There is not a "Humidity sensor" on the truck, BUT humidity can affect electrical performance, particularly the high-tension electricity of the ignition coils and spark plug wires. But, you have already replaced the wires? It could be dampness in the engine ECU. Just a guess, or it could be corrosion in the ECU cables and plugs. It could be an intermittant ground. Have you checked your ground wire from the battery to the frame? Have you checked the grounding strap from the starter to the frame? It is good to take these connections off, and scrape the frame to bare metal then reattach. The only way the engine has a complete electrical path is thru the ground straps thru the frame to the battery. Also note the battery negative lead..on its way down to where it is bolted to the frame, as a little lug about half-way down its length that is attached to a lug where other ground wires are attached. This needs to be cleaned up also. Make sure all of the electrical connections from both negative and positive battery terminals are good and clean and tight. Make no mistake about it, corrosion on power cables can build up UNDER the cable, particularly on trucks that see some off-road activity.

 

I'll check these - the truck drove wonderfully after the snafu this morning but I didn't really do anything. I expect it to not run properly again in the AM. The vehicle always starts - just misses horribly at times. I had replaced the negative battery terminal but did not check the others. Would you reccomend a electical (spray) contact cleaner for the ECU connections?

Thanks. Peter

 

First off - thanks to all who participate in the forum - especially those who are lending thier expertise to my (formally reliable) Disco 1998.

So my problem of missing and chugging continues to be an intermitent one. Sometimes it runs like on it is on only 1/2 of engine - won't go over 1500rpms without backfire and stalling. But only sometimes and just for a bit (20min), usually in AM and with humidity.

Recent repair : (5 days) New plugs, wires, (plugs not wet), no error codes (had "misfire may have damaged cats"), cleaned throttle opening, cleaned and replaced most vacuum hoses.

Following the cleaning of the throttle - it was running bloody aweful - chugging, running rough, missing. Turned off Rover, then pulled the MAF and Air filter. Started the motor - IT Sounded GREAT!!! Turned off Rover. Reinstalled MAF and Air Filter. Runs like a dream.

Do I have a spotty short in the MAF harness? Every bone in my body wants to clean the MAF with MAF cleaner - but DiscoMike suggested that I leave it alone........

Question: What the heck is going on?
Ideas?[sm=wtf.gif]

 

So, when you start it and it appears to be running rough, what happens when you shut it off and try starting it up again?

 

It is certainly possible that the MAF sensor could have had a dirty plug to the wiring harness, and when you removed it and replugged it in, it made a better connection. But it is just as likely you have other problems. It is always a good idea to inspect (unplug and plug back in) all sensors and electronic devices on a vehicle, and make sure the plugs are fully seated. The friction of doing this can ensure a better connection overall.

 

If I start it and it runs rough, restarting immediately doesn't really seem to have an effect. Letting run for a few minutes or driving for about 2 miles also seems to clear it up. It is the strangest thing. If I accelerate above 1500 RPMs it will through a (misfire / Damage Cats code).

I have been re-seating every connection that I come across. Have PCV kit on order. And seated several grounds.


Thanks.

 

There was a guy who just had a similar problem, and it turned out to be an injector shorting out. It was shorting out the entire right bank, so when it would mess up, he lost half the engine.

Next time this happens, unplug each injector and ohm it out. Just a thought...

 

do me a favor when you have a cold engine and a free 5 minutes... start it, if its running bad, turn it right off, dont let it warm up, and then turn the key on, so the dash is lit up for about 5 minutes and start it again, see if its better... im thinking 02 sensor goin bad, dumping fuel and causing it to run like crap

 

I am thinking that it is being flooded. It is getting too much fuel because it is getting a bad signal and the ECU is dumping too much fuel into the cylinders. Once it clears out then it runs fine.

 

Hey Guys -

Which O2 sensor are you thinking is bad? The damn thing is so intermitent.I will try the suggestion from roverguy7 - Also - maybe because of recent gas prices and I'm watching the gauge more - but I seem to be blasting through fuel lately as well.

P-