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| 88 Sierra starts then runs rough flat spots then cuts out ?? https://auszookers.com/forum/viewtopic.php?f=5&t=55937 |
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| Author: | Sierragirl86 [ Fri Jul 12, 2019 5:43 pm ] |
| Post subject: | 88 Sierra starts then runs rough flat spots then cuts out ?? |
Hey everybody If someone could help that would b appreciated I have replaced spark plugs leads dizzy cap fuel filter and checked timing all good there but car still wont run good I cleaned out the carby inspected all hoses and connections. The car was running fine 3 days ago but has now decided to pack it in... it was easy to start before but now it seems to struggle to start but when I does start it will idle ok and acceleration is not optimal as there is a noticeable flat spot and won’t rev up to its full extent... after a minute running it and trying to rev it up it will start to cough and splutter like as if it’s fuel starved and won’t maintain idle and eventually stall even after all the parts replaced. There’s fuel spark and does seem to idle fine once it starts but not for long and continues to cough splutter and cut out.... could anybody help if they could please I cleaned the carby and jets etc out I’m at a loss really!! |
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| Author: | HarryHoudini [ Sun Jul 14, 2019 10:42 am ] |
| Post subject: | Re: 88 Sierra starts then runs rough flat spots then cuts ou |
I would replace Carby(Ebay Toyota $80) if you have checked that the fuel line is flowing OK,filter not blocked etc. If you have spark then timing may be out,belt jumped a tooth. |
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| Author: | bumstein [ Mon Jul 15, 2019 6:27 pm ] |
| Post subject: | 88 Sierra starts then runs rough flat spots then cuts out ?? |
It’s a game of elimination. You have spark, but is it good strong spark? How have you tested it? Assuming your right and the spark is good, check your timing. As Houdini points out, make sure the timing belt is set properly. Google search will tell you how to do this or refer to the FSM. How old is the fuel? If it’s more than a few months then replace it. If you haven’t already, replace the fuel filter. If you have then visually check it for crud. Check the fuel lines, are there any breaking down? Any part of the fuel system leaking air might cause the issues. IS THERE A VACUUM LEAK? I type this in bold because it’s really important. A vac line that’s old and breaking down? Something that’s fallen off a vac port in the manifold? You can chase your tail for forever and a day only to find out that it’s sucking air somewhere. All those carby vac lines should be considered potential suspects until proven otherwise. Take the jets out and clean them if you haven’t already, I know you said you’d cleaned them but just make sure there’s not gunk blocking the jets. Does the fuel pump work? Google suggestions to check the fuel pump. If all that checks fine then yep, as Houdini points out, consider a Toyota 3k or 4K carby (or other carby if something else strikes your fancy). Edit: oh, I should have checked Sierragirls last log on. Seems she gave up all hope of an instant reply when nobody had fixed the problem after 41 minutes |
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| Author: | Sierragirl86 [ Sat Jul 20, 2019 7:50 pm ] |
| Post subject: | Re: 88 Sierra starts then runs rough flat spots then cuts ou |
Thanks everyone for your input so I decided to try an eBay special that was a dodge $178 fuel leaked out of everywhere even thru the gasket on the top housing WTF I torqued the top screws to maybe prevent the leaking but to no avail seems as though the fuel just floods the **** out of it and leak out everywhere so I decided to use the carby on my other zook I’m doing up that is going... put it all in and hey presto still idles like crap won’t accelerate idles for a minute then chugs coughs and stalls... checked all vacuum lines etc the only thing I haven’t done is to check the timing belt for a skipped tooth so will get a timing light on it tomoz Fuel pump seems to provide substantial flow but I wonder if it’s not maintaining pressure so will check that out Thanks again for the comments much appreciated |
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| Author: | Sierragirl86 [ Sat Jul 20, 2019 8:47 pm ] |
| Post subject: | Re: 88 Sierra starts then runs rough flat spots then cuts ou |
Thanks everyone for your input so I decided to try an eBay special that was a dodge $178 fuel leaked out of everywhere even thru the gasket on the top housing WTF I torqued the top screws to maybe prevent the leaking but to no avail seems as though the fuel just floods the **** out of it and leak out everywhere so I decided to use the carby on my other zook I’m doing up that is going... put it all in and hey presto still idles like crap won’t accelerate idles for a minute then chugs coughs and stalls... checked all vacuum lines etc the only thing I haven’t done is to check the timing belt for a skipped tooth so will get a timing light on it tomoz Fuel pump seems to provide substantial flow but I wonder if it’s not maintaining pressure so will check that out Thanks again for the comments much appreciated |
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| Author: | MrRocky [ Sun Jul 21, 2019 8:16 am ] |
| Post subject: | Re: 88 Sierra starts then runs rough flat spots then cuts ou |
Im guessing your sparkplugs resemble charcoal |
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| Author: | Sierragirl86 [ Sun Jul 21, 2019 10:34 am ] |
| Post subject: | Re: 88 Sierra starts then runs rough flat spots then cuts ou |
Hahaha most likely definitely cleaning those up again I am at a loss really to why it’s all of a sudden decided to stop running |
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| Author: | bumstein [ Sun Jul 21, 2019 11:06 am ] |
| Post subject: | 88 Sierra starts then runs rough flat spots then cuts out ?? |
Sierragirl86 wrote: the only thing I haven’t done is to check the timing belt for a skipped tooth so will get a timing light on it tomoz Looks like you’re narrowing down the problem! Good work. A timing light won’t tell you if there is a skipper tooth. It is a good step and will tell you if the dizzy is set to the right position thus making spark at the right time. To check the belt you’ll need to take the radiator out, remove the cover from the front of the motor and check the marks on the crank and cam timing pulleys. If you don’t know when the last time your timing belt was changed and you’re going to check the belt, just replace it. While you’re in there it’s easy to replace and cheap insurance so you know the timing belt is Mickey Mouse. I like to change the water pump too at this stage unless I know it’s new. Glad to see you back! It is sometimes disheartening when you spend time to reply to a question and the OP doesn’t come back. Sorry for the comment and bloody good to have you back here! MrRocky wrote: Im guessing your sparkplugs resemble charcoal I suspect your right |
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| Author: | Sierragirl86 [ Sun Jul 21, 2019 10:22 pm ] |
| Post subject: | Re: 88 Sierra starts then runs rough flat spots then cuts ou |
Yeah cheers bumstein thanks for the ideas yeah will take the cover off and check the timing marks inspect the good ol belt and check that the dizzy is in the absolute correct position.... today I tinkered a bit but after 3 carbs which 2 of them worked before just a week ago I’m thinking it has to be something else... do u think the fuel pump even though fuel is pumped out that it doesn’t maintain sufficient pressure and starving of fuel or ignition timing is just out or the coil is playing up ( it has spark tho but maybe just not enough... they r new plugs too spark seems good but I don’t really have anything to compare to but a mower haha ) slowly but surely I shall get to the bottom of it I guess... probs end up replacing everything in the end today I manage to get a whole 20 seconds to idle ( very rough tho ) then the coughing spluttering pop in the carb then kaput!! Then flatten the battery once again n back on charge after flattening my power pack :-/ oh and all good bout the comment |
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| Author: | bumstein [ Mon Jul 22, 2019 2:29 pm ] |
| Post subject: | Re: 88 Sierra starts then runs rough flat spots then cuts ou |
Sierragirl86 wrote: do u think the fuel pump even though fuel is pumped out that it doesn’t maintain sufficient pressure and starving of fuel It's possible, I'm not sure what you have done to check the fuel pump but if you're on top of it and sure its working well enough then move on. Sierragirl86 wrote: ignition timing is just out or the coil is playing up definately check the timing but you said you've already done that. What degress BTDC have you set it at and what fuel are you using,. 91, 95 or 98? I'm assuming that you have known fresh fuel in there. Something else while it pops to mind, yours is '88 so it might have a drain plug on the fuel tank or it might not. I like to drop the fuel out the tank and see whats in there, if you aren't convinced that the fuel is fresh then do this for sure and replace it with fresh fuel. As for the coil you can check it with a multimeter or just swap it out, you should be able to find a cheap or free one if you know a couple of people with parts laying around, or buy one. They aren't a huge cost and might be handy to have around, but a free one will do. Sierragirl86 wrote: it has spark tho but maybe just not enough... they r new plugs too spark seems good but I don’t really have anything to compare to but a mower haha ) Theres a few ways to go here, and yep if there is spark it might be a weak spark. Spark should look strong and usually be a blue or white, a weak spark will look yellow or red. I reiterate, check your spark plug gaps while they're out. you can be chasing your tail when its a simple case of plug gap. The way to test this is take the plug out, check the gap then pop it on a part of the motor that is well earthed and crank the motor over. Do that for all of the spark plugs, if one or two are giving weak spark then its likely that leads are your problem. If they all are giving weak spark then start thinking of the HT lead from coil to the dizzy, dizzy cap (although i think you said you've already changed it), rotor can be burnt, pitted or damaged. this might help https://www.youtube.com/watch?v=mUOmsGiirTU Sierragirl86 wrote: probs end up replacing everything in the end A systematic approach should negate the need to replace everything. hopefully Another thought that occurs to me, although by the description of your problem I dont think its likely to be this, is the switch that sits at the top of the clutch can sometimes cause problems. It usually presents as a good idle but cuts out as soon as you start feeding the clutch out. You can remove the two wires, bridge them together and it will fix the issue but I really dont think this is the case here. |
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| Author: | MrRocky [ Tue Jul 23, 2019 12:05 am ] |
| Post subject: | Re: 88 Sierra starts then runs rough flat spots then cuts ou |
Blocked charcoal cannister or breather lines coming out of the breather tank behind the cover inside the tub can also cause rough running. Backfire (pop) in the carb can indicate a timing issue. Maybe mark where the dizzy is at present, loosen the bolt and have a play with it to see of you can get a better result |
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| Author: | Sierragirl86 [ Tue Jul 23, 2019 8:35 pm ] |
| Post subject: | Re: 88 Sierra starts then runs rough flat spots then cuts ou |
Thanks guys much appreciated as usual will update further down the track You guys have been a big help !!! Talk soon |
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