Help! Don't know whats happening

[Rob Rangel]

I have a 1993 pickup with a 350 and until recently its been running great. Recently i have started to hear escaping air from the passenger side of the engine. Now suddenly the the truck idles really rough and at pretty low rpm, and when i rev the engine the rpm will jump about 700 rpm for a second and then go back down to the rpm it was supposed to be at (does that about every 10 seconds when reving the engine). Also when I slow down suddenly (such as getting off the freeway) the truck dies sometimes. I thought maybe i had dirty fuel injectors so I used fuel injector cleaner and it seemed to work for a week or two, but now the truck dies out again. My dad seems to think that the sound of escaping air from th epassenger side of the engine must be the problem, but we can't seem to find a leak in any hoses or anything. Has anyone had this problem, or know how to remedy the situation? Thanks for any help

[AKWE-gt]

kinda sounds like theres a vacuum hose disconnected or broken like the one going to the map sensor. had any codes flashing?

[localyokel]

Hi,get ya can o carb cleaner and spray any specific place it sounds like its sucking air from.(while motor is running)When the rpms increase you've found the source.Sometimes the gasket that goes around the tbi cracks.Its below the air cleaner housing...

[Rob Rangel]

Originally Posted by AKWE-gt

kinda sounds like theres a vacuum hose disconnected or broken like the one going to the map sensor. had any codes flashing?

where is that hose that you're talking about? and by codes flashing do you mean warnings by the gauges? if so then yeah the "service engine soon" light has been turning on and off for a while now and we couldnt identify what service it wanted

[Rob Rangel]

ive been looking for vaccum hose diagrams, but have been unsuccessful. Ive been told that there should be one under the hood, but mines not there, if anyone can get a pic of theirs, i would really appreciate it
thanks

[TaNK_Em]

I have a repair book that has the disgrams, Ill see if i can copy them tommorw and get them up here.

- Kevin

[AKWE-gt]

Originally Posted by Rob Rangel

ive been looking for vaccum hose diagrams, but have been unsuccessful. Ive been told that there should be one under the hood, but mines not there, if anyone can get a pic of theirs, i would really appreciate it
thanks

if you have a ses light on then there should be a code stored. if you don't know how to retrieve the codes then check this page out http://www.troublecodes.net/GM/ .
just remember when your retrieving codes that the first number to flash is a 12(three flashes) then the trouble code flashes after that. the 12 flashes to confirm that the ses light is working or something like that. this would make things a bit easier to know what to look for.

[J-Ri]

12 is 3 flashes, 1 then a pause then 2. I've always used a scan tool to get the codes, but I thought code 12 was only displayed if no other codes were present.

[AKWE-gt]

Originally Posted by J-Ri

12 is 3 flashes, 1 then a pause then 2. I've always used a scan tool to get the codes, but I thought code 12 was only displayed if no other codes were present.

no the 12 flashes first to confirm the system is working or just a greeting and then the trouble code flashes after. need a scan tool if its OBDII but not OBDI.

[J-Ri]

Well, ya never stop learning! I've always just used the scan tool even for OBDI, just because I have access to one. With multiple codes, it's a lot easier.

[mbumgua]

The 12 code flashes to indicate no distributer reference pulse; i.e. the engine is not running.