89w100 318tbi 4spd 4wd. Then I first start my truck it runs and drives like crap. Really doggy and feels like like the engine has the wrong a/r. When its goes into closed loop it runs perfect, all its power and throttle response. Just want to know if that normal or if it's a problem that happens with truck and if so how to fix it.
Thanks

 

If your truck is running poorly when it is cold yes you do have a problem as this is not normal. As always I recommend checking the easy and cheap things first. On our engines that would be the injectors.

Engine running when still cold. Look down in the throat of the throttle body to check the injector cones. There should be a fine cone of fuel with no gaps and no streams at the base of each injector. The cones should reach the sides of the TB. Low ambient light and a flashlight shows the cones best.

If the cones are OK you will have to start doing the electrical/electronic tests to find out what is not working as designed when cold.

 

bump1

 

So Im still having the same problem but worse. The problem is so bad now that i cant really even drive the truck untill is warmed up. When i first start it I can drive it fine for about 2-3 mins but after that I can even drive it unless I get up into 3000 rpms range. I have to go wot but really pulses and dead. One night i was at a stop sign in a little hill, and when i would try to go it would bog way down and want to die. I have to rev it up and ride the clutch on and off to get across the road. The turck starts great and idea good to. I've replaced the o2 sensor, Temp sensor, new atc. The cat is removed but still has stock headers just to a cherry bomb. Air pump and egr have been removed also. If I unplug the temp sensor it drives better but has no upper power, so i thought i was the temp sensor bad. how mush would the air temp sensor play a role in any of this. Also the atc seems to be really slow, my truck will almost die or just die before its pushes on the throttle, is that normal? And Is 4th gear really a dead power gear or is it just like that for me cuz of my issues.

 

How much does removing the cat on the tbi system affect it. I have a 2.5 cherrybomb and full exhaust out the back and thats it. I have tested everything I can think of and cant figure out what else it could be.

 

It shouldn't do much at all, since there are no sensors in or after the cat. Your oxygen sensor is in your driver side exhaust manifold. You can try unplugging it when the truck is warm to see if its really an open vs closed loop issue, or a less specific hot vs cold issue.

When you say ATC, do you mean this part? http://www.rockauto.com/catalog/more...118&cc=1084744

 

hmmmm.....

lots of hard things to diagnose here....

I think the others are really giving some good tips to try first.

Like Seal recommended.... check Your spray pattern of your injectors.... how does it look?

Have You checked your fuel pressure while the engine is running? Maybe You have a clogged fuel filter or weak fuel pump or a bad fuel pressure regulator?

Another thing to check is to check the ohm range of your coolant temp sensor when cold and when at 180 degrees water temp. You should be in the proper range of resistance when cold or hot for the sensor to output a correct signal to the computer. I know You replaced that, but maybe something is off with that?

I used to have lots of turbo dodge cars from 89 to 93 and they were very sensitive to the coolant temp sensor being a high quality, Mopar part that was in good working order.


Have you checked the voltage signal from your TPS at idle, part throttle, and WOT?

How about your map sensor?
Is the vacuum line in good shape going to it? does it out put a good voltage signal range at high vacuum, mid vacuum, and then at zero (atmospheric- WOT)?

Sometimes a vacuum line missing, cracked, or a bad MAP sensor can cause these issues....

 

Ok was thinking more of backpressure. Ive read that the tbi will run lean if u run straight pipe exhaust cuz the computer can't compensate for it. Yes thats the atc.

Fuel pressure is at 12psi at ldel.
Tps ive watched it on a volt meter. No flat spots and moves smoothly up and down.
Ive watched the o2 sensor, tps map and temp sensor right the computer.
When I first start it up I watch the o2 warm up and start going up in volt. Then it drops off to .00 at idel. I know it work cuz if I open the throttle and close it it gose up .7-.8 then comes back down to .0 -.01 . If I un hook the map sensor it goes to .90-.97 so it runs rich. So I know its woking properly. Timming is on too. But when its warming up it higher then 15 btdc , I moves to where I cant see the mark anymore. Does any body have a ohm reading on what the temp sensor should be at?