dgoad

Ok, here is the final words on this subject. The engine computer solved most of the trouble. The engine still did not run that good with the new computer, however, it was running and acting mostly normal or mostly below normal. I did not replace the coil at the time that I replaced the plugs, wires, cap and rotor and even though I had spark, it looked more yellowish or something that did not look bright blue. So, I changed the coil and all of the engine troubles are gone. It runs great.

As to the timing pulses to the injectors. The old CPU was putting out pulse that are very close to what it said it was doing. It was asking for 3.8 - 4.2 msec pulses at idle. Remember, I was getting too much fuel flow with both injectors hooked-up and it almost ran good with only one injector. Well, the new CPU is asking for 1.6msec pulses and it runs right with both injectors and the fuel flow is minimal at idle as one would expect.

What was learned from all of this? Well, parts do where out and should be changed from time to time before all crap out at once. This truck was equiped with the original spark plugs, wires, cap, rotor and coil. I should have changed them all, period. The O2 sensor needed to be replaced. The MAP sensor does not appear to have need to be replaced, as the old CPU reported both as bad and the new CPU has NO error codes. The IAC and the EGR valve where stuck and dirty just like the whole TBI. I cleaned them up and freed the pistons on the valves and they both are working and moving just fine. This is the opinion of both myself and my scan tool. The old injectors were leaking. You can tell by the little streams coming out of the bottom of the injector along with the normal spray pattern of fuel. The little streams should not be there. They needed to be replaced and so they were. The fuel pump I believe will strike at any time. While it is to produce 13psi and is allowed to fall to around 10psi at full throttle, this one is producing around 11psi and will drop to around 8 or 9 when throttled up. But, for now it is getting by. I did replace about 4 foot of several different sizes of vacuum hose and a couple of fittings. Almost all had cracks and tears. The CPU was more than likely taken out when jumper cables were used to jump start the truck and they were let to arc. I am now learning that the truck started going down hill after that event.

So, here we are after several weeks of fun with about $500 bucks worth of parts and priceless patches of hair missing, but I have my son's truck running again. I think the water pump and/or the fuel pump will fail shortly, but what the heck, he will soon be back in his own vehicle. I say soon because, I just found that when you place your foot on the brake pedal that the engine runs poorly again and its idle speed races up to about 1500 rpm, classic vacuum leak stuff. I pulled the vacuum hose off of the power boost unit and sealed it with my hand and it does not do this anymore. I guess it is back to the parts store for a power boost unit and I guess a new set of brakes while I'm at it. If is was not for keeping your kids in vehicles, what would dads be good for, right?

Thanks to all that sent replies to help with my ordeal. I checked out and looked at everyone of them. I put a lot of words into this post and my others so that maybe someone might be helped by something that was covered here. There is a lot of stuff here and we replaced a lot of stuff. All but the MAP sensor was needed and every item made a difference, even if a small difference, in the way the engine ran. Even now faced with a major brake job that will cost another couple of hundred dollars, the truck will live again and it beats the hell out of a car/truck note, not to mention insurance and tags.

Paininthebrain, I too had that problem several years ago with small chevy. Yes, when the fuel pump pumps the fuel right back in the tank it will not make the correct amount of fuel pressure for the TBI system or injectors. Not knowing what is wrong and how to fix it can be a hardship. I have felt your pain.

Good luck with all of your projects and many thanks to those that are willing to share a little part of their knowledge and interest with myself and others.

DGoad