1991 GMC Jimmy GMC Jimmy HELP PLEASE!

COREY469

MEMBER
1991 GMC JIMMY
6 CYL
4WD
AUTOMATIC
100,000 MILES

Ok I have a 1991 GMC JIMMY with a 4.3 liter fuel injection and it is 4 wheel drive and I had a new motor put in. So now I have a 93' motor and my check engine light flickers on and off along with my parking brake light and sence it has been cold here it wont start but if I charge the battery or even jump it, it will run but it runs really rough and when I try to leave it idle my head lights dim and the they get brighter and then it eventually will stall out and quit. Also wheni put it in park and let it idle when its warm it runs at about 2000 rpms and then it goes down to about 500. Can u help me with my problem?

1 Reply

JOHN HUTCHINGS

MEMBER
2 POSTS

There is a little gizmo at the side of your throttle body called a throttle postion sensor and if your engine light is coming on and off then your ecm has some stored codes in it making this happen.
If you either purchase the little plastic box to get the codes to come up when you turn the key on or take it to a garage and get them to read what codes are stored on the computer- I bought mine at canadian tire store for about 30 bucks and its not fancy but it works.
Since in your case however, the jimmy is slowing down to normal idle after a few moments it may be a computer issue with your prom so personally if it were me I would take it to a garage where they have a decent mechanic who is well trained in gm diagnostics.
I had a cherokee once that started off at about 1500 rpm then slowed to about 1200 and it was that throttle pos sensor.
If it were staying at high idle would probably be sticking linkage or throttle cable.
I know the take it to the garage thing is not probably what you wanted to hear so I hope the rest of my explanation helps some