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| Gearheadotaku | L98 running cold with 195 stat | ||
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My '88 L98 (what else would that year have?) is running oddly cold. Crusing at moderate speeds, say 50mph, it will barely break 155 degrees. Stop at a light and you might see 170. Takes forever to warm up - hangs around 140 forever. It will go over 200 on a hot day with the a/c running, even 225 in heavy traffic w/ac. Yes it a 195 t-stat, even put in a fresh Delco one to be sure that wasn't the issue. Good heat through the heater, but it does smell like its running rich. No codes and runs fine otherwise.
ideas? maybe not worry about it? |
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Posted on: 2008/6/24 1:15
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| CentralCoaster | Re: L98 running cold with 195 stat | ||
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Are you using drilled stats?
If the car can reach 225 it sounds like the sensor is at least working to some degree. |
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Posted on: 2008/6/24 1:24
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| Gearheadotaku | Re: L98 running cold with 195 stat | ||
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yes, the stat has the little "jiggle valve" as I call it, to prevent air lock.
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Posted on: 2008/6/24 1:33
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| bogus | Re: L98 running cold with 195 stat | ||
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Grand Imperial Pooh-Bah
 
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interesting. The stat seems ok...
I wonder if the sensors are just a little slow or have a dead spot? I mean, at those temps you are not getting out of open loop. |
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Posted on: 2008/6/24 4:09
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| Gearheadotaku | Re: L98 running cold with 195 stat | ||
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Quote:
Thats kind of what I was thinking, hence the rich smell. Does the computer and guage use the same sensor? Can't recall if the '88 has that extra cold start injector or not. My fuel mileage is down, but not dismal (yet). |
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Posted on: 2008/6/25 11:39
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| Matatk | Re: L98 running cold with 195 stat | ||
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88 was the last year of the cold start injector. 89 started without.
Do you smell extra fuel all the time? I would check the fuel pressure - it's possible you have leaking injectors. I'd ohm them, too. Matthew |
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Posted on: 2008/6/25 13:30
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| CentralCoaster | Re: L98 running cold with 195 stat | ||
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The computer uses a different sensor than the dash.
Does the dash reading coincide with fan operating points? The computer sensor, if I recall, is on the front of the intake base. The other should be on the head by the alternator. I honestly can't quite remember anymore. |
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Posted on: 2008/6/25 18:47
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| toptechx6 | Re: L98 running cold with 195 stat | ||
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Not sure where you came up with that theory, put a scan tool on your car then start it up cold and give it enough throttle to simulate normal driving say 1500 RPM (not idling) while you monitor loop status. If your O2 sensor is working you should be in closed loop before the coolant temp reaches 120, less than 2 minutes run time. |
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Posted on: 2008/6/25 20:18
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| Gearheadotaku | Re: L98 running cold with 195 stat | ||
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Yeah, going closed loop sooner makes sense now that I think about it. Don't have a scan tool to check it with though. There are two sensors at the front of the manifold, one on the head + fan switch. My memory is clearing as we disscuss this. Guage sensor is on the head, along with the fan switch. The cold start sensor and the engine temp sensor are seperate, right? ( the 2 on the front)
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Posted on: 2008/6/26 23:28
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| toptechx6 | Re: L98 running cold with 195 stat | ||
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Sorry I can't confirm the sensor location on your L98, but it sounds correct. Understand that low engine temperatures can reduce fuel economy even if it is warm enough to be in closed loop. |
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Posted on: 2008/6/27 10:31
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| vetteoz | Re: L98 running cold with 195 stat | ||
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Correct Sensor between 6 + 8 for gauges Switch between 1 + 3 for fan Cold start switch; intake RHS CTS ( for ECM ) ;intake center |
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Posted on: 2008/6/29 7:48
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| bogus | Re: L98 running cold with 195 stat | ||
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Grand Imperial Pooh-Bah
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The theory comes from experience. I have monitored my 92 and my wifes L98, and neither dropped into closed loop until past 150. I have never seen one kick at 120, hell, I barely have heat in the core at that temp. The LT1 will stall if the heat sensor fails, too. H15 code, IIRC. |
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Posted on: 2008/6/29 21:48
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| toptechx6 | Re: L98 running cold with 195 stat | ||
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The numbers I stated came from actual test on my 93, my newer OBDII cars with heated O'2s go into closed loop before the coolant temp reaches 90*, about 1 minute of run time.
You lost me on the heat sensor "failure" does that mean open or shorted? A coolant sensor can read an incorrect value for a given engine temperature without setting a code. |
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Posted on: 2008/6/29 22:34
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| bogus | Re: L98 running cold with 195 stat | ||
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Grand Imperial Pooh-Bah
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Hm... I wonder why your car went into closed sooner? I use the FAST system.
The temp sensor on the waterpump failed. I am assuming it shorted out internally. At about 140F, it would spaz on the digital temp gauge. The numbers would go all over the place... 170, 30, 190, 20, 130, then, once it reach about 150F, it would settle down. If I happened to stop the car during that period, it would simply die. I had to floor it to restart it... most annoying. It would then set the H15 code. |
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Posted on: 2008/6/29 22:41
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The single biggest problem with communication is the illusion that it has taken place. - George Bernard Shaw Education is the best tool to overcome irrational fear. - me |
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| toptechx6 | Re: L98 running cold with 195 stat | ||
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Quote:
I'm not familiar with FAST, is it an added computer that just runs the fuel injection or does it replace the factory ECM entirely? That could easily explain the difference I guess, but that temp seems very high to enter closed loop, seems like it would decrease fuel economy. The factory ECM uses a shunt circuit in the coolant temp return signal that switches at about the 140* point you mentioned, have to wonder how the two computers interact if FAST is a separate control for injection and the original ECM communicates with CCM? Does your FAST system still operate the air pump? I imagine that would also affect the transition time to closed loop, just some thoughts on the differences, but it now seems like we are comparing apples and oranges. |
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Posted on: 2008/6/30 9:51
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| hulagan808 | Re: L98 running cold with 195 stat | ||
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Whenever I have run into this I strap an old school coolant temp gauge probe to the lower rad hose and see whats going on. I mean, really how cool can a l98 run? I know my readings won't be super accurate but you can see how things are getting on. You can infrared the head as well as just check all the temp sensors one at a time. A cold running l98, never heard of that
 PS, can everyone go out and get a wide band o2 please? They are getting very affordable now, these should be pennies by now if more people bought them. 90% of the ass scratching would go away. Aloha |
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Posted on: 2008/6/30 11:59
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| CentralCoaster | Re: L98 running cold with 195 stat | ||
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If the guage sending unit isn't grounded properly it will read low. Too much teflon tape on the threads can do this.
Or resistance in the connector or harness will do the same. |
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Posted on: 2008/6/30 14:20
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| Gearheadotaku | Re: L98 running cold with 195 stat | ||
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I hadn't thought of that. The temp guage wire got melted and replaced a while back. Hope to get in there this weekend and start working on this stuff
Thanks everyone! |
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Posted on: 2008/7/2 13:14
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In the servitude of my fiberglass Mistress |
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| CentralCoaster | Re: L98 running cold with 195 stat | ||
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There's a chart in the FSM that tells you how many Ohms = how many degrees F.
You could measure the circuit resistance to ground and see if the sensor+connector is accurate. |
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Posted on: 2008/7/2 14:42
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1985 Z51, ZF6 |
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| Gearheadotaku | Re: L98 running cold with 195 stat | ||
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So 4th of July weekend I go to change out the sensors and I see I'm leaking power steering fluid. Pick up new hoses, start taking things apart, and proceed to cut open my hand on the exhaust manifold heat sheild. Trip to the clinic, half a dozen stitches and a tetnus shot later... I can't wait to see the bill.
Now a week later everythings back together but... Some how I managed to break off that little plastic switch on the side of the master cylinder. Dealer says discontinued, aftermarket doesn't have...anyone got an old master lying around? This has been the klutz job from hell... |
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Posted on: 2008/7/15 20:36
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In the servitude of my fiberglass Mistress |
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| CentralCoaster | Re: L98 running cold with 195 stat | ||
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That surprises me. Ecklers carries it if you can't find it elsewhere. I may have one laying around also, I'll check. |
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Posted on: 2008/7/15 21:44
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| Gearheadotaku | Re: L98 running cold with 195 stat | ||
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Corvette Central is out, MAD doesn't carry it, so Ecklers it is...
Should have it together this weekend. (now watch as it pours down rain...) |
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Posted on: 2008/7/16 17:30
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In the servitude of my fiberglass Mistress |
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| Gearheadotaku | Re: L98 running cold with 195 stat | ||
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Ok, so after a month of distractions, I drove the Vette all wekend without incident. Temps are slow, but get to 170-180 on the hiway and 200 in traffic without the a/c.
seems to be fixed! thanks for the help. |
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Posted on: 2008/8/4 20:28
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In the servitude of my fiberglass Mistress |
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