with the CTS, but the latter problem seems like it maybe an all together different problem. Maybe TPS related.
coolant temp. sensor
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Melting Slicks
Joined: Jun 2005
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From: Everyone needs something to believe in, I believe I'll have another beer. Wisconsin
coolant temp. sensor
Would a faulty coolant temp. sensor cause a driveability problem, (ie, engine stall on start and hesitation on takeoff, sometimes engine dies after stop sign or red light. Can't check for codes as ses light must be burned out. It's a 91 L98
Le Mans Master
Joined: Feb 2006
Posts: 8,753
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From: Louisiana
A faulty CTS can cause all sorts of drivability problems. Since you don't know if it is throwing a code, you can ohm it with an ohm meter. Disconnect the connector and touch the two terminals with the two meter leads. Report back with the engine temperature and how many ohms it showed. I'm not sure where the CTS is on a 91, but on my 86E it's on the front of the intake manifold. 
Last edited by RRT vette; Jul 28, 2006 at 08:47 PM.
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Joined: Sep 2000
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From: The Top of Utah
Hell yes! First replace that bulb. Without codes you could be barking up the wrong tree. Think of the ECT sensor as your choke stove, in a carbed car. If the choke isn't working, you are plagued by a lean mixture on a cold start up and no cold idle to keep it running while it warms up. Or stuck at the other extreme, it will run pig rich when it warms up and have way too fast an idle.
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Coolant temp sensor is one of the sensors the ECM uses to run the engine all the time, especially in open loop. If it goes nuts then anything can happen.
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Melting Slicks
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From: Everyone needs something to believe in, I believe I'll have another beer. Wisconsin
The vette is in the shop right now for a couple of other fix's. the shop called yesterday and wanted to change that sensor, i gave them the go ahead, 4 hours latter they call back and tell me they cant get the sensor out and it's approaching closeing time, so it'll be monday before i know anything. O yea, i did notice that when doing most any mph, lets just say 35-40mph and i took my foot off the gas pedal, the car would stay at that speed and not slow down, also when in D not OD, the upshift light wouldn't come on as it always did at around 50 or so.
Last edited by The Green Hornet; Jul 29, 2006 at 07:24 AM.
Instructor
Joined: May 2006
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From: Gautier MS
With out testing it, they are probably replacing something that already works. I would replace the SES light in the DIC for starters. If they didn't use a scan tool, they're just spitting in the wind. Which most mechanic shops do.
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Melting Slicks
Joined: Feb 2006
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From: backwoods upstate ny
i've had a bunch of CTS failures, and they often cause cold driveability problems like stalling...but even cars that are running ok, but have a few years ''experience'', often have a CTS that is not accurate and run better with a fresh CTS, so a new one won't hurt...BUT, check the new one with a VOM before you put it in, some of the new ones are ''marginal''
i'm a bit concerned that your shop needs more than 4 hours to change a CTS...most gm vehicles, tpi's included, are really ez to change (why?)--15 min to drain the coolant down, 5 min to change the CTS, 10 min to refill the cooling system....ok, maybe they couldn't get a new CTS.
bad news is that 35-40mph with no foot, sounds like an egr valve related prob.
i'm a bit concerned that your shop needs more than 4 hours to change a CTS...most gm vehicles, tpi's included, are really ez to change (why?)--15 min to drain the coolant down, 5 min to change the CTS, 10 min to refill the cooling system....ok, maybe they couldn't get a new CTS.
bad news is that 35-40mph with no foot, sounds like an egr valve related prob.
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Melting Slicks
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From: Everyone needs something to believe in, I believe I'll have another beer. Wisconsin
The reason they told me they couldn't get it out was because it wouldn't come loose, so they were going to use a penetrant on it to see if that helped, they don't want to snap it off and end up having to pull the intake. As for the speed problem, the car idles fine, it just likes to stay at whetever speed it's at when the foot is taken off the accelerator
Melting Slicks
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From: backwoods upstate ny
Originally Posted by steelblue shark
The reason they told me they couldn't get it out was because it wouldn't come loose, so they were going to use a penetrant on it to see if that helped, they don't want to snap it off and end up having to pull the intake. As for the speed problem, the car idles fine, it just likes to stay at whetever speed it's at when the foot is taken off the accelerator
if it idles ok, egr is ok...if you rev it standing still using the gas pedal or by reaching in and turning the throttle lever by hand, does the engine return to idle, normally ?
Last edited by redrose; Jul 29, 2006 at 07:27 PM.
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Melting Slicks
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From: Everyone needs something to believe in, I believe I'll have another beer. Wisconsin
if it idles ok, egr is ok...if you rev it standing still using the gas pedal or by reaching in and turning the throttle lever by hand, does the engine return to idle, normally ?[/QUOTE]
Yes, the idle returns to normal when the car isn't moving, originally, the oil pressure sensor and the vss, vehical speed sensor were leaking so i set up an appointment to have them changed but then the other problems popped up
Yes, the idle returns to normal when the car isn't moving, originally, the oil pressure sensor and the vss, vehical speed sensor were leaking so i set up an appointment to have them changed but then the other problems popped up
Melting Slicks
Joined: Feb 2006
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From: backwoods upstate ny
Originally Posted by steelblue shark
if it idles ok, egr is ok...if you rev it standing still using the gas pedal or by reaching in and turning the throttle lever by hand, does the engine return to idle, normally ?
[/QUOTE]ok, sounds like the throttle cable, linkage, throttlebody and return spring are not the problem...now i'd warm up the engine, unplug the IAC (expect mil to come on) and drive it with the IAC unplugged..it may stall when you slow down, but we're looking here to see if the 30+ mph thing goes away - isolate the cause.
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Melting Slicks
Joined: Jun 2005
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From: Everyone needs something to believe in, I believe I'll have another beer. Wisconsin
Got the vette back from the shop, seems the cts was causing most of the problems, the stalling and the driveability issues with the speed. they said there is also a fuel trim data issue at idle only, no problem under load,said may be caused by #7 injector, so i think i'll try some tecron or other fuel system cleaner in it and see what happens,other than that, she runs real good. Thanks everyone for your input
