1990 Dodge Grand Caravan 3.3l V6 Stalling/rough idle

I have a 1990 Dodge Grand Caravan with about 130,000 Miles on it. It
has Chrysler's 3.3L V6 engine. Recently, I've had an issue with it
idling. What happens is that the idle will drop to about 300 RPM for a
second, then it will shoot up to about 1000 RPM, then it will fall to
the normal 600 RPM for about a second, and repeat. A few times it has
outright stalled.
Unfortunately, this is intermittant. It has only happened after the
engine has sat a few hours (though it's only happened 4 times or so, so
it may be concidence) or it may be related to a cooler engine temp.
When it's happened, hitting the gas to bring it up to about 3000 RPM,
then letting it fall back to idle seems to fix it - the car will
happily idle then. Anything above idle and the car runs fine. The
idle is a BIT rough, but keep in mind it is 15 years old. No violent
shaking or anything, but not perfectly smooth like a new car would be.
I've used my scan tool (Actron CP9150) and no faults are being logged.
The voltage on the TPS does change, but I haven't had the tool on it
while the fault is actually occuring (what idiot put the connector
under the hood! )
This happened once about 2 months ago, and I asked around and was told
to clean the throttle body. So we took off the throttle body, cleaned
all the gunk out, put it back together and it didn't happen after that,
so I assumed it was fixed. Then this started happening this afternoon.
I also should note that we did change the timing chain a few days ago.
I doubt it is related, as this did occur once before back in december
(though the car wouldn't idle at all then, just started and died) but
figure I should mention that.
Any thoughts/suggestions/tests would be appreciated.

Thanks,
Eric Kotz

 

What step is the AIS motor on, 16 is a good number with the a/c off and a
clean throttle body.

What idiot made an after market scan tool with such a short wire after it
was designed for the DRB?

Was the Tamper proof plug removed on the Screw that adjusts the throttle
blade angle??
Glenn Beasley
Chrysler Tech

 

How do I read what step the AIS motor is on? I have a TPS voltage
reading (which is at .57v at idle) but I didn't see anything about the
AIS motor?
The scan tool has a 6 foot cable - hardly long enough to reach out the
front of the hood and back into the passenger compartment.

Unfortunately, yes, the tamper proof plug has been removed that
protects the throttle blade angle. How can I properly reset it?

 

Have you thought about extending the cable? If it's a ribbon, it
should not be terribly difficult although you might want to ask
someone who fixes or does electronics. There are lots of different
connectors and cables, flat ribbons and what not, but you need
to order from electronics warehouses. Radio Shack has close to
nothing, unless you are very lucky, having driven all the little
stores out of business, as Walmart's is doing big-time, so you
can't find any electronics stores except Rat Shack now. Either
adding on to the cable is safest, or cutting the cable in two,
and adding your own connectors.

Almost never found any connector that was really proprietary.
But I can remember going through AMP catalog looking for
weird connectors, but found them and ordered them from
Newark or Digi-Key = DigiKey.com [used to be a really patient
company for newbies - find parts and so on].

If this goes well, maybe a small business set up here? Must be
lots of other people who want to extend their devices. Unless
and this is a big unless the device is not stable with more than
six feet of cable. This can happen but with very good cable,
usually low capacitance, they almost always can be extended.
I remember when printer cables had to be six feet, but now
I see them as long as 50 feet or 25 feet without amplifiers.

I barely know what an AIS motor is so can't help with the auto
part of your question.

 

I have never used that generic scan tool and don't know what it is capable
of doing, But I would assume if you can read voltages on it you should be
able to read sensor values. And It should show what step it is on. If the
throttle body was dirty and someone adjusted the Throttle blade angle/TPS
sensor..... That may be your problem.. I normally put the system into a
minimum air flow test and adjust the idle/sensor that way. Once again, not
sure if your scanner is capable of doing that....Turn the screw out about a
half turn to see if that stops it

 

OK, I looked through the scan tool again and found that the AIS
position is generally about 65-70
A couple new developments today. The engine seems to do it more when
it is cold/not do it when it is warm. While it was doing it today, I
had the oppertunity to hook my scan tool up and nothing looked terribly
out of the ordinary, but it's hard to tell. While it was happening,
the O2 sensor was reading rich.
It also no longer seems to be an idle problem, as when I held my foot
on the gas it was still having the issue, up to about 1500RPM. Past
that it seemed fine. Also, one time I hit the gas and it seemed like
the engine speed did not increase. Additionally, I heard 2 clunk
noises coming from the engine at one point. Perhaps it was just
backfiring, but it did sound like it came from the engine, not the
exhaust.
I plan on disconnecting the EGR valve today and seeing what happens,
but any more insight is appreciated.

 

65 to 70 steps? thats too high, you need to get the the throttle blade set
back and make sure the blade and bore is clean.Typically the out of adjusted
TPS will cause problems when cold and could also cause a hestitation and
other problems

 

Can you give me any advice on re-setting it properly? My scan tool
doesn't seem to have a minimum airflow test - are there any other
things that test can be called?
Failing that, is there another way I could set this screw properly?
The blade and bore should be clean - about 2 months ago I took them off
and used a toothbrush and about 1/2 a can of carb/choke cleaner to
clean them and they were virtualy spotless. The van has only been
driven about 1000 miles since then, so they should be clean.

 

Back off the screw about a half turn, restart and see if that changes, if
not back off some more and recheck, see if that makes a difference, Our
scanner allows us to perform these tests by programed tests in the scanner.
keep in mind that you may have other problems and it isnt related to the
adjustment. Do you have a sensor value for adaptive fuel memory on your
scanner?

 

REPAIR PROCEDURE:
This bulletin involves checking the throttle body calibration for settings
that effect operation at idle.

1.. Remove the air cleaner.
2.. Remove the vacuum line from the PCV valve and install the 0.185 inch
orifice tool, No. 6714 into the vacuum line.
3.. Disconnect the 3/16" canister purge hose at the front of the throttle
body and cap the nipple.
4.. Install the Scan Tool (DRB II) and start the engine. Warm the engine
to operating temperature.
5.. Using the Scan Tool (DRB II), scroll through the menus as follows:
select - System, select - Engine, select - Fuel and Ignition, select -
Actuator Tests, select - Engine RPM, select - Minimum Air Flow. The Scan
Tool will count down to stabilize the idle rpm, and display the minimum air
flow idle rpm. The Idle RPM should be between 500 and 900 RPM. If the idle
is outside these specifications, replace the throttle body.
6.. Remove the Scan Tool.
7.. Remove the orifice tool and install the vacuum line on the PCV valve.
8.. Install the idle purge hose on the throttle body
9.. Install the air cleaner.
The reason why it says replace the throttle body is because legally we cant
remove the plug to adjust the angle, but when someone does tamper with it,
here is a guidline to the proper setting to get it back, However this test
is no good to you because your scanner sounds like it is just a read out box

 

Well, what should I expect to see? I backed it out 1/2 a turn and when
starting the engine the AIS was about 35. After running for a couple
minutes, it worked its way down to about 30.
Also, does this engine have an EGR valve? The service manual is
unclear - it seems to imply that all US versions have it, but then has
a California-specific section. I can't find the EGR valve - is it just
not there, or am I just missing it.
My scan tool can cause the AIS motor to move, but unfortunately it
doesn't give me control over it (just cycles open-closed-open...)
Thanks!

 

the emission sticker under the hood will tell you if the vehicle is equiped
with an egr valve or not, if it has one it would be just behind the throttle
body on the bottom

 

I assume you mean the sticker in the middle of the hood that says "This
vehicle conforms to the US EPA regulations applicable to 1990 model
year new light-duty trucks at all altitudes" and has a diagram of some
of the emission stuff. There's no mention of an EGR valve - I would
take it that means there is not one?
Also what should I target for the AIS position - ie should I turn that
screw further? It started at about 34 or so when I started the cold
engine. After running for about 8 minutes it was down to 27 or so.
Thanks!

 

If it doesnt say it on the sticker, it has no EGR valve, unless the engine
was swapped out with a used one,, leave the setting at that position and see
if it makes a difference. 16 steps was a good setting for that yr

 

OK, so no EGR valve then.
Earlier today I took a bunch of connectors, unplugged them, shot some
cleaner in them, plugged them back in. No difference :-(
Also, when the engine is at full temperature, the AIS motor went down
to about 18.
The problem seems to manifest itself when the engine is warming up.
Something like 110° through 135° coolant temperature. Engine seems
to be fine when dead cold or hot, but unhappy while warming up.
Problem no longer seems to be an idle problem - rather, a generic
running problem.
Also, I hear a whistling noise from the engine that seems loudest at
about 1200RPM. Sounds like it could possibly be a vaccuum leak, but we
can't find a source. It *SOUNDS* like it is coming from the bracket
directly above the alternator - but obviously metal brackets don't have
vaccuum leaks
I'd also like to point out the cam sensor was severely disturbed when
we changed the timing chain. Chrystler's directions, for some reason,
said to remove it, which we attempted to do. The stupid thing refused
to come out. Ultimately we gave up on removing it and discovered there
was no need to remove it anyway.
Also, what is a normal value for the MAP sensor? My scan tool is
showing about 275 Torr.
Any more help would be much appreciated.

Thanks,
Eric Kotz

 

OK, so no EGR valve then.
Earlier today I took a bunch of connectors, unplugged them, shot some
cleaner in them, plugged them back in. No difference :-(
Also, when the engine is at full temperature, the AIS motor went down
to about 18.
The problem seems to manifest itself when the engine is warming up.
Something like 110° through 135° coolant temperature. Engine seems
to be fine when dead cold or hot, but unhappy while warming up.
Problem no longer seems to be an idle problem - rather, a generic
running problem.
Also, I hear a whistling noise from the engine that seems loudest at
about 1200RPM. Sounds like it could possibly be a vaccuum leak, but we
can't find a source. It *SOUNDS* like it is coming from the bracket
directly above the alternator - but obviously metal brackets don't have
vaccuum leaks
I'd also like to point out the cam sensor was severely disturbed when
we changed the timing chain. Chrystler's directions, for some reason,
said to remove it, which we attempted to do. The stupid thing refused
to come out. Ultimately we gave up on removing it and discovered there
was no need to remove it anyway.
Also, what is a normal value for the MAP sensor? My scan tool is
showing about 275 Torr.
Any more help would be much appreciated.

Thanks,
Eric Kotz

Aww info coming......If you disturbed the sensor in any way trying to
loosen it, you may have changed the air gap in it and this could cause
problems....Did you say this problem was an after fact of the timing
chain?.....And if its a vacuum leak, that could pose problems as well.. They
say to remove the sensor so you don't break it and then install it back with
the proper setting using a paper shim that sticks to the sensor as you
install it.
Do you have at least 18 inches of vacuum at idle?

 

275 Torr equals (appx) 10.8 inches of mercury
Assuming a baro reading of 29.X inches of mercury, that puts your
manifold vacuum around 18 inches of mercury.

If your scan tool gives a voltage reading for the MAP sensor, I'd
expect to see it around 1.5 volts or slightly less...

 

My question was somewhat different. Original Post mentioned changing the
timing chain.

Why was this done? My only experience with a chain was on my Saturn, and I
had 170,000 miles with no suggestion from anyone that the chain should be
changed...as long as we kept oil in the engine.

Should I anticipate changing the chain on my Dodge 3.3 V6? At which point?
And how much can I expect to pay to have a mechanic do that?

Thanks.

Barry in C'ville
Driving my first Dodge.

 

There is no normal maintenance schedule for chain replacement, normally an
1/8 inch of stretch or when it rattles, I would say about 4 hrs labor, maybe
150.00 parts, don't quote me on that

 

I've changed timing chains on 3.3s at 110K miles, I've seen vans
with 200K that didn't need one. Maintenance goes a long way here.
The chain stretch can be determined by labscoping the camshaft
sensor and crankshaft sensor signals and comparing the two for
offset.

Labor charges to replace the chain depends on which generation
mini-van you have, third generation being the hardest to do
because of underhood access.
I don't have my labor books handy, but I believe it's going to be
higher than the 4 hours Glenn mentioned. Front motor mount has
to come off as does the oil pan...
If you want specific labor times, post the model year and I'll
look it up tomorrow at work.