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Discussion Starter · #1 ·
I love my T4 but this week it's giving me grief.

We brought it 2 years ago and a wedding gift with the money we'd recieved from our wedding. It's been a really niced van. No power steering but otherwise fab. We even too it to Germany last year with no problems.

It's always been a little rough on cold idle but nothing too serious. It's old afterall.

A couple of weeks ago it started to get spouts of kangerooing but this was when driving gently and consistantly- so when I was going through a 20 or 40mph are and just feathering the throttle. If I changed up the juddering would stop. Very annoying. It also pops lightly (backfire I assume) especially when rolling downhill in gear.

Had it on VAGcom and it had two faults but these were from sensors we'd disconected whilst running. After clearing them it stayed clear.

So we've done all the things we've read on here -cleaned the throttle and idle air control valve. Tested and changed the vacuum hoses. Changed the temp sensor. Non of this helped.

So I brought a new Lambda sensor only to discover we didn't have one (slightly embarressing) So then changed the fuel filter as I had one from the last service that I hadn't actually got around to changing (always end up covered in fuel).

Then the van starts easier and runs smooth. But after about 30-40 seconds it struggle to hold. The red battery light flicks on as it almost stalls. Every now and then it will actually stall. I tried to give it a bit of a drive thinking it might need to settle in or reset itself. But when you put your foot on the gas and hold it at something like 2300rpm, the engine revs up, holds for a second and then drops. Can't tell exactly what levels as we don't have a tacho. This makes driving it virtually impossible and the power does not relate to the peddle. There might be nothing and then a few second later there will be loads and you go hurtling at the car in front.

Then I strip out the plugs and leads and they look okay (only changed them last year). A little darker then normal but nothing serious. Probably a symptom rather then the cause. Take the distributer cap appart and that looks good (also new). Work back to the coil pack and there is a huge crack around the back. Obviously not good so I get a new one of those today and fit that. Starts up a treat. Runs smooth but then after 30-40 sec again it goes rough.

Now I'm really confused. The symptoms seemed to change after the fuel filter change. So I start to wonder if I've put that on the wrong way. But I check it with the drawings and it all appears correct.

I read about bad relays for the ecu and fuel pump. So I check these and they seem fine. Got a couple of spares so I checked with those plugged in and it's no different.

If i disconnect the throttle then the engine runs slightly rougher but not much in it. I don't think it's a hole in the exhaust. Nothings been changed and there is no sign of damage. Same for the inlet manifold.

Obviously the coil pack and temp sensor have helped as it sounds much better but they are obviously not the main problem.

My current thoughts are (getting expensive):

MAP sensor and ECU problem (don't suppose any-one has instructions for overhauling these?
Injectors (unlikely as van starts up real nice)
Fuel issue - pump or regulator as it runs okay for a while - maybe then pressure drops
TPS - not sure how I can check this - although the deceleration fuel cut off might be causing the revs to drop??
IACV - works but maybe not properly.

Any help would be greatly recieved as I'm a bit lost on where to go now. All appears expensive and no obvious guarentee!

ps sorry this is sooo long. It's been a bit involved!
 

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i had the same issues with mine and it turned out to be the tps there about 25-30 quid on ebay, well worth changing in my opinion i changed everything else apart from this and it turned out to be the last on the list lol
 

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I had a similar thing with my van, 1.9TD

Turns out it was the fuel timing. As the cambelt wears it does stretch slightly and in doing so knocked the fuel pump timing out of sync slightly, enough to give me rough starts, lumpy idle and kangarooing.
 

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I had a Idle problem on my old AAC 2.0.

It was a number of things, try the following:

1) replace and change every vacuum pipe, as even the slightest leak will cause you problems. Over time they perish. Check they are all present and in the correct placings aswell.

2) Idle control valve (expensive new), but dont forget that engine is similar to golf mk2 and mk3 engines. Some use the same part number (yourll find it on the side)

3) Air flow (MAF sensor, air filters, etc) and fueling system (fuel filter, fuel pump, etc). check and replace as required.


My van went from being a juicy lumpy petrol engine to a purring smooth revver......

Good Luck.
 

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Discussion Starter · #7 ·
I'm picking up a TPS shortly.

Webbe01 - I hadn't thought of the cambelt. It's probably due a change. Would a change put it all back in allignment or would I have to do something else? I thought the hall sender would have controlled the injector timing?

Transporter2.0 - I've changed the vacuum hoses. I havent done the IACV yet as I need to find an affordable one. I took the air filter out briefly to check if that was a cause but it wasn't. I've got an inlet temp sensor and Manifold pressure sensor instead of the MAF sensor. Will have to look into the fueling though. Relay is good and pumps definately kicking in. Might have to look at replacing the fuel lines.

Green Rhino - I've already replaced relay 30.

All good ideas though!
 

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Discussion Starter · #8 ·
Update:

I've fitted the TPS. It's better now. It doesn't change revs so much and is therefore quite drivable - Good call DonnyG.

It's still lumpy on idle (after about 30 sec) and still has the popping noise although either this has died down slightly or I'm becoming used to it!

As I've changed so a few parts should I be resetting it (leave the battery off overnight etc) or driving it around for a while to improve the mix?
 

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In addition to what others have already said:

MAP sensor and ECU problem (don't suppose any-one has instructions for overhauling these?
Injectors (unlikely as van starts up real nice)
Fuel issue - pump or regulator as it runs okay for a while - maybe then pressure drops
Have you tried a squirt of WD40 down the vacuum connector on the fuel pressure regulator? They can get sticky.
TPS - not sure how I can check this - although the deceleration fuel cut off might be causing the revs to drop??
IACV - works but maybe not properly.
This should only cut in when idling and you should be able to unplug it once the engine's warmed up. This should help eliminate it.
 

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Discussion Starter · #11 ·
Spent most of the day on the van. Made progress of sorts.

Satisfied the IACV is functioning correctly.

Took the regulated out and gave a bit of a clean but appeared in good nick. Hard to tell if it's functioning alright but there was no reason to doubt it.

We eventually found the reset for the TPS and this made the van run perfect. But once we switch off and switch back on then it runs a little rougher and still pops. Generally much better though and only light kangerooing.

All symptoms are gone after TPS but before restarting leading me to think that maybe I've not completed the reset. Procedure

1. start van,
2. disconnect coolent temp sensor 2 pin
3. rev engine over 3500rpm three times
4. reconnect sensor

Any ideas?

Incidently we also tried to reset the idle position (release full stop dolt until just grips a piece of paper and then tighten half a turn) but this led to the engine being too weak and wanting to stall. Original position was about 2.5 turns after gripping paper and we've ended up about half a turn looser than this.

We also sprung a leak at the coolant bleed screw (above coolant reservoir) and then broke the screw so had to fix that. It's been a trying day.

Thanks again for all the help. Think we must be getting near!
 

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Well done, sounds like you've made progress.

I think there is a procedure for matching the TPS to the ECU by using VAG-COM or similar. I think it's meant for fitting a new TPS, but if that's where the problem seems to be it might be worth pursuing.

I sympathise with the water bleed screw - I did the same thing myself a few months ago!
 

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Discussion Starter · #13 ·
The problem is we keep making progress but not solving it!

We're now at the point where it runs reasonable but backfires when not under load. Is there a way to test the MAP sensor to see if it's duff?

I've found a company in Plymouth (ECU doctors - 40 mins away) that test ECU's for £30.

If I could find the sensor on it's own I know some guys who work in avionics and can therefore do a top job of soldering the new sensor in but cannot seem to find the sensor on it's own.
 

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Any solution SassyK?

Following this intently, as my '98 T4 2.0i AAC has had similar issues with driveability and idle, just down to the last remaining issue which is a very low idle rpm on a cold start, to the point where the engine will cut out unless a little throttle is maintained. A temp fix was to adjust the idle screw raising the idle revs a tad, which has helped, although warm idle rpm is a tad high.

Have a new TPS on order for tomorrow, as with mine it makes absolutely no difference to the idle whether connected or not, cold or warm engine. Need to get it sorted as she's up sale soon, and don't feel right selling with a known problem.

ISV buzzes irrespective of TPS connected or not

So far replaced:
Vac pipes
Dizzy cap / rotor arm
New spark / plugs / HT leads
Temp Coolant Sensor

and flushed / cleaned
ISV
Throttle Body

Is that the "official" reset for the TPS?

All the best
H
 

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I know that when I had a similar issue with my van that it would be terrible at idle and would not accelerate when I got to round abouts but was fine everywhere else I too it to VW and there was a problem with the relay which I think you have already replaced and then there was the issue of oil in the MAP sensor which is part of the ECU and you will need to take the ECU out and then check the tube that connects the pressure sensor to the casing and see if it is choked up. I took mine off again recently and the whole tube was full of oil. The other thing that was causing my issue was a faulty fuel pressure regulator. After this work was done the van was back to normal again. So checking or replacing the fuel pressure regulator may help.
 

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Discussion Starter · #16 ·
Sorry guys - I've not been on for a little while. Still havent solved it but here is an update anyway.

Had it in to Volkscraft on monday (he'd been off for a while so there was a bit of a wait). Matt reset the throttle position using vagcom as apparently it's quite sensitive. He also checked for leaks using a vacuum pump and checked timing which was only fractionally out anyway. I think he spent longer than the hour he charged me for but still couldn't find anything. He did say he'd managed to get it to run well by clamping the fuel return after the regulator. But basically he's lost now for things to check without spending indefinate time and money on it.

I changed the regulator today but there was no difference- as expected.

Now having had the throttle set right it cuts out when returning to idle. I'm guessing this is due to the fact it's running rough and when it runs smooth I susspect this will work.

We have taken out the ECU opened her up and cleaned the insides. All looked good. My final guess is the MAP sensor. I've found the ECU doctor near plymouth and am going to make contact re testing (£30). The bummer is I have access to soldering experts (avionics) and if I could get a new sensor I could have it fitted for a favour. Bummer is no one seems to supply the part except to dealers.
 

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Discussion Starter · #17 ·
Just heard back from the ECU repair guys. My ECU is functioning normally including the MAP sensor.

He advised me to check the vacuum hose as there may be a block!

I'm going to check the other side of all the connectors since the hoses are all new and the system has been checked for leaks!

After that I'm completely out of ideas!!!!!!!!!
 

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He did say he'd managed to get it to run well by clamping the fuel return after the regulator.
Have you had the fuel pressure checked? I wonder if it might be a fuel pump or fuel pump relay problem. Clamping the fuel return would have the effect of increasing the fuel pressure in the injector rail and getting more fuel into the engine for each opening of the injectors.

Sorry not to reply when you originally posted this but we've moved house, so not been online as much recently.
 

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Discussion Starter · #19 ·
I've been pondering along those same lines.

The relay and regulator have both been changed.

The pump sounds like it's working but I don't know if they wear so that fuel doesn't actually move despite it running? Is there anyway to test this? I have jobs with fuel!

I was going to swap the injectors since I have spares. I wondered whether the added fuel pressure would help cover for a bad injector?

I'm also wondering whether a hole in the exhaust would affect combustion (although on initial inspection I cannot find one).
 

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Hi I had a similar problem on my 2.0 petrol as well , eventually I solved it by accident . I removed the Idle control valve and damaged the rubber seal that holds it in the inlet manifold , when I replaced the seal the idle returned to normal !!!! your van is nearly 20 years old now and they do perish letting just a little to much air into the system , and about £5 from VW and 10 mins fitting .
Also you could try another cure , because your engine is fairly simple compared to later vehicles it is often overlooked , the ecu depends on the engine coolant temp sender to send the signal to the ecu . If your thermostat is a little dodgy ie not opening properly it good be giving a misleading temp reading to the ecu . I know this cure has worked in the past as I got it from the gti forum , the thermostat is located inside the water pump which means that you really need a ramp to change it but as winter is coming why not change the thermostat & antifreeze and give it a good flush as well hope this helps .
 
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