I would like to know what the timing is set at. Be sure to unplug the spout connector (little gray tab in a socket). Sorry that I don't exactly know where it is on an 88 300. It will be either near the distributer or up on the firewall by the master cylinder.

Adrianspeeder

 

I will look at the timing tomorrow, Since it ran like a top before it was parked, I begining to think my fuel pressure or flow is low, or my injectors are plugged from its long 1 year plus sit in the garage.. and really low miles before that, that last tank of gas could have been in there for over 2 years in. That could have raised hell on the pump or injectors.

It basicaly is not getting enough fuel... everything else seems to be functioning.. If i was getting real low pressure or my injectors were real bad, this would explain the lean error on the O2 sensor when I pulled codes..

I looked at the O2 sensor and wiring when I was under the truck an it looked very new, still shiny no currosion on it...it stuck out like a soar thumb under this truck.

I reall think getting the pressure test done and vacume test done will sort out the unknowns at this point.. at least i can say i have larned alot about where allthe parts are on this truck so far.. And im sure i will learn more.. and more and more

Jason

 

Interesting. Did you unplug the wiring harness from the MAP or the vacume?

 

I unpluged the wiring harness, just unplugged it started it and imediatly noticed a big diffrence, it still stumbled a bunch but was 50% better. i could drive below 2000 rpm and it idled better.

 

Definitely need to find out what your vacume and fuel pressure is. Try unplugging the vacume from the map and plugging the vacume feed hole. Leave the vacume bung on the MAP unplugged and leave the wiring harness plugged in.

Try to get vacume and fuel pressure checked. You will want a remote fuel pressure gauage that you can put under your wiper blade and drive down the street and see how the fuel pressure reacts when driving. During heavy load the fuel pressure should move up from 35-38 PSI up to 40 PSI. During deacceleration and higher RPM's ( no load) the fuel pressure may drop to 20-30 PSI. This is all normal.

 

WOW!

I unplugged the vacume line from the MAP sensor and left it pluged into the wiring harness and started it( its' cold, 13 degrees out sitting outside all day)

It fired right up and idled smooth.. WOW.. slowly went throughthe rpms in nutral, Didn't have any sputter at all..(normally it sputters like mad at 1500to 2000 RPM) So I shut the hood and back up, no sputter or the need for huge rpms to drive... SO im really impressed now...

OK so i take of down the street, its running really well a sputter now and then but not bad... very driveable.. i did noice when it was floored it would sputter more... So I take off driving it slowly through the rpms, in first and second it great very little sputter, third still very little sputter.. 4th its sputters below 1500 but less than before.. so drive about 4 blocks and go to turn down a street, let off the gas and push the clutch in... Motor dies and power steering become armstrong steering

Made the turn but it was a supprise.. anyway so after the enging ran for about 5 minutes it won't idle anymore.. but if I fetather the gas to keep it idleing, it runs pretty good... Now its begining to warn up and I start to notice its running rich, I can smell gas a little in the exhaust.. Its still running fairly good but at more than 1/2 throttle and it sputters a bit but does run quite a bit better.

SO i drove it home and shut it off and imediatly pop the hood and i can smell rick exhause inthe engine compartment.. I can tell it was running rich..

I did notice the enging tapping at times when i was driving it, like lower rpms and more throttle, so i tried to avoid this as much as possble.. another sign of running rich..

So what does all this tell you?

Jason

 

This tells us your MAP sensor is working, it also tells us that you have some vacume on your truck. I knew that unplugging the MAP would make your truck run rich. I wanted to see how it would counter it running lean. I previous told you in a post that it would run really rich and probably not idle. Your truck pretty much did what was expected. I'm actually suprised that it ran very well when it was cold.

Well you be able to provide us with vacume and fuel pressure results soon?


Its very important that you test the fuel pressure while driving the truck. Reving the motor in neutrual will not test the fuel pressure when the engine is under load. We really need to know how the fuel pressure responds when under normal driving conditions.

 

I will be getting the truck into a shop to get those test done, Hopefully this next week while im traveling for business.

I will report the findings then

Jason

 

FOund a big issue tonight, gasket on the TB was colapsed allow a bunch of air in the gap left open... right into the manifold.. I removes the gasket and have sealed it with forma gasket... this should not colaps in to the cavity.. Im letting it cure now and then when its done i will fire it up and see what it does.

Jason

 

That might affect idle a little bit, but I cant see that affecting and making the problems that you describe. Not unless its leaking in coolant from the EGR spacer. Luckly on a speed density type vehicle the amount of air coming in isn't metered. If this was a MAF ( Mass Air Flow) type vehicle you bet your butt that you would have some major issues like you are describing.

 

Well, I let the seal cure over night, drove it 60 miles today to work and back and its running so much better, it idles its hesitation is reduce 90%, At this point its very drivable and usable... I will br drivingit more today, first im going to reset the computer and see if i get any codes from it anymore...

Im pleased that its running really well now compairded to before.. Still not perfect but it could now be the EGR system or the injectors being dirty, I filled the tank and added a can of seafoam to clean them out as well as possable with out replacing them.. i will drive a couple tanks of gas this way and see what happens..

I have corrected all the major issues now.. besides a leaking front seal on the motor...

Jason

 

That is good to hear. I wonder if coolant was leaking into the intake. That would cause the issues you described. Were you having any coolant disappearing issues?

I still cant see how extra air coming in on a speed density engine causing those problems that you describe. Anyways.. Keep us posted on your progress.

 

I have not seen any coolant issues, what do you mean coolant in the intake.. I dont understand why and or how would i get coolant nto the intake??? OR are you saying a leaking head gasket leaking into the cylinder...

Either way coolant levels are good.. drove 100 miles today only some hesitation here and there.. runs rood at hiway speeds.. and also now can be in 5th at 1000k and floor it all the way up to 60mph with no problems at all no hesitation ect.

I dont quite understand how this worked either but,, it did make a diffrence, quite a large one..

I think my next major hurtle is the oil seal onthe front of the motor is leaking pretty good, i added a quart the last tankfull of gas i used up.. that a pretty significant leak.. I bet the seal dried out and or tore from it long sit with out being ran.. and or tore on start up after sitting for so long.. I have to say not being driven seems to hurt cars more than driving them. I guess that a big deal to me becuase i have a 05 chev colorado that is sitting the the driveway, 7k mile son it and i have not even started it all winter.. Just sits there.. covered in snow.. The only reason i dont drive it is its a 2wd and in MN are roads are pretty slick most of the time so i drive my old rusty trusty jeep cherokee with 200,000K+ miles on itm it always get me where i whant to go and then some.. Its got a i6 too.. I love I6's

Jason

 

Hey can I get an update on this? I have a 1990 6 cyl/5-speed doing this now. The funny thing is, I know it have a bad alt too! I tuned it up and charged the battery so it now read 12 volts but it still stumbles over 2500 UNLESS I EASE into it


Thanks!!!

 

You might want to check the PCV system. Positive Crankcase Ventilation.
"The PCV system simply relieves crankcase pressure by routing crankcase vapors and comustion blow-by gases into the intake manifold, where they mix with the normal air/fuel charge and are burned in the combustion process. However, the can only accept small amounts of these vapors at idle or it will misfire." Hynes repair manual.

I had a bad PCV valve once and it caused alot of problems. It is located on top of the valve cover back by the firewall. It just pulls out by hand (it should) and all you have to do is shake it a little. If it rattles, it is still GOOD. If not, replace it.

Just something else you might want to check. I hope you find the problem soon. Little things like this make me mad and impatient.. Good luck to ya....