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after 20 min it feels like it is running on half power have been through my book all new sensors checked compression changed intake gasket checked vacuum i back probed the tps it should be 4 volts wide open i have 3.75 some of the other sensors crankps camps checked volts from pcm i have 9.75 on both should be 8? dont know about cat converter is this a one time question?

Submitted: 645 days and 14 hours ago.

Category: Car

Value: $15

Status: AWAITING CUSTOMER ACTION

Optional Information:
1993 Jeep grand cheroke 4.0 6cyl

Already Tried:
everything i know

Posted by AMEDEE 645 days and 12 hours ago.

Answer

Sounds like plugged exhaust. The easiest way to check for this is to hook up a vacuum gage to any vacuum source from the intake manifold. It should read about 17 to 19 inches of steady vacuum at idle. Upon snapping the throttle quickly to about 3000 rpm and letting off back to idle, you should see the vacuum gage go from steady 18 inches of vacuum to 0, back past 18 inches of vacuum, to about 23 or 24 inches of vacuum back to about 18. If it does not go back past 18 inches to 23 or 24 before returning to 18 something in the exhaust is definitely plugged up.

Or you can always pull the o2 sensors and see if it makes any difference. :)

645 days and 12 hours ago.

Reply

i did that it doesnt drop all the way to 0 but to 10 then goes above to 25 the o2 sensor is new

Accepted Answer

I don't think you snapped the throttle fast enough.

FLoor it real fast, then let off before you do engine damaged.

Snap the throttle to about 2000 rpm, then let off.

I was talking about removing the o2 sensor to see if the engine breaths better in case it has plugged exhaust.

Accepts:
Expert:	AMEDEE
Pos. Feedback:	97.8 %
Answered:	2/16/2008

ASE MASTER TECH

ADVANCED LEVEL SPECIALIST

645 days and 10 hours ago.

Reply

ok i did the check all fine reads what it should what else can i try

Posted by AMEDEE 645 days and 10 hours ago.

Answer

You could have a bad fuel pump. I would rec to check fuel pressure. Fuel injected cars are very fuel pressure sensitive. Fuel pressure is very important and must be within specifications! But if the pressure is low, it does not mean the pump is bad. A plugged fuel filter, a pinched line, and low voltage at the pump can contribute to low fuel pressure. All three must be check before replacing the pump! You can get a fuel pressure gage at a local auto parts store for cheap.

645 days and 10 hours ago.

Reply

new fuel pump has proper fuel pressure and new filter checked the lines disconected all blew out

Posted by AMEDEE 645 days and 10 hours ago.

Info Request

What is engine vacuum at idle?

What about ignition timing?

645 days and 9 hours ago.

Reply

18,ignition timing how do I check that

Posted by AMEDEE 645 days and 9 hours ago.

Answer

The ignition timing is controlled by the pcm. You are not supposed to be able to set it. But I think you can check it. You would need either a scan tool or a timing light.

UNder full throttle, what is the o2 sensor doing? Rich or lean?

Edited by AMEDEE on 2/16/2008 at 12:29 PM

645 days and 9 hours ago.

Reply

do I have to back prob the O2 sensor to get that reading. everything is top dead center..

Posted by AMEDEE 645 days and 9 hours ago.

Answer

YES!

Or you would have to have a scan tool to plug into the diagnostic connector.

645 days and 9 hours ago.

Reply

will check that next thanks

Posted by AMEDEE 645 days and 9 hours ago.

Answer

Sounds good!

I will be waiting!

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Optional Information: 1993 Jeep grand cheroke 4.0 6cylAlready Tried: everything i know

Answer

Reply

i did that it doesnt drop all the way to 0 but to 10 then goes above to 25 the o2 sensor is new

Accepted Answer

I don't think you snapped the throttle fast enough. FLoor it real fast, then let off before you do engine damaged. Snap the throttle to about 2000 rpm, then let off. I was talking about removing the o2 sensor to see if the engine breaths better in case it has plugged exhaust.

Reply

ok i did the check all fine reads what it should what else can i try

Answer

Reply

new fuel pump has proper fuel pressure and new filter checked the lines disconected all blew out

Info Request

What is engine vacuum at idle?What about ignition timing?

Reply

18,ignition timing how do I check that

Answer

The ignition timing is controlled by the pcm. You are not supposed to be able to set it. But I think you can check it. You would need either a scan tool or a timing light. UNder full throttle, what is the o2 sensor doing? Rich or lean?Edited by AMEDEE on 2/16/2008 at 12:29 PM

Reply

do I have to back prob the O2 sensor to get that reading. everything is top dead center..

Answer

YES!Or you would have to have a scan tool to plug into the diagnostic connector.

Reply

will check that next thanks

Answer

Sounds good!I will be waiting!

Related Car Questions

Optional Information:
1993 Jeep grand cheroke 4.0 6cyl

Already Tried:
everything i know

I don't think you snapped the throttle fast enough.

FLoor it real fast, then let off before you do engine damaged.

Snap the throttle to about 2000 rpm, then let off.

I was talking about removing the o2 sensor to see if the engine breaths better in case it has plugged exhaust.

What is engine vacuum at idle?

What about ignition timing?

The ignition timing is controlled by the pcm. You are not supposed to be able to set it. But I think you can check it. You would need either a scan tool or a timing light.

UNder full throttle, what is the o2 sensor doing? Rich or lean?

Edited by AMEDEE on 2/16/2008 at 12:29 PM

YES!

Or you would have to have a scan tool to plug into the diagnostic connector.

Sounds good!

I will be waiting!