My girlfriends brother has a 1988 Chevy truck, i want to say its a Silverado but i dont think they made those in 88 perhaps a C/K 1500? does that make any sense to anyone? I'm truck stupid but i got a little info from him about the truck.

From what he's told me, it has a chevy 350 motor, tranny is new within the last 3 years. everything in it when idrove it seemd ok, other than it is missing on one cylinder, maybe two. I didnt have anything to hook up to it to figure out which, but this is what it does.

it starts up perfectly. drops from cold start after a few moments and idles nicely. then i put it in drive and drove around for 15 miles till it warmed to regular driving temps, and parked, and the idle began to get rough. then i took it out again (not shutting it down when it started to run rough), and at speed (45mph) this is where i felt the miss, but it might besomething else i dunno about. The car would stutter at 45mph. When i got above that it drove a little better but if it went into over drive, it would do the same thing. if i kept it out it woudln't do it as bad cause as i could get the rpms and mph up a little more and then it was fine.

now im not very educated about the GM motors as i grew up on ford 5.0 motors...to me it feels very similar to what my mustang did when one of my injectors was sticking open.

I am going to pull the injectors but before i do i wanted to know if anyone could point me in other directions or could ask me questions to see if i can look at other possiblities.

any info at all or ideas are greatly appreciated. he's talking spending major cash on a new motor money he doesn't have so i wanna save him as much money as possible and atleast try to fix this before he drops major cash on a new motor from summit.
Thanks guys
Travis

 

Get a timing light and check all the wires. The wires might be breaking down after the temps. get up. Id say just go ahead and replace the plugs, wires, etc just to be done with it. Check the EGR valve for correct operation. At idle you chould be able to push up on the diaphram and the engine start to stumble. Check the plastic vaccum lines for cracks since the dont hold up with age and heat. Thats where I would start.

 

Most of my dad's fleet are all 88-98 Chevys, and I've had some experience tinkering with them. As stated before, I would replace the plugs, wires, cap, rotor, etc. Get a timing light too, and check the timing.

If the problem still persists, and you want to look at the injectors, then all you have to do is pull the air filter assembly, and look at how they are spraying. I did this at the begining of the summer on one of our trucks that was surging real bad. Anyway, I was able to see the injectors spray pattern sucked. One of them was even driping! We ran two tanks worth of injector cleaner through it, and it's a TON better now. Were probably going to have to replace them, but that should give you an idea of what you're up against. Good luck and keep us posted.

 

time for a tune up, when the vehicle goes into overdrive, it puts the most stress on the coil, plugwires, plugs, and distributor, ive seen alot of problems with the coil wires cracking and causing jerking,no-start and other things, you could pull the ditributor cap off and see if theres carbon build up on the rotor or distributor cap, try to powerbrake it and see what happens, if it start to missfire the that usually ignition related problem, like chevymec said, you should replace dist cap, rotor, plugs. wires and set base timing with timing light

 

i forgot to add which was just brought to my attention today while i was in the middle of a tune up...rear plug, passenger side, fouled to ****...entire thing was covered in oil...
i put a set of new plugs in, the local parts store didn't have the rest of the stuff instock but should be here tomorrow sometime. but after the new plugs were in and i drove it for about an hour, the plug was already nearly completely coated in oil...no oil dripping anywhere else though...drained teh oil...no coolant in there, flushed teh coolant system no signs of oil from what i could see...

what do you guys think?
Travis

 

Check compression. If the compression is good then look at intake manifold gaskets. Ask how much oil it's consuming. Could be valve seals too I guess. If it's burning oil the O2 sensor is shot. (TBI, right?) When the truck starts it's in open loop. If the O2 sensor isn't working right this might explain why it idles bad after warmed up - closed loop.

 

if the compression is bad...could that be a piston ring being shot? would that cause oil to foul a plug? when i drain the oil it didnt seem like it had burned off too much. No other visible oil leaks other than where the one plug is. I dont have any tools to check the compression so ill have to run it by a shop this week. I appreciate the info fellas
Thanks
Travis