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Ive got an 86 bII with a 2.9. It starts up fine but for about the first 1-2 minutes, it gets really hesitant. It almost dies out completely. Its also putting out a little black smoke. Do you think it could be the fuel pump regulator? Once i get going....it seems to run fine. I have to get it smogged in the next month so i want to get it running good. Any suggestions?

well i would start by cleaning the IAC ...... located on the side of the intake manifold..... it a cylindrical shaped metal mo0tor looking device that allows more air in for the truck at idle when the engine is cold........ on drivers side of intake manifold and has 2 wires goin into it, takes 2 bolts to remove, then spray it untill it is clean inside with carb and choke cleaner, spray it till it looks new inside, see if that helps you.

1 question does it do it everytime you start the truck, or just when its cold and hasnt been run in a while, for say if you stop at gas station go in get soda and go back out get in and start it back up ..... would it do it then ....... or would it run ok then ........ becasue if it does it every time you start it i would say, check the timing in it, it should be @ 10 BTDC with spout connector pulled out ... the spout connector is a black plug connected to a yellow wire on the passenger side by the firewall that connects the distributor to the computer, it does the same job as the old vacuum advances did on the old style distributors but it is adjusted by the computer based off all the information returned by the sensors , to check timing shut motor off and remove the spout connector, restart motor, then check timing, adjust to 10 degrees BTDC (before top dead center on number 1 cylinder) once adjusted, shut motor off reattach spout connector and restart motor, the timing will then adjust up to aproximatly 23 degrees off by the pc adjustment but the base setting for the computer to make all necessary adjustments from is 10 BTDC.... and must be set with the spout connector unplugged.... if you decide to check it once spout connector is reattached you may or may not see a difference in the timing depending on the info returned from the sensors in hte motor compartment

also the O2 sensor could be affecting the motor but i think this is unlikely

if it only does it when the motor is cold it sounds like the IAC (Idle Air Controller) needs cleaning, one way to tell if the IAC is the problem is unplug it, it should just about die and quit running, it should make about a 300 rpm difference on the motor running, teh approprieta idle setting for a 2.9 L is around 950 - 1000 rpm from the literature i have read.

also check the TPS (throttle positioning sensor), to check the TPS you need the key on but motor off, it is located where the air filter box tube connects to the throttle body, it is a black sensor directly across from where the throttle linkage attaches to the throttle body, you need a volt meter to check it, the center wire when read to ground shoud read between 0.9 v to 1.0 volts attach the red lead to the center wire of the TPS and the black lead to the motor on a metal surface, or the negative battery terminal, MUST BE CHECKED with key on but motor not running. it is said to adjust this you turn the screw located at the bottom of the plate where the throttle linkage hooks up, but before adjusting this i would suggest turning off the key, or risk flooding the truck as you will probably find it hard to reach without moving the throttle linkage position which would fire fuel into the manifold causing the truck to possibly become flooded with fuel..... just a thought ....... but i always shut the key off when i was adjusting for the new TPS i installed on my truck.


another thing that could be the problem with it being when you first start it is the fuel filter could be gumming up, or it could be dirty fuel injectors,
also a dirty air filter that is mostly stopped up can also cause problems when idling with a cold engine, and reduce gas milage, and believe it or not a stopped up fuel filter can reduce gas milage, because of the miss it incrues on the motor, the truck will not run at peak power and will reduce milage, as well as will the timing being off, and a simple thought that people overlook anymore, the pcv valve, this used to be a normal change as part of a tune up on a motor, but seems anymore that noone thinks about them, and i have ahd 4 cyl. FI motors that wont run without foot on brake one on gas, becasue of a bad PCV (POSITIVE CRANKCASE VENTILATION) VALVE i recommend changing it as they are usually quite cheap, and i believe on my 4.0 i am running now it has an electrical connector on it that feeds back to the computer.

bones101

Sound like a classic vacuum problem . . .
(Vacuum leak.)

Thoroughly check ALL of your vacuum lines, connectors and related devices, such as your PCV valve and the rubber grommet it is seated in. I strongly suspect you have a significant vacuum leak somewhere in your system. Also note that use of spray cleaners and solvents on the intake and vacuum system can degrade 'rubber' and plastic lines and fittings, so if you use this stuff, make sure to check all your lines and connectors afterwards.
Good Luck.

CraigK

Ok, well after checking some lines and making sure everything was ok...i found a broken line. Here it is below...

WHAT IS IT FOR?

HERE IT IS FROM A FARTHER VIEW



IT CONNECTS TO/FROM THIS BOX NEXT TO THE RADIATOR.


ALSO...WHERE IS THE IAC? CAN YOU SEE IT IN ANY OF THOSE PICTURES?
I KINDA KNOW WHAT IT LOOKS LIKE FROM YOUR GUYS' DESCRIPTION...BUT IM NOT POSITIVE IF THATS IT.

The truck starts up rough every time i start it....even if it is warm... So it could be the timing....or it could be that tube......I guess I'll find out. But let me know what you guys think of that tube.....

bones101

The broken vacuum hose on your throttle body goes to your carbon canister, and then to your fuel tank, as per the vacuum hose routing sticker that should be on the front of your engine compartment. (The one shown here is from my '87 B2.) This could easily cause rough engine running, especially at idle and low rpm's. Easy fix.

The IAC is the big silver and grey cylinder attached to the passenger side of the intake manifold. Attaches with two bolt. Again, this pix is my '87 B2.

CraigK

Sweet! Thanks guys for your help. Ill let you know what happens im gona be gona be gone on vacation for a week so ill let you know.

Thanks Again.

Well, i had enough time so i fixed the leak, i just have to run to the store to pick up some carb cleaner to help clean the IAC.

well regardless of whether it fixes the problem, it should help with fuel milage fixing the carbon canister vacuum line, and the IAC wont hurt to clean it as its been known in the past to cause problems for people.

well i did all of it and it still runs a little rough when I first start it. It does definatly run better though. The rpms dont drop to 400 like last time. The problem now is when I first start out driving down the road....it will not want to die....but it wont respond to gas pedal inputs and it runs really rough and makes puttering noises. It only does it for about 5-6 seconds and then its fine......it even does this when its warm and i start it. So im guessing that its the timing....What do you guys think?

YES, check timing, check the plugs wires, check the distributor cap for cracks or worn contact points inside, and check the rotor button, and change the fuel filter located on the inside of the frame under the drivers door which is covered by a metal plate, and by all means check for vacuum leaks else where, and REPLACE THE PCV (positive crankcase ventilation) VALVE, check to see how dirty your air filter is and replace if needed.

a stopped up pcv valve can cause a miss in smaller motors, especially 4 cylinders and small v6 motors like the 2.8 and 2.9 literes, it normally does not show much effect in larger V8 motors, if a pcv valve is stopped up you would normally be able to pull that vacuum line off it and the motor will idle up.

most problems occuring with a miss in a motor even on newer model cars and truck a miss in the motor is from the need to do routine maintenance.

Make sure you follow the directions for setting timing, and be sure to remove the spout connector before setting or checking the timing, it disables the computers ability to affect the timing, and the base setting is 10 degress BTDC, with spout disconnected, which will be a yellow wire located in the wiring harness going to the distributor, at the ecm module .... the spout connector is a black rubber coated plug that will resemble a flat type fuse, it contains a yellow wire going in to it and also a yellow wire out of it..... remove it with the motor off then, start the motor to check the timing, once adjusted, shut motor off before reinstalling. the spout connec tor enables the computer to acts in the same manner an old vacuum advance used to work on distributors in older model motors before computers were being used.




i also want to note that excess valve clatter would point to possible other problems, how loud is the knock from the lifters, i know its normal for a 2.9 motor to have lifter noise, but once all other options are exhausted, if the miss still exists in your motor, and your idle rpm is correct for the motor, you might have to pay more attention to just how much noise the valves are making, excess valve clatter indicates that the rockers might need adjusting, which could also cause a miss in a motor, BUT THIS IS A LAST STEP ITEM TO CHECK ..... I WOULD PERFORM ( A TUNE UP) ALL THE OTHER ROUTINE MAINTENANCE, BEFORE ATTEMPTING TO CHECK THE CLEARANCES ON ROCKER ARMS.

i would definatly check spark plugs to see if they are tight and i would check to see the condition they are in you might have carbon built up on them and need to change them.....

i also forgot to mention your 02 sensor, i have heard some people have unplugged the plug going to it and had a miss leave the motor, they just simply unplugged it, either way if it is working it should effect the way it runs if you unplug it...... might just unplug it and start it to see if it is still misses...... i would recommend this as opposed to changing it because they are in an akward position to remove and reinstall.... you should have a plug on the passenger side attached to the inside fender well leading to the 02 sensor you can unplug to check it.

if unplugging the 02 sensor makes no changes to the way it runs, then you might need to change it.

another thing that can cause a miss is dirty fuel injectors, there are plenty of fuel injector cleaning solutions on the market available form part stores, and water in a fuel system is also capable of causing a miss or hesitation,

BUT THE MOST COMMON CAUSE OF A MISS IS

>>>>> IGNITION TIMING<<<<<<<

I hope these options given can help with finding a cure for the issue your having at a low cost and at an un time consuming event....

I would start with the cheapest and least time consuming of these and work my way through them ......

Well i put in a new PCV and it worked! It runs hell of alot better! Ive only taken it on two test drives....but it seems to be working great! I'm still going to check the timing to be sure but other than that....it good. Thanks guys for all your help!