hey chevy truck forum. been watchin a little while an man you guys got some nice trucks. ya'll seem to really know your stuff too and are cool about helpin out us rank amateurs too. i'm hoping for some of that help myself. i've had my 87 for seven years now and havn't had to do much outside of keepin oil in it. best vehicle i've ever owned! just had the trany(700r4) rebuilt. did the timing chain and gears and seals at same time,- leaky old motor. Pretty dry now, but i didn't know i needed to silicone the oil pan gasket at the timing cover. little leak there. i'm learning about this truck everytime i open the hood but i'm still a rank amateur mechanic. great carpenter... slow mechanic. the truck has alway had a high idle, but it's gotten worse lately. also smells rich and blows carbon out the pipes. nice stripe on the concrete. usually a little water if it's been sittin. i think thats condensation in the pipes. i've checked for vacuum leaks, found some, made some, cured some. i'm pulling 20hg at the line to the vac resevoir, 18hg at the line to the MAP. I thought it was the egr but i took it off, checked it out it seemed to be working or at least not stuck open - might not be opening when it needs to. how do you check that out.? Also, i'm running just a Catalytic Converter with no muffler. is that generaly a problem? (besides sounding crappy). How do i know if the CAT is clogging? will that cause high idle and black soot? i checked the timing after installing the new chain/sprockets, it was still at zero with the ecm diconnected. but when i hook up the computer (and reset the ecm) it idles way advanced -off the scale then when it goes into closed circuit (ecm turns on at operating temp) it drops some but still 10-12 degrees advanced. is that normal? I don't have a real manual for this, i cant find a chiltons localy - have to order but i've been planning to get the chevy shop manual, only theres like three, the shop manual, the maintenance manual, and the service manual and they're like a hundred each. Anyway, thanks to anyone taking the time to read all this. Any help is appreciated. including any kind of general advice on the truck in general especialy the emissions control system, electronic spark timing, or any of that stuff. Thanks
Not sure I can help but, will try. Okay the running to rich might mean the carb needs to be cleaned and checked {exsp. if its a quard-jet} simple kit will take care of this or have a pro. look at it. The only way I know to check the cat is to rattle it and if you hear something rolling around its bad, and yes not running a muffler will cause future problems. pretty much anywhere there is a gasket you need to put some kind of gasket sealer on it and I have alway preferred cork gaskets due to they seal better and don't strech as bad. On another note does your state require emmissions?? if not get rid of all the emmissions bs. Good luck hope this helps. BTW local liaberey for copies of the books you need or check on-line you never know what you'll find. And if you get the one for your truck they pretty much say the same thing.
Thanks. I have a throttle body and i might pull it off this afternoon just to play with it - i already got that gasket. I took out the plug on the bottom of the cat - shopvac'd a gallon of what looks like bird seed out, put a freeze plug in the hole. now it sounds like tame straight pipes. I don't think it was clogged or not much, but a leak i had at the manifold to pipe joint got a little better. I put an extra spring on the throttle and now it idles down better. Still looking for a vac leak, might be the TB gasket. I probably will yank the rest of the emissions junk and keep it in case they bring back the testing. I'm in Florida and they used to check then they stopped.
Also if your distributor has a vaccum advance, the vaccum line will have to be unplugged and capped off along with unpluging the ECS to set your base timing.
......Sounds like you got everything lined out, yeah my state still has emissions but, my truck is too old for the testing, The only thing I had to do was put my old breather back on the truck and the guy just opened the hood and looked for a second and then checked everything else and I went on about my business. Good luck with the truck, if you have any more ???? ask these guys they know there stuff.
Quick tip... Easiest way to find vacuum leaks is to run the engine and spray brake clean around the intake manifold gaskets and any and all vacuum lines... if the idle jumps higher while you spray than you found a vacuum leak.
timing?? Ok just need to know were to look for this ecm disconnetion? I have not found it yet and my timing is just guess work till I findout how to do this. thanks for any help here Roy
timing Hey, about the ecm wire. This wire is a small wire with a weather pac fitting and will be on the drivers side of the truck by where the wiring harness comes thru the firewall just below the mastercyclinder toward the inner fenderwell. Just unplug this and the idle will drop and then make sure that (if you have a vacum advance that it is plugged at the throttle body) then just go thru the reguler timing just like any engine. Have fun............
Hey The Carpenter, I'm sure you have this fixed by now. You have to connect the ecm to adjust the timing. The distributor has a 6 prong ignition module that is wired to the ECM, it will advance your timing based on exhaust/heat ..
Is your check engine light on, if not is it working? The light should come on momentarily when the truck is started. If the ECM has set trouble codes you need to correct those issues before doing anything else. IAC (idle air control) valve could be bad. Low fuel pressure causes all kind of strange symptoms. You could have a bad temperature sensor and the ECM thinks the engine is cold so it keeps the idle speed up. This truck has two temperature sensors, one for the gauge in the instrument panel and one for the ECM. The one for the gauge is in the driver side cylinder head and the one for the ECM is in the intake manifold next to the thermostat housing. The only way to see what temperature the ECM is reading is to access the ECM through the ALDL connector with test equipment. If you are going to be working on this truck I STRONGLY recommend that you download the WinALDL program and build or buy yourself a cable. This is a free program that will allow you to read and reset trouble codes and see all of the data from all of the sensors that the ECM uses. It is almost impossible to troubleshoot problems on an ECM controlled engine without knowing what the ECM is doing. Most of the time you are just throwing expensive parts at a problem without any logic as to why. http://winaldl.joby.se/ For the manuals, I would not buy them at this time. Buy yourself a $20 Haynes book for this model truck. This book will give you most of the basic information that you need. Don
Hay DonM I was scanning posts and found your reference to the scanner, reader. I just wanted to Say Thanks!!! This is one I've been looking for for months. I've found all kinds of code readers but this one is a jewel and a half, most don't tell how to build the cable. Great link!!! Thanks again
