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| Engine Hesitating on Acceleration, Stalling | |
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| Tweet Topic Started: Oct 5 2017, 01:29 PM (609 Views) | |
| VladTheImpala | Oct 5 2017, 01:29 PM Post #1 |
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Hey Guys, So my 91 Automatic has been having trouble starting in various situations, it's had random problems starting for a long time, but it would only happen like once a month so I never worried about it. Started happening more often recently, and it seemed to happen when we had a few really wet rainy days, so I thought maybe it's the distributor cap and rotor. It didn't happen very often and the car never actually let me down, so I didn't address the problem until it started to get worse. Funny thing is, lately it would have trouble starting about once a week, and it would eventually start after 20 minutes or a half hour of trying (taking short breaks and trying again), and it seemed to happen on the weekends when I didn't have anywhere important to be, when I actually have to be somewhere important it always starts right up, so the car hasn't actually "let me down" in a real life situation yet. Weird thing is, the car always starts fine when you first start it up in the morning, but then you drive it around for 20 minutes or a half hour, go into a store, and when you come out it won't start. It seems like the starting issue it's having lately only happens after you drive it for a bit. When you leave it in the garage overnight or for a few hours, it always starts right up. But once the engine warms up, if you turn it off, it seems to be a coin toss as to whether it will start again. Then a couple of weeks ago it started to hesitate on acceleration. It only happens from stop, or from a very low speed, like when you slow right down at a yield and then try to accelerate again. Once you press the gas pedal further down, it goes fine, but if you're trying to gently accelerate, it hesitates. This was going on for a couple of weeks, but it's so intermittent and happens so randomly that it's hard to figure out any pattern. The only pattern we noticed is that it never hesitates during the first few minutes of driving, only after it warms up. It also goes a day or two without hesitating once, but then it'll have a bad day where it hesitates all over the place. The other day it actually stalled when my girlfriend dropped me off and wouldn't start. After a few tries it started again, and drove perfectly with no hesitation for the rest of the drive. I have replaced the distributor cap and rotor, coil, and fuel filter, and for 40 or 50 miles it really seemed like that did the trick, but this morning it hesitated again multiple times in a row. Then, it drove fine the rest of the trip. The car has exactly 100k miles on it (163 km). I have not checked the timing belt, tps, fuel injectors, or anything like that yet. The car is not leaking oil, although it did look like my coolant levels might be dropping slightly, so I marked the level a few days ago just to keep an eye on it. Haven't looked at it again yet. I noticed that the thermostat I replaced last year had a slight leak on the bottom of where the thermostat housing is - probably the gasket I bought isn't perfect. It doesn't look bad, just a small amount of fluid snuck through the gasket and dried up, it looks like it's not leaking anymore and I don't think it would cause significant coolant level loss. Any idea what this could be? It seems to happen only when the car is warmed up? I suspect it might be an electrical issue. The old coil had a pretty rusty connector, which made me suspect that it was the coil. But I replaced it and it seems to be fine. Although the connectors that are attached the car did not look great. I cleaned them up with some sandpaper and wd-40 before reconnecting them onto the new coil. Maybe I should get the soldering iron out and actually solder on some better connectors. I have other minor electrical issues - the left headlight is still intermittent - I replaced the ballast, the grounding connector going from the ballast to the battery, but it's still intermittent. It might be a pigtail or something. Every time I think it's fixed it surprises me that it still doesn't work. I replaced the lightbulb, the ballast, soldered a clean ground connector onto it, but it's still intermittent. I suspect there might be a bad wire somewhere in the harness. Any other wires I should be checking? Maybe the connectors attached to the TPS? I have a compression tester but the shrader valve on it was defective right out of the box. A few months ago I did all the work of performing a compression test, with none of the results - the compression tester wouldn't hold the pressure at all. The needle would spike and immediately drop. I thought maybe the cylinders are THAT bad, so I tested all 3 of them, but it was the compression tester, it just kept dropping the pressure. I'll have to take a look at that shrader valve, and test the compression tester on my air compressor to make sure it works, then I can re-attempt the compression test. Edited by VladTheImpala, Oct 5 2017, 01:32 PM.
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| VladTheImpala | Oct 5 2017, 02:45 PM Post #2 |
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Another detail I forgot to mention is that the check engine light sometimes comes on briefly when it's hesitating or about to stall, but then turns off again. I have not read the codes, as I do not own an OBD scan tool. Looking at purchasing one soon. Edit: did some research and it looks like I don't need a scan tool to read OBD1 codes. I'll do the jumper wire method tonight and report back if any codes are showing. Edited by VladTheImpala, Oct 5 2017, 03:27 PM.
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| Metromightymouse | Oct 5 2017, 04:27 PM Post #3 |
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Powdercoat Wizard
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Good possibility it's the injector. Look down the throttle body when it won't start. Lots of gas pooled is bad and no cone of fuel spraying is bad. |
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| Moringa | Oct 5 2017, 05:26 PM Post #4 |
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Living BOT
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It does sound like a fuel issue, but it would be very helpful to read both the pending code(s), and hard faults. Some of the auto parts stores in this state, will read OBD2 codes for free. |
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| Metromightymouse | Oct 5 2017, 05:47 PM Post #5 |
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Powdercoat Wizard
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He has OBD1 |
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| Moringa | Oct 5 2017, 07:37 PM Post #6 |
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Living BOT
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OOPs |
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| MR1 Kingsbury | Oct 5 2017, 08:09 PM Post #7 |
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Exp. builder/rebuilder
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Should check the ground connections behind the throttle body too... they can act weird if a connection is beginning to fail... |
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| Crvett69 | Oct 5 2017, 08:20 PM Post #8 |
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You can plug a fuse Into empty fuse slot under the dash to get the fault codes |
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| Woodie | Oct 6 2017, 06:12 AM Post #9 |
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Won't start when hot is very often a fuel injector that doesn't close completely. When you turn it off, the pressure in the system pushes gas into the engine flooding it. Once all of that gas evaporates it will start again. Get the car good and hot and turn it off. Take off the top of the air cleaner and look down the throttle body with a flashlight. If it looks wet, then your injector is not shutting off. Need another, or to send yours out to be professionally cleaned. |
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| VladTheImpala | Oct 6 2017, 02:52 PM Post #10 |
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Thanks for all the awesome tips, guys! Unfortunately I did not have enough time last night to check for the OBD codes. But good news is that the car drove fine this morning without hesitations. I had changed the fuel filter Wednesday night, just two days ago, so when the car hesitated again the next morning, I assumed that the fuel filter was not the issue. Now I'm wondering if it takes a few miles for the fuel inside the fuel lines to get burned up. Maybe the hesitation yesterday was the result of dirty gas still in the fuel lines. Isn't there like a gallon of gas in the fuel lines? It would take quite a few miles to burn a gallon of gas in this car, so if the car hesitated again right away, maybe it's due to the dirty gas still in the fuel lines? Or maybe if the dirty gas gummed up the fuel injectors, the problem won't immediately go away as soon as I change the fuel filter (maybe it needs a while to clean itself and recover)? I don't want to celebrate quite yet, because in the past it has gone a day without hesitating and then the problem returned. But the fact that it drove fine this morning is promising. So I'll wait and see if it hesitates again over the next few days. But the idea that all of this might have been caused by dirty fuel kind of makes sense. I watched this Chris Fix video about how disgusting fuel filters get, and I was astonished at how gross the fuel coming out of a dirty fuel filter is. The fuel filter on my 91 automatic has never been changed in its 27 years and 100k miles. I did suspect the fuel injector myself (I really hope it's not, because fuel injectors are expensive), so last week I put in a half a bottle of Gumout fuel injector cleaner into the tank, but this was before I changed the fuel filter, so I don't how effective that Gumout could have been if it was passing through a disgusting fuel filter. I imagine the fuel injector cleaner is much more effective now that the care has a clean fuel filter, so I'll put the rest of the bottle in and hope for the best. Basically, I'm hoping that if the problem is the fuel injector, that it's due to it receiving such dirty fuel all this time, and that now that I have the fuel filter replaced, that the fuel injector can recover with the help of clean fuel and some fuel injector cleaner. The idea that it might be a bad ground somewhere is also on my short list, as the grounding on these cars is so weird. I was also reading the routine maintenance thread by Johnny Mullet and it recommends checking and cleaning all the grounds every few months, and this is something I have NEVER done. I have tried cleaning the ground terminal on the battery, but I've never cleaned any of the grounds attached to the chassis. Another car forum I was reading where someone was having a similar issue, one of the posters recommended checking for any electrical connectors or grounds that are close to the engine, which might start to behave weird once the engine gets hot. Something else to consider. Anyway, I really appreciate all the suggestions, and I will definitely keep trying to figure this out (although I'm hoping that it just doesn't hesitate again) |
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| freegeo | Oct 6 2017, 04:10 PM Post #11 |
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If your sprint is like the metro then the throttle body has a return line on it to send gas back to the tank. The gas gets circulated fairly fast. I would not think it would be a bad gas issue unless your whole tank was that way. |
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| VladTheImpala | Oct 6 2017, 04:20 PM Post #12 |
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Interesting, I did not know that about the throttle body sending gas back to the tank. Why does it do that, do you know? What I'm hoping is that is the issue is not a direct result of the bad gas, but that the bad gas caused something to get gummed up in the fuel lines or the fuel injection system, and now that the fuel filter is clean, it will work itself out. I'm just imagining and hoping that this is the case - I don't have anything concrete to go on. |
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| freegeo | Oct 6 2017, 06:26 PM Post #13 |
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That is just how it was designed. Fuel injection system uses a higher pressure than the older carb type setup. If the system didn't have a return line, the pump would constantly be pumping and the fuel would only be used as the injector opened. With the pump always running it would get hotter than normal and burn the pump up. With the return line in place the pump can constantly run and with the fuel flowing through it helps to cool the pump off.
Edited by freegeo, Oct 6 2017, 08:03 PM.
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| suzukitom | Oct 6 2017, 07:06 PM Post #14 |
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Tom
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Cooled fuel itself is a good thing.. carburetor equipped cars (in the olden days) used to vapor lock during hot weather conditions. |
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| ptcapboy | Oct 7 2017, 06:25 AM Post #15 |
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I remember for awhile I was getting vapor lock on my 95 only when the weather was very warm-I shut my motor off to wait at the drawbridge and 10 minutes later when it was time to go my car wouldn't start and I had to go onto the shoulder-luckilly I was on a hill-a few minutes later the car started-the problem went away the next time I replaced the head-bad valve(s) are the only thing I could think of- |
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