremlin may reside within.

So with some difficulty (Philips head screws? …really? Christ-on-a-cracker, Honda engineers! This isn’t a lawnmower carb!) I removed the IACV from beneath the throttle body and found mild carbon yuckiness. Nonetheless, it soaks in carb cleaner as I write this. I’ll re-attach after I confirm the valve portion can move freely (it doesn’t presently, from what I can feel). If that doesn’t solve the idle problem, I’ll purchase an aftermarket IACV and install it. And if that doesn’t do the trick, I’m driving the thing to the Honda shop.

[lothian]

Success.

I replaced the IACV (16022-P8A-A03) after the cleaned-up original 15yo part did not fix the idle problem. We’ll see how the engine behaves over the coming days. I’m still incredulous the problem was with the IACV (…there’s just no pleasing some people.)

For those who find this thread after a keyword search of “engine surge” and its many, many variants… check your IACV!

[Author]

Replies