I've been doing a little homework and I'm wondering if a malfunctioning coolant temp sensor could be the source of my trouble?

In Open Loop the ECM ignores the 02 sensor and relies on the MAF and CTS, as well the info. stored in the memcal. A bad CTS signal could explain my Open Loop hesitation trouble. A bad CTS could also explain my poor fuel economy. If the CTS is telling the ECM that the engine is colder than it really is, wouldn't the ECM then fatten up the fuel mixture to compensate?

On an occasion or two, my A/F ratio gauge has indicated a temporary rich condition. Rather than a steady bouncing back and forth, it hung in the rich zone momentarily. Hmmmmm.

The CTS only relays info. to the ECM and the gauge in the dash relies on it's own independent temp sender, correct?

 

Could. CTS affects alot more than anyone gives it credit for.

 

Yes. Yes. You can test the sensor with an ohm/multimeter, or just replace it. $10 part that could potentially cause those problems.

 

When you test it, Bret, the ohm reading wil probably be approximate. With our sensors at work they usually fail by either going open or closed. You can't really get a spot on accurate reading at any temp outside of laboratory conditions except for 32* f. If you make an icebath with @75% ice, not critical but more ice than water, you will have 32*. That chart looks pretty linear, so 32* would be about 10500 ohms.

 

Bret,
Do you have a scanner like an Auo Xray 5000? I have one and it helps tremendously. It will monitor many readings as you're driving the car. One of them is what the ECM thinks is the temp reading from CTS!! You can also read what the ECM is seeing for lean/rich.

For example, I had a bad O2 sensor last month. It was putting out very low Mv's to the ECM (lean), so the ECM adjusted by adding more fuel making my car run super rich, lost 6 MPG, but at the same time setting a LEAN O2 code!!!. With my scanner, I had the problem resolved in seconds. Without it, I could be still pulling out my hair!!
There are at least 30 different important readings you can monitor while driving your car. They cost under $200.00 and can save you a bunch pretty quick.

 

Can you save that to a file for looking at later or is it something you have to be looking at while you drive?

 

I don't think you can save it to a file, but you can press the scan button and that will freeze the values, and then continue to monitor.
We all know what Brett is going through right now trying to resolve his problem. If he had the Auto Xray scanner it would certainly pin point the problem.

Brett, I grew up in Woodland Hills, lived there from 1955 when I was 9 and moved away in 1972. I lived on Oxnard St. between Woodlake and Sadring.

 

I have an Actron/SunPro scanner. This is one of the first home scanners that was available. It does an adeqaute job, but there are some readings it doesn't display and a couple that it doesn't display accurately.

I also have an Auto Xray EZ-Link. When I bought it I was under the impression it read both OBD I and OBD II and all I needed to do was purchase the additional OBD I cable (it only comes with OBD II). So, I ordered a cable thru Summit just the other day. Well, the scanner is capable of reading OBD I, except that you must first contact Auto Xray and pay another $99 for the access code.

Auto Xray also offers a trade-in upgrade to the EZ-Scan 4000 and 6000 models. I went for broke and ordered the 6000. It will read OBD I and II on various makes, plus enhanced OBD II for GM, Ford and Toyota. It also comes with PC-Link software so you can download scan data to a PC and graph it or create a spread sheet. The 6000 scanner is also upgradeable online thru Auto Xray's web site, so this should be last unit I'll need to buy for a while. The upgrade was $349 and I then need to send them my EZ-Link scanner after the 6000 arrives. Typical retail on the EZ-Scan 6000 is around $600. For an extra $5 I got 2nd Day Air shipping and should have the unit on Friday or Saturday.

To take full advantage of the 6000, I'll need to pick up a PC (I'm a Mac user). Most likely I'll get a PC laptop. I have some other uses it would also come in handy for.


That's just down the street from me. I've lived in WH my whole life.

 

Bret, for a laptop check out www.notebookavenue.com. They repair new laptops that come back on warranty. The manufacturers don't repair computers on warranty, they just replace them. We have a bunch of laptops at work we've bought from them. Prices are good, and we have had excellent results.

 

Wow Brett, this is getting expensive I have a AutoXray that you could have used but I thought you were okay. Oh well. I would like to compare the units when you get yours.

 

You know how it goes, you can never have too many tools. Plus, the 6000 scanner will do even more on my '96 Cadillac. I also hope to be in the market for a new truck within the next year or so.

 

My car warms up, then its usually warm (220) and the fan would kick in to keep it that way. Now its way above that and the fan kicks in randomly, what should I do!!!?

 

Bringing the car to the Berry Farm this weekend? I can bring my scan tool if so, hook it up to your car and check it out.

 

thanks madmax, the car will make it with no problem ITS A CHEVY FOR *** SAKES