Why does my '89 hesitate when it's cold?

[Mark W]

Ambient temperature doesn't matter. What I mean is, for the first two minutes or so, it hesitates on acceleration when I first start to drive it, then it runs normally pretty much for the rest of the day. Reason?

 

[sdpatt]

In the warm-up stage, the engine is operating in "open loop" mode where the air:fuel ratio is governed by preset tables in the engine control program. This mixture is usually much more rich than the "closed loop" mode where the mixture is regulated by the various engine sensors to be very close to the optimal 14.7:1 air:fuel ratio.

In this warm-up phase, any engine parameter that can farther enrich the mixture, or make it less likely that the mixture will fully combust, can result in the hesitation that you describe. The conditions that can contribute to this effect include, but are not limited to, the following.

• <font size="2" face="Verdana, Helvetica, sans-serif">Dirty mass air flow (MAF) sensor filaments.
• <font size="2" face="Verdana, Helvetica, sans-serif">Improper spark plugs.
• <font size="2" face="Verdana, Helvetica, sans-serif">Too large a gap on the spark plugs.
• <font size="2" face="Verdana, Helvetica, sans-serif">Leaking spark plug wires.
• <font size="2" face="Verdana, Helvetica, sans-serif">Restrictive or dirty air filter.
• <font size="2" face="Verdana, Helvetica, sans-serif">Incorrect reading barometric pressure sensor.

<font size="2" face="Verdana, Helvetica, sans-serif">
Reading the EEC codes (see links in my signature) can assist in diagnosing possible sources of this condition.

<small>[ September 19, 2003, 11:15 PM: Message edited by: sdpatt ]</small>

 

[Mark W]

Scott, you are the Master.

I suspect it must be the MAF or the barometric pressure sensor, as I have a "new" K&N, wires, plugs, etc. I've checked the codes more than once, so I know how that drill works.

Thanks much.

 

[MilTownSHO]

The 92 is the same way, sometimes it feels like it doesn't really want to move before it warms up. I don't mind to much cause I don't get on it until it warms up anyhow. Still though it can be quite annoying

 

[rangerj]

You will understand when you get older!!!

And Steve, don't say anything. rangerj

 

[Machspeed]

My sho does the same thing. It just hates to be ran cold. I warm it up into normal b4 i drvie it and its fine. thumb