Erratic Idle

[Rod_Lei]

Alrighty, then I'm off to buy the booster and hopefully a new clip, thanks a ton guys! I'll reply with the results.

[Rod_Lei]

Alright, Booster changed out! Man, I discovered the use for a Universal Joint... Brakes glide now and no vacuum problems!

Problem is, truck still does the erratic idle we started with. I tried the jumpercables to create a ground trick, the truck didn't react to either so it's not that.

This morning, I changed the oil, started it up and is started flooding?? It would idle, and the injectors would pour gas, and then it would choke on the gas, then it would return to normal, kept doing this till I turned it off. I started back up with the air cleaner off and saw the injectors flooding the truck. Could this be a bad Coolant Temp sensor? The idle rising thing only happens when I drive it, if I restart it the idle goes down to a wonderful level, once it warms up or starts driving it'll mess up:P

[ChevyTech]

Originally Posted by Rod_Lei

I started back up with the air cleaner off and saw the injectors flooding the truck. Could this be a bad Coolant Temp sensor?

Yes,

It could be a bad coolant sensor, but it sounds like a bad connection to the coolant sensor on the intake manifold.

Check the wiring and the condition of the connector at the sensor.

[Rod_Lei]

Well, I had already changed the sensor and the pigtail. After fiddling with it and screaming at the truck for an hour, it runs perfectly. I haven't had problems in two days, no idle problems, the truck is running smooth:P

Thanks a lot guys!

[ChevyTech]

Glad to hear it is running well.

No twisting wires together, or crimp connectors, should be used on ECM sensor circuits.

When you replace the sensor connector, “pigtail”, the wires need to be soldered. Any resistance in connections will lower the temperature the ECM is reading.

[Rod_Lei]

soldered?? woah, how would I do that? like I know how to solder, but like how would I do it?

[ChevyTech]

Originally Posted by Rod_Lei

soldered?? woah, how would I do that? like I know how to solder, but like how would I do it?

Always use a rosin-core solder (this has a rosin flux in the center) for soldering electrical wiring.

http://www.doityourself.com/stry/h2weld

[Rod_Lei]

Oh it's an early Christmas present!! When my truck was flooding itself, naturally the truck got some codes, well I got 15, 22, 32, 45.

15 I got from fiddling with the coolant sensor.
22 is Throttle Position Sensor? could that have caused the flooding?
32 is the EGR code, I set that on the highway last night.
45 should be from when it was flooding.

[ChevyTech]

After you solder the coolant sensor wires, check the grounds. Some of these items share a ground at the front of the intake.

The ECM and engine sensors ground at the front of the intake manifold under the front intake bolts/studs or by the thermostat.

There is a ground wire between the back of the passenger side cylinder head and the fire wall.

Also check the ground between the battery and the fender.

So many people are so bad at testing grounds I usually suggest putting a jumper cable between the engine and other spot and see if it makes a difference.

[Rod_Lei]

Ok cool, thanks for the soldering tip, got to it today and yes its idle is rock solid And yeah that ground on the intake looks a little crispy, should I splice or solder as well?

[piecesparts]

Have you looked at your EGR valve. I just had to replace mine, due ti the engine idling low and then faultering. You would think that after 300,000 miles it would still have something left in it.

[ChevyTech]

Originally Posted by Rod_Lei

Ok cool, thanks for the soldering tip, got to it today and yes its idle is rock solid And yeah that ground on the intake looks a little crispy, should I splice or solder as well?

Glad that you have the idle fixed.

It is hard to tell what is needed without seeing it. Often they can be cleaned up and reused if they are just dirty.

If you replace the eyelet use one that is just as heavy as the original eyelet was.

The ECM and sensor grounds terminate at the front of the intake and it is very important they are well connected to the engine – ground.

At the dealership here, the tool is available for the techs to get a very good crimp when replacing the eyelet. If I was doing one at home I would solder it.

If the grounds are on a stud at the thermostat housing, I usually move them to an intake stud.

[Rod_Lei]

Alright cool, yeah I had my electrician neighbor look at it, he said it was just fine. And yeah the EGR is coming off once it warms up down here in Texas, I'm gonna clean it and put it back on with a new gasket.

[Rod_Lei]

Ok so the idle problem started again, but I caught it and figured out what was causing it. I unplugged the Throttle Position Sensor and started the truck up, purred like a kitten. Turned it off and reconnected the TPS, truck ran excellently, perfect shift point and very low steady idle.
The TPS is already new, can I buy a new connector?

[piecesparts]

If all else fails, go to the salvage yard.

[ChevyTech]

If a new TPS connector does not fix it, AND YOU SOLDERED the wires to the new connecter, it sounds like poor grounds are causing the problem.

Just because the TPS is new does not guaranty it is a good part.

[Rod_Lei]

Sweet, I'm gonna look for that connector and I'll get a new TPS just to be sure.
Thanks for your input!

[ChevyTech]

If your truck did not set codes I would want you to test the fuel pressure with the engine running.

With the codes it has set I am suspicious of a poor ground. Possibly at the front of the intake. This is where the ECM and sensor grounds terminate.

[Rod_Lei]

Well that ground at the intake was replaced a year ago because it was bad. I brought the old TPS to get checked out at AutoZone, the plugged a meter to it and it threw some very erratic resistance levels, they gave me the new one and so far, smoooooth sailing. Thanks guys for all your help, it's running well, and hopefully on less gas, you guys have been a super help!!

[ChevyTech]

Glad it is running well.

The TPS is not a rugged part.

Be careful never to get carburetor cleaner on them.

[QKENUF4U]

Originally Posted by ChevyTech

Be careful never to get carburetor cleaner on them.

hmm thats kinda funny youve said that twice now .... i must have gotten lucky cause ive used carb cleaner to clean my throttle body on my 91 a few times... its only now having the idle problems.... ive had the truck since late 07 and nothing till the last year or so....