Rough Idle on new MJ

Bucketheadben · Apr 11, 2007

I just bought an 88 MJ 4.0 manual 4x4 with 130,xxx miles that wouldn't start. I replaced the spark plugs, wires, cap, and rotor and now it will start but idles rough. Most of the time it will start up and then die unless I give it gas. Sometimes it will run well for about 5 secs then it will act like it's about to die then start running good again for about 5 secs...... It loops like that. I just bough a fuel filter and will replace that tomorrow along with cleaning the TB.
Do you have any other suggestions as to what I should do to get it running? Thanks
Ben

Ecomike · Apr 11, 2007

Bucketheadben said:
I just bought an 88 MJ 4.0 manual 4x4 with 130,xxx miles that wouldn't start. I replaced the spark plugs, wires, cap, and rotor and now it will start but idles rough. Most of the time it will start up and then die unless I give it gas. Sometimes it will run well for about 5 secs then it will act like it's about to die then start running good again for about 5 secs...... It loops like that. I just bough a fuel filter and will replace that tomorrow along with cleaning the TB.
Do you have any other suggestions as to what I should do to get it running? Thanks
Ben

Search for and read up on cleaning and oiling the IAC, Idle Air Controller in the throttle body. Also pull, and clean each and every single ground wire connection at the battery, engine (2) and the firewall (2).

Has it been setting up a long time?

Bucketheadben · Apr 14, 2007

I think it's been sitting for about a month. I cleaned the IAC and it's still the same. It does have some cheep battery connections. I'll try replacing them.
Thanks
Ben

Bucketheadben · Apr 14, 2007

I also checked the tps' voltage. I was getting 1.7 input, .71 output and 4.7 at WOT. Is that acceptable or should I replace the TPS. It sounds to me like I've got a bad connection since the input is low. But wouldn't that effect the output? THanks
Ben

87manche · Apr 14, 2007

something is definitly strange with your TPS.
you say 1.7v input?
what terminals gave you that measurement?
here's al ink to the adjustment procedure, just so we're all on the same page:
http://www.lunghd.com/Downloads_and_Links/Adjusting_TPS.zip

Ecomike · Apr 16, 2007

Bucketheadben said:
I also checked the tps' voltage. I was getting 1.7 input, .71 output and 4.7 at WOT. Is that acceptable or should I replace the TPS. It sounds to me like I've got a bad connection since the input is low. But wouldn't that effect the output? THanks
Ben

Sounds like you wrote down the numbers backwards, or measured the wrong wires.

Was this measured on the three pin or 4 pin connector? It should have been taken on the 3 pin connector. If you did not make a mistake then you may have the 3 pin connector to the TPS attached backwards. I made that mistake once myself. It does not sound like a bad TPS, sounds like the connector is attached backwards, or you posted or measured the numbers backwards.

Bucketheadben · Jun 6, 2007

Thanks for the help guys. I finally got back to working on the MJ. It turned out to be a bad EGR valve. I replaced that and it runs like a champ now. Thanks again.

Rough Idle on new MJ

Bucketheadben

NAXJA Forum User

Ecomike

NAXJA# 2091

Bucketheadben

NAXJA Forum User

Bucketheadben

NAXJA Forum User

87manche

NAXJA Forum User

Ecomike

NAXJA# 2091

Bucketheadben

NAXJA Forum User

Similar threads