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1992-1999 Series I L27 (1992-1994 SE,SLE, SSE) & Series II L36 (1995-1999 SE, SSE, SLE) and common problems for the Series I and II L67 (all supercharged models 92-99) Including Olds 88's, Olds LSS's and Buick Lesabres Please use General Chat for non-mechanical issues, and Performance and Brainstorming for improvements.

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Old 12-27-2007, 11:15 PM   #11
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Z,

A lot of info - thanks. I'll see what I can do. I do need some clarification though on some things. Thanks for hanging in with me.
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Are you sure that the MAP sensor was not damaged during all of this work and has a good vacuum source? (Good seal or vacuum hose)
Are you refering to the MAP sensor that is on top of the PCV valve? I can tell you that a little piece of the rubber seal is ripped off. It'* right on the end of the sensor though - were it touches the one end of the PCV valve. I actually wrapped a little teflon tape around it to insure it was making a tight seal. I don't see any vacuum lines going to it. Just a electrical connector. Am I looking at the right thing here?

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You should use a vacuum gage on one of the manifold vacuum ports to confirm the scan readings
I'll have to get a vacuum gauge. Can I use ANY vacuum line, like the evap lines?

Again, my software (Proscan 5.1) will not read the TPS voltage. I only have the intro level package. I can't read the IAC counts either. I'll work on getting those scanned somewhere and try to get that info for you. I have replaced the TPS...it'* brand new. I also have the old (orginal oem) one too. The last MAF sensor reading I got today was .505302 lbs/min. Don't know if that helps or not.

Thanks again.
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Old 12-27-2007, 11:52 PM   #12
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Quote:
Originally Posted by BMWhound
Are you refering to the MAP sensor that is on top of the PCV valve? I can tell you that a little piece of the rubber seal is ripped off. It'* right on the end of the sensor though - were it touches the one end of the PCV valve. I actually wrapped a little teflon tape around it to insure it was making a tight seal. I don't see any vacuum lines going to it. Just a electrical connector. Am I looking at the right thing here?
Yes, some GM models use the rubber seal and some models use a vacuum line. Very important not to have a leak here!

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I'll have to get a vacuum gauge. Can I use ANY vacuum line, like the evap lines?
Yes
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Again, my software (Proscan 5.1) will not read the TPS voltage. I only have the intro level package. I can't read the IAC counts either. I'll work on getting those scanned somewhere and try to get that info for you. I have replaced the TPS...it'* brand new. I also have the old (orginal oem) one too. The last MAF sensor reading I got today was .505302 lbs/min. Don't know if that helps or not.

Thanks again.
Have you disconnected the MAF sensor while it is idling to see if there is any change? The reading looks OK. You may not need the new TPS, get those readings first.
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Old 12-29-2007, 08:51 PM   #13
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Bought a vacuum gauge and hooked it inline with the FPR. Looks like a healthy 17.5 in hg (@1000 RPM) I asked about getting a scan that would tell me all the info your looking for and it looks like the only way I can get that done would be to let go of some cash. I'll look into that on monday.

On another note, I think the hard starting when it'* cold might be a bad coolant temp sensor. I tried to ohm it out, but I see 3 pins on the connector. It'* also hard to see/get to the pins on the sensor itself. Does anyone know which pins I need to ohm out ?

Pulling the connector on the MAF sensor would make it jump up a little to 1200 RPM for just a second, then it would go back to idling just like it was before I pulled the connector off. Replacing the connector would make it idle down a little bit 800 rpm for a second or less and then it would go right back to it'* normal idle of 1000 rpm. I would think that the MAF is sending info to the PCM right ?

Thanks again for your help.
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Old 12-29-2007, 09:45 PM   #14
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Quote:
Bought a vacuum gauge and hooked it inline with the FPR. Looks like a healthy 17.5 in hg (@1000 RPM) I asked about getting a scan that would tell me all the info your looking for and it looks like the only way I can get that done would be to let go of some cash. I'll look into that on monday.
Looks like your MAP sensor does not agree with actual manifold vacuum. Have this check again with a vehicle specific full function capable scanner, with bi-directional control.

Quote:
On another note, I think the hard starting when it'* cold might be a bad coolant temp sensor. I tried to ohm it out, but I see 3 pins on the connector. It'* also hard to see/get to the pins on the sensor itself. Does anyone know which pins I need to ohm out ?
The coolant temp sensor (CTS) does have an effect on cold starts, in fact it acts like a choke on the older cars. The sensor uses 5v reference voltage from the PCM on one wire and varies output voltage back to the PCM on the other wire based on coolant temp. (sensor resistance) The third connector is ground.

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Pulling the connector on the MAF sensor would make it jump up a little to 1200 RPM for just a second, then it would go back to idling just like it was before I pulled the connector off. Replacing the connector would make it idle down a little bit 800 rpm for a second or less and then it would go right back to it'* normal idle of 1000 rpm. I would think that the MAF is sending info to the PCM right ?
This is correct, you just eliminated the MAF as a potiental source of the problem!
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Old 12-29-2007, 10:40 PM   #15
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Z,

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Looks like your MAP sensor does not agree with actual manifold vacuum. Have this check again with a vehicle specific full function capable scanner, with bi-directional control.
Does this make you think that the MAP sensor is bad? Or is there something feeding it bad info therfore it is sending the PCM bad info? I guess the scan will tell huh

Thanks again for your help.
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Old 12-29-2007, 11:10 PM   #16
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IF you want to try some DIY testing of the MAP sensor, you can run jumper wires between its terminals and wiring harness per the service manual'* instructions. Turn the ignition to the ON position and take a voltage reading. Spec for this MAP is about 4.5-5.0 volts. With the engine running and warmed up, take another voltage reading. It should measure 1.5 to 2.1 volts with engine @ idle. In addition, the voltage should fluctuate when the engine is revved.

BTW, the PCM provides the MAP sensor with the 5v reference, and uses the sensor variable feedback to help calculate ignition timing @ fuel requirements.
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Old 12-30-2007, 01:18 AM   #17
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Quote:
Originally Posted by HotZ28
IF you want to try some DIY testing of the MAP sensor, you can run jumper wires between its terminals and wiring harness per the service manual'* instructions.
You wouldn't happen to have the pinouts for that connector do you? I actually have access to the AllData at work, but I don't go back to work till Wednesday.

thanks.
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Old 12-30-2007, 11:07 AM   #18
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The grey wire is 5v reference & light green is variable, black is ground.
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Old 12-30-2007, 11:41 AM   #19
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Z,

Thanks for the diagram. So with the ignition on (engine not running) I can put my DVM positive red lead to the grey wire and the black lead to chassis ground and I should have 4.5 - 5.0 vdc right? THis would tell me that the PCM is giving the sensor it'* 5.0 reference right? Then I want to start the car, let it warm up and check the light green wire for 1.5 - 2.1 vdc (red lead to light green wire and black lead to ground). This is the signal back to the PCM telling it what is sees as far as the vacuum right. If it'* out of range then the MAP sensor is bad. Is my thinking correct here? The grey wire should be 5 vdc all the time right?

Thanks again.
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Old 12-30-2007, 12:11 PM   #20
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I cut back a little of the insulation on the wire harness and checked the voltage. 5.03 vdc on the grey - thats good. Started the engine , let it warm up a bit and checked the light green wire to ground. .115 vdc. Not good. I'm thinking the MAP sensor is bad. I have a 2000 silverado and I think the MAP sensor is the same one. I think I'm going to pull it and put it in the Bonny and see what I get. The Bonny wasn't warmed up all the way but I don' tthink that would have made a diff. The output voltage did vary a little like from .115 - .124 when I goosed the accelerator a little.

Whadda think? Am I on the right track here?
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