Hesitation under load

Daveymaclad · 09-05-14, 11:34 AM

Hi guys

The great news is my UR's finally got a new MOT on it. The not so great news is that my car still has a small running issue.

So, when parked up the engine revs free and cleanly through the range but when out and about driving it gets to 3,000 rpm and then hesitates not going up in revs at all.

So far I've been told it could be two things:

Meine air temp sensor ist kaput. I've replaced with a 22ohm resistor but am unsure if that will help or hinder the running under load problem I have.

My distributor was refitted 180 degrees out and have been told to check the rotor arm to see if it's showing burnt signs or not.

What's other peoples thoughts on what could be causing that hesitation at 3k rpm? Would either/both of the above cause/remedy the problem or are there other things I should be looking at ahead or in addition to those?

As always many thanks

Dave

john johnson · 09-05-14, 11:55 AM

Send me a picture of your rotor arm .... I have a shelf full and can send one down to plop on to try

msh · 09-05-14, 01:42 PM

Resistor in place of IAT sensor means incorrect air mass calculation, used here to determine engine load for ignition timing and boost control [I guess?] purposes, but unlikely to cause something that severe. What does "My distributor was refitted 180 degrees out" mean?

Daveymaclad · 09-05-14, 02:23 PM

Quote:

Originally Posted by msh

Resistor in place of IAT sensor means incorrect air mass calculation, used here to determine engine load for ignition timing and boost control [I guess?] purposes, but unlikely to cause something that severe. What does "My distributor was refitted 180 degrees out" mean?

Best explained with photo's! Will get car back in the morning so will post then. But essentially the plug for the wiring to the distributor should be facing the bulkhead. Mines facing the front of the engine bay.

msh · 09-05-14, 03:49 PM

That shouldn't mean anything - apart from cosmetic considerations [dunno about early engines, late 5 pot engines uses covers with three sockets raised and HT lead plugs in 90 degree angle, making any but one correct combination looking messy, with leads pointing in all directions] , distributor plug could be facing any direction, as long as rotor arm is positioned correctly.

Daveymaclad · 09-05-14, 03:52 PM

Quote:

Originally Posted by msh

That shouldn't mean anything - apart from cosmetic considerations [dunno about early engines, late 5 pot engines uses covers with three sockets raised and HT lead plugs in 90 degree angle, making any but one correct combination looking messy, with leads pointing in all directions] , distributor plug could be facing any direction, as long as rotor arm is positioned correctly.

That's what I thought and has been said to me - cosmetic. Just wanted to put it out there in case it did mean anything else!

I'll get the cap off tomorrow and take some photo's of the rotor arm in case somethings amiss there.

Cheers

Hanuman · 09-05-14, 04:35 PM

The discussion regarding the inlet temperature sensor so far has revolved around the fact the actual resistance is quite low, but with quite a wide acceptable range;11-31ohms, and nominal resistance of about 22ohms. It's been the subject of much debate about its importance. Several knowledgeable folks have achieved a working result using the 22ohm fudge. This is the nominal resistance that the ECU sees, and changes in relation to air temperature. Giving the ECU a resistance of 22ohms means that it won't control for air temperature, but in general, the WR isn't being stressed that highly in most conditions, anyway.

In your case, Dave, the actual resistance is completely missing. Take a look at the photo of Conor's sensor, (other thread) and you'll see the remnants of the 'resistor', which should be across the ends of the 2 prongs shielded by the plastic.
Where yours has gone is anyone's guess, but gone it has. So there is actual an open circuit. When I measured across the terminals, the reading was the circuit impedance in the ECU.
Hence, the 22ohm resistor is an option. At least for now.

The other issue you have, is the undocumented and uncontrolled mods on the car, which may well include a doctored ECU, so you need to take some care, here also.

Hanuman · 09-05-14, 04:54 PM

This is simply out of position for the purposes of lead lengths, and looking correct. There is the long term issue of the leads being strained. I can't remember how the hall sensor connection is coping. On my car, that would be too tight. If I hadn't been dressed for an interview, I could have sorted it the other day.

Fix-
Remove the cap.
Undo the clamping bolt.
Take a note of which way the cap should be oriented to get the leads in the right place.
Pull the dizzy out, turn through 180degrees, approximately, and reinsert. Align the body of the dizzy with the centre of the rotor arm. Clamp it up.
Worth while checking the static timing while you are at it. I'm driving by your place Sunday evening if you want a hand.

msh · 09-05-14, 05:51 PM

You forgot to mention that engine must be turned first so that rotor arm would align to mark.

Hanuman · 09-05-14, 05:57 PM

As mentioned before, the rotor arm is aligned with respect to the distributor body. It is of no consequence really, how the shaft is oriented, so long as the rotor is aligned to the timing mark on the dizzy. The issue with being approximately 180degrees out is simply one of proper routing, and to some extent, reach, of the various cables. Irrespective of the position of the engine when you start, this will overcome most of the issues.

However.
If the engine were aligned for the static timing to be checked, beforehand, then this would make things even easier.

09-05-14, 11:55 AM	#2
john johnson Moderator of sausages Classic Audi Club Member Join Date: Sep 2008 Location: sheffield Posts: 13,331	Send me a picture of your rotor arm .... I have a shelf full and can send one down to plop on to try __________________ Mr OCD http://s159.photobucket.com/albums/t144/jsquatts/ Daily rs4 b7 with buckets that play havoc with my piles And if you are reading this as James may would say ' you're a cock '

09-05-14, 04:35 PM	#7
Hanuman Trickster Classic Audi Club Member Join Date: May 2009 Location: Heckling from the cheap seats, Phnom Penh, KoW Posts: 7,024	The discussion regarding the inlet temperature sensor so far has revolved around the fact the actual resistance is quite low, but with quite a wide acceptable range;11-31ohms, and nominal resistance of about 22ohms. It's been the subject of much debate about its importance. Several knowledgeable folks have achieved a working result using the 22ohm fudge. This is the nominal resistance that the ECU sees, and changes in relation to air temperature. Giving the ECU a resistance of 22ohms means that it won't control for air temperature, but in general, the WR isn't being stressed that highly in most conditions, anyway. In your case, Dave, the actual resistance is completely missing. Take a look at the photo of Conor's sensor, (other thread) and you'll see the remnants of the 'resistor', which should be across the ends of the 2 prongs shielded by the plastic. Where yours has gone is anyone's guess, but gone it has. So there is actual an open circuit. When I measured across the terminals, the reading was the circuit impedance in the ECU. Hence, the 22ohm resistor is an option. At least for now. The other issue you have, is the undocumented and uncontrolled mods on the car, which may well include a doctored ECU, so you need to take some care, here also. __________________ I wish they would keep the damned Chinese away now that I can go home, so that I can enjoy Fish amok and a draught Angkor Last edited by Hanuman; 09-05-14 at 04:46 PM.

09-05-14, 04:54 PM	#8
Hanuman Trickster Classic Audi Club Member Join Date: May 2009 Location: Heckling from the cheap seats, Phnom Penh, KoW Posts: 7,024	Distributor. This is simply out of position for the purposes of lead lengths, and looking correct. There is the long term issue of the leads being strained. I can't remember how the hall sensor connection is coping. On my car, that would be too tight. If I hadn't been dressed for an interview, I could have sorted it the other day. Fix- Remove the cap. Undo the clamping bolt. Take a note of which way the cap should be oriented to get the leads in the right place. Pull the dizzy out, turn through 180degrees, approximately, and reinsert. Align the body of the dizzy with the centre of the rotor arm. Clamp it up. Worth while checking the static timing while you are at it. I'm driving by your place Sunday evening if you want a hand. __________________ I wish they would keep the damned Chinese away now that I can go home, so that I can enjoy Fish amok and a draught Angkor

09-05-14, 05:57 PM	#10
Hanuman Trickster Classic Audi Club Member Join Date: May 2009 Location: Heckling from the cheap seats, Phnom Penh, KoW Posts: 7,024	As mentioned before, the rotor arm is aligned with respect to the distributor body. It is of no consequence really, how the shaft is oriented, so long as the rotor is aligned to the timing mark on the dizzy. The issue with being approximately 180degrees out is simply one of proper routing, and to some extent, reach, of the various cables. Irrespective of the position of the engine when you start, this will overcome most of the issues. However. If the engine were aligned for the static timing to be checked, beforehand, then this would make things even easier. __________________ I wish they would keep the damned Chinese away now that I can go home, so that I can enjoy Fish amok and a draught Angkor Last edited by Hanuman; 09-05-14 at 05:59 PM.

09-05-14, 01:42 PM	#3
msh 4 ring whore! Join Date: Jun 2008 Location: Rucava, Latvija Posts: 3,816	Resistor in place of IAT sensor means incorrect air mass calculation, used here to determine engine load for ignition timing and boost control [I guess?] purposes, but unlikely to cause something that severe. What does "My distributor was refitted 180 degrees out" mean?

09-05-14, 03:49 PM	#5
msh 4 ring whore! Join Date: Jun 2008 Location: Rucava, Latvija Posts: 3,816	That shouldn't mean anything - apart from cosmetic considerations [dunno about early engines, late 5 pot engines uses covers with three sockets raised and HT lead plugs in 90 degree angle, making any but one correct combination looking messy, with leads pointing in all directions] , distributor plug could be facing any direction, as long as rotor arm is positioned correctly.

09-05-14, 05:51 PM	#9
msh 4 ring whore! Join Date: Jun 2008 Location: Rucava, Latvija Posts: 3,816	You forgot to mention that engine must be turned first so that rotor arm would align to mark.