trottle body backfires and loseses pressure and cuts off on 1990 GMC Jimmy

my 1988 gmc jimmy backfires through the throttle body and looses pressure when driving , and cuts off. can anyone help me?

3 answers 3 comments
is the check engine light flashing ? if it is count the flashes write then down those are your codes then you can take it from there.
Had the same problem with my 1990. Check ur distributor cap and button.One or the other might be bad.
i just put a new cap, button, wires, plugs, fulfiller, EGR, and cat. what can it be
My 88 jimmy is currently in the shop now for the same thing. The exhaust valve seats were bad but that didn't fix it 100%... But there was some broken grounds... If u figure it out I would lik to know what it was
remoove valve covers.Cech valve hieght.If rocker to loose on exhaust when intake opens the cylinder pressure release through intake causing backfire through throttle body.Seen this many times Doug dkmazur@telus.net
Pull valve covers.Jimmy is good for broken rocker [real cheap to repair] push rod comes partially through causing exhaust valve to not vent. On intake when intake valve opens pressure releases through intake.Seen this often