Chunky throttle; no idle - 2.5l RENIX

[Comanchemodder]

Greetings,

 

Over the past couple of days, my idle and low speed is been getting really chunky.  Almost undriveable.  Only if I push in the clutch and rev will it pull out.  But even at medium throttle, there will be periods of "dead" throttle for a few seconds.

 

Symptoms:

 

1) a spark plug had very trace amounts of white; almost like running lean.

2) I changed out the distributor cap and rotor.  The rotor had some evidence of wear on the leading edge.  If this is of interest, I will post a pic.

3) I cleaned the TBI with choke cleaner.

4) There seems to be a high frequency "flapper valve" clicking coming from the throttle body.  It does not seem normal.  Sounds like tractor.

5) when looking into the throttle body at idle, there appears to be liquid gas wetting the butterfly valve.  Seems kind of rich, I guess I never noticed that before.  Not sure if that is normal.

 

Any ideas?

[cruiser54]

The clicking in the throttle body is the injector. Normal.

 

Make sure your intake manifold bolts haven't loosened up and check the hoses to it below the throttle body for vacuum leaks.

[Comanchemodder]

I replaced the TPS.  On a test drive, seems to be running much better.  I need to wait until i am stuck in afternoon traffic to be sure.  

 

I used Cruiser's Renix tips to swap the TPS.  However, there is something strange with mine.  My reference voltage 5.07V is between B-C (as marked on the plug).  the output voltage was set to 17% (.86V) between A-B.  I checked three times about the plug labels.  but it does seem to be running better.  I used Duralast P/N TPS128.

[cruiser54]

I replaced the TPS.  On a test drive, seems to be running much better.  I need to wait until i am stuck in afternoon traffic to be sure.  

 

I used Cruiser's Renix tips to swap the TPS.  However, there is something strange with mine.  My reference voltage 5.07V is between B-C (as marked on the plug).  the output voltage was set to 17% (.86V) between A-B.  I checked three times about the plug labels.  but it does seem to be running better.  I used Duralast P/N TPS128.

Calculates out just fine. Run it and report back.

[Comanchemodder]

We have cooler weather here in Houston.  I took an hour road trip and the tuck ran like new.  On the way back, I got stuck in traffic; Stop-n-go in a construction zone.  The truck started to heat up and the chunky throttle returned.  Once I got past the construction and up to speed, the truck settled down and ran great.

 

I suspect the throttle issue is a result of overheating.  Come to think of it, the chunky throttle issue was almost constant during the hot weather and stop-light traffic.

 

I do not have a fan shroud.  It is just the mechanical fan.  I always knew cooling was not optimal. I am thinking I need to address the cooling issue next and am considering an electric fan (with shroud).

[Dillithium]

Fan shrouds make a huge difference, I've also heard of people heatwrapping their intake to protect it from exhaust heat. But I'd definitely start with the fan shroud. :thumbsup:

[Jeep Driver]

Don't overlook the temp sender in the intake.

 

And the air temp sender too.

[Comanchemodder]

Well,  the issue is still there.  Notables:

 

 

1) Runs fantastic when it is cool 40-60 degrees outside.  If the weather is warm, runs really intermittent with hesitation.

2) Once the engine warms up the hesitation comes back.  Push in the clutch, rev it, and its okay for a few seconds.

3) Sometime when cruising at 40 mph runs like a dream.  but when in traffic, hesitates/revs all over the place.

4) If i had to do any freeway driving, it would not be drive able.  But my commute is jsut city streets, max speed 45mph so not a show stopper.

 

Seems like a fuel issue but I'm not sure what to try next.  

* I checked the fuel pressure and it was 15 PSI at the throttle body.  Only checked it for about 30 seconds but it was solid with no fluctuation.

* MAT/IAT sensor was checked when the engine was hot and read about 480 ohms.  seems okay.

 

 

Any ideas?

[cruiser54]

You have the C101 connector, don't you?

 

See Tip 2. Then look at 27.

[Comanchemodder]

I cleaned the C101.  I used almost a full can of electrical cleaner, a small brass and nylon brush.  The connections are shiny.  I noted one "was not like the others" and seemed to be more recessed than the others (red box).  If that one is a fuel injection connection, I will need to get a small tool to tweak it per Cruisers Tips.

 

I will see how it runs and report back.

 

[cruiser54]

You could always do Tip # 27......

 

But, tweak the terminals anyway. 

[Comanchemodder]

Update:

 

The truck was running sluggish for a few months and has gotten worse.  Runs OK when cold but once warmed up idling was intermittent and when accelerating, would give out.  If I feathered (pumped) the gas peddle while driving, it would drive ok for a few hundred yards, then I would need to pump the gas again.

 

At a loss, I decided to change the O2 sensor.  Very preliminary results are promising but I am reluctant to declare victory.  The new O2 sensor is a Bosch 12008.  The surprising thing was the condition of the old sensor.  I don't know what I should expect, but white seems odd...  

 

Does the old sensor look normal or should it be brown?