Jeep Grand Cherokee - Engine running rough

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Hello everyone, first let me say that a few months ago I used this site to determine a problem I was having with my 1996 Jeep Grand Cherokee Laredo (V8) and the response I received from cmeseadoin was very helpful. So, I just wanted to thank all you car enthuisists in advance for offering up your knowledge.

In the last month my engine has started running rough and idling rough.

I took the car to my mechanic last night and he said he is not sure exactly what it might be. So he said it could be a pulley...but he wasn't positive on that or which pulley it might be. He said it almost sounds like it could be the air conditioning pulley, which is the most expensive. Never heard of pulleys in a car : )

I have been doing searches on the internet and there are so many possible causes for a rough running engine, but I have never seen pulley listed...I have however seen 'idle-air-control' listed as a problem.

Anyway, I was hoping maybe someone had the same problem and could let me know whether to allow my mechanic to replace this 'pulley' thing or if I should steer him in another direction.

Any other info I can offer, please just ask, and i'll do my best...

posted by  jeffcravener

This may help. I am not the author.
IAC Valve

First
Remove four hex screws holding the plastic cover

Check the cable harness carrying voltage to your IAC-

Disconnect lAC valve,

Key on, engine off.
Measure Voltage PWR circuit voltage at the lAC valve harness connector.

Test Connectors supply of power to your IAC


Is voltage greater than 10,5 volts?
Yes;
KEY OFF, GO to KE3 (My valve measured 11.2 volts)

No;
REPAIR open circuit.

(My hope is that this is not your problem……As repair of an open circuit may be more difficult to trouble shoot than the
IAC alone)
************************************************** **********
KE3 CHECK lAC VALVE RESISTANCE

lAC valve disconnected,
Measure lAC valve resistance between the two pins,


Is resistance between 6.0 and 13.0 ohms?
Yes
GO to KE4
No
REPLACE lAC valve,

(Mine measured 0.022 therefore was very suspect at this point)
******************************************

KE4 CHECK lAC VALVE FOR AN INTERNAL
SHORT TO lAC CASE
Measure the resistance from either lAC valve pin to lAC valve case,

Is resistance greater than 10,000 ohms?
Yes

GOto KE5

No
REPLACE. lAC valve,

(With this my valve measured OL and therefore it became clear that a repair cleaning was of little use )

Anyway - Further checks go on as follows if yours passes the above tests
KE5 CHECK AIR INLET FOR PLUGGING

Inspect the entire intake air system for debris, blockage and other damage.

Remove and inspect lAC air tubes (if equipped) for blockage and other
damage.

Remove and inspect the air cleaner element for excessive dirt.

Is the intake air system OK?
Yes
RESTORE inlet air system. GO to
KE6 CHECK FOR INLET AIR LEAKS
Key on, engine running.

With engine running at idle, listen for vacuum leaks.

Inspect the entire intake air system from the mass air flow (MAF) sensor
to the intake manifold for leaks such as:
Cracked or punctured intake air tube.
Damaged or loose lAC air tubes.
Loose intake air tube at air cleaner housing or throttle body.


lAC valve or gasket seal.
EGR valve gasket seal.
Vacuum supply connector and hose.

Many on the net have written about cleaning the IAC then re-installiung it- Well I think that is fine but- Only when it passes the electrical tests above – and cleaning also carries the added cash savings of about $65 or, in my case $88.00 dealer cost- I have only two warnings about it though and that is this;-

There may be a chance that while cleaning your untested valve, you perhaps may just rattle an intermitant internal short connection enough to make it work for a week or two – then when you least expect it- got ya!

posted by  lectroid

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