91 jimmys not running right

91s15jimmy · #1 06-04-2009, 01:21 PM

hello all. i have a 4.3 s15 jimmy. for about the past 4 or 5 months i have had an on going problem with my car randomly bogging down and just running rough. here is a list of all of the things that i have replaced. plugs, wires, cap and rotor, ignition coil, egr, removed cat, map sens, checked vacum lines, and i have recently had a new fuel pump sending unit and fuel filter put in. it no longer runs rough and i have all of the power that i used to have when i first bought it years ago but i still have the problem of it suddenly just lossing power untill i hit the gas and it is fine again. i currently dont have a full exaust from when i cut the cat off thinking that it might be plugged up so i put together a home made exaust with jb weld which of course didnt hold, do you think that this could be causing the problem? any respones would be greatly appreciated!

91s15jimmy · #2 06-04-2009, 11:38 PM

just some things that i forgot, its a 4.3 tbi with 202000mi. has a new ignition module and it only seems to bog down at low rpms and regains power when i accelerate like nothing ever happen. thats all that i can think of for now. thanks for the help all!

toddman67 · #3 06-05-2009, 06:58 AM

Take a look at the shower head pattern on the injectors. If they are not giving a clean pattern and showing signs of dripping or puddling, they will need to be cleaned or replaced. Another thing to look for is the TB base gasket and or the rest of the asm. gaskets. Make sure the IAC valve is not varnished and lastly a good cleaning of the entire TB might be the ticket.

91s15jimmy · #4 06-05-2009, 04:15 PM

thank you for the quick response. im going to double check the injectors but i have replaced one already when the whole problem started and and they seem to be spraying alright. i replaced the tbi unit about a year ago do you think that it could have gone bad already?

toddman67 · #5 06-05-2009, 04:50 PM

I doubt that it is bad already but it would'nt hurt to clean it all up. Carbon builds up over time and create these small issues.

91s15jimmy · #6 06-06-2009, 12:09 AM

will do, ill keep you all updated on the issue and we'll see what happens i guesse.

91s15jimmy · #7 06-07-2009, 11:57 PM

the tb and injectors are clean as a whistle and the problem persists. next is the exaust and then i dont really know where to go from there. i appresiate the advice and hope to have this thing running like the champ it is. i have plans to rebuilt the motor and possibly put a mild cam in it if i can find one that is.

91s15jimmy · #8 06-11-2009, 06:54 PM

so i went to the parts store today and got to talking to a guy that works there and told him about my situation and he told me to unhook my egr vacum line because the egr vaulve is opening premature. so, when i got home i did so and took it for a drive around the block and it seems to of resolved the problem. is there a way to fix this or is this just something that comes with alot of miles on the motor?

toddman67 · #9 06-11-2009, 07:34 PM

I,m not 100% sure but I believe that the EGR is controlled by an EGR vacuum solenoid which may be defective. To be sure you will need to test it with a vacuum gauge and see if it is working properly in the right range. It would'nt hurt to clean the EGR valve itself either.
I do not know the specs for the solenoid but I'm sure someone here could weigh in on this or perhaps a little web search may help. Of coarse there are manuals but I'm not sure if they would help.
If I get a chance I'll do some seaching later.

91s15jimmy · #10 06-11-2009, 09:00 PM

i have been considering replacing that little filter in that solenoid if they even sell them but for some reason i had never thought of just replacing the whole thing. iv replaced just about everthing else that has to do with vacuum and ignition including the egr itself. im kind of wondering if i could maybe clean it with some carb cleaner maybe but i dont want to mess it up because i know that it runs like crap if that little filter is out of the solenoid. again thanks for the responses it always to help make things make alittle more sence with outside input.

toddman67 · #11 06-11-2009, 09:54 PM

you could try and un-hook the elctrical portion of the solenoid and see if vacuum is passing through it. It should either have no vacuum or full vacuum. you might find one in a salvage yard or spend around $60 for a new one if it fails the test. It's likely that a code will be set off which can be cleared by removing the ECU fuse after the road test.
Just a thought.

91s15jimmy · #12 06-12-2009, 01:21 AM

i drove it tonight with the vacuum line off and it ran just like it should be! i think the idle may be off just a little but you can hardly notice it. i think i may hit it with some carb cleaner tomorow and hook it back up and see what happens. other wise ill just plug up the egr vacuum and just let it go.. thanks for the advice toddman

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