Bogs down intermittently '88 2.9L V6

[dieseldane]

I am trying to help my brother in law out with his truck.

Going down the road going say, 60mph, it will be running fine and then all the sudden you will start losing speed, and with the throttle in the same position drop down to about 52-55mph, it will stay bogged down for a bit, then snap back out of it and boogie back on up to 60. Check engine light never comes on.

It does this hot or cold, sitting at idle in neutral or going down the highway, in all gears, doesn't seem to be any condition that this problem is specific to.

I have checked fuel pressure and fuel return volume. I replaced the pressure regulator as it was bad, but didn't affect this issue.

New plugs.

New air filter.

This truck has sat a lot in the past, but it has had fresh fuel put in along with one fuel filter, although the old one wasn't clogged at all. I think it should have two filters, but there was not a filter in between the pumps. I took everything apart to find there was no cartridge in there, and the one napa gave me didn't seem to fit so I did not put one back in.

Help please!

 

[dieseldane]

Just went home to self test and get the codes (having to run back and forth to the library to use the internet sucks) and here they are:

KOEO (Key On Engine Off)
11-11 System Pass

CM (Continues Memory)
-63 TPS circuit has intermittently failed below minimum 0.6 volts.
-95 Fuel pump secondary circuit failure. The EEC senses infinite resistance to
ground from the fuel pump on the Fuel Pump Monitor circuit.

Did a KOER (Key On Engine Running) test as well, but I did not realize it needed user input, so here I go home to do it again...

 

[84bluebronco2]

Sounds as if the problem may have explained it's self with your two continuous memory codes. Check your wiring to the fuel pump, especially the grounds. If the TPS shows less than .6V, one would be led to check the condition of the sensor itself, or check the wiring to and from the TPS.

 

[dieseldane]

I forgot to mention that I had previously checked that out as well. The sensor itself seems to be good, but I haven't ruled out any wiring issues.

Also I did the KOER self test and it came up with this code:
41 No HEGO switching detected always lean (right side).

I could se the oxygen sensor being bad. When he brought it to me first thind I did was check the fuel pressure and the regulator was bad, leaking gas into the vacuum line, and I wonder if the truck running extremely rich could have fouled it out or something... But would it be intermittent like it is?

Or is it more likely in the wiring?

 

[adsm08]

There are certain conditions that happen during normal driving where the input from the O2 sensor carries less weight or is ignored completely. A bad sensor can bog the engine down and make it seem completely random to someone who doesn't know when the sensor is being ignored.

Running extremely rich could foul it. Try replacing it and resetting the memory.

 

[freedom5]

Also remove the throttle body and clean it good with a carbuerator cleaner. If it had been sitting a long time I'd bet it is pretty dirty. I had a similar problem with my 2.9, changed the TPS,MAP, O2 and IAC. When I cleaned the throttle body I was amazed how much crap washed out of it. It could cause the vane that operates the TPS to stick or be sluggish which would cause some of your symptoms.

freedom5

 

[adsm08]

Be careful with cleaning the TB though. I cleaned mine once and my truck went from running well to idling at 2000 RPM.

I had to go back and reset the idle speed because of how much crap I'd cleaned off.

 

[dieseldane]

Replacing the oxygen sensor did the trick.

 

[SmokeEater829]

Ok guys, try not to laugh me off of the forum but I have a question. I recently bought an 88 B2 with the 2.9. Taking my time and trying to get her running right with ALOT of help from a buddy. He is a mechanic, I just own tools. Anyway, the O2 sensor just has the wires cut and hanging. I want to replace the sensor, but can't for the life of me find where it should plug in. Can anyone help me out??

 

[dieseldane]

If the truck was close to me, I take some pics to show you where the wires run, but it isn't. You might have a little better luck getting a helpful response if you start a new thread for your question.

 

[freedom5]

Sounds like the problem has been solved by replacing the O2 sensor. Guess you found where the wires run. My diagram shows four wires. (1) Gry/Y to the fuse panel 10 amp hot w/key on, DG/P joins Gry/LB attached to the EEC #29, O to EEC #49 and BK/W to Grnd. If the wires were just hanging down they should have a plug that connects to the O2.

freedom5

 

[dieseldane]

I never had a problem with wires. I fixed this truck months ago but never posted what it turned out to be, so I was just adding that so that others who might have this problem can see. SmokeEater829 was just asking about his wiring problem.

 

[hopster]

Ok guys, try not to laugh me off of the forum but I have a question. I recently bought an 88 B2 with the 2.9. Taking my time and trying to get her running right with ALOT of help from a buddy. He is a mechanic, I just own tools. Anyway, the O2 sensor just has the wires cut and hanging. I want to replace the sensor, but can't for the life of me find where it should plug in. Can anyone help me out??

the plug for the o2 should be attached to a bellhousing bolt via a bracket