Idling Problem

Owens 40828

Active User
Oct 2, 2016
67
5
8
So have been having some idling trouble. Did a base idle reset. Nothing changed. Did a check of my TPS. it was good. Cleaned IAC. No change. Cleaned MAF. Helped alittle but not enough to really think it was a problem. Just maybe a dirty filter.
Nothing I do changes anything. It stays the same. So I licked my wounds and took it to a professional. At whites motor sports in Bristol Tn. About 2 hours away. They seamed very intelligent. Helped me a sight.
Now for my question. They told me my brake booster had no vacuum at all. The tech told me that he was 95 percent sure that, that was causing all my problems. The booster it's self is bad. Way to hard to push the brakes almost like manual brakes. So I will replace it aways this week. But my second question is... could no vacuum case all my idling issue. If I had checked everthing else.. thanks and sorry about the long post.
 
  • Sponsors (?)


Anytime you have an intake leak, yes your vehicle will run rough. But your comment could no vacuum cause rough idle. Not to be a wise ass, but you have to have vacuum to have a vacuum leak. I would also have your mechanic check your fuel pressure, and check fuel pressure regulator vacuum line, to see if theirs any fuel in it. A common failure could be the fuel pressure regulator. You commented she is smelling like gas and running rich. Have them check, if they haven't already. I'm also assuming the ran a Dtc test with a scanner. All shops do this, but again you never know. If you have a bad sensor, or electronics issue, it's nice to take care of it now. Keep us posted with results.


Sent from my iPhone using Tapatalk
 
I would assume if they are replacing the booster it's due to a leak. That in itself is a vac leak because the booster vac line had to be pulling something if the booster won't build vac.


Of course, we are also diagnosing based on info the shop provided the OP.


Sent from my iPhone using Tapatalk
 
you should hear a hissing sound. WHen you put your foot on the brake with the key off and then turn the car it should drop but still have resistance, The fact it feels like manual brakes means the booster is not holding vaucuum and either the diaphragm is leaking or the booster itself is rusted and leaking. The other thing to look at is the check valve on the booster. Make sure they are not trying to get you for a booster if its only check valve.

If iether is bad then that will cause an idling problem as it creates a vacuum leak.
 
Buddy of mine has a 5.0 explorer that was running like crap, he tried everything and then at the end of his rope checked the booster vacuum, turned out his booster was leaking and now that he replaced it ,runs perfect.
 
So have been having some idling trouble. Did a base idle reset. Nothing changed. Did a check of my TPS. it was good. Cleaned IAC. No change. Cleaned MAF. Helped alittle but not enough to really think it was a problem. Just maybe a dirty filter.
Nothing I do changes anything. It stays the same. So I licked my wounds and took it to a professional. At whites motor sports in Bristol Tn. About 2 hours away. They seamed very intelligent. Helped me a sight.
Now for my question. They told me my brake booster had no vacuum at all. The tech told me that he was 95 percent sure that, that was causing all my problems. The booster it's self is bad. Way to hard to push the brakes almost like manual brakes. So I will replace it aways this week. But my second question is... could no vacuum case all my idling issue. If I had checked everthing else.. thanks and sorry about the long post.
Please clarify, you said your booster had no vacuum at all? Was the vacuum line pulling vacuum? Yes check the check valve. Vacuum line sucks air, check valve only works one direction.
 
I am going to change the booster my self when it comes in. It should be here Monday evening. Now about that diaphragm. How would I check that. And what location.

To the best of my knowledge they didn't do a Dtc scan. He got in the car felt the brakes check the vaccum line and told me what to fix and why. Then he took it back put it on a lift. To find my oil leak. The weild on my pan was broke (canton) right where a bolt goes threw it.. Drips about 1 Oz a night. Not bad. It will have to take a back seat to this idling problem.
 
Not sure what you mean. Ok, easy check list,
Pull vacuum line at booster, with engine running you should feel/ hear air sucking, if not pull vacuum line from tree on fire wall, same thing, feel/hear air sucking, if not, find the vacuum line that feeds the tree. Same thing.
If you have vacuum at the line fitted to the booster, but you have a hard peddle, first unplug the vacuum line step on brake, it will feel like a manuel (non power) brakes, very hard to depress peddle, with light pressure on peddle have someone plug the vacuum hose back on booster, should feel the peddle move. If it does not feel any movement I'd change the booster. I think there is a check valve at the booster but they rarely go bad.
 
1476649158657.jpg
 
Sorry about the miss info. I am really new to this kind of thing. But I do know this car is heavy modded. Just had it about 1 month, it runs great at10 percent throttle and more. Just the 1st 10 percent is bad. To include idling
 
I don't know if I missed it in your posts, but what is your engine vacuum with motor at idle and guage hooked up. With a high performance cam, and other high performance parts, you'll always have lower vacuum than the 17-22 inches your supposed to have. That being said, you still need vacuum to make booster work. They make an electric vacuum pump, that will give your booster the proper 20 inches of vacuum it needs. That said why not plug up your hose going to booster, see if your motor smooths out. If it does, then maybe your booster is bad. Let us know what you find out.


Sent from my iPhone using Tapatalk
 
I don't know if I missed it in your posts, but what is your engine vacuum with motor at idle and guage hooked up. With a high performance cam, and other high performance parts, you'll always have lower vacuum than the 17-22 inches your supposed to have. That being said, you still need vacuum to make booster work. They make an electric vacuum pump, that will give your booster the proper 20 inches of vacuum it needs. That said why not plug up your hose going to booster, see if your motor smooths out. If it does, then maybe your booster is bad. Let us know what you find out.


Sent from my iPhone using Tapatalk




What do you mean booster
 
Your mc/ brake booster, sorry I'm old school. Grew up with manual brakes. That big round thing behind your master cylinder! I've driven cars and trucks with brakes that you had to think about stopping 1/2 block away. Thank god for disc/ abs brakes. I used to drive motorcycles with cable/ drum brakes. Seemed normal to us.


Sent from my iPhone using Tapatalk