Flat Spot At Low Rpms

[ke55boy90]

hey i have a ke55 with a 4age 16v engine in it and it just has had its timing belt done and now it seems to have a flat spot at low rmps when reving up in gears. i was wondering if any one could give me some advice on what it could be. all the timing marks line up fine and i just put in new plugs. could it be the leads???? any help would be great i have tryed looking all over the net and can't really find a answer.

 

cheers blake

[bAKER]

stock ecu?

[ke55boy90]

yes stock ecu

[rian]

When does the flat spot start and end? Maybe your TVIS isn't plugged in?

[Trev]

Do anything else?

[ke55boy90]

i will check the tvis tomorrow and no just a flat spot at low rpms. have no tacho so can't tell you when but i think its around the 2k mark.

[Trev]

So you didn't drop the water or anything like that?

[ke55boy90]

no i didnt

[altezzaclub]

I think something electrical like leads would show up in other places, not just a flat spot. You could have a look at night and see if there are any sparks juming around, just whip the bonnet off for a quick drive one night, particularly a damp or wet one.

 

If nothing else was touched then it has to be cam timing related, and if that is correct now it suggests it wasn't correct before and the tuning was covering the fault. You might have to re-tune timing/fuel a bit.

 

Usual causes I can think of would be mixture going lean at that range, or too rich, and the other would be that spark timing is too advanced just there.

 

Pop up a couple of real photos (not bloody phone ones!) of the timing marks lining up and maybe some 4AGE guru can tell you. Check the ignition timing and tell us what it is. Then I'm afraid its a dyno run for air/fuel ratios under load.

 

I'm surprised you don't have a rev counter on a conversion like that.

[ke70dave]

id do the following as a diagnostic process, hopefully you find a problem along the way.

 

-camshaft timing - double check, tripple check

-ignition timing - put the T1 and E1 together, should be around 10-12BDTC with a timing light.

-pull the spark plugs, check condition, attack with wire brush if all black. (even if they are new,they might have been blackened from running rich cuase by some other problem). check the resistance of your ignition cables. check the rotor and distributer cap condition. attack with a bit of sandpaper if coroded.

-enter diagnostic mode on your ecu (google it) check for any codes, if you don't have a check engine light hooked up, get one.

-make sure the TVIS opens as it should, I'm fairly sure it opens around 3500rpm. you can see it working if you rev it at idle i think. can't remember if it is load dependant or not.

-check the TPS adjustment, theres a procedure around for this. google it.

 

thats about it based on what you describe, if you havent found the problem after that id be suprised :S

 

also note, on my old 4age, i had my ignition timing out 2 teeth for about 3 months, i thought the epic indicuction roar was normal. i didnt notice any large flat spots. it wasnt exactly slow, and it certainly didnt have any flat spots. it drove very well actaully (i didnt feel the need to try and fix it). drove ALOT better once i fixed it thats for sure, only found out it was wrong when i changed the timing belt.

Edited July 17, 2012 by ke70dave

[B.L.Z.BUB]

Did you line the timing pulley up to the zero on the timing cover (red) or to the tensioner (blue)?

Its different depending on the 4AGE you have EDIT: I should say depending on what pulley you have. Mine has an aftermarket anodised pulley. The AW pulley has the timing marks on the pulley and uses the timing belt tensioner spike to time it.

 

 

 

I had mine set to the zero on the timing cover, and had a similar issue, then I set it to the cambelt tensioner spike and it went fine.

 

 

http://mitchee.com/a...4A-GEManual.pdf

Edited July 17, 2012 by B.L.Z.BUB

[ke55boy90]

yeah mine is set to zero i checked it today so i should set it to 10????