i have an 88 std cab rngr it came stock with a 2.0 and now has a 2.3 carbed from 85.(i didn't do the swap). i went to schucks to pull some codes yesterday. but couldn't pull any. the code reader said that the vehicle wasn't responding. also my mtr revs up to 2.2k at idle, when i got the truck it idled at 1.5k. how do i adjust idle. how do i find out why puter doesn't respond. i have to make an 8 hr trip this weekend and need this truck . i did a full tune up to include the pcv valve. HELP me PLease even if just to say hi...........

 

no i know that someone out there has knowledge about this subject.

 

It has a carbureated engine? You're not going to get any codes unless it had an EFI system at one time. There was a small computer that controlled the feedback carbureator system, called the MCU (don't ask me what the acronym means, it has been a while. If an engine swap was done, I wouldn't be suprised if someone neglected to connect the self-test port, or cut the wiring. It is only capable of giving very basic codes if memory serves me right...essentially it says if it is working or not.

If the truck does have a carburetor, there is an idle control screw that is on the throttle kicker/dashpot (the solenoid mounted to the side of the carb; it raises idle speed when the A/C is on, and to help the car warm up faster in cold weather). There is probably also a stop screw on the body of the carb itself. Depending on the carb, the stop screw may or may not be the absolute idle speed adjustment. If unplugging the solenoid lowers the idle speed, then the circuit controlling it may just be shorted out. A simple fix is to leave the solenoid unplugged, and leave the idle speed set to 1000 rpm or so with the set screw. The dashpot (the diaghpram that keeps the throttle plate from simply slamming shut) should still work properly without the solenoid plugged in.

 

thank you very much i have been wondering about said puter system. it has an idel speed control bo on the right inner fender. what would happen if i get rid of that thing and the mess of wires that go with it??

 

Well, you can't really get rid of it. Look to see if there is an oxygen sensor in the exhaust somewhere. If there is, the computer controls the carburetor mixture via a mixture feedback motor mounted somewhere on the carb. Totally removing the computer will make the truck run poorly unless you swap out the carb for a full mechanical one with a vaccum actuated metering rod. If my memory serves me right, the MCU has no spark control at all.

However, unlike a fuel injection system, it isn't going to go ape if you disconnect the idle solenoid on the carb...it just won't be able to control idle speed. You should probably look to see if the solenoid has an adjustment screw first before totally disabling it.

Bart

 

i looked every where and didn't see an o2 sensor. which puzzles me. so last night i pulled the sys out and truck still runns ths same. just a note to anyone who wishes to do this is that the dist and choke are tied into the wires for the isc (idle speed control). the truck is carbed the original mtr was carbed so i don't have a real computer system. just a chessy wannabe. i have swaped out isc's and dist controllers to no avail. another issue i'm having is timing. i set the timing like your supposed to 10btc with vac line off and plugged, when i plug the line back on the timing jumps up to 30btc. i think i have too much vacum going to dist. am i right?? wish i had a vac guage. the timing marks on the cam shaft sits at the middle tit thingy (i saw a pic of this thing but can't remember where) when the timing jumos sto 30btc the cam mark rides the right tit thingy..

 

I agree that it sounds like the truck's engine control system has been modified which could be responsible for the lack of computer response and inability to pull codes. In any case, this Tech Article might help you get a better understanding of how things are supposed to work:

http://www.smpcorp.com/download/view/Tt4Q98.PDF

 

that still doesn't answer my timing question. why does the timing jump so much after hooking up vac line. i set the timing to 8 btc then i hook up the vac line and it jumps to 30 btc.