She's got a little skip after it warms up (1 Viewer)

[gswest]

My "88 Fj62 just got a valve job and I've been struggling to get her running smooth every since. Timing should be right, plugs are new, wires look OK, but I'll be changing them next. I'll try a new fuel filter as well. But I hate wasting money replacing parts needlessly. The vacuum seems OK, if I take off the oil filler cap off she starts to really run bad, so I'm assuming it has good vacuum. I've sprayed carb cleaner around the engine with no noticeable change. What's also strange is it runs better with the A/C on, but that could be because the idle raises with it on. And when you first start it up when it's cold it runs smooth, it starts to skip as it warms up. Need help before I replace every part under the hood.

 

[bigbrown]

try blocking off the egr valve to see if it helps. if it doesn't, check ALL the vacuum lines. if it does than you probably have an egr problem (clean or replace)

here's a pic someone else posted.

 

[bigbrown]

actually it's more like bypassing the egr, not blocking it off.

that part shown is the vacuum modulator. the hose with the screw in it goes down to the egr valve.

 

[overhanger]

Sounds as if Throttle Position Sensor adjustment might be real close to a borderline, especially if raising the idle speed, which the A/C switch does automatically, seems to eliminate the problem. A free fix, if it works.

 

[agent orange]

Overhanger, how does one adjust that sensor? Adjust it to a particular ohm reading? I need a 3fe manual....

 

[gswest]

I've got a manual, but the throtle position sensor seemed rather complex for the short-bus rider that I am. But, I have pulled a trouble code previously dealing with the throtle position sensor, but that was a while ago when it ran smooth, before the valve job. I haven't pulled the codes lately though. I'll try bypassing the EGR valve. All the vacuum lines look good and I'm not looking forward to replacing them all, but maybe it's inevitable with 215,000 miles. Next is plug wires and fuel filter if the EGR and throtle position sensor checks out. Has anyone adjusted their throtle position sensor? It looks like it pivots by loosening the top screw. I've proven I'm not afraid to screw things up in search of the nirvanna-like engine tune.

 

[bigbertha]

TPS

To adjust the TPS loosen the top philips head screw and pivot the sensor, it should be lose enough to adjust without taking anything else offf the engine. Use a diagnostic tach to get an accurate rpm reading. When you have the idle speed dialed in then tighten the screw.

Good luck!

 

[overhanger]

Overhanger, how does one adjust that sensor? Adjust it to a particular ohm reading? I need a 3fe manual....

Yes, you do need the '89 or '90 FSM for the 62. NOT the '88 manual which is merely a supplement to the '84 Heavy Duty FJ60 manual and it costs the same from Toyota as the complete manuals for the later two years. And yes, you need an ohmmeter to adjust the sensor accurately. Doing it by reading a tach will not give you the accuracy of the ohmmeter. Then again I prefer setting ignition timing with a timing light rather than by ear so YMMV. You are dealing with a window of roughly .0125" where the ECU is being informed correctly by the TPS of when the ignition advance curve should kick in as opposed to the base timing that the ECU sees at engine idle speed. Big difference, advance-wise and I had the same sort of random idle surge prior to proper TPS adjustment that I'm guessing is causing the symptom you describe.
As for loosening only the top screw and twisting on the plastic bodied TPS I'll leave that to your discretion. The only metal on the OEM TPS is the insert inside the holes the two mounting screws go through so hefty twisting can crack the body. If you have the right length - long - #2 Phillips you might be able to get at the pesky bottom TPS screw but I usually wind up removing the Idle Speed Controller to have a clear shot at the screw. Leave both screws a little tight and you can better control the amount of twist on the TPS body for some repeatable meter readings. All of this and the specs of the feeler gauges needed to get the right adjustment or exactly where to put them hasn't even been mentioned. It really is a fairly easy adjustment but having the FSM makes it doable. Don't know if the Haynes or Chilton books cover it.

 

[gswest]

Thanks, I have the 1989 service manual and it does go over what you mention. I guess like everything else, the first time I try something new on this truck, I wonder if I'll make things worse.
I'm thinking if I make the adjustment and reset the computer, I can check for another fault code.
With the help of all the guys here, I've been able to do quite a bit, from rebuilding the steering knuckles, doing the fan shroud modification, replacing the rear output shaft seal and rear diff input seal, new speedo cable, right rear spring shims and this latest adventure and current struggle; the valve job. I also had an exhaust shop re-route my exhaust up over the frame and deleated the cats, adding a flowmaster. She's a bit loud now, but that's OK as long as the engine runs right.

 

[dd113]

Dont mess with the TPS yet.

You need to get a vac reading and what the rpm is. The Rpm should be around 800-900 and drop to 750-850 ish in gear. Vac should be around 18 in and steady. if the rpm is low by a bit you can raise it with the adj screw on the ft of the throttle body

If it ran OK prior to head work look at all vac lines first then dbl check valve adj. A bad adj will fxxx with a 3fe.

 

[gswest]

Thanks. I've done the valve adjustment several times and It's getting easier, but still a pain. I'll get a vacuum gauge and start there. But, it definately bogs down when I take the oil cap off, so I was assuming this indicated a good vacuum situation. At one point after I did the valve adjustment (after the valve job), I tore the gasket re-installing the valve cover. The thing leaked oil (of course), and my first reaction was, now I know why it's running bad. Well, after putting in a new valve cover gasket, it still runs rough and
#%$& if it still doesn't leak oil around the valve cover. I'll try tightening the studs to solve the oil leak, but jeez!
So, check w/ vacuum gauge, possible TPS adj. then maybe new plug wires and filter.

 

[PabloCruise]

Not sure why the 3FE would run rough with the oil cap off?