My 90 2.8 recently started to really strain to idle after inital start up. It works it out by its self eventually or if I punch the gas briefly a cople of times its ok. Then after driving a while if I shut it down and re start it (right away like for a quick trip to the store or something)it seems flooded ..anyway I found a past post that someone described the same exact problem and in that post it was suggested that it may be a burnt valve..among other things.. but I wanted to pull the plug wires 1 at a time to see if I could hear a diffence but I suspect the comp. does not allow this to work because there was only a brief diffenence and then it seemed to compensate for the missing plug, and they all sounded the same. Even if all the cyl. are ok there still should have been a difference when I disconnected the plugs unless this is what is happening right? Im I crazy or is this what is happening?
Thanks
J.P

It only works if you are trying to find an IGNITION based problem.

Time to get out the compression gauge.

Michael

Right...right thats it...Ill tell you I bought this 90 a few years ago for 2500.00 and it had 120,000 on it since then I have put in a couple of starters, a new oil sending unit ( only because my batt. cable made contact with it and fried it) a new electric fan (because I could not get a blade replacement quickly and I needed the truck) and just recently changed out the orig clutch with over 150,000 on it. I love this darn thing. I also had a 96 but had to sell it for capital for my business..I miss that one..anyway thanks for the reply.....You know one more thing while Im here I used to fequent this site a few years ago and remember the search was kinda..well...it <img src="/forums/images/graemlins/baby.gif" alt="" />'ed you know what I mean is there some sort of trick for using this or what? I did a search to find out the capac of my fuel tank the books says 21 gal yea right..but I got all kinds of totally unrelated stuff...any suggestions would be appreciated. I know there is a wealth of information in the past posts but trying to get to it..for me anyway has been frustrating.
Thanks again

yes it can be trying at times
look at these
Search Tutorial

and this thread about something else but addresses the search function with a good tip or two, using the + sign and making sure you have the correct time parameters
click here and scroll down a few posts

hth

//bc

Should be 21.9 gallons, much as the book says. There were not gas tank size options for these trucks; so unless yours is bashed in or was replaced with a tank from another vehicle, its 21.9.

well, a different point of view:

in my experience with other engines, the pull-the-ignition-wire-off-the-plug cheap-man's diagnostic aide, works irrespective if the problem is IGNITION related or not.

what you are testing here, or rather looking for, is an indication that a cylinder is or is not contributing it's equal share. if it is not, that will show up as no, or little, decrease in rpm when that plug wire is disconnected. it really doesn't matter *why*, just *if*, as far as this diagnostic test is concerned.

so in my opinion, ONEOFAKIND , your original bafflement was valid. ""Even if all the cyl. are ok there still should have been a difference..."" if all was well, then each plug wire pulled should show an equal drop in rpm; if one cylinder had problems (for whatever reason), then the rpm drop would have been less or negligible because that cylinder was not fully contributing its fair share, and so it didn't have its full complement of "contributing rpm" to begin with.

i am interested in why you didn't experience *any* drop from *any* cylinders. could it be the mlclark factor? :-)

as to whether the computer masks small rpm drops, i don't *know*, but it sounds logical.

anyway, that's my take. . .

all this being said, the compression test (and a leak-down test) will of course give you more definitive data as to valves, rings, etc. whether you do the ignition wire routine or not.

//bc