93 Ranger 4x4 4.0 High Idle / Drivability Problems

[Denisefwd93]

I take that as a no on the pictures lol I'm sitting here watching television not looing at throttle bodies .

 

[Vincenthdfan]

Not mine, but this is what the hole looks like.

 

[Denisefwd93]

OMG! I have a 93 and a 94 with 4.0 in them neither one have a hole in the throttle plate like that!! Plug it.

Not mine, but this is what the hole looks like.

View attachment 23700

I think it was an old school carburetor trick. https://www.corvetteforum.com/forum...illed-in-the-throttle-body-blade-hurt-me.html

 

[Vincenthdfan]

Hmmm...well, that's weird?

This post (linked below: #83) is what got me experimenting with this hole today.

http://www.therangerstation.com/forums/showthread.php?t=66359&highlight=air+leaks&page=9

 

[Vincenthdfan]

Hmm...perhaps I was pre-mature in regards to excellent drivability with hole covered.

I experienced stalling on downhill corners when coasting through them in 2nd or 3rd gear at normal speeds...18-19'ish mph...stall, restarted right away.

Did that a couple of times. Drilled 3/32 hole in tape covering hole, still stalled, albeit not as bad.

Pretty well ready to find a short, yet tall cliff to drive this puppy off of...anybody need any parts first??!!

 

[Vincenthdfan]

Well, I calmed down a little and did some more troubleshooting with a level head.

I did a TPS check and it was perfectly within specs.

Then I performed a very thorough smoke test (still cant get the taste of cigar out of my mouth...yuck!!).

The only smoke I got was from the cool/warm air bimetallic disc hose going into the air box...it had a decent amount of smoke coming from it

And the shaft of the throttle body itself had some wisps of smoke coming out on the throttle cable side.

I removed the throttle body to clean and better inspect the bore for wear and as I suspected, there was a considerable groove worn into the spring side inside of the bore from the butterfly shifting to one side and rubbing it over the years.

This left a substantial gap on the other side, as evidenced even more by the amount of crud built up on the TPS side of the butterfly...it was obvious there's been a lot of airflow going through that edge.

I ordered a newly refurbished throttle body from rock auto....they offer a very reasonable exchange on them with the core deduction taken into consideration. Price wise, it comes out just a little more than a used junkyard one would cost. I'll give it a try...certainly cant hurt.

I think I will probably take the cool/warm air system out of play and just plug that part of the hose off...I'm not real convinced the liability with that system is worth the benefits.

I also found some weather checking/rubbing through areas on the airbox end of the intake tube between the MAF and the throttle body. This would certainly contribute to run-ability issues by introducing lots of unmetered air into the system before the throttle body. I'm sealing all of that up and will probably go scour the junkyards for a better one.

As far as the rest goes, I got absolutely zero indication of a vacuum leak from any other areas...especially the lower intake area. Nothing came out of the oil filler cap or dipstick, indicating the PVC seemed to be working also.

If the above items don't remedy my idle issue, I will probably just commence with a full re-gasketing of the intakes and valve covers.

 

[Denisefwd93]

Well, I calmed down a little and did some more troubleshooting with a level head.

I did a TPS check and it was perfectly within specs.

Then I performed a very thorough smoke test (still cant get the taste of cigar out of my mouth...yuck!!).

The only smoke I got was from the cool/warm air bimetallic disc hose going into the air box...it had a decent amount of smoke coming from it

And the shaft of the throttle body itself had some wisps of smoke coming out on the throttle cable side.

I removed the throttle body to clean and better inspect the bore for wear and as I suspected, there was a considerable groove worn into the spring side inside of the bore from the butterfly shifting to one side and rubbing it over the years.

This left a substantial gap on the other side, as evidenced even more by the amount of crud built up on the TPS side of the butterfly...it was obvious there's been a lot of airflow going through that edge.

I ordered a newly refurbished throttle body from rock auto....they offer a very reasonable exchange on them with the core deduction taken into consideration. Price wise, it comes out just a little more than a used junkyard one would cost. I'll give it a try...certainly cant hurt.

I think I will probably take the cool/warm air system out of play and just plug that part of the hose off...I'm not real convinced the liability with that system is worth the benefits.

I also found some weather checking/rubbing through areas on the airbox end of the intake tube between the MAF and the throttle body. This would certainly contribute to run-ability issues by introducing lots of unmetered air into the system before the throttle body. I'm sealing all of that up and will probably go scour the junkyards for a better one.

As far as the rest goes, I got absolutely zero indication of a vacuum leak from any other areas...especially the lower intake area. Nothing came out of the oil filler cap or dipstick, indicating the PVC seemed to be working also.

If the above items don't remedy my idle issue, I will probably just commence with a full re-gasketing of the intakes and valve covers.

Maybe a vacuum gauge would help, they're not expensive

 

[mplummer08]

I didnt see a reference above, but did you remove the vacuum line that went to the auto trans modulator? If that's installed with nothing on the bottom end then it could be sucking air way back there.

Sent from my SM-G892U using Tapatalk

 

[Vincenthdfan]

Maybe a vacuum gauge would help, they're not expensive

Yeah, I meant to do that yesterday but got wrapped up in my smoke test and derailed my plans.

If this new T Body makes no difference I'll give that a shot too.

 

[Vincenthdfan]

I didnt see a reference above, but did you remove the vacuum line that went to the auto trans modulator? If that's installed with nothing on the bottom end then it could be sucking air way back there.

Sent from my SM-G892U using Tapatalk

Yes, I capped it off at the port when I removed the auto...good thinking though.

 

[Ewgoetz]

Old cracked valve cover gaskets can be a source of a vacuum leak.

 

[Vincenthdfan]

OK, new update today.

I received my newly refurbished throttle body today and bolted it on, tweaked my TPS to "in-specs" and fired it up.

Whoala...warmed up to a nice, calm idle, even with IAC connected.

New throttle body worked just as intended and the truck sounded so nice, idling down so calmly....sewing machine like.

So I can pretty well rule out vacuum leaks now.


However, there is still a glaring drivability issue.

It has to be electrical input related because it only does it when I have the IAC connected...

When I am driving along at any speed above 15 mph, the idle will not drop below 1800 rpm's....this is ONLY WITH IAC CONNECTED.

When idling along on level ground I can literally lift my foot off the gas pedal and have it act like cruise control at 25 mph.

Then, if I drag the brake I can get it to slow down (by force), and then when it hits 15 mph...bam, idle drops back down to normal.

In addition, at anything above 15 mph I can push the clutch in and watch the idle stay at 1800 rpm's....again, IAC controlled fast idle.

One thing of note also, my speedometer is consistently reading 10 to 15 mph faster than true speed when driving along anywhere (checked against GPS). No bouncing, just too fast.

I swapped in a different VSS from a different truck and it made no difference.

My question is...are the fast speedo speeds related to these fast idle inputs to the IAC?

I'm not quite clear yet on how they correlate with each other....still doing a ton of reading.


I did take the truck out with the IAC disconnected and it drove great with the idle set at about 750 rpm. Best its ever driven for me...which isn't saying too much I guess, since I have never even left my local neighborhood with yet!!

However, if I stopped too suddenly it would cause the engine to stall unexpectedly.

I'm trying to figure out a way to prevent that from happening so I can at least use the truck a little bit until I get the un-commanded fast idle inputs from happening all the time.

I sure could use some advice on how the systems correlate with each other so I can better understand what my issue might be....anybody??

Thanks!

 

[RonD]

1993 Ranger speedometer is cable driven, VSS is for cruise control and computer

You need to change the Driven gear on the speedo cable/VSS part in the transfer case

Transfer case uses a 7 tooth Drive Gear
Calculator here: http://www.fordspeedo.com/Calculator.html

Example: 7 tooth drive gear, 3.73 rear axle ratio, 30" tires, needs an 18 tooth Driven gear


Yes, on some computers with manual transmissions the computer will hold idle high until speedometer is under 5MPH, its an emissions thing, it will also high idle high when shifting, but only for a few seconds
And we don't "know" what speed computer is seeing from VSS, we assume same as speedometer.

Do the calculation and replace speedo gear to get correct/true speed and see if that helps.

After engine is warmed up unplug IAC and set idle down to 500RPM, then plug it back in.
1993 4.0l manual warmed up should idle at 625-650RPM

 

[Denisefwd93]

I don't know if this relates to you but I'll just toss it in here. Replacing the IAC twice on this truck has helped, the original one was defective, the new one was defective, the third one seems to be okay although I still get a burst of high RPM (2300) when it first starts but it drops right down to 1000

I'm embarrassed but I'll be the first to admit I'm not always right about everything sometimes I'm not right about anything lol anyhow fussing around the truck today there is a hole in the throttle plate!

 

[Vincenthdfan]

1993 Ranger speedometer is cable driven, VSS is for cruise control and computer

You need to change the Driven gear on the speedo cable/VSS part in the transfer case

Transfer case uses a 7 tooth Drive Gear
Calculator here: http://www.fordspeedo.com/Calculator.html

Example: 7 tooth drive gear, 3.73 rear axle ratio, 30" tires, needs an 18 tooth Driven gear


Yes, on some computers with manual transmissions the computer will hold idle high until speedometer is under 5MPH, its an emissions thing, it will also high idle high when shifting, but only for a few seconds
And we don't "know" what speed computer is seeing from VSS, we assume same as speedometer.

Do the calculation and replace speedo gear to get correct/true speed and see if that helps.

After engine is warmed up unplug IAC and set idle down to 500RPM, then plug it back in.
1993 4.0l manual warmed up should idle at 625-650RPM

Yes, I already have an 18 driven gear on my speedo cable with my 30" tires.

The speedo still reads way too fast. I have a new "used" speedo head to install in it and just bought a new VSS so we'll see how that goes.

I just replaced the TPS today, even though it was reading within specs, I HAVE TO get to the bottom of this drivability problem, its driving me nuts...seriously.

The new TPS seems to have calmed the RPM's some, I'm hoping the computer is still learning the new part since I cleared it when I changed the TPS....we'll see?

However, when I turned off 45 mph road to go toward my house, it stalled again in the corner when I cut the throttle...acting as though the Dashpot function isn't working.

I have it up on the lift again now to change out the VSS, so we'll see if that has any effect as well?