'87 bad idle and then dies.

[Vetteman61]

Hello everyone,

I have searched many, many threads and this time I haven't been able to find my exact problem. I have an '87 K5. It currently has a 350 from the same year truck. Recently, the truck will run OK when I first start it and it is in fast idle, then it begins to idle rough and eventually dies out. It will restart fine each time. Also, there is a miss when driving, but otherwise drives OK.

I just put a new 02 sensor on, so that isn't the problem and I've read a lot about IAC, but I'm not sure.


Any help would be appreciated,
Thanks

 

[diesel4me]

Have you checked for vacuum leaks?....on computer controlled engines usually a vacuum leak makes the check engine light come on,but not always..look for cracked hoses going to things like the power brake booster and PCV valve ..that can make it idle rough,miss,and stall..

It could be a multitude of other things too--maybe the fuel pump pressure is low,I assume its EFI,not carberated..ignition wires can cause issues like this too,or a bad distributor cap or rotor..

 

[Vetteman61]

Thanks for the reply. I have checked the vacuum lines and there don't appear to be any cracks or holes, but I'll check again. I also forgot to mention at first that I just replaced the cap, rotor, plugs and wires.

I also just bought an old snap-on tech tool (the red brick) and I hooked it up for codes but it shows no codes.

From what I've read from others' problems that are similar, but not exact, are that perhaps the first places I should check are my distributor and the Idle Air Control valve. Would these be likely candidates for this problem? When I took the cap and rotor off of my distributor it was quite rusty inside, however because (I don't think) there aren't any mechanical weights inside I wasn't sure if this was an issue I needed to worry about as far as causing this problem.

Thanks

 

[diesel4me]

There was another thread here about rusted distributors being an issue..

The module and or computer do the advancing of the timing,but perhaps if the module has a poor ground due to rust that could affect it?..


Since I dont own anything newer than 1980's I dont have that much experience with EFI so I'm not of much help there,I do know the idle air control valve does set the idle speed and can cause that kind of problem,sometimes just taking it off and cleaning the carbon off the pintle and port it closes off will help...if its a costly part new,a junkyard one will be cheaper to try and see if that makes a difference..

I had one engine that would stall after it came off fast idle,and I looked everywhere for a vacuum leak and found none..eventually I discovered the PCV valve was stuck open,it was a cheap POS one made of plastic and it had warped from heat and wouldn't close up when it was supposed too..I found that by unplugging its hose and plugging it with a bolt temporarily..another truck I had ,the power brake booster developed a crack in its diaphram,and it would die every time you applied the brakes!....I replaced that in a hurry!..