New grounds, now idles rough

[NewBreedCustom]

I have an 89 4.0 that came from the previous owner with only one ground left on it. So I added one from the firewall to the engine with 4awg wire and another from the battery to the fender with 4awg and bang! No more electrical issues but now it idles horribly but accelerates fine. It idled very well before these grounds. Can anyone help please?

 

[bcmaxx]

check all other connections including power, See it the line the goes from the throttle body to the map sensor mounted on the firewall was distured, cracked or broken. They get brittle sometimes. There is also 4 grounds that attach to the dipstick retainer bolt and run to the main harness above the motor on the firewall. Make sure these wires are all there and intact . I had a broken one hidden in the plastic sheath causing me severe headaches.

 

[KD3NE_]

Have you tried removing the new grounds, one at a time to see if one of them is somehow effecting the idle?

Take off one, check idle.
If idle still rough, reinstall the ground and remove the second new one.
If idle is still rough, remove them both and check the idle.

That will show if it is related to the new grounds or not.

It may be something totally unrelated, or it could be related to you doing the install and knocking something else loose.

 

[Shorty]

The TPS is extremely sensitive to changes in reference voltage. Any time you've altered the ground connections, the reference voltage will change and throw the TPS signal off. Adjust your TPS now that you've improved the ground connections.

 

[xjtrailrider]

The TPS is extremely sensitive to changes in reference voltage. Any time you've altered the ground connections, the reference voltage will change and throw the TPS signal off. Adjust your TPS now that you've improved the ground connections.

Bingo!

 

[NewBreedCustom]

Wow thanks guys for the quick replies. This forum is way better than cherokee forum and people actually seem to know what they are talking about on here. So the TPS sounds like the culprit so my next question would be how do I adjust it? Thanks again

 

[xjtrailrider]

Wow thanks guys for the quick replies. This forum is way better than cherokee forum and people actually seem to know what they are talking about on here. So the TPS sounds like the culprit so my next question would be how do I adjust it? Thanks again

If your gonna own a RENIX XJ then you need the RENIX Fuel Injection Manual! Check you pm's

 

[NewBreedCustom]

Thanks. Sent u a pm back

 

[Spearfisher XJ]

Can I get a copy of that?