High rev on warm start

[Kmansinger]

Hello, I have a 1988 2.9 v6 that runs great. My only problem is that when it gets warmed up and I shut it down the next time I start it up while it is still warm the engine revs real high and then comes back down to a normal idle. It does not do this when it is cold. Any thoughts? Thanks Kmansinger

[enriched&beyound]

run codes...

how long does it rev high?

you might have excesive carbon build up in the upper intake. Take a peek at the throttle plate, ( engine off), take a wipe with a rag at the back side of throttle plate...if'n it all gunky...remove all vacuum ports and see if they are covered over, or partially blocked...

if thats the case , you maybe time and effort ahead to remove the upper intake and clean it. Reason being is that if you would leave it on and clean it with it running,(spray can), you may run the risk of dislodgeing a chunk of carbon loose and get lodged some where down stream, causing more harm then good.

you can clean the AIC too (Air Idle Control), which may help.

[Kmansinger]

Hello Enriched,
It revs up for about 2 seconds and drops right back to a nice idle. I don't have a tach but I think it goes up around 2500 rpm. When it is cold it does the same thing but it only revs up to about 1000 rpms. In the past I have cleaned out the intake and the AIC and that really helped make it idle better but didn't solve the reving problem. Once I took it into the local ford dealer and had the machnic listen and he said that it was normal. I have never had a car do this and it doesn't seem normal to me. I find it hard to live with and I'm not a picky guy.
Thanks for your input. I'll look forward to any suggestions.

[enriched&beyound]

Originally Posted by Kmansinger

Hello Enriched,
It revs up for about 2 seconds and drops right back to a nice idle. I don't have a tach but I think it goes up around 2500 rpm. When it is cold it does the same thing but it only revs up to about 1000 rpms. In the past I have cleaned out the intake and the AIC and that really helped make it idle better but didn't solve the reving problem. Once I took it into the local ford dealer and had the machnic listen and he said that it was normal. I have never had a car do this and it doesn't seem normal to me. I find it hard to live with and I'm not a picky guy.
Thanks for your input. I'll look forward to any suggestions.

Well I'd get codes out it anyway...some parts store will do it for ya.
I'd be inclined to say that it maybe the engine temp sensor (the one for the engine computer- not the dash)...don't think that they're terrible expensive.

That being said, it could also be other things to...so, back to getting codes. It help zero in on things quicker. Don't think/beleive that just because you're not getting Check Engine Light (CEL) on, that it still might have codes stored.

1 other thing would be go over the vacuum line very carefully.

and it could be very normal...if you have the factory fan clutch...thinking it has 2speed or varible speed? AYWAY, when shuting off warm and come back in a few min.

restart... engine heat is pooling (for lack of better discription), under the hood, from radiator to block. the fan clutch has thermo coil so the warmer it is the faster it will go...with the pooling effect in place ,upon restart then coolant is again recirculateing again and senses the down turn in temp and returns to a normal speed. If it seems out of the ordinary/normal then maybe have the fan clutch checked it might be getting weak and over sensitive.

[Kmansinger]

This maybe beyond hope. This engine is out of a 88 ranger and is installed in a 1971 VW bus. Like I said it runs great and is fun to drive. My wife and I take it on lots of camping trips. I don't have any of the specs for it that would have been on the ranger hood. The timing specs and such.

When I installed it I never saw where the CEL was suppose to hook up. Does it come from the ECA box? Do you know the pin number for the CEL on the 60 pin connector?

Four months ago I got a good book on how to tune and modify you ford engine and I did a code check on it and found that the engine temp sensor was bad. I replace it and it seemed to idle better. But still has the reving thing when hot.

Today, because it was easy to do, I disconnected the wire going to the engine temp sensor and drove it around some. Funny thing was it ran smoother on deceleration and lugged better then it ever has. But the idle was rough and smelled rich. It may be that it is running to lean when the engine temp sensor it hooked up.

This thing is a bear to work on. The only access is though the rear lid. I'd love to be able to access it from above but this year's model only has a rear access lid. You do a lot of feeling around.

Thanks for the help
Kirk

[enriched&beyound]

Originally Posted by Kmansinger

This maybe beyond hope. This engine is out of a 88 ranger and is installed in a 1971 VW bus. Like I said it runs great and is fun to drive. My wife and I take it on lots of camping trips. I don't have any of the specs for it that would have been on the ranger hood. The timing specs and such.

When I installed it I never saw where the CEL was suppose to hook up. Does it come from the ECA box? Do you know the pin number for the CEL on the 60 pin connector?

Four months ago I got a good book on how to tune and modify you ford engine and I did a code check on it and found that the engine temp sensor was bad. I replace it and it seemed to idle better. But still has the reving thing when hot.

Today, because it was easy to do, I disconnected the wire going to the engine temp sensor and drove it around some. Funny thing was it ran smoother on deceleration and lugged better then it ever has. But the idle was rough and smelled rich. It may be that it is running to lean when the engine temp sensor it hooked up.

This thing is a bear to work on. The only access is though the rear lid. I'd love to be able to access it from above but this year's model only has a rear access lid. You do a lot of feeling around.


Thanks for the help
Kirk

a transplant...to a VW??? bus, no less!!! WHOOO-dogges

timing is set at 10degs with spout plug out.

try this...plug the temp sensor back in....and unplug the O2 sensor and see how it drives. if it drives equally better as with the temp sensor unplugged without the over fueling...that might be the culprit.

has the plug been retained for dianostics, it'll look a bit house shaped or hotel shaped from monpoly game, generally red in color.

If you can get the codes would be good.

[Kmansinger]

I unplugged the O2 sensor and I still have the original problem with the reving when hot. It seems that it even revs a little longer with it unplugged. With the O2 sensor unplugged it idles better and deceleration is soother. A couple of times I had it feel like it was maybe flooding when it was warmed up and I had just started out accelerating. Never had it so that before. It clear up pretty quit. Most of the time it runs great. It also lugs better with it unplugged. Now my question is maybe I have the O2 sensor in the wrong place. I installed it where I thought it would work. Just an educated guess. It did have a single exhaust system but I installed a dual system. Looking at how it runs with the O2 unplugged can you tell if maybe it needs to be closer or farther away from the engine?
Kirk

[enriched&beyound]

Originally Posted by Kmansinger

I unplugged the O2 sensor and I still have the original problem with the reving when hot. It seems that it even revs a little longer with it unplugged. With the O2 sensor unplugged it idles better and deceleration is soother. A couple of times I had it feel like it was maybe flooding when it was warmed up and I had just started out accelerating. Never had it so that before. It clear up pretty quit. Most of the time it runs great. It also lugs better with it unplugged. Now my question is maybe I have the O2 sensor in the wrong place. I installed it where I thought it would work. Just an educated guess. It did have a single exhaust system but I installed a dual system. Looking at how it runs with the O2 unplugged can you tell if maybe it needs to be closer or farther away from the engine?
Kirk

the o2 sensor is just in the single section of pipe (where both sides merge), less than 2 foot from the manifolds, On the ranger it came from.

now for your appilcation, I wouldn't have the foggest as to whether you are too close or too far away...do know that the O2 sensor is before the Cat in the ranger.

concidering that the confined space that it is in...you might need a electric pusher fan to move air past the engine to help keep things cool.

the diagnoses plug in on the ranger was located on the innner fender of the passanger side, under the hood. It was just a few inches from the ecm, the ecm which was just inside on the passager , just infront of the door. Where you may have relocated it ..IDK.

If you don't have the diagnois port anymore you maybe down to replacing parts 1 at a time till cured.

a list of suspects, in no picticular order
fan clutch
TPS (throttle position sensor)
O2 sensor
AIC
temperature sensor
vacuum leak -look for too soft of hose

[Kmansinger]

I have the diag. plug and have done a code test a while ago.
I'll do it again to check where things are.
Do you have any clues about the Check engine light lead? Where does it originate ?
What is the AIC?
Also: there is no fan on the motor. It has an electric fan behind the radiator up front.
The engine seems to stay cool back there. It has good ventilation vents on the sides and lots of airflow around the engine.
I have replaced the TPS a while ago.

[enriched&beyound]

Originally Posted by Kmansinger

I have the diag. plug and have done a code test a while ago.
I'll do it again to check where things are.
Do you have any clues about the Check engine light lead? Where does it originate ?
What is the AIC?
Also: there is no fan on the motor. It has an electric fan behind the radiator up front.
The engine seems to stay cool back there. It has good ventilation vents on the sides and lots of airflow around the engine.
I have replaced the TPS a while ago.

getting codes would be good.

no clue as to where the CE light comes from. DO know that in the ranger you don't nescarily have to have the CEL on in the dash to have a code tripped. I realize that doesn't really help with your transplanted application.

the AIC is Air Idle Control...looking at the water pump...it would be mounted on the left side of the upper intake...round about inch in diameter , with 2 mounting bolts and wires attached at the rear. typically it acts up more when on a cold start and hunting idle.

the ignition module or TFI are know to be temperature sensitive...so hence the quizing on air flow and cooling. Sometimes with mechnical fan clutch gets weak and stick on high and make it sound like the engine is reving really high....but...you went to electric, so that can't be it.

[Lead Head]

I'd place my bets on the IAC (Idle Air Control). My 2.9 has a crappy one, it likes to stick randomly, you'll start it up and it fly right up to 2500-3000 for a couple of seconds then shoot right down to 700

[Kmansinger]

Ian,
Your rig sounds like it has the same problem as mine all right. Have you changed yours out yet? Mine revs up like that every time I start it when it is warmed up. There was one time in the last year that it didn't rev up and when that happened it made me think maybe it wasn't suppose to be doing that rev-up thing.
Is the IAC one of those parts that you can take apart and clean and get working again or do you just have to buy a new one?
Kman

[Lead Head]

They are fairly cheap, you can try and clean the ones on the 2.9. I took mine apart, had two philips head screws, I soaked the valve portion in every kind of degreaser, solvent, cleaner imaginable. It works intermittent now. I'm just to cheap to replace it.

[Kmansinger]

I finally got the codes out today and I have a #67 on the KOEO on demand codes and an #11 on the memory codes.The first time I did the KOEO test the memory codes came up with O2 sensor and the temp sensor codes which makes sense because I was driving around with those unhooked just to test what would happen when I did. I cleared the code and still got the #67 code.Also a #12 and #13 on the KOER on demand codes.
I think I can live with the #67 code but the 12 and 13 seem to point to the Throttle air bypass Valve (BYP). I have taken it off and replaced it with a used one and it still does the high rev thing. I'm beginning to think maybe I have a vacuum leak. Also a vacuum leak might explain why it runs better with the O2 sensor unplugged. Does this make sense?
The bitch is that because of the lack of access to the engine in the bus it makes it hard to check for vacuum leaks while it is running. I guess I'll rig up a hose to a propane tank and snake it around where I can and see what happens. Also when I disconnected the wires going to the BYP the engine slowed some but continued to idle. I was told that it should die after a few seconds. What's up with that?
Eager for some feedback.
Thanks
Kman

[Lead Head]

If the engine keeps running with the IAC unplugged, then it is probably gummed up or you have a vacuum leak. My 2.9 dies almost instantly with it unplugged. Thankfully the 2.9 Rangers (at least mine) don't have a terribly complicated vacuum line system, so it should be easy to find.