ECT sensor question

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ebk06

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Feb 23, 2007

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Mar 30, 2010

#1

• Mar 30, 2010

• #1

Will an ECT sensor going out always throw a code? Ive been battling an idle issue and not getting any codes. Im figuring since the problem is still somewhat intermitent it may not throw a code. The symptoms are that of an ECT being bad though and I havent found any vacuum leaks.

 

liljoe07

5 Year Member

Feb 18, 2009

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Cartersville,Ga

Mar 30, 2010

#2

• Mar 30, 2010

• #2

There is a chance that the ECT readings can be abnormaly high and effect the timing and fuel, but not throw a code. Code range on the high side is 250*. But ECM adjustments are made at temps lower than that. 220* range I believe. I'd have to check.

What you may do is get the engine to the point where the problem is present. And take voltage readings from the ECT. Just put a voltmeter across the two wires at the sensor. One is a ground, so you will get a reading. Then compare it to a ECT sensor voltage chart.

 

liljoe07

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Mar 30, 2010

#3

• Mar 30, 2010

• #3

I will also add that you may need to go over the 10 PIN connections behind the intake.

Also intermittent codes can be found in the memory codes.

Maybe you could describe your problems?

 

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ebk06

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Mar 31, 2010

#4

• Mar 31, 2010

• #4

Well I was looking through my stash of parts and found a new ECT sensor so I just replaced it. The car is still idling funky but it only did it at 2 stop light on the way to work and not all of them lol. So maybe the ecu is relearning with the new sensor.....wishful thinking.

Before you ask I've pulled KOEO and KOER codes get nothing. I cleaned the IAC and it wasnt too dirty and the cleaning didnt seem to help. Maybe that needs to be replaced now? But the voltage on it was normal. When I start the car it idles at around 1200 rpms for a second and the seems to drop down to 900-100 rpms after a minute. I thought the idle would stay higher until the engine got suffeciently warm but its not. The idle is surging from 500-900 rpms only when the engine is warm and it only does it sometimes. I replaced the BAP sensor and it seemed to slow the frequency of the idle surge but not stop it. The TPS just got replaced a month ago since i was getting a code for it. The ACT was gunked up and I cleaned it as well.

Now I did set the idle with the IAC and spout unplugged but set it a bit low to 500 rpms so I need to reset it to 600. The weird thing is sometime when I pull the IAC the car will die and other times it wont. Ill recheck the 10 pin but I just cleaned them and added some electric grease to the pins so they should be getting a good connection.

I sprayed down the vacuum lines, which were replaced not long ago, and didnt get any weird surging from that. Im thinking maybe the intake is leaking somewhere now but the fact that the idle is only surging when the engine is warm makes me think its a sensor.

 

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ebk06

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Mar 31, 2010

#5

• Mar 31, 2010

• #5

Also the alternator voltage was 15 volts at warm idle. Its the stock alt. and my car is an '87. The voltage seems higher than it should be......could this be causing an overcharge issue/idle issue?

 

HISSIN50

"How long does it take to get help in here?

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Mar 31, 2010

#6

• Mar 31, 2010

• #6

The alt should not cause issues. To be a little high is better than a little low (strange things start happening at about 11.0V).

It still sounds like a vac leak issue to me.

Good luck.

 

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ebk06

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Mar 31, 2010

#7

• Mar 31, 2010

• #7

Would a blown out gasket on the upper to lower intake cause a vacuum leak? I hope thats the issue and not the lower intake gasket. Im probably going to pull the upper intake and replace all the hoses again and check the gaskets. Other than that im not sure where else a vacuum leak could be coming from....any ideas?

 

liljoe07

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Mar 31, 2010

#8

• Mar 31, 2010

• #8

Good place to start is by setting the idle closer to the ECM designated Idle(672). This puts the IAC duty cycle lower.

 

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ebk06

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Mar 31, 2010

#9

• Mar 31, 2010

• #9

I didnt have time to mess with the idle tonight but I did replace the vacuum lines. Once I did that I took it for a quick drive and let it just sit and idle for a bit. I still have a surge although it seems to only fluctuate about 200 rpms now and not 300-400. Ill try and set the idle tomorrow and see what happens. This is really frustrating now.

 

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ebk06

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Apr 1, 2010

#10

• Apr 1, 2010

• #10

Nevermind the surge is exactly the same. The only vacuum lines I didnt change out were the hard plastic lines but from experience those seem to crack in half when the go bad and not crumble like the rubber lines. I guess next I will change my fuel filter even though its not that old either. *sigh*

 

HISSIN50

"How long does it take to get help in here?

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Apr 1, 2010

#11

• Apr 1, 2010

• #11

It's prob not going to be the fuel filter.

If you disconnect the IAC electrical connector, does it still surge while idling in your driveway (don't drive it like this, as it might stall on you)?

 

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ebk06

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Apr 1, 2010

#12

• Apr 1, 2010

• #12

HISSIN50 said:

It's prob not going to be the fuel filter.

If you disconnect the IAC electrical connector, does it still surge while idling in your driveway (don't drive it like this, as it might stall on you)?

Click to expand...

I cant remember off the top of my head but I want to say no.

Lets says it doesnt what does that mean? The IAC is bad? And what if it does continue surging what does that mean?

 

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ebk06

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Apr 6, 2010

#13

• Apr 6, 2010

• #13

Ok Hissin I finally got time to mess with the car again and it does in fact keep surging when the IAC is unplugged. Any advice?

 

HISSIN50

"How long does it take to get help in here?

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Apr 6, 2010

#14

• Apr 6, 2010

• #14

I'd still keep lookin for vac leaks.

 

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ebk06

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Apr 7, 2010

#15

• Apr 7, 2010

• #15

Will do, thanks.

 

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ebk06

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May 11, 2010

#16

• May 11, 2010

• #16

Well just to update I finally got the idle issue fixed. This past weekend I started getting a code 34 so i replaced the egr sensor. The code still stuck around (maybe the car needed to drive for a bit) so I pulled off the throttle body and egr plate. The egr plate had 23 years of carbon built up on it so I soaked it and chistled away the carbon. The holes where the egr valve recirculates the air were almost completely clogged up with carbon and the throttle body was pretty dirty.

Also I rerouted the throttle cables and double checked the torque on the intake. Last I double checked the pins on the salt and pepper shakers. Once everything got put back together the car ran fine and has continued to for the last 4 days. I do need to adjust the idle since it a little high but im glad to finally have the car running right.