OK, I replaced the valve stem seals just in #5 today since that's the plug that always oil fouls after a few thousand miles. I still have the lope in the idle, but I'm expecting the fouling to go away. It's nice that Napa will sell you individual seals instead of the entire set.

One thing that I've noticed is that my temperature guage barely registers above C. Is the sensor that feeds the dash guage the same sensor that feeds the computer? I've got a fresh 195 degree thermostat in there that I put in to correct this problem. If it's all one sensor, I'm going to replace the sensor and see if that helps anything.

Since replacing the TPS sensor, I've noticed that under very light throttle I get a jittery throttle response, but that goes away as I open the throttle up further. I'm going to try putting the original TPS back on and see if this goes away. On a related note, why does coolant need to flow through the throttle body? After reading the cold air induction discussions, it seems this would be counter-productive.

I still haven't replaced the harmonic balancer, but I'm not sure how much this would contribute to the loping idle and bouncy tach needle at idle. I'm going to try to junkyard this to save a few bucks since it's not as cheap as the other parts I've replaced.

Should I be thinking that this is a sensor problem of some sort, or am I barking up the wrong tree?

I've cleared the codes and rechecked, but haven't gotten anything engine-related. Just a few codes about the VSS and neutral switch.

 

I would suspect the plug wires you bought....

Pull the #5 wire with the truck running....and see if there is a change in the way the engine idles....if not...then you have discovered your problem...

also try popping the hood at night with no lights....chances are your #5 plug wire is arcing to the closest ground....cutting electrical energy from the #5 cylinder.

Also try "wiggling" the injector electrical signal plugs while idling....
if there is a change then you have found a problem there....if not keep searching...

good luck!!!

 

As far as the coolant into the throttle body....do a search for "cooling down the throttle body add horsepower". There was a thread a few months back that went on for quite some time(something like 3 pages) that discussed this very issue. Some good tips there for you.

 

Also with the TPS, make sure that it reads .99v at idle (check with the engine off, key on). This is what tells the computer that you are pressing the gas. The computer looks at 1v to 5v if I remember right. I forget what wires to look at on the tps, but I did notice an improvment on my Bronco (89 - 302) when I did that.

 

Bypassed the throttle body cooling lines today, and also "capped" the EGR tubing internally as was discussed in the same thread. I'm still a bit unsure about whether or not that was a good idea, but it hasn't changed driveability at all. I may put it back the way it is supposed to be.

The TPS voltage at idle was 1.07V; is this so much that it could cause a problem and I should rotate the TPS to 0.99V, or is this acceptable?

 

Humor me by changing your fuel filter..... Sounds identical to the problem I was having........ Costs under 10.00 and takes 5 minutes......

Good Luck.... I hope it's as simple as this

 

I had a similiar problem, but it was corrected by replacing the EGR valve itself...not the sensor. Well, it was actually a combination of things. I also took off the air hosing from the filter to the throttle body, because I thought it was the TPS, and cleaned everything out with "Berryman's Chemtool". The assembly was gross with buildup. I also changed out the TPS, but it was not the problem. After doing so I could feel a real difference. It was just a try and see thing.

Wayne

 

Installed a new fuel filter three weeks ago when I did the TPS and O2 sensor. That little trio improved power, but did not correct the uneven idle.

By cleaning out the assembly, I assume you're talking about the throttle body and IAC? I've got those cleaned up pretty well, but right where the EGR blows into the intake I've got a lot of carbon buildup. I've cleaned some of it out, but I'm going to have to take the throttle body off again and try and clean some more out of the plenum.

 

Sound to me like an intake gasket failure. It may be sucking air in from inside the liftervalley in the #5 intake runner. It would also pull oil in there too. Loping Idle is the first indicator of a vaccume leak.

 

I would reset it to .99v, because the tps is telling the computer that you are hitting the gas, but the other sensors are saying that the engine is at idle.

Also, I've seen old ERG valves create odd drivability problems. The spring gets weak over time and it either doesn't close all the way anymore or it opens too soon. You might be able to make a restrictor plate for it. I know it works on the I6 carb motors. Take two gaskets and cut a thin steel plate to fit between it. Drill an 1/8 inch hole to restrict the flow. Or just replace that one and be done with it.

 

Well, since Monday is my day off, it looks like I've got it planned out. I hadn't thought about the vacuum leak at the intake runner--that was good thinking. That would explain the oil fouling; it would also mean I didn't have to replace those stem seals a few nights ago...

I'll replace the intake gasket, and while I'm at it, I'll put fresh O-rings on the injectors. Can't hurt, and I want to get everything cleaned up and put some clear paint on it. That will also give me a chance to clean the carbon and other dirt out of the plenum, and to adjust the TPS to read correctly at idle.

I'll get back Monday night with results; hopefully this will solve everything.

And by the way, I did block off the EGR a few nights ago. I undid the large fitting that goes into the valve and put a dime inside of it; it was the perfect size to block off the pipe and still allow me to hook everything back up. If anybody thinks that this is a bad idea, I'd love to hear your thoughts.

 

Hey 'bigric'....have you checked your gas cap? Your system might not be pressuring up due to a bad gasket around your cap.

Wayne

 

OK, pulled both intakes. The throttle body had a lot of brown and black buildup just behind the throttle plates, so I cleaned that pretty thorougly. Next, there was a lot of carbon buildup right where the EGR enters the plenum. The rest of the plenum and intake had a lot of oil and carbon buildup, so I dropped it at the machine shop to get tanked. I'll get it back tomorrow. I also reset the TPS to 0.99V at idle.

When I removed the sensor half-way back on the left side of the intake (has two wires), I noticed that the sensing end was covered in hard black buildup. I'm not sure what this sensor does or if it is related to my problem, but I'd love to know what it is so that I can get another one.

Since everything else went pretty smoothly, the RF intake bolt broke right at the head. Swell. It looks like it's been getting coolant on it and it's frozen in there pretty well. I guess I'll have to get somebody with a tap to drill it out and tap it for me. I'm guessing that I could run into real problems if I left that bolt out.

All of the injector O-rings look pretty good, so should I bother replacing them, or should I just put a little oil on them and slide them back in?

 

I really appreciate everybody's help with this, and I think that today was very telling considering the condition of the TB and intakes. When I was removing the injector rail, part of the end of one of the injectors broke off, leaving it looking like this:


It looks to me as though the injector will still seal properly. Does anybody else agree/disagree that it would be OK to put the rail back on with the injector like this?

Additionally, I've done some searching around, and based on what I've seen, the ICTS being dirty like this will make it always feed back as though the air is cold. I'm still unclear whether this is a good or bad thing for driveability/mileage. I've cleaned this up as best I can without damaging the center electrode (it's pretty delicate) and I was hoping to reuse it, but I don't think that it's ever going to be able to give a reading other than cold.

The condition of this sensor should give you an idea what it looked like inside the plenum and intake, and why it's now soaking in solvent at the machine shop. I think that this seriously contributed to some of my problems. It also makes a lot of sense about the vacuum leak at #5 intake causing my seemingly-unsolvable lope.

 

I would'nt replace the o rings unless they look cut or nicked.As for the broken bolt you can try an easy out or drill it out and put in a heli coil.The sensor sounds like the air charge temp sensor.I just saw your latest post.You broke the pintle cap on the injector.They are cheap to replace.It may not leak,but if it does you could have a fire.Replace it.I'd replace the senor too.

CB