Flat spot in acceleration....

TeamGreen · March 2, 2002

When my truck is cold after it has sat all night or day there is a flat spot when I accelerate around 15mph. It feels like the truck is sputtering until I give it more gas then it runs fine. It only does this when its cold though. Once the engine warms up the problem goes away. It is and 89, but was wondering if this is normal?

Joel · March 3, 2002

I know where your coming from, I wont even put 'er in drive till she's 140 degrees. Then I can drive it but it will die if I hit the gas. Not sure whats up but since its so old and runs fair when at op temp I forget about it. Although it would be real nice to be able to start it up in the morning and go without waiting 5 minutes min to go anywhere.

Joel

BrokeKnee2500 · March 8, 2002

It sounds like the engine is just over compensating with the choke and pouring too much fuel into your poor babies ;( may be worth a warranty paided trip to the dealer.

- You may also want to check and make sure your air filter is clean and not all clogged up. If its surging for air when the motor is choking the extra fuel its a sure fire way for it to cause a sputter or even kill it.

Sierra Bob · March 11, 2002

I had the same problem. The dealer said that there was a service note and re programed the computer. Ran great after, even when cold.

CMNTMXR81 · March 11, 2002

Yup, this is the dreaded cold start hesitation with our live by wire throttle system. There is a PCM re-flash the dealer needs to do in order to correct this.

I keep saying I'm gonna Auto-Tap mine when it does this, but I keep forgetting and I'm running out of time with the cold weather.

Colorado Kid · March 14, 2002

He's not going to get a warranty visit on his '89, it isn't a drive-by-wire throttle problem, it doesn't have a choke and reprograming isn't going to fix it.

It may be a mostly plugged fuel filter--fuel demand is pretty high initially accelerating a cold engine. It may be less than perfect injectors. It may be normal, my '91 stumbles a little in the first couple blocks in the morning. I wouldn't (and won't) spend any money trying to track it down until and unless it gets a lot worse. (I would change the fuel filter, I just got a new filter and in tank pump because the pump failed...I haven't noticed the hessitation because the '91 now sits out at night and by the time I have the windows clean it runs fine).

Lester · September 22, 2003

As to the problem TeamGreen was having, have you checked the temp sensors yet? If they are off on a 4.3 I know the engine will barely run untill warm, and with the addition of two more cylinders (V-8) it will probably run better untill warm. Might get a repair manual at a local parts store and meter those sensors. Any TBI vehicles I have driven (SBC V-8 or V-6) have started cold and ran just as good as the two SFI engines I have owned. (Well almost as good, given the more accurate delivery of fuel.)