1984 2.5L Duke (indy)

So the car has been running seemingly fine outside of the one in a blue moon no start. Still working on that one..

Ok on to the problem...
I recently drove it on the HWY 45 on way, then back. Only hit a few traffic lights. Car was fine. No codes.

Then the other day in the AM I had to take it out and about. Well it was running fine for the 25 minute drive. Then I had to pull over for a phone call and it had to sit and idle on the side of the road. Sat there 4-5 min and it started to surge and run rough then it tripped a code. I hurried off the phone and started to drive it again. The CEL went off then I got another call and pulled over. It idled a few minutes and then same thing ran rough and tripped a code. I then got back on the road the CEL went off. It stayed off for about 20 minutes. It had been run on the intestate and Hwy. I got near my Mom's and it started to run rough and threw the CEL again. This time I was smelling gas like crazy. I made my turn and got on it a bit the CEL went off. Then I slowed to pull in the driveway. The CEL came on again and the car nearly stalled out. The volts dropped to 10 and then it idled back up and the volts evened off at 13ish. It was running rough and stumbling with the CEL on though. Gas smeall was aweful from the exhaust. So I cut it off and smelled around. NOt gas smell, so I think that was isolated to the exhaust when it was running.

So the car sat overnight and till about 6PM. I got in it. Started it up and it was running rough still. The voltage was sitting on 15. I ran to the back and looked things over. All seemed well as I got it in gear and started ot drive the volts came back around 14. I pulled out of hte driveway and went to the stop sign. As i waited for traffic the CEL came on. My friend in the car behind me said it smelled like I had dumped a gas can over and the car was running horrible and stumbling. Traffic cleared & I got on it as I pulled out. The CEL went off and the car seemed to run fine the gas smell went away. Then I got to a traffic light. The same thing CEL came on and the car ran rough and smelled of gas. So I finally got it home. The only odd thing I noticed was that when the turn signals were on the cars volts would jump b/w 13 and 15. Hazards did not affect it. (may not have anthing to do with it???)

So I pull the codes... 33 and 45
I checked here

code 33: MAP Sensor
"The ECM will set code 33 when a problem with the MAP sensor is detected (unusual low vacuum/high pressure). Check the vacuum hoses from the MAP sensor. Check all connections and replace the MAP sensor if necessary. "

Code 45: Rich exhaust
"The ECM will set code 45 when the ECM detects a high voltage from the oxygen sensor, throttle is applied and the system is operating in Closed Loop (conditions must exist for longer than 50 seconds and engine must be running for at least 1 minute).

Check the oxygen sensor and replace if necessary.

Check fuel pressure. The system will go rich if the fuel pressure is too high.

Check for rich injectors.

Check for leaking injectors.

Check for fuel contamination (specifically for contamination with oil).

Check for proper ignition module shielding. If the ignition module is not properly shielded, the ECM might mistake the electro-magnetic interference for reference pulses, causing too much fuel to be delivered to the system.

Check the canister purge for fuel. If full, check canister control and hoses.

Check the MAP sensor. If the ECM detects a lower than normal vacuum then this will cause the system to go rich. Disconnect the MAP sensor. If the rich condition goes away, then a problem exists with the MAP sensor.

Check for leaking fuel pressure regulator by checking the vacuum line to the regulator for fuel.

Check TPS. An irregular TPS output will cause the system to go rich due to a false indication of accelerating. "


So I search...
I find a few things to try.
But they all say start with the lowest code first. A bad MAP can cuase the rich exhaust

Here are my results.
Please help me to determine if the MAP is bad...

1. Start car. it idles in the garage...
My fan is hotwired to run on all the time.
check battery volts 14.89 volts
Car sits & runs for 15 minutes at idle. No CEL...
Check battery 14.54 volts
1000 rpm
car is not running rich according to the nose and eye check...LOL

2. I decide its warmed up no sence waiting for the code...
So I unplug the electrical on the MAP
the car runs rough for a bit, CEL comes on.
Then it evens out at 1000-900rpm
Exhaust smells ok...
I wait a few minutes then the exhaust gets nasty rich

3. I plug the electical back in.
Car runs at 1500rpm
exhaust goes back to normal.
CEL goes off
14.48 volts
a few minutes later the car stablizes at 1000rpm again.

4. I pull the vacuum line and the car drops rpms bad and then just barely limps along. I did this a few times. Most of the time it would run, but towards the end it would just stall completely out.

Then I did some eletrical reads on the MAP sensor.
1. engine off with key turned to on
A & C = 5.01
A & B = 4.70
WOT = no voltage change
2. engine running
A & C = 5.01
A & B = .78
WOT = 2.3ish (way jumpy hard to read alone)

after all this I smell of gas so bad that my significant other coughs at the smell on me when we sit on the couch together to relax... LOL

So I did not see online what the volts should be for a 2.5l, just a 2.8. Are these within tolerance? From what I can tell the vacuum line is fine with no cracks. Is there a way to spray somehting on the line to tell for sure?

Just want to be sure before I go spend $50 for a new MAP...

Thank you!

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"I'm just a girl..."
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[This message has been edited by redraif (edited 06-22-2008).]

All GM map sensors (except for 2 bar on forced induction) will test the same.

Just tap the snesor line with a digital multimeter and see what the voltage is, key on engine off. Should be ~.5 IIRC. Then put a hose on it and suck on it, you should see the volts rise. If you've got a vaccum pump, put that on there, it should read ~4.5 volts as high as the vac pump goes, watch for a smooth transistion through the range as you slowly release the vaccum.

I could be backwards on those voltages, it might be 4.5v at atmisphere and .5 at vac.

Mainly I would check the vac lines to it first, make sure nothing poped loose. Other than that, the code could very well have been thrown just from it running rough and choking. The MAP code might only have set once, and the rich code was the one you saw all the other times.

quote Originally posted by 86GT3.4DOHC: All GM map sensors (except for 2 bar on forced induction) will test the same. Just tap the snesor line with a digital multimeter and see what the voltage is, key on engine off. Should be ~.5 IIRC. Then put a hose on it and suck on it, you should see the volts rise. If you've got a vaccum pump, put that on there, it should read ~4.5 volts as high as the vac pump goes, watch for a smooth transistion through the range as you slowly release the vaccum. I could be backwards on those voltages, it might be 4.5v at atmisphere and .5 at vac. Mainly I would check the vac lines to it first, make sure nothing poped loose. Other than that, the code could very well have been thrown just from it running rough and choking. The MAP code might only have set once, and the rich code was the one you saw all the other times.

I don't have a vacuum tester, but this is what I got when I used a mutlimeter...

from obove....
Then I did some eletrical reads on the MAP sensor.
1. engine off with key turned to on
A & C = 5.01
A & B = 4.70
WOT = no voltage change
2. engine running
A & C = 5.01
A & B = .78
WOT = 2.3ish (way jumpy hard to read alone)

those look ok from a electical stand point?

quote Originally posted by redraif: I don't have a vacuum tester, but this is what I got when I used a mutlimeter... from obove.... Then I did some eletrical reads on the MAP sensor. 1. engine off with key turned to on A & C = 5.01 A & B = 4.70 WOT = no voltage change 2. engine running A & C = 5.01 A & B = .78 WOT = 2.3ish (way jumpy hard to read alone) those look ok from a electical stand point?

Those readings can be interpreted as acceptable.

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87GT - 3800SC Series III engine, 3.4" Pulley, N* TB, LS1 MAF, Flotech Exhaust Autolite 104's Custom CAI 4T65eHD w. custom axles
87GT - 3.4L Turbocharged engine, modified TH125H
" I'M ON THE LOOSE WITHOUT THE JUICE "

Any thoughts as to what might be going on?

I disconnected the battery last night to get a fresh start and to see if any codes or odd behavior occurs today. I'm going over to Summit's cruise in about 30 minutes away.

To check vacuum lines you first clean them with a rag then roll them between your thumb and index finger, if your fingers get black on them then they need replaced.

The only vacuum line on my MAP is a plastic hard line. The rubber ends have not left any residue on me.

What is the best way to test the vac lines? I've heard people mention a vacuum testor, but I have never seen one. I assume its a simple thing I can get at the parts store... That being said what is the best way to use it to test the line. Does it use a T fitting to tap the line??? Just want to be sure i'm doing the test right.

Also I have heard of people using water and/or card cleaner to test the lines. What response do I look for in the car if there is a leak? Bogging or idling up???

Note: Also with initial testing the car has both ran poorly with the vacuum line off, but kept running. Then later it was completely stalling out when the Vacuum line was disconnected.

[This message has been edited by redraif (edited 06-24-2008).]

quote Originally posted by 86GT3.4DOHC: All GM map sensors (except for 2 bar on forced induction) will test the same. Just tap the snesor line with a digital multimeter and see what the voltage is, key on engine off. Should be ~.5 IIRC. Then put a hose on it and suck on it, you should see the volts rise. If you've got a vaccum pump, put that on there, it should read ~4.5 volts as high as the vac pump goes, watch for a smooth transistion through the range as you slowly release the vaccum. I could be backwards on those voltages, it might be 4.5v at atmisphere and .5 at vac. Mainly I would check the vac lines to it first, make sure nothing poped loose. Other than that, the code could very well have been thrown just from it running rough and choking. The MAP code might only have set once, and the rich code was the one you saw all the other times.

Will this test of the vacuum show if the sensor is working of if I have vacuum line issues? In other words if the sensor reads different with a vacuum tester attached to it then might I suspect my lines?

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So we did not take the fiero over to Summit. Did not want to risk a break down when the drivability concern does not have a clear culprit.

One thing to note with the electrical testing. The only one that was spot on all the time was the A&C reading (5.01). The other tended to jump around a bit and was harder to get a clear read. Not sure if this was me having issues with probing thru the wire coating or if there is an electrical gremlin... If it is a gremlin, is it the MAP or car.

So if the MAP sensor electical readings are within acceptable limits, does this then point to me having vacuum line issues? Would it only be the map vacuum line that I need to look at or could any of the vacuum lines on the engine cause the car to set a code 33?

[This message has been edited by redraif (edited 06-24-2008).]

The Vac tester just lets you run the sensor from vac to atmisphere slowly to make sure the sensor reads smooth.

If the vac lines arent cracked or off, they are fine, they dont go bad, just get brittle and break.

A is 5v signal from the ECM, C is ground. (it could be the other way around) so the reason you got a steady reading is because you're just reading the ECM output. B is the sensor wire, you want to measure B to ground (whichever that is) to see how many volts the ECM is getting from the sensor.

With the engine running, you will see a lot of variation because the vac is constantly changing.

So in measuring A & C adn A&B I might not have covered it all? Should I have Measured B&C?

dont know, all that matters is that you measure from sensor pin to ground. You should have .5v at idle and 4.5v with the engine off, or something close to that.