98 Bonnie shuts off while driving. sometimes. PLEASE HELP.

[chevrolet.power.420]

okay. here we go. 98 bonneville SLE. i bought a week or so ago from a friend who knows very little of cars. he describes some small issues but nothing too crazy.
anyway, here is the issues. the car starts pretty good most, if not all of the time. at random intervals it will just drop to 0 RPM and beep at me some and die. now this can happen as soon as i back out of my driveway, or an hour into driving. literally no rhyme or reason to it. generally i am on the brakes at the time of the stall. if i put the car in neutral i can coast and start the car back up, at this point it will die after a second or two unless i keep my foot into the gas.

now what i have done to try to fix the issue. most of my attempts to fix it have come from posts on here but nothing so far seems to work long term. most diving i have gotten with no stall so far was 45 min to an hour.

i replaced the MAF sensor. bought one from a well known salvage yard and cleaned with maf sensor cleaner before installing .
i replaced the starter. because one time when it died it wouldnt start back up and i burnt up the starter trying. nostart due to ground buss
i cleaned and slightly modified the ground buss under in the cabin. driver side. and checked the pass. for moisture
i have looked over fuse panels and such. noting that i could tell all fuses looked in tact
i have visually inspected the grounds under the hood, whatever ones i did find. they looked good, but rusty nuts.
i have looked over vacuum lines, fuel lines, hoses. cant see any leaks. dont smell any fuel.
i have checked engine oil and transmission fluid levels. oil level might be a little overt what it should, but not a drastic amount. trans looks to be fine.
i have checked my check engine light with a cheaper code reader. throwing code P0102, which is for mass or volume air flow A circuit low
i have cleared this code many times with said cheap code reader. light goes away. then comes back on, but this too is random. 30 seconds to an hour. this light comes on everytime the car is about to stall, but the car doesnt stall every time the light is on.
i have driven around with the code reader plugged in and checked and cleared the light every time it comes on. always the same code
i used a fuel system cleaner, small silver bottle that i mixed in with a full tank of gas.
i have checked the positive and negative wires at the MAF. both read as should. chevked with a carquest digital multi tester (model. cpe30425) on the DCV 20 setting, like i read to do.
i have checked the cables at the battery, both, well all 3, are in good shape. scraped minor corrosion from them. no change.
i have disconnected my amp and subwoofer. no change.
i have looked over the motor and such to the best of my mechanical knowledge. which honestly isnt much. but i do my own work, so i learn what i need to know when i need to know it. so i have a pretty decent amount of it figured out.
spark plug wires seem in good shape. havent pulled them from the plugs though.
im sure there are a few other things that i may have forgotten to mention. as you can see i have done a lot.

symptoms- related and non related just in case its something im missing.

stalling (sometimes)
rough idle (sometimes)
alternator hums, not sure how else to describe it.
rough restart after stall
stalling immediately after restart, 80% of the time.
possible odd smell, i say this cause i only smelled it one time outside, after it stalled 4 times in a row sitting in the drive.
when first started generally the rpms arent at an approiate level whether they are too low or high, they bounce form one to the other like its trying to save it but almost fails then overshoots it so drops back off, does this for the first 30 seconds of running then usually stabilizes at a normal level, until stall occurs
there is a crack in the rubber piece between the throttle body and the airbox, before the air gets to the MAF. i dont believe this is the clupret, because i believe i accidently did this when i wasnt nice about pulling it off the TB so i could inspect the inside of TB
power steering loss at time of stall
heat doesnt blow some of the time. doesnt seem to be at all timed with the stalling or CEL or any of that. i acutally got it to work one time by moving a hose or something that runs with what i believe to be a fuel line ( i could be very far off with this one) into the firewall.


i have read multiple threads on here, and have some ideas of my own as to my problem. many people with very similar symptoms, and have replaced a lot of parts one by one with no luck at all. i cant nearly afford to take it in a shop. and the auo parts stores around here all just have basic code readers like the one i have been using. i have no access to fancy scopes, or scanners. i have a digital multi tester, model number mentioned in above. i have a buddy with decent mechanical knowledge, and tools. i need to get this figured out as cheap as possible, but i want the solution even if it isnt cheap.

i dont believe it to be the crankshaft position sensor. because most with this problem deal with a no-start condition, which i do not get. the one time i got the no-start was due to the ground buss i repaired. im sure of this because before i repaired the buss i ran the car for a minute and grabbed it to see if it was getting hot. really hot. what happened was the fuel pump, one of many grounds on this bus, wasnt working and causing my no-start. hasnt happened since.

i believe it could be a faulty junkyard MAF. but i have noticed that many people with this problem dont generally deal with stalling so much as inconsistent RPMs and rough idle. i know replacing with junkyard parts is always a gamble. the tag on it said tested. but you really never know. it has a 90day on it, so if this is the problem or a high possibility i could take it back and gamble it on another one. dont believe they do refunds, and i only paid $30, new they are $100 and i dont have that kind of money right away. hence the junkyard gamble.

i have read posts with similar symptoms and have tried a lot, and have a few things i am going to try. such as disconnecting the battery overnight because the computer may have made adjustments to try to make up for the previously failing MAF, and i read that by disconnecting power over night can fully reset the computer, and take it back to some kind of factory settings or something along those lines. also i plan to check better for vacuum leaks using the spray bottle and water trick. i need to find out what is all grounded to the buss i repaired to see if something still isnt right there. but i have not tucked the buss back under the carpet and i check it a lot for heat. none. i also wiggle the wires and mess with it when the car is idling fine with no CEL on, and it doesnt do anything from what i can tell. i also will test the alternator and batt with my multi tester per instructions found online. i also plan to test the wires at the TPS and IAC, possibly pull the IAC to check for buildup. maybe pull apart the whole airbox and inspect for any issues.

as you can see i have done my research. i have reed countless posts on here, the problem is most people dont get enough responses or those who do, never came back to say whether it was fixed, or they gave up on this forum, or anything. so i made my own post. i am open to any ideas. but am on a strict (by that i mean non existent) budget. i have a limited supply of tools personally but can use some from a couple people. if i have done any previous testing and may have done it wrong, let me know. if i have been wrong about anything, let me know. im going off of forums, youtube, and some backyard mechanics.

im pretty determined and desperate to get this issue resolved. personally i love the car itself. has 175k, interior and paint arent really tore up, drives pretty awesome when its not stalling every half a block. hopefully someone can help me out. maybe im missing something. maybe you know vacuum lines known to fail, or that specifically could result in my symptoms. i will check back regularly and answer any questions that could help figure it out to the best of my ability.

sorry for the long read, but from reading all the other posts i figured id put as much info as i could think of and maybe that would help. will also make sure to post if my problem has been resolved, and reveal the troll causing all this ruckus

thanks for your time
Shane

[michtom]

As you mentioned check for any vacuum leaks at egr, intake, throttle body etc... Check pcv valve is working correctly and air cleaner for restrictions.

[J Wikoff]

I feel like it's either vacuum leak or fuel pressure related.

A can of throttle body cleaner, spraying around gasketed joints, vacuum lines, etc at idle will help point out vacuum leaks. You can also listen for hissing. Some is normal, some isn't, so if you hear some, try your best to locate it with spray or visually, but don't go too nuts if you can't pinpoint it.

I'd be checking every vacuum line for cracks and for deteriorated rubber boots on the ends.

Test the fuel pressure. A lot of places will loan you a fuel pressure tester for a refundable deposit. Test it at idle with and without the vacuum line on the fuel pressure regulator (FPR), then turn the car off and see if the pressure holds or drops and how quickly. Also check the vacuum line at the FPR for any fuel leaking into it. It could be liquid or just fumes. Pull the line off right after running and feel/sniff it. Then after running the engine again, turn the car off and check it again maybe 20 minutes later.

[chevrolet.power.420]

Will try thoseand get back with yall thanks.

[chevrolet.power.420]

okay, it was somewhat nice out today. so i did some testing.. first thing i did was reconnect the battery, because like i said i was trying to force the computer to fully restart by leaving it unhooked over night. fired up great which is usual. i let it sit and idle for a good 45 min, rand fine he whole time. took it for a spin around town. was fine. took it to the next town over (about 10 min drive) to go to autozone. ran rine. had my battery tested as well as alternator there. he said my alt is good my bat is good except for CCA. drove home and around my town some more with no problems. no CEL no stalling no rough idle. a small ammount of hesitation mut nothing too crazy or comstant. then i let it idle in the drive for another 45 min or so. ran fine. until i messed with the plug going to the MAF. i instantly heard a small difference in idle, and low and behold the CEL lit up. code p0102, same as always. so i messed with the plug again, cleared the code and it ran good again for a while. then went to walmart, by the autozone i was previously at for some shopping. ran fine there. but once i parked and sat for a min, cel lit up again. i got out, tapped on the MAF with my lighter, only thing i had ready. cleared the light and was good for half the paring lot. then it lit up again and stalled. i had to doublefooot it home keeping the rpm high enough not to stall until the 4th or 5th time i cleared the light. ran good the rest of the way home. went to mcdonalds and stalled a handful of times. clearing the light repetedly. only for it to return within seconds. what the hell? if it was MAF how did it run so good for so long? is this common at all?!

[chevrolet.power.420]

also tried checking vacuum lines with a spraybottle and water, the only one showing rot or looking like a leak is the one that goes into the fiewall right by the passenger strut, im guessing something to do with the heater or something. its all rotted out. when i disconnected it the car seemed to idle a little higher. but nothing crazy

[CMNTMXR57]

No, it's common. It's part of the diagnostic aid section of testing when P0101 is present;

From GM;

Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection.

Damaged harness.
- Inspect the wiring harness for damage. If the harness appears to be OK, observe the scan tool while moving connectors and wiring harnesses related to the MAF sensor. A change in the display will indicate the location of the malfunction.

Since you replaced the MAF, I doubt it's the spade terminals inside the MAF. My guess is that it's in the weatherpack connector. Fix that and you'll be fine.

[chevrolet.power.420]

i looked over it to the best of my knowledge, didnt look to be bad in any way, i did get the MAF from a scrap yard. so im thinking it could be faulty. i just feel like if it was faulty it would be more regular.. i dont have access to a scan tool yet, but i think my buddy is bringing one saturday. the replacement MAF is under a 90day from the salvage yard, so im going to take in and exchange it for a different one tomorrow. hopefully that one will be good. will a faulty one work for hours before messing up, then mess up constantly? or is it more than likely a wiring issue? the connecter looks to be okay and the wire harness seems to be good..

[CMNTMXR57]

The car stalled like this before you replaced the MAF. The car then stalled like this with the newer MAF. Then you jiggled the connector to the MAF and you got it to stumble/stall and generate a DTC. Troubleshooting 101 tells me that it's most likely NOT the MAF then. It's the connectors INSIDE the plug, Are they loose, damaged, is the wire into the terminals damaged? While I am not 100% ruling it out, to me replacing the MAF with another isn't fixing the issue. It's in the plug, especially if it stumbles/stalls when jiggling it.

There isn't always Rhyme/reason for intermittent electrical/electronic problems.

[chevrolet.power.420]

i looked in the connector. they dont look bad, they dont look loose. the wires dont look bad going to the connector. there really isnt a sure-fire way to tell without a fancy computer i guess is there? other that testing when it is failing, which is hard to do being its usually while driving.

[CMNTMXR57]

There are three wires in the harness going to the MAF

1) Power (usually pink or the letter C)
2) Ground (either black or black/white or the letter B)
3) MAF sensor signal (yellow? or the letter A)

Connecting a DMM to the MAF sensor signal (A) and then a good chassis ground, with the ignition on, you should get 5 volts. If not, there is a problem.

Otherwise, connect the DMM, ground lead to the ground circuit (B) of the MAF harness. And the other lead to the power circuit (C) of the MAF harness.

- If you get the 5v or the light gos on, this tells you right away that the connector/terminals or something in the connector is bad or not properly connecting.

- If you don't get the 5v or the test light doesn't come on, now connect the DMM/test light, one end to the power circuit (C) of the in the harness, the other end to a chassis ground. If you now get the 5v or the light comes on... Repair the ground circuit (B) in the harness to the MAF. If it doesn't light, then it's something in the power side (C) of the harness to the MAF

[chevrolet.power.420]

okay, thank you for the advice. tomorrow i will look into it, granted the snow storm we have planned doesnt hit. if snow comes ill look into it after it gets decent again. im really hoping to get it fixed. im looking to get a cord and program to use my pc as a scan tool. would one of these programs allow me to see all the info i would need, like sensor information and such? Any recommendations on that topic?? cheaper the better, but has to be what im looking for.

[chevrolet.power.420]

http://www.amazon.com/gp/aw/d/B00H9S71L ... ref=plSrch

Would this be a worthwhile investment? It says shows real time senser information.

[CMNTMXR57]

Unfortunately, since I have a Tech2, I have not paid much attention to the aftermarket options. I know a lot of people run stuff like this though on their smartphone.

The only issue is, this stuff is purely read only. It doesn't have bi-lateral controls (I.E. being able to command stuff and run system diagnostics), like a genuine diagnostic tool.

[chevrolet.power.420]

Signal wire only gave out a little over 2v. Positive and ground connected gave around 14v. What does this mean???

[chevrolet.power.420]

does this mean it is the sensor or wiring..?

[michtom]

Possible over sized terminal in one of the three terminals of the sensor connector. Disconnect sensor connector and look at the three terminals, closely comparing them to see if any of the contact areas look to be more spread out then the others. If so you can either go to scrap yard and cut one off and splice it to yours or use a small pick and try to bend the terminal so that contact area is tighter.

[SSEBonne4evr]

Possible over sized terminal in one of the three terminals of the sensor connector. Disconnect sensor connector and look at the three terminals, closely comparing them to see if any of the contact areas look to be more spread out then the others. If so you can either go to scrap yard and cut one off and splice it to yours or use a small pick and try to bend the terminal so that contact area is tighter.

^^This^^ Either a bad terminal, or wire. You sometimes can get behind the term prong
with a tiny screwdriver and tighten it up.
If that doesn't work, do the junk yard option. The fact that you messed with the wires and
got a code, means a good possibility a wire went bad.

[chevrolet.power.420]

i will try this tomorrow. found out today i can keep it from stalling by keeping my foot on the gas a bit when slowing down and such. not a fix, but keeps me on the road for now. would love to solve the problem altogether

[CMNTMXR57]

Guys, I said this 3x already;

No, it's common. It's part of the diagnostic aid section of testing when P0101 is present;

From GM;
Quote:
Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection.

Damaged harness.
- Inspect the wiring harness for damage. If the harness appears to be OK, observe the scan tool while moving connectors and wiring harnesses related to the MAF sensor. A change in the display will indicate the location of the malfunction.


Since you replaced the MAF, I doubt it's the spade terminals inside the MAF. My guess is that it's in the weatherpack connector. Fix that and you'll be fine.

Troubleshooting 101 tells me that it's most likely NOT the MAF then. It's the connectors INSIDE the plug, Are they loose, damaged, is the wire into the terminals damaged?

There are three wires in the harness going to the MAF

1) Power (usually pink or the letter C)
2) Ground (either black or black/white or the letter B)
3) MAF sensor signal (yellow? or the letter A)

Connecting a DMM to the MAF sensor signal (A) and then a good chassis ground, with the ignition on, you should get 5 volts. If not, there is a problem.

Otherwise, connect the DMM, ground lead to the ground circuit (B) of the MAF harness. And the other lead to the power circuit (C) of the MAF harness.

- If you get the 5v or the light gos on, this tells you right away that the connector/terminals or something in the connector is bad or not properly connecting.

- If you don't get the 5v or the test light doesn't come on, now connect the DMM/test light, one end to the power circuit (C) of the in the harness, the other end to a chassis ground. If you now get the 5v or the light comes on... Repair the ground circuit (B) in the harness to the MAF. If it doesn't light, then it's something in the power side (C) of the harness to the MAF