Flat spot comes and goes

[danielj]

Since last winter T2 has been running very flat now and then. Generally it runs fine but now and then it just goes very flat and dead. If I stop and turn off the engine and start it up again it runs perfectly again. When it happens it revs fine if clutch is pressed but has no power when clutch released and its under load. For example it wouldn't make it up a short hill this morning not even in 1st gear and conked out. Once I started it again it roared up the hill no problem.
The MAF was changed about 2 years ago and the fuel pump was supposed to have been reconditioned at the same time. Fuel filter only changed recently, also drained off the fuel filter at the drain plug and cleaned out the bolt in the fuel line (where some appear to have a mini filter I have a hollow bolt with a hole on one side of the bolt).
Anyone any ideas.

 

[clivvy]

hmm..odd, ok, all i can do is throw around a few ideas, such as electrical issue, perhaps and earth wire problem?? just seems odd that when it does it, its ok after you start the engine again, unless the action of restarting the engine is clearing a blockage of some sort??

 

[Muckypup]

Sounds similar to what my Mav was doing when the cat was blocked... but, it would take about ten mins for it to cool before it would run again whereas yours appears to be ok as soon as you re-start it

 

[DEE]

Pump

Sound like the pump Has it got a zexel pump on it :doh Every one to there own But there crap Had two vehicles in my time with them pumps on nothing but trouble Hope you get to the bottom of it

 

[danielj]

Have Bosch pump.
It is very strange. Usually only happens when it has been in and around freezing. But happened again this afternoon and it was 6 to 8 degrees all day. I had been driving along normally in 5th gear but slowed down by putting in the clutch and easing on the brake as there was a pedestrian with a dog walking on the road. I then knocked it into 3rd gear and left out the clutch and it was running flat and wouldn't pick up speed. This seems to be the kind of situation when it normally happens. When it happened I could still get up the revs on the flat while in gear but the truck wouldn't pick up speed. It wouldn't rev going up a steep hill though and would only go up the hill in 1st gear. It would rev in 1st gear and pick up a bit of speed but as soon as went up to 2nd it wouldn't pick up and I had to keep dropping back to 1st.
Without turning off the engine I disconnected the maf and drove it. No difference. I then took out the air filter and there was strong suction on the inlet pipe. When I tried to move off in 1st with air filter out it conked out. I restarted it immediately and as before it ran fine again.

 

[leafy1]

Could be insufficient fuel supply .............try changing the fuel filter again ??

 

[badger]

MAF sensor.
best way to test, drive up a hill in a high gear 4th ish.
this at lowish speed loads engine the most, if symptoms get worse or are at worse, change maf.

 

[briggie]

so there is no difference when you unplug the maf ...sounds to me like the maf isnt working , try cleaning it by spraying a good contact cleaner or similar through the mesh , and also cleaning the connecttions .

 

[badger]

on the drive at home, even at full throtle air mass is low, testing going up a hill will be sucking in huge volumes of air, if ecu doesnt see this air due to maf fault/failing, it will lower fuel ratio being injected, that combinded with the actual huge amount of air that is going in (but ecu thinks otherwise) will result in a realy realy lean burn, so all kinds of things, bunny hopping holding back, loud noise.
is it a hitachi or bosch maf?
bosch has a self cleaning system, which is why they fail!
hitachi needs cleaning from time to time.

 

[danielj]

Apologies about delay in replying back to posts.
Leafy1--changed fuel filter again this weekend. There was some gunky brown stuff on plastic section that goes in the bottom of the filter. Scraped and blew it out. Did a 120 mile drive in sub zero temp last night with no problems so will see if filter change helps.
Badger--no problem going up-hill in 4th. Steep hill up to my house and I can make it in 4th no problem (too steep to make it in 5th though and normal driving would be in 3rd towards the top) when the intermittent problem is not happening.
Briggie--I meant there was no difference unplugging the MAF when the intermittent problem is happening. When its not happening there would be a huge difference. Took off MAF yesterday and gave it good spray of contact cleaner. Connections seem to be in good condition and clean. Have also had mesh out for cleaning. It was clean.
Badger--it's a bosch MAF. Would a faulty MAF give such intermittent problems, start giving a problem while driving for a while and be corrected once turn off key. Will probably change MAF if it continues to happen.
Hoping at this point that change of filter and removal of gunky stuff from filter housing yesterday may have sorted problem.

 

[ocelot]

Hi Daniel,

sounds daft but is there any water in the fuel filter? the symtoms indicate a MAF fault tho, you can clean them carefully with wet wipes and a little WD40, if you have any switch cleaner, spray some on the connections as well.......
good luck

Dave

 

[danielj]

Hi Daniel,

sounds daft but is there any water in the fuel filter? the symtoms indicate a MAF fault tho, you can clean them carefully with wet wipes and a little WD40, if you have any switch cleaner, spray some on the connections as well.......
good luck

Dave

Dave, I have done a few hundred miles in temperatures down to -8 since changing fuel filter and cleaning maf and no problem yet. It may be as you suggest and maybe due to water in fuel filter housing, maybe freezing and blocking something. Lets hope problem solved.

 

[ocelot]

Good luck then Daniel, might be worth carrying a spare fuel filter though, certainly worth cleaning the MAF at an opportune moment, WD will do but very ilght solvent is better, a little washing up liquid will also do a good job, should if the Bosche one fitted, give better MPG as well................

Enjoy the snow, not much here on the wirral.........

Dave