Hey all,

First Cherokee I've owned, day 3 of owning it and more issues. [SIGH]

Got in this morning, cold start, she really struggled to start. Started, cut out, started again and I had to keep the foot on the throttle to keep the revs above 1000rpm. The revs just went up and down up and down. Started to stabilise at around 700rpm, I put her in gear and drove off.

Drove around for 20 minutes, engine temp was midway, stopped at a petrol station to fill up, when I went to start her same thing, really struggled to start, then when she did the revs was going up and down and I had to keep the foot on the throttle for a minute or two.

I'm new to jeeps, and to be honest, new to petrol as been driving diesel for a decade.

My thoughts:

Starting issue:
A) Battery is broken and has low amps.
B) Battery is being drained (I charged it fully the day before), however the starter motor did struggle for a few turns before she started, on my landy if the battery is low the starter motor simply clicks and won't turn over.

Poor running (rev going up and down) issue:
A) Spark plugs
B) Injectors


Is there anything I'm missing? How can I check all the above and how can I replace the busted bits?

Your help is appreciated, 3 days In and i'm ready to set her on fire. Which is a shame as when she's driving she's great fun.

 

Try cleaning the Idle Air Control. It's probably very dirty. Actually remove and clean the entire throttle body. Be careful not to get solvent in the Throttle Position Sensor.

A low battery condition sometimes will confuse the computer enough so it won't start.

 

That sounds simple.

I'll have a google for some instructions, what would you use to clean it? I have WD 40 and carb cleaner at present, other than that will have to buy something specific if needed.

 

Carb cleaner or brake cleaner works good and an old toothbrush to get into the tight places. If you remove the IAC , TPS, and MAP sensor if it's attached, there isn't much you can harm cleaning it. Just be careful with the idle control plunger. Don't try to move it or twist it because it's attached to a motor.

I just read something about WD40. It was originally made for NASA to spray on rocket bodies so that the ice caused by supercold liquid oxygen would break off the instant the rocket motor started. It has found itself many other uses, but it's not a good lubricant because it eventually evaporates.

 

A man with all the knowledge... I never knew that. Love those kinda facts.

I'll get cleaning it tonight, see if that makes a difference.

What about the starter motor sounding like its struggling? How would you suggest testing if its battery AMPs, Voltage or new motor time?

 

@dave1123 I've found a video, looks very simple.

Do I need any gaskets when removing the throttle body? Seems like there may be one that would need to be replaced If i remove it?

 

I too was going to say IAC valve but Dave beat me to it. I couldn't say about any gaskets as I haven't removed my throttle body before.

Also, not to scare you off but it did take me a few months of problem fixing to get everything happy with mine after being sat for 7 years. I've done a lot since but I love owning it. I think up until march this year, since June 2018 I've had to fix something at least once a month. Enjoy your purchase

 

what year is it?
A bad battery can cause heaps of issues on it's own.

 

You'll keep getting asked this. If you go onto your forum profile you can fill in the details, it makes life here easier.

 

Have the battery checked, I have had a bad battery do that on a few different XJs.

 

Replace battery if it's suspect and clean (don't just look at) your battery terminals and ground connections by taking them off and cleaning the surfaces with a wire brush. Low voltage and bad grounds can make the vehicle computer go all kinds of wonky. The reference voltages for these sensors are only 5 volts so it doesn't take much to screw everything up.

Close, it was used as a corrosion preventative on fuel tanks, and rocket skins, specifically the Atlas ICBM. The tanks used to contain the fuels were paper thin to cut down on weight. Every pound you fly into space requires a huge pile of money. Even dropping a wrench on these tanks could easily rupture them, so any corrosion could cause failure of the tanks. In fact, A dropped socket almost blew up sizable portion of Arkansas lol.

https://interestingengineering.com/1...uclear-missile

https://www.wd40.com/history/

 

Yeah, I remember that missile silo fire! One of my Dad's friends was on that response team. He said he just had a feeling it was going to be his last day on earth.

I'm not an electronics guru, but I was told the reason low battery voltage makes the computer go wonky is because they have a voltage reduction stage that changes 12v to 5v for the solid state circuits and if it doesn't get 12v in, it doesn't put 5v out.

 

Most of the regulators used in the electronics need about 1.5-2 volts above the final voltage to regulate properly. The older Renix ignition module seems to need 9-10 volts minimum to fire reliably, and a certain speed when cranking before the ecm even tries to fire. So yes, a eak battery can cause problems. I would suggest visiting cruiser54.com and start cleaning all of the ground connections.

 

@dave1123 and anyone else who fancies pitching in.

This is a video of her starting this morning.

Hard to hear her struggling on the first attempt but it's a very slow, quite, turning over of the starter motor.

I think I flooded her which is why she struggled the second time. I then have to keep my foot on the throttle which I'm guessing is the idle air sensor you mentioned dave.

 

There's no video on your post.