stevenjoseph82 Posted March 24, 2003 Report Posted March 24, 2003 Hey, this is my first post and I appreciate any responses to my inquiry here. I have an '89 Grand Prix SE, 3.1L, automatic. My problem is that after driving my car and it comes up to temperature, I have a no-start condition after it sits for about an hour. If the car sits for around 2 hours or longer, it fires right up. And even after the hour, the car will eventually fire up after about 10 to 15 minutes of trying. I just had the fuel pump replaced about 5000 miles ago, and at first I thought my problem was a fuel delivery problem. Even sometimes coming up to speed on the highway around 2000 to 3000 rpm it will just die or stumble really hard. I went to check the diagnostic jumpers and got a code 33, meaning a possible faulty manifold absolute pressure (MAP) sensor. So I took the sensor and had it checked and it read that it was ok. I checked the wires and the vacuum line running to the sensor and it is receiving power and vacuum. I hear no vacuum leaks elsewhere, so I'm lost here. Now I'm thinking maybe the ECM went bad. I thought I read on the forum here that the ECM doesn't do anything while the engine is cold, but as it comes up to temp, the ECM takes over. I don't wanna waste 45 bucks on a new MAP sensor or 90 on an ECM if it's not gonna fix my problem. So any help anyone can give me is greatly appreciated.......thx guys Quote
Robby1870 Posted March 24, 2003 Report Posted March 24, 2003 Well, it may be the ECM. The wire from the MAP to the ECM is intact correct? Well, this is puzzling. I would go to a junk yard and pull and ECM out of another car with a 3.1L and try it and see if your problem is fixed. If thats not it, pull a MAP out of a car in a junk yard and try it. How did they check your MAP?? I didnt know they could be checked. Anway, wait for more responses and keep us posted. Welcome to the site man, hope you enjoy it. Yeah, I dont think the ECM controls much of the MAP until its up to temp, cuz I broke the vacuum line on mine while changing plug wires and didnt know it, and it would run fine until it hit like 170 or 175* and then it would sputter out. Robby Quote
JS91Z34 Posted March 24, 2003 Report Posted March 24, 2003 It sounds like you have a vapor-lock problem. I would check for a restricted fuel return line Quote
paulo57509 Posted March 24, 2003 Report Posted March 24, 2003 I think Robby is on the right track here. I believe there is a way to check the MAP by probing the teminals with a DVM and watching for resistance changes as the vacuum line is disconnected...don't quote me on this. You'll need to check a shop manual. Vapor lock? Not with the kind of fuel pressure that port fuel injection operates at. If the fuel return line is restricted, the fuel pressure would increase, further eliminating vapor lock as a possibility. Quote
JS91Z34 Posted March 24, 2003 Report Posted March 24, 2003 I had a beretta 2.8 come in to work with a restricted fuel return line. I dealt with that thing for a week trying to figure out why the fuel pressure was so high. Every sensor got replaced on that car, no luck. Then the customer came in and told us what he did to the car before this condition happened. Basically the moral of the story is fuel pressure means nothing. If you have no where for the return fuel to go, you got problems. Then again I could be wrong too. I'm human like everyone else, we all make mistakes. Vapor lock can happen on any car! Quote
stevenjoseph82 Posted March 24, 2003 Author Report Posted March 24, 2003 I took it to autozone because they said they could check it. What they did was hook a vacuum pump up to the nipple on the sensor and they had a book that told them the right pressure....at least that's what I assume. They had some sort of a meter, either volt or ohm, and hooked that up to the female part of the plug on the map sensor. Then he got a read out on the meter and told me that a certain range of numbers said it was good and and if it fell out of those numbers it was bad. I'm sorry I don't have more details, sadly enough, the autozone guy was so fat I couldn't actually see around him to see what he was doing .......and for that vapor lock possibility..... I live in Indiana, and this problem has just showed itself since the temperature around here got up to 60-70 degrees. So I guess that could be a possibility too. I think I may just end up taking it somewhere and let them mess with it, unfortunately, since I hate letting other people work on my car ....anyways, thx guys for the help Quote
Speedwagon Posted March 25, 2003 Report Posted March 25, 2003 I'm having almost this exact same problem. It's an 89 Grand prix with a 2.8L engine. Code 33. Cars in so-so shape(just bought it). Could it be a vacuum leak causing this? On the top left side of the engine(just to the right of the intake manifold if looking from the front), there's a set of 4 vacuum hoses that go into a rubber piece on the engine. Looks like it's not in that great of shape. Might replacing this fix this condition? Quote
Robby1870 Posted March 25, 2003 Report Posted March 25, 2003 if your gettin a code 33, then you MAP is to blame, check the vacuum line coming from the MAP. I broke mine changing my back plug wires, had a hard time gettin it back together. Yeah check those four your are talking about and check the ones going into the TB, the MAP vacuum line leads there. Robby Quote
stevenjoseph82 Posted March 25, 2003 Author Report Posted March 25, 2003 Ok, now i'm gettin' mad at this thing......ever since I took the MAP sensor out to have it checked, the diagnostic check just keeps giving me straight "12's"........i guess this means that there's no problems found......oh, by the way, i just drove the thing and as i was merging from an on-ramp, i punched it and the car took off at first and then it just stumbled really, really hard. After that I had a problem almost anytime I hit the gas hard. I was wondering if the fuel return line is clogged, then is it possible that the fuel pump is dumping entirely too much gas into the motor, causing it to flood. I didn't know if this is possible or not, but I'd sure like to know......meanwhile, i'm saving up the money to fix the problem once i pinpoint it :? Quote
Robby1870 Posted March 25, 2003 Report Posted March 25, 2003 yeah it maybe the return line, cuz now that your MAP is working, thats all I could think it could be. Robby Quote
Speedwagon Posted March 25, 2003 Report Posted March 25, 2003 Do you know where the MAP on the 2.8 is? I think I saw it on the rear of the intake, but I'm not sure. The rubber piece that holds the 4 lines in, is pretty loose all around. Looks like the line that goes from what I think might be the MAP sensor to this rubber piece, just goes in and out easily. Quote
Robby1870 Posted March 25, 2003 Report Posted March 25, 2003 Do you know where the MAP on the 2.8 is? I think I saw it on the rear of the intake, but I'm not sure. The rubber piece that holds the 4 lines in, is pretty loose all around. Looks like the line that goes from what I think might be the MAP sensor to this rubber piece, just goes in and out easily. yeah the MAP is on the back of the upper intake, what you are calling the intake. Its in the middle of the back of the upper intake, its on a clip attached to the intake. It has a vacuum line coming out of, and one electrical connector attached to it. Yeah check that rubber peice that attaches the plastic vacuum line to the nipple on that MAP, that may be dry rotted and old. Hope this helps. keep me posted on your progress, if you cant get me on the forum, IM me or something Im always at the computer. Robby Quote
Speedwagon Posted March 30, 2003 Report Posted March 30, 2003 Ok.. so I went to my local Pontiac dealer, and they got me the vacuum lines. Apparently, it's a whole kit. So, I get this, and start working on it. One has to take off the upper intake manifold for this, and this resulted in breaking the gasket there. Picked up a new one, and finished the job. Now the car has a new upper intake manifold gasket set, and new vacuum lines. The code 33 is gone, and she's running MUCH better. Still some hesitation on occasion, but the stumbling, surging, stalling is all gone, as well as my SES light. Quote
Spcboyd1 Posted March 30, 2003 Report Posted March 30, 2003 How much did the vacuum line kit cost Quote
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