Surging?
 

What causes surging at idle? My car has a D.S.S. 331 with AFR 185's and an X-303. Timing is set at about 14 and fuel pressure is at 39. Thanks for any help!

most common factor =) speed density

most common cause for surging in a efi car is a vaccum leak or with a x cam it could be just too much cam and not enough of a vaccum signal granted these symptoms are generally found at idle but could spill over into off idle speeds if too sevre

Hi everyone, I have a question about my mustang. I figure it might fit in this thread rather than starting a new thread.

My 1988 Ford Mustang 5.0 recently has started bogging when I start up the car. The idle goes up and down and will die unless I keep giving it gas. This is happening before I even put the car in drive. Once in drive it will idle up and down and almost die until I drive it around for maybe 5 -10 minutes.. then its fine, no problems at all. This happens when the car is sitting at a light or sitting in park. If I drive the car around.. park for like 10 minutes or so, then start it up again and drive, it seems fine. It seems to happen only if the car is sitting for a few hours or so. After I drive it for a few minutes after starting it is fine. Even at stops it idles perfectly. Just happens when I first start the car after awhile.

I hope any of this made sense and someone can give me thier input!

:D

The car seems fine at times and then all of a sudden it will start surging. It will surge for a few minutes like its trying to find a place to idle and then it will smooth out for a minute or two and then go back to surging? It was also doing this before this motor change. Thanks for the help!

mine dose the same...start it and its fine...then ill pull up to a stop sign and it will just start surging almost die..surge more then eventually die..unless i give it gas and hold it..but once i do that for awhile and let off it will idle..dont know what it is...when im driving it, it seems fine but sometimes the check engine light flashes on and off....

one thing to check is the IAC(idle air controler) on the front of the TB...dont know exactly how to check it...but..could try mabe cleaning it or just replacing it

Does anyone know the answer to this one? Idle Control Valve maybe?

Should I start a new thread? :(

Well Sicy, If your familiar with working on your own car I would first try this. Take the black plastic/rubber air intake tube off. Start the car up and take a bottle of carb cleaner and spray into the intake. You will have to manually rev the engine up to keep it from stalling. There is a spring mechanism on the side of the throttle body that moves. This is what you will want to push on to rev it up. Spray the throttle body really good. You will probably notice a lot of black exhaust while doing this. Sometimes this is all it takes to fix idle problems. If it keeps doing it then you may need to take the Idle Air Bypass off and clean it. That is the long cylinder shaped piece that bolts to the side of your throttle body. Take it off and clean that with carb cleaner also. You may need to let it sit for a while. After cleaning that place it back on. Unhooking the battery for 10 minutes while doign this might be a good thing. That way you reset the computer. If it keeps up then I would check for codes. It could be a number of things after that. Hope this helps

Wow.. :o Kinda scared to do all that by myself but I really appreciate your advice!

Forgive me if this is a dumb question.. but if the intake just needed to be cleaned.. wouldnt it cause odd idleing at all times, and not just the first 5 minutes I start the car? :confused:

You are right.. It probably would be a problem all the time. I just suggested it because its a free fix. Do you get a check engine light? If you dont you can still have codes. The only time the light comes on is when its not meeting emissions. But like I said, it could be a number of things. Things like, coolant temp sensor, or even an air temp sensor. I would suggest checking for codes.

The check engine light is not coming on. And the strange thing is (I dont think this would have anything to do with it.. ) I had disconnected the battery the night before to install a new brake light switch, and the next morning is when the weird idleing started.

In any case.. I'm going to have to get a diagnostics check because I dont know how to check the codes myself. Yeah I'm just a dumb girl :p ;) I actually used to change my oil and replace minor things myself but anything else I get paranoid and rather have someone else do it. :o

Well you could pay someone $45 to check codes for you. It isnt that hard to check codes for yourself. You can buy a code reader for around $20 or so and you will always have it in the future to use. Once you learn how to do it its easy. Just so you know :)

Oh cool.. I didnt know they were so cheap. Then why do they charge so much for diagnostics? :mad:

Thanks for your advice.. I should invest in one :cool:

what type of computer do you have in it and what other mods are done? there are many differnt ways to check with the problems just a little more info is needed.

Something to think about: if the engine has a lot of miles on it, the problem could be caused by the build up of carbon on the back of the intake valves. When started up the carbon "absorbs" some of the fuel and thus the engine goes lean untill the carbon is saturated with fuel. Once the engine is hot and then is allowed to sit for some time the fuel will evaporate off of the carbon and the process starts all over again. Sounds strange but it does happen. And it may not be the case here, but it is a possibility.

my 90 did the same thing...remove and clean your throtle body real good that fixed mine up...no more surges

I know this sounds crazy but it works. Get your engine good and hot, and remove a vacuum line going to your intake. Take the line and slowly stick it in some break fluid. Rev the engine so it doesnt stall and do this repeatedly. Let the engine sit for around 10 minutes off. Start it up and go drive it. Brake fluid works great for removing a lot of carbon deposits inside the intake, etc. I read this off a web site on Mustangs and tried it myself.

My car has 130,000 miles on it. I'm not sure what kind of computer it has.. ? It's an LX 5.0 '88. The only modifications I've made to it is putting after market headers and exhaust (h-pipe).

I wish I could clean my throttle body myself. I'm sure its not that difficult, but I'm the type of person that feels much better having mechanic do it. :o I will mention this to them when I bring the car in. I found some guys that know Fords.

I did change my oil pressure sending unit by myself once *applaud* :D

Wow LOL.. that sounds eh... interesting! :D