Golf Mk2 ABF DTH jenveys with DTA issue with hesitation/jolting at certian tps/revs

Hi,

Wondering if any one has any suggestions in what could be the problem with my car. As per the title it is a Mk2 golf running an ABF with jenvey DTH throttle bodies on a DTA E48 ECU. The crank sensor is an external 36-1 wheel instead of the OE internal one but other than that the engine is standard.

Basically I got the car mapped and a couple of days later I noticed at a particular point (throttle position 3 between 1750 - 2250) the car will hesitate / jolt and the AFR meter will flicker from stoich to lean (14 - 17ish). I spoke to the mapper and he said to enrichen that area of the map to see if it goes away, tried that and it doesn't. When driving with "real time mapping" displayed I have noticed that when this happens the throttle position will jump from 3 to 1 to 3 to 1 (missing 2) and so on therefore the reason why its going stoich to lean to stoich to lean etc... When depressing the throttle pedal with the engine off or even when the engine is on when stationary the throttle will smoothly flow from 0 to 100%.

I have changed sparkplugs and that does not change the problem.

When viewing the diagnostic display I have noticed that the short term TPS errors have reasonable high figures next them (100+) after a few days, however if I drive with the diagnostic display live on the lap top when the car actually hesitates it does not go up instantly. What are these short term errors?

Tonight I am thinking of changing the crank sensor to rule that out even though the diagnostic display says it is good (no sync errors etc...)

Any other ideas?

Thanks
Tim.

 

Post a screenshot of the map.
You shouldn't need to have cells for 1, 2 and 3 percent throttle, that's very fine, and will cause the problem you are describing if the fuel amounts are very different, which they shouldn't be.

ETA - Don't change your crank sensor, it's fine from what you've said.

 

TPS seems to be noisy though, therefore as the only load source if noise is causing it to move, areas of the fuel table for less load/airflow will be picked up in error and lead to a lean misfire and subsequent shuffle.

 

I meant throttle column 3. So it jumps from throttle column 3 to 1 etc.
throttle column 1 = 0 - 2%
throttle column 2 = 3 - 5%
throttle column 3 = 6 - 10%

Will post the fuel map tonight.
Thanks.

 

Toyotec.
Ok thanks for the info. I've never noticed it previously though, all of the wiring is twisted pairs to eliminate noise interference and the crank wiring is shielded. I do have a spare tps to try just incase to rule it out.

Could it be the coil or ht leads missing?

 

Ah, OK. That makes more sense. Also post your map columns set up.

As toyotec says, this sounds like a noisy TPS. Could be failing, or could be noise from elsewhere. This could be from the coil or HT leads, or any number of other places.

 

Fuel table and throttle columns for info.



Thanks

 

^^Looks reasonable for an alpha N fuel table and is not the root cause of your issue.

 

Thanks for confirming that.

Well after a nightmare drive home I went out plugged in the laptop to see what's going on. There were more short term TPS errors there again so cleared them, left it on the diagnosis page, went to pull off and it hesitated / jolted and I saw the TPS error count go up so done it again and managed to see it flicker to fail and then same again and again. So changed the TPS sensor and its sorted it.

Thanks to sparrow and toyotec for all the help / suggestions.

 

Excellent

 

Super! And thanks for reporting the solution.