Gain extra benefits by becoming a Supporting Member Click here find out how!
Classic Performance Products Classic Parts
American Auto Wire Classic Industries
Join the Community todayDanchuk Catalog
Hellwig Products IncPerformance Rod & CustomEcklers AutoMotive
Nu-Relics Power Windows
Impala Bob's Bob's Chevy Trucks Bob's Chevelle Parts Bob's Classic Chevy



 Page 1 of 2 ALL12
Username Post: Rough start and idle 5.7 TBI 1995        (Topic#176155)
G20_van 
Member
Posts: 84

Reg: 12-28-06
12-02-07 03:37 PM - Post#1309189    

Getting increasingly difficult to start my van. A few weeks ago it would fire up then shut off immediately. Give a little throttle while cranking it and it'd fire up. Now it takes a lot of throttle to get it started and I have a lot of rich black smoke, especially if it is a cold start. Hit the throttle and it hesitates badly.

Runs well after reaching normal operating temp.

I am thinking the IAC valve might be gunked up and not operating properly. Can't find this in my manual. How do I remove it - it looks like it just threads in, is this correct?

Any other ideas?

Thanks.





 
Chevytech 
Subject Matter Expert - Senior Member
Posts: 3825
Chevytech
Loc: Twin Cities, Minnesota, U...
Reg: 04-25-04
12-02-07 03:48 PM - Post#1309198    
    In response to G20_van

Yes the IAC unscrews.

IAC passages can get plugged up with carbon or muck. The IAC units get erratic as they get old and stick. Use care when cleaning the IAC. The IAC should not be cleaned with carburetor cleaner or other harsh chemicals. If the chemicals get down inside the IAC, it will damage it.

I do not suggest unscrewing the pintle (plunger). If you don’t get in back in far enough, the IAC can get damaged if the “pintle” (plunger) bottoms out in the TBI, when you screw the IAC back in.


Another possibility is that the coolant temp sensor is failing.


For those of you that are wondering why you are not getting replies to your thread:

Did you give the model, year, engine, fuel system type, and transmission information?

If your vehicle has been altered from stock, let us know about that too.


 
G20_van 
Member
Posts: 84

Reg: 12-28-06
12-02-07 04:23 PM - Post#1309226    
    In response to Chevytech

Wow....could you tell me why the coolant temp sensor might affect this condition? I never considered that as a possibility.

And thanks for the quick reply!




 
Chevytech 
Subject Matter Expert - Senior Member
Posts: 3825
Chevytech
Loc: Twin Cities, Minnesota, U...
Reg: 04-25-04
12-02-07 04:53 PM - Post#1309246    
    In response to G20_van

The computer uses a coolant temp sensor that is separate from the coolant sensor for the dash gauge/light.

The coolant temp sensor reading is one of the criteria used by the ECM/PCM to determine how much fuel to inject. It screws into the intake manifold by the Thermostat.

If you have an ohm meter I can give you the specifications for it.


For those of you that are wondering why you are not getting replies to your thread:

Did you give the model, year, engine, fuel system type, and transmission information?

If your vehicle has been altered from stock, let us know about that too.


 
G20_van 
Member
Posts: 84

Reg: 12-28-06
12-02-07 06:33 PM - Post#1309312    
    In response to Chevytech

I do have an ohm meter and would greatly appreciate the specs on that........

Pulled codes tonight and guess what came up.....15.

Thank you for your help with this.



 
Chevytech 
Subject Matter Expert - Senior Member
Posts: 3825
Chevytech
Loc: Twin Cities, Minnesota, U...
Reg: 04-25-04
12-02-07 07:45 PM - Post#1309364    
    In response to G20_van

You’re welcome. A thank you is always appreciated.

It is much more enjoyable for me to help when the replies come back fairly quickly, as this thread has.

Sounds like the sensor or the wires connecting to it are the problem.


15 - Coolant Sensor Circuit - Excessive Low temperature indicated


To test the coolant sensor, unplug the wire connector and test the resistance across the two terminals of the SENSOR with an ohm meter.

The sensor screws into the intake manifold, on the front passenger side, by the thermostat housing.

Coolant sensor approximate resistance specifications:
177 ohms @ 212 deg. F. or 100 deg. C.
241 ohms @ 194 deg. F. or 90 deg. C.
332 ohms @ 176 deg. F. or 80 deg. C.
467 ohms @ 158 deg. F. or 70 deg. C.
667 ohms @ 140 deg. F. or 60 deg. C.
973 ohms @ 122 deg. F. or 50 deg. C.
1188 ohms @ 113 deg. F. or45 deg. C.
1459 ohms @ 104 deg. F. or 40 deg. C.
1802 ohms @ 95 deg. F. or 35 deg. C.
2238 ohms @ 86 deg. F. or 30 deg. C.
2796 ohms @ 77 deg. F. or 25 deg. C.
3520 ohms @ 68 deg. F. or 20 deg. C.
4450 ohms @ 59 deg. F. or 15 deg. C.
5670 ohms @ 50 deg. F. or 10 deg. C.
7280 ohms @ 41 deg. F. or 5 deg. C.
9420 ohms @ 32 deg. F. or 0 deg. C.
12300 ohms @ 23 deg. F. or -5 deg. C.
16180 ohms @ 14 deg. F. or -10 deg. C.
21450 ohms @ 5 deg. F. or -15 deg. C.
28680 ohms @ -4 deg. F. or -20 deg. C.
52700 ohms @ -22 deg. F. or -30 deg. C.
100700 ohms @ -40 deg. F. or - 40 deg. C.


Let us know what you find.

For those of you that are wondering why you are not getting replies to your thread:

Did you give the model, year, engine, fuel system type, and transmission information?

If your vehicle has been altered from stock, let us know about that too.


 
G20_van 
Member
Posts: 84

Reg: 12-28-06
12-03-07 06:44 PM - Post#1310110    
    In response to Chevytech

YES!!!!!!!!!!!!!

You are the man! The housing on the plug connector on top of the coolant sensor was broken and had been for a long time - the prongs on the sensor were rusted. Anyway, quick trip to the local parts store and BANG now she fires right up, no smoke, idles smooth, beautiful.

Thank you so much for the suggestions. I really appreciate all your help and quick answers.

Please email me your snail mail address. Thanks again.



John

jperlette@bellsouth.net



 
Chevytech 
Subject Matter Expert - Senior Member
Posts: 3825
Chevytech
Loc: Twin Cities, Minnesota, U...
Reg: 04-25-04
12-04-07 09:40 AM - Post#1310567    
    In response to G20_van

You are welcome!

I am glad things worked out, and thanks for the feedback.

I will send you a “Private Topic” (message)


For those of you that are wondering why you are not getting replies to your thread:

Did you give the model, year, engine, fuel system type, and transmission information?

If your vehicle has been altered from stock, let us know about that too.


 
tworude 
Forum Newbie
Posts: 1

Reg: 09-15-09
09-15-09 11:00 AM - Post#1772373    
    In response to Chevytech

Thank you Chevytech. This problem has been consuming my thoughts. I'll get a new sensor on it today. Appreciate the help



 
Chevytech 
Subject Matter Expert - Senior Member
Posts: 3825
Chevytech
Loc: Twin Cities, Minnesota, U...
Reg: 04-25-04
09-15-09 03:11 PM - Post#1772517    
    In response to tworude

You’re welcome. A thank you is always appreciated.

It is nice to see someone using the search feature and finding what they need.

I see it’s your first post. Welcome to the message board.



For those of you that are wondering why you are not getting replies to your thread:

Did you give the model, year, engine, fuel system type, and transmission information?

If your vehicle has been altered from stock, let us know about that too.


 
ltlvt 
Senior Member
Posts: 1744

Age: 67
Loc: Wichita Falls Texas USA
Reg: 09-17-00
01-16-10 05:53 PM - Post#1843582    
    In response to Chevytech

since i am such a dummie i had to research how to use an ohm meter.

http://www.ehow.com/how_2282412_use-ohmme ter.html

Runs like a Scalded Dog!!


 
Chevytech 
Subject Matter Expert - Senior Member
Posts: 3825
Chevytech
Loc: Twin Cities, Minnesota, U...
Reg: 04-25-04
01-17-10 09:38 AM - Post#1843849    
    In response to ltlvt

Ohm Meter Instructions – how to use an Ohm Meter.

Instructions on using an ohm meter are different depending on the meter.

With analog meters you want to use a scale the puts your reading as close to the center of the scale as possible. This is much different then how you use a digital meter. On a digital meter you want to use the lowest scale that will accommodate the resistance you are testing.

What confuses many people is that on analog meters the reading is multiplied by the x factor on the range you have selected. On digital meters you do not multiple the reading. This confuses people that are used to using older equipment.

Never hook an analog meter to the ECM or any wiring connected to the ECM. Some tests on some circuits could damage the ECM.

I have many different ohm meters and some of them are very confusing on selecting a range.

I suggest you test something of a known resistance to make sure you understand your meter. I have a large amount of resistors, so when I start to question a meter reading, I test the meter on a resistor I know the value of.

Here are the best how to sites that I could find with a search:

Digital

http://www.8886.co.uk/ref/ohm_meter.htm

http://yotatech.com/f131/using-ohm-meter- 109532/


Analog ohmmeters

http://www.wikihow.com/Use-an-Ohmmeter

http://www.allaboutcircuits.com/vol_6/chpt_2/2.htm...


For those of you that are wondering why you are not getting replies to your thread:

Did you give the model, year, engine, fuel system type, and transmission information?

If your vehicle has been altered from stock, let us know about that too.


 
Nick94 
Forum Newbie
Posts: 66

Reg: 05-07-12
05-07-12 11:16 AM - Post#2223440    
    In response to Chevytech

What is the IAC?



 
CowboyTrukr 
"8th Year" Silver Supporting Member
Posts: 4244
CowboyTrukr
Loc: Salt Lake City
Reg: 06-20-09
05-07-12 03:52 PM - Post#2223506    
    In response to Nick94

Nick, it's the Idle Air Control servo located in the 10:00 position at the base of the TBI when viewed from the top. It has a four wire plug and controls the idle speed.

Greg

Greg

'95 K1500 Z71 EC Short Step 5.7L+0.040/NV3500
'00 Explorer XLT 4.0 V6 Auto
'94 K2500 5.7 NV4500 ECLB - SOLD
‘87 GMC S15 SCLB 4.3 Auto - SOLD

"The only thing necessary for evil to triumph is for good men to do nothing" Sir Edmund Burke


 
Biff383 
Forum Newbie
Posts: 5

Reg: 01-29-13
01-30-13 11:28 AM - Post#2312075    
    In response to CowboyTrukr

Thank you soooooooo much. CTS was the answer to a BUNCH of problems.
I still have a bad motor....but I can drive it down the road now.
This was truly a lifesaver.



 
Chevytech 
Subject Matter Expert - Senior Member
Posts: 3825
Chevytech
Loc: Twin Cities, Minnesota, U...
Reg: 04-25-04
01-30-13 05:45 PM - Post#2312174    
    In response to Biff383

You're welcome!

I am always glad to see people finding threads using the search feature or looking in the FAQs thread.

It's nice to see these old threads from when I was a frequent poster are still helping people.

With almost 9500 views, my guess is this thread has helped a lot of people.

For those of you that are wondering why you are not getting replies to your thread:

Did you give the model, year, engine, fuel system type, and transmission information?

If your vehicle has been altered from stock, let us know about that too.


 
HMAJNG 
Contributor
Posts: 214

Loc: Hawaii
Reg: 01-21-13
02-04-13 04:51 PM - Post#2313699    
    In response to Chevytech

  • Chevytech Said:
You're welcome!

I am always glad to see people finding threads using the search feature or looking in the FAQs thread.

It's nice to see these old threads from when I was a frequent poster are still helping people.

With almost 9500 views, my guess is this thread has helped a lot of people.


WOW!
This thread is 6 yrs old and still going...it's helped me today by giving me knowledge on such a problem. I'm not currently experiencing the problem the OP had, but when...and not if I do, I'll know what to do/look for as a place to start.
Mahalo!

Aloha...Woody
1990 Silverado K2500 5.7


 
markss 
Forum Newbie
Posts: 75

Age: 65
Loc: Palm Beach County, Fl
Reg: 12-02-11
02-05-13 07:01 AM - Post#2313876    
    In response to HMAJNG

  • HMAJNG Said:
  • Chevytech Said:
You're welcome!

I am always glad to see people finding threads using the search feature or looking in the FAQs thread.

It's nice to see these old threads from when I was a frequent poster are still helping people.

With almost 9500 views, my guess is this thread has helped a lot of people.


WOW!
This thread is 6 yrs old and still going...it's helped me today by giving me knowledge on such a problem. I'm not currently experiencing the problem the OP had, but when...and not if I do, I'll know what to do/look for as a place to start.
Mahalo!


I'll second that! The guys like Richard (Someotherguy) and Chevytech who take their time to help us less knowledgable guys are invaluable. I bought my '89 G20 new and never knew/did anything to it but oil changes, plugs, wires, caps, and rotors. Then I got an '89 pickup about 1 1/2 years ago and found this site about a year ago and the info I've gained has been HUGE! The van has served me well with few problems, luckily, and the pickup (SCSB 5.7 5 speed) is a blast to drive. Now when either of them has an issue I know where to look.
Thanks again, Mark



 
jimbochevelle 
Forum Newbie
Posts: 5

Age: 24
Reg: 01-18-14
01-18-14 08:29 PM - Post#2417990    
    In response to Chevytech

what is a mater if there is no reading I get 8.7 with k ohms on my multi meter and 0 at regular ohms.



 
Chevytech 
Subject Matter Expert - Senior Member
Posts: 3825
Chevytech
Loc: Twin Cities, Minnesota, U...
Reg: 04-25-04
01-19-14 08:53 AM - Post#2418098    
    In response to jimbochevelle

  • jimbochevelle Said:
what is a mater if there is no reading I get 8.7 with k ohms on my multi meter and 0 at regular ohms.


Careful trying to read ohm meters. I put the links in the thread because it is hard to interpret what some meters are showing.
8.7K
8700 ohms
It depends on what the temperature of the sensor was when you tested it.
A little above freezing and it is ok.

Zero ohms would not be ok.

For those of you that are wondering why you are not getting replies to your thread:

Did you give the model, year, engine, fuel system type, and transmission information?

If your vehicle has been altered from stock, let us know about that too.


 
anchor59 
Forum Newbie
Posts: 1

Reg: 02-19-14
02-19-14 09:30 AM - Post#2428342    
    In response to Chevytech

Can you check the wires from the CTS back through the harness to the ECM?
Will it read a voltage from the ECM?
I've installed a new CTS and just want to verify the wiring.



 
Chevytech 
Subject Matter Expert - Senior Member
Posts: 3825
Chevytech
Loc: Twin Cities, Minnesota, U...
Reg: 04-25-04
02-19-14 03:15 PM - Post#2428414    
    In response to anchor59

  • anchor59 Said:
Can you check the wires from the CTS back through the harness to the ECM?
Will it read a voltage from the ECM?
I've installed a new CTS and just want to verify the wiring.


Yes you can do that testing.

The black wire should be connected to ground.

With the key on, engine off, wire connector unplugged from the sensor there should be close to 5 volts on the yellow wire.

Welcome to the board!

For those of you that are wondering why you are not getting replies to your thread:

Did you give the model, year, engine, fuel system type, and transmission information?

If your vehicle has been altered from stock, let us know about that too.


 
1bignordic 
Forum Newbie
Posts: 17

Age: 56
Loc: Twin Cities
Reg: 08-13-14
09-30-14 08:36 AM - Post#2487681    
    In response to Chevytech

I too am just learning how to read and use a multi-meter, never been very good with anything wires/electicity. Time to learn!!! Thanks to everyone here at Chevytalk!!!



 
someotherguy 
Senior Moderator
Posts: 28994
someotherguy
Age: 49
Loc: Texas
Reg: 08-01-03
09-30-14 08:47 AM - Post#2487684    
    In response to 1bignordic

Haven't read through it or watched the video but these guys are a good source of info; check out - How to Use a Multimeter (SparkFun website) https://learn.sparkfun.com/tutorials/how-to-use- a-...

Be careful checking around computer pinouts on your truck; you don't want to just go crazy poking the leads around. Also be sure to never pierce the wires to check them. Always test at the pin itself and if necessary get a connector from a junk harness so you can plug it in and use it as a "breakout" so you're not shoving random objects into the pin in an attempt to reach it.

Richard

06 Silverado ISS / 06 Silverado SS / 06 300C SRT8


 
mccla.case 
Forum Newbie
Posts: 1

Reg: 11-25-15
11-25-15 04:13 PM - Post#2591514    
    In response to Chevytech

I have an issue with the voltage. I run test from the box it put out the 5 volts but at the sensor is only 2.8v. I need help on this asap



 
Chevytech 
Subject Matter Expert - Senior Member
Posts: 3825
Chevytech
Loc: Twin Cities, Minnesota, U...
Reg: 04-25-04
11-26-15 08:01 AM - Post#2591646    
    In response to mccla.case

  • mccla.case Said:
I have an issue with the voltage. I run test from the box it put out the 5 volts but at the sensor is only 2.8v. I need help on this asap


Welcome to the message board.

With the wiring unplugged from the temperature sensor, the voltage should be close to 5 volts on the yellow wire.

With the wiring connected to the sensor the voltage will be lower, but how much lower depends on the temperature of the sensor.

If you are getting 2.8 volts on the yellow wire while it is unplugged from the sensor then there is a problem. If this is happening I would be inspecting the wiring and connections between the ECM and the sensor.

The ECM and sensor ground wiring connects to the engine at the front area of the intake manifold, often at the thermostat or close to it. Make sure those grounds are clean and tight.

For those of you that are wondering why you are not getting replies to your thread:

Did you give the model, year, engine, fuel system type, and transmission information?

If your vehicle has been altered from stock, let us know about that too.


 
digital dummy 
Forum Newbie
Posts: 19

Reg: 01-19-12
01-16-16 04:49 PM - Post#2602554    
    In response to Chevytech

I am amazed that this was posted 8 years ago, and I am just reading it now, and realizing how valuable it is.

I tested my coolant sensor the following way:

I have a very inexpensive digital meter, however hopefully it is accurate enough.

with the setting at 20K on the meter, when I test the sensor, it says 3.17. I took a temperature gun and it read somewhere around 62F but not sure if that is the correct way or not.

I have 5 volts from the yellow wire, so the connection is good.

My question according to the chart the oms are about 10 percent low for the temperature.

Is that enough to worry about or are those numbers just a guideline?

My issue is rough idling and very bad fuel mileage. When the engine is cold, it starts right up and idles fine for about a minute, then starts to get rough. If I shut off the engine, then restart it, it's about a 8-10 seconds before it starts, and idles poorly.

And, mine is a 96 5.7 vortex .

The sensor is probably not the issue, but I was so impressed with the way your answers were laid out, I thought I would try.

Excellent site guys(and gals)

DD



Edited by digital dummy on 01-16-16 04:51 PM. Reason for edit: No reason given.

 
Chevytech 
Subject Matter Expert - Senior Member
Posts: 3825
Chevytech
Loc: Twin Cities, Minnesota, U...
Reg: 04-25-04
01-16-16 05:19 PM - Post#2602562    
    In response to digital dummy

Re: DD

The resistance specifications are approximate.

That one reading alone would not worry me.

I have a RAYTEK infrared thermometer and it always reads about 6 degrees low. Yours may be the same.

I would test the sensor at a different temperature, like fully warmed up and see if it is correct when near 195 degrees which is the thermostat opening temp.

For your 1996 Vortec, and the symptoms it has, my first guess would be a leaking fuel pressure regulator, or another fuel system leak under the plenum.

Do a search on “upgrading the spider” and you should find information on this. Or, start a new thread because your Vortec is a much different system then a TBI system that this thread is about.

I am glad you found the thread helpful!

For those of you that are wondering why you are not getting replies to your thread:

Did you give the model, year, engine, fuel system type, and transmission information?

If your vehicle has been altered from stock, let us know about that too.


 
digital dummy 
Forum Newbie
Posts: 19

Reg: 01-19-12
01-16-16 05:52 PM - Post#2602567    
    In response to Chevytech

Thanks for the info.

I will do a search.

DD



 
Hans_k1500_5.7-90 
Forum Newbie
Posts: 1

Age: 31
Loc: nj
Reg: 02-24-16
02-24-16 11:29 AM - Post#2611203    
    In response to Chevytech

amazing stuff gents! Thank you for helping all of us lost novice wrenchers! ready??

1990 k1500 5.7L - iddle is up and down, current codes are 15, 32(not worried about egr until this puzzle is completed), and 45(taking this as a confirmation that i'm running rich)

the etc is brand new, i confirmed it's ohms match the temp. the connection has a smidge over 5volts yellow wire. the black wire has continuity.

after reading this and other write-ups i feel as though some where in the circuit is added resistance, may you point me in the right direction? what other grounds can i confirm?

i want to confirm that the connector is not the issue any way to do this measuring ohms?

thank you guys in advance.



 
 Page 1 of 2 ALL12
Icon Legend Permissions Topic Options
Report Post

Quote Post

Quick Reply

Print Topic

Email Topic

47516 Views
FusionBB
FusionBB™ Version 2.1
©2003-2006 InteractivePHP, Inc.
Execution time: 0.119 seconds.   Total Queries: 13   Zlib Compression is on.
All times are (GMT -0800) Pacific. Current time is 07:16 AM
Top