View Full Version : MAF?

disco stu
09-22-2008, 09:45 AM
97 Disco 1 Auto

Hey guys... there was a k+n on the truck when i bought it but switched to the stock filter as of now, and soon after I had bad misfires randomly one day when on the highway, loss of power, didnt sound good when over 80... and in Drive it was worse when it shifted into 4th gear. (auto) and seemed to rev better and higher when in 3rd... as i had to use that, then second to climb the mountain road to my house. all the old plugs were fouled and looked rich... i changed the plugs and wires and it ran sweet. way better cruising speeds, and snappy. cruised around for a day, no highway driving yet though. then the next day i went for an hour stint out on the the highway and sure enough after 25 minutes of cruising at highway speed it started to hunt a bit up and down, then starts the misfires again, this time throwing the check engine light(havent pulled the codes yet). so i limped it home, and here it sits.... i think the maf is the trouble, would it be dangerous to unplug it and the airbox sensor and drive around for a half hour to check? Also there has been a funny idle and seemed to clear itself mostly when the fresh plugs and wires were in. and i have already cleaned the throttle body and IAC valve, so i dont think they are to blame... maf aswell???

disco stu

disco stu
09-22-2008, 12:09 PM
Or does this seem more like a TPS problem... sounds like allot the guys with my issues fixed theirs with a new tps... orrr maybe the sticky exhaust valve problem... ?

09-22-2008, 08:56 PM
Was your K&N overoiled, by chance? A lot of MAF's get toasted when a K&N is used, the oil ends up on the hotwire.....

Don't get me wrong, for a carbureted car on a track, a K&N is great, but, for a car in dirty dusty conditions (like offroad), especially on one that uses electronic bits (like a MAF), I wouldn't use one.

But, I wouldn't be surprised if you have either a TPS problem or a MAF problem. Both are reasonable places to start....

disco stu
09-22-2008, 11:32 PM
the k&n was already on the truck when i got it.... ran it for a bit then took it out when the problem arose... so what it was treated to before that i am unsure of.

tonight i unplugged the maf, changed a bit, but not too much... still was rough.

then i took out the tps and there was a bunch of white corrosion in behind there. so i cleaned with brake parts cleaner ... no silicone... and reinstalled. still running rough.

the new plugs i had in have become fouled, so this may be why its misfiring still.

is that corrosion behind the tps normal or is it indicative of the sensor being junked.

the codes are getting pulled tomorrow, so we'll see what they say...

anyone know where to stick a multimeter on the tps to check for voltages, and possibly the values that are normal?

disco stu
09-23-2008, 06:02 PM
So the codes are:

p1313 bank A misfire - could damage cat

p1314 bank B misfire - could damage cat

p1316 excess emissions misfire

p0300 random/multiple misfire

and misfires on all 8 cylinders (p0301 - p0308)

on my way back from the shop my last 1 ft of muffler ... or should i say rust, came off and it actually seemed to help the misfiring. the cats are new, the muffler is good, and there are no other leaks in the rest of the exhaust... it rusted off right after the last clamp in the rear... should that be rewelded or fixed... or is that a 'must replace' the last bit of exhaust?

unplugged vehicle speed sensor to see if that remedied the little spurts of power loss at highway speed, but only ran it down the road and back because of the misfiring.

the tps is on order, be here in two days... in the mean time should i change the plugs and see if the vss was the problem by leaving it unplugged... only if it is the tps then it will foul them again :(

oh and with the subs cranked and all the lights on (including two floods) the battery is reading around 13.85v at idle... that seems fine to me... is that low enough to cause idle issues? its about 13.93v with lights and stereo off... and only drops about .3v with the subs only... and like .8v with just the lights on.

disco stu

disco stu
09-26-2008, 05:30 PM
new tps fitted today. instantly idled up to 2500rpm and stayed no matter wat untill it warmed up a bit, then still at 1700... got into gear and went down to just over 1000rpm and upon driving still had alot of backfiring... didnt like going over 2000 rpm when in gear. the plugs are black around the porcelin and centre and white on the arm... tried first with the vss unplugged, again with the same results plugged in... and unplugging the maf made no difference. any ideas?

10-04-2008, 03:46 PM
disco stu, how much mileage is on ur engine?

disco stu
10-05-2008, 09:04 PM
240 000 km.

disco stu
10-07-2008, 10:45 AM
Could the cats be plugged causing it to misfire/backfire out the intake?

i had forgotten that i ran a tank of 87octane through by mistake one time only... soon after the cats were fitted. maybe that did it?

the plugs were checked with a megger and although there is some carbon, they are not shorted or carbon fouled.

disco stu
12-12-2008, 10:31 AM
soo, after saving some moula and watching the rover collect dust i remedied the wierd idle with a new stepper motor... the cats are flowing, now its just running rich, o2 sensors are being checked this week. thought i better update and not leave the thread dead.

disco stu
12-16-2008, 07:51 AM
hopefully the last update on this thread.... iac remedied the idle, in the previous processes i had adjusted the throttle cable rich to compensate for the high idle. so after turning that back down, and a little tweek with the iac adjustment screw everything runs smooth!

thanks to everyone who lended advice, disco stu.