Whenever I start up my car the idle goes up and down sometimes just a few times then levels out. Other times it jumps around for a minute or so then levels out. The motor runs fine other than that. Any ideas on what it could be?

 

what kind of car/engine? sounds like a Fast Idle Thermo Valve (FITV) located under the throttle body. There's an easy fix for that. Or you might have a IACV (Idle Air Control Valve) located on the back of the intake manifold that could be sticking. Other than that timing, or low coolant level can cause this too. Any Check Engine Lights(CEL)?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by SirRevvs &raquo;</TD></TR><TR><TD CLASS="quote">what kind of car/engine? sounds like a Fast Idle Thermo Valve (FITV) located under the throttle body. There's an easy fix for that. Or you might have a IACV (Idle Air Control Valve) located on the back of the intake manifold that could be sticking. Other than that timing, or low coolant level can cause this too. Any Check Engine Lights(CEL)?</TD></TR></TABLE>

If these ideas don't happen to pan out, look for an intake air or vacuum leak around the intake manifold and throttle body.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by RonJ@HT &raquo;</TD></TR><TR><TD CLASS="quote">

If these ideas don't happen to pan out, look for an intake air or vacuum leak around the intake manifold and throttle body.</TD></TR></TABLE>

If he had a vaccuum leak like that it would idle like that all the time. Your idle adjustment screw on the throttle body maybe backing itself out or your butterfly valve maybe sticking sometimes and that could cause a vaccuum leak, just some more ideas.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by SirRevvs &raquo;</TD></TR><TR><TD CLASS="quote">

If he had a vaccuum leak like that it would idle like that all the time. Your idle adjustment screw on the throttle body maybe backing itself out or your butterfly valve maybe sticking sometimes and that could cause a vaccuum leak, just some more ideas.</TD></TR></TABLE>

Not necessarily. Heating of the engine might reduce or eliminate such a leak.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by RonJ@HT &raquo;</TD></TR><TR><TD CLASS="quote">

Not necessarily. Heating of the engine might reduce or eliminate such a leak.</TD></TR></TABLE>

probable but unlikely,honda's are notorious for idle problems. If he hasn't replaced the I/M gasket or TB gasket recently then its prob one on the 10 things that usually cause idle problems on a honda. I'm not saying that your wrong, just unlikely.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by SirRevvs &raquo;</TD></TR><TR><TD CLASS="quote">

probable but unlikely,honda's are notorious for idle problems. If he hasn't replaced the I/M gasket or TB gasket recently then its prob one on the 10 things that usually cause idle problems on a honda. I'm not saying that your wrong, just unlikely.</TD></TR></TABLE>

Actually, without additional information, you are really unable to guess how unlikely or likely my suggestion was.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by RonJ@HT &raquo;</TD></TR><TR><TD CLASS="quote">

Actually, without additional information, you are really unable to guess how unlikely or likely my suggestion was.</TD></TR></TABLE>

Agreed more info in this thread is needed to make any kind of logical reasoning.

 

Respectful well reasoned debate makes for a good forum. Thoughtless denouncing of ideas, on the other hand, fails to serve anyone.

 

I have a similar situation, When I did an engine swap to a sohc zc vtec, its been jumping around 200-1500 at cold start then when it warms up it drops down to bout 400, which is very low. I checkd the IACV, and Leaks, came out good. Checked the thottle linkage and the trhottle adjuster screw on the TB and cant fix the problem. When I adjust the screw at warm start it seems to find its way back to what its been doing. The timing is good. What else can it be? Loyd