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post #1 of 11 Old 03-30-2020, 07:07 PM Thread Starter
MackJartel
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Help please!!!!

I have a 1995 Grand ZJ 5.2 that has a low idle (which it has had since I got it 5 years ago, runs a bit hot, cold air only comes out, and when it reaches running temp (or just above) it surges then stalls.

I checked the fuel pressure and it’s ok. Cleaned out throttle body. I replaced the fuel filter, battery, serpentine belt, map sensor, iac, TPS, coolant temp sensor, couple pulleys, water pump, radiator, thermostat, alternator, cap, rotor, spark plugs, plug wires, and air filter. The coolant is new and not leaking. I also replaced the valve cover gaskets that were leaking. It was running cold until I replaced the coolant temp sensor but soon after this surging happened. Wtf is going on???

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post #2 of 11 Old 03-30-2020, 07:14 PM Thread Starter
MackJartel
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*It surges under 1500 RPM
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post #3 of 11 Old 03-30-2020, 08:32 PM
RefinedSouthern
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What was wrong with the previous temp sensor?

Did you replace the thermostat and if not are you sure itís not sticking?

Have you checked for vacuum leaks?

96 ZJ, work in progress
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post #4 of 11 Old 03-31-2020, 12:17 AM Thread Starter
MackJartel
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It was running cold and horrible fuel economy. I replace the temp sensor and that fixed it. Now I have this problem. Thought the thermostat was leaking so I replaced it but it was the bypass hose so I fixed that but still no luck....
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post #5 of 11 Old 03-31-2020, 04:56 AM
V8GCZJ
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Quote:
I checked the fuel pressure and itís ok.
What psi? And is it constant when running?

You have two temp sensors, One for the gauge and one for the pcm. What brand iac? And when you replaced it then started it did it rev up then go down in rpm? And what about codes?

https://www.quadratec.com/jeep_knowl...article-24.htm
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post #6 of 11 Old 03-31-2020, 02:40 PM Thread Starter
MackJartel
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It’s 38 psi and it’s steady even when surging. I replaced the temp sensor that’s on the left of the thermostat I'm assuming it’s for the gauge. I’m not sure the brand of the IAC but it is adjustable unlike the original one which I put back in. When I start it up it has a big kick then goes to 700rpm then when warm it’s running about 350rpm. No codes reported. I’m looking for vacuum leaks and found a broken hose that’s connected to this part in the picture I’m not sure what that is, can you tell me?
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post #7 of 11 Old 03-31-2020, 03:18 PM
1996maroonzjf
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Its called the speed control servo - its what controls the cruise control.

The short vacuum hose that connects to it is no longer made as far as I've found, but when I replaced mine I used the small hose that comes in this kit -

https://www.ebay.com/itm/Engine-Cran...-/132283071259

I just made it in to a loop to take up the extra slack since it is longer than the OEM. The connectors on either end fit on to the existing vacuum hoses and have a tight fit.



Is that a picture of your ZJ? If so I'm interested in the location of the battery. Why / how did you move it to where the coolant overflow bottle normally is?

-Tim
(2) '96 4.0s
#1-'10-'18
#2- HP30/Ford 8.8 - 4.56, OME HDs, 5100's, IRO Adj Arms/Track Bars
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post #8 of 11 Old 04-01-2020, 03:11 PM Thread Starter
MackJartel
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That’s a random picture as I didn’t have one of mine at the time. No wonder my cruise control didn’t work. Where do you recommend I buy vacuum lines and connections? Lordco doesn’t have a great selection.
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post #9 of 11 Old 04-01-2020, 04:06 PM
LordHobbit
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dont' know exactly what size you'll need, but this might work:

http://www.amazon.com/Universal-Diam...5778715&sr=8-2

93 red ZJ 196k 4.0. Spent more money than I should have ...
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post #10 of 11 Old 04-01-2020, 04:42 PM
1996maroonzjf
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This is the Dorman part I linked to above. It is Dorman part #46006. It should be sold at most any auto parts store. I've seen this kit for as low as $9.99 at O'Reilly Auto Parts in the US.

https://www.dormanproducts.com/p-3285-46006.aspx


I used the smaller hose that is taped to the larger CCV breather hose in the pictures. The connections are a perfect fit, the hose is just a bit longer than the stock hose so you have to loop it around to take up the extra slack.

-Tim
(2) '96 4.0s
#1-'10-'18
#2- HP30/Ford 8.8 - 4.56, OME HDs, 5100's, IRO Adj Arms/Track Bars
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post #11 of 11 Old 04-10-2020, 04:16 PM Thread Starter
MackJartel
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I replaced both coolant temp sensors and still no luck...
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