Closed Loop Help

OffRoadSonoma · #1 02-12-2005, 07:33 PM

I have a '95 noma, 4.3l tbi. OK. So when I first start my truck for the day and its completely cold it runs awesome and takes off great and accelerates great. But after about 10 minutes when its warmed up it hisitates and doesn't accelerate very good, So here's my question, I know that when a car is cold it runs on a closed loop, so is there a way to go in and tell it to always run on that closed loop, or is there an easy way to find which sensor is telling it bad info so I can replace that sensor or dissable it. Thanks guys.

BlazerLT · #2 02-13-2005, 01:00 AM

first of all, have you ever done a tuneup?

OffRoadSonoma · #3 02-13-2005, 12:56 PM

What all consist of a tuneup? I've replaced plugs, wires, distributer cap, used fuel injecter cleaner, high flow air filter, flowmaster muffler, new egr valve, switched to synthetic oil. So I've replaced alot of stuff and don't know wut else to replace. It eats ALOT of gas, and the egr valve kept getting stuck open, so thats when I first did the plugs, wires, and egr valve. So its almost likes it either dumping too much gas or not burning it all. Do u think it could be a bad fuel injecter? Thanks blazer.

BlazerLT · #4 02-13-2005, 02:57 PM

Well, I would first check your timing.

Sounds like it is overly advanced.

You do know where the timing wire is right?

Disconnect it and time the engine to zero with a timing gun.

OffRoadSonoma · #5 02-13-2005, 08:27 PM

No, not sure. I've never had to time an engine. I thought on the newer cars the computer controlled all that? Wouldn't that mean theres something wrong in my computer settings? And if I redo the timing by hand won't the computer just come in and see that it has changed when I plug the wire back in, and change it to what it was set to before? If I were to purchase on of those power programmers that you can read all the info and change it, would that work?

BlazerLT · #6 02-13-2005, 09:08 PM

Quote:

Originally Posted by OffRoadSonoma

No, not sure. I've never had to time an engine. I thought on the newer cars the computer controlled all that? Wouldn't that mean theres something wrong in my computer settings? And if I redo the timing by hand won't the computer just come in and see that it has changed when I plug the wire back in, and change it to what it was set to before? If I were to purchase on of those power programmers that you can read all the info and change it, would that work?

You sure you have a TBI or do you have the orange and black vortec plate on the top of your engine?

OffRoadSonoma · #7 02-13-2005, 09:36 PM

Yep, I'm sure. 4.3L TBI Z type in the VIN. Fuel injecters spray right on top of the engine. Two injecter. Why? Does that change anything if I would have had the CPI?

BlazerLT · #8 02-13-2005, 09:50 PM

Yes, your Vin Z is manually base set timed and the Vin W is completely unadjustable.

Remove the beige and brown timing wire from the PCM under the dash and set the timing to zero with a timing gun.

Reconnect the wire after setting the timing and the timing should be set.

OffRoadSonoma · #9 02-14-2005, 04:03 AM

Thanks, I'll try that probably tomorrow, and let your know if it helps.

OffRoadSonoma · #10 02-14-2005, 08:04 PM

Hey Blazer, I tried to find that wire under the dash, but I couldn't. Is it under the driver side, or on the passenger side by the computer? What will happen if I don't unplug that wire when I adjust the timing? I also heard from someone that you can do a break torque while someone is under the hook, and while you're doing the break torque they advance it untill it begins to spark knock, then turn it back untill it stops. I have never heard of this way, so I was wondering if you have? Thanks.

BlazerLT · #11 02-14-2005, 10:01 PM

Quote:

Originally Posted by OffRoadSonoma

Hey Blazer, I tried to find that wire under the dash, but I couldn't. Is it under the driver side, or on the passenger side by the computer? What will happen if I don't unplug that wire when I adjust the timing? I also heard from someone that you can do a break torque while someone is under the hook, and while you're doing the break torque they advance it untill it begins to spark knock, then turn it back untill it stops. I have never heard of this way, so I was wondering if you have? Thanks.

Do you have the computer on top of the passenger wheel well in the engine compartment?

OffRoadSonoma · #12 02-15-2005, 02:04 PM

It is on top of the passenger wheelwell. I didn't know if I was supposed to look over there or if I was looking under the steering collumn. I'll look over on the passenger side and let you know what happens. Thanks.

BlazerLT · #13 02-15-2005, 02:55 PM

Ok, if the computer is on top of the wheel well, there should be a beige and brown timing wire attached to it that you will have to remove while timing.

You sure you have a TBI? Does it have the round air filter assembly on top of the engine?

OffRoadSonoma · #14 02-15-2005, 09:02 PM

Yep, round air filter on top. I'll have to try that. Thanks again.

BKFT_HOTRODER · #15 03-04-2005, 11:31 PM

If you hook up a scan tool you can run the car while you go into a thing called datasteam, this tells you what every important thing on the truck is doing. The fist thing I would check is your O2 crosscounts to see if you are running rich or lean, another thing I would check id the coolant temp sensor to see if it is giving you a believable reading, you may have to use an inferred thermometer to check the real temp of the coolant.

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