surging at idle

[dirtnap]

when I'm at a stop light, in drive, with the brakes on, it starts to surge, any ideas as to what would cause this?

 

[Four0Sport]

could possibly be a vaccum leak. check all the clamps on your intake tube, air filter box, etc.. feel for air around your intake (not an easy task), you may also want to clean your MAF. does your truck have an EGR system?

 

[Four0Sport]

i just looked and saw you are driving a 92, your vehicle shouldnt have an EGR system so that eliminates that. idle air control valve, air charge temp sensor, and MAF are a few things i would take a look at. there are tons of threads on how to check/clean MAFs and IACs. simply taking out the air charge temp sensor and cleaning it with electronic cleaner fixed a problem i had once. hope this helps.

 

[walterd140]

Mine does it because of a bad T-stat. When the engine gets hot it sticks closed, then pow! It opens & surges the idle.

 

[dirtnap]

I cleaned the MAF, no good, I forgot to mention, just before this problem started, I went to start the engine, heard a pop, and got the smell of sulphur, so I'm thinking I burned up some sort of sensor, but my check engine light isn't coming on, so I don't know.

 

[James909]

I cleaned the MAF, no good, I forgot to mention, just before this problem started, I went to start the engine, heard a pop, and got the smell of sulphur, so I'm thinking I burned up some sort of sensor, but my check engine light isn't coming on, so I don't know.

Could you explain this a little more? Were you cranking it when you heard this pop? Did you let go of the key a little early and the engine popped but didn't start? If this is what happened it sounds like the engine "coughed" back through the intake (for lack of a better term). This is not uncommon if you didn't crank it long enough when trying to start it. If so what probably happened is it blew the vacuum lines off of the vacuum tree. Therefore a vacuum leak, as Four0Sport mentioned may be causing the surging.

 

[dirtnap]

I was trying to crank it, it popped, but didn't crank, then started right upafter a second attempt, at a stop it idles fine for 20-30 seconds, then starts to surge. I've checked the vacuum lines, and the MAF, not sure what else to do but have my local mechanic hook it to a code reader, but since the check engine light hasn't made an appearance I doubt that would help.