Technical 2.4JTD no pull at low revs

Currently reading:
Technical 2.4JTD no pull at low revs

x19fan

New member
Joined
Jul 1, 2006
Messages
35
Points
12
Location
Gloucester
Hoping someone may have an idea what is ailing my 2.4jtd marea weekend. It has no grunt at all until about 2000 revs when the turbo kicks in and its off like a rocket until flattening out at about 3500revs.
I have replaced the MAF, I have cleaned the EGR (which wasn't particularly sooty), cleaned the MAP sensor, I have given the car a regular service and replaced all filters, but it still won't pull the skin off a rice pudding at low revs.
No unusual smoke or oil consumption. Sounds fine and idles as it should. Just went through an MOT without comment.
As an indication it won't even pull from 40mph in 5th gear, you have to drop a gear.
Fuel consumption is poor as you have to leave your foot planted in the shagpile.
The brakes are not binding. Only 80K on the clock. Can't think of anything else to tell.
Any ideas gratefully received as I can't get to the bottom of the problem and I have absolutely no faith in the local Fiat Stealership as their solution to any marea problem is "may as well scrap it mate".
Thanks in advance
 
Did you clean out the 2 hidden (soot) side venturi inside the EGR body? Cleaning is harder to do properly than it seems, did you also strip and clean the solenoid side? Just change it IMO...
 
Yeah, I gave it a really good clean and checked its operation as per instructions in Fiat technical manual. Seemed okay. Could the solenoid be the culprit? How much is an EGR?
 
Check all boost hoses for splits and intercooler for damage. Sounds like you're losing boost at low revs.

Wow just realised which Marea it is...

please don't scrap me :)

DSC0004110.JPG
 
Last edited:
Well I have removed all the induction pipework from air filter to engine and the intercooler and all the pipework and intercooler are in good condition, no damage, splits or holes. All are securely clamped. I even filled the intercooler with water to check for pinhole leaks but not a thing.
Still the problem persists.
Pulled the EGR again and it is spotlessly clean and operating freely with a vacuum pump attached.
I have one question. There is a approx 3/4" tapped hole on the engine block just a couple of inches from the thermostat housing (towards the bulkhead). Any idea what it is. There is a space in the casting behind the hole so it does not look like a hole for a bracket or similar. There are no loose sensors. ?????

Whats next on the collective diagnosis.
 
I tried blanking off the egr to take that completely out of the equation but still no improvement.
Any further ideas?
 
do you think it is boosting at low revs at all ? when you say its off like a rocket from 2000 rpm, does it have full power ? that would prob be normal enough anyway. perhaps the exhaust/cat is clogged ? should be simple to disconnect it below turbo and see if that makes any difference.. other than that, use FiatECUscan to do a bit of diagnosis and see whats actually happening..
 
I'm new to OBD but game to try it. Can you point me in the right direction for a compatible cable and any other bits and pieces required to get set up?

Also could someone have a quick look and see if they have the same tapped hole in their block as I have in mine. (See above)
Thanks.
 
Okay, so I have now got myself all high tech and checked the OBD with FiatEcuScan. Nice bit of kit. Make sure you install the driver before you insert the cable, it won't work the other way around.
Error codes were:
Glowplugs - Ongoing - Will not reset but does not effect starting
MAF
EGR
Throttle position
All reset and do not reappear, probably errors due to my testing earlier in this process. All the above parameters seem to be reacting normally to conditions.
For example the throttle position sensor gives a linear response from 0 to 100% and the voltage values match those in the Fiat tech data.

Any other live tests I can try?
 
I gave the car a drive with the OBD connected and I get a stored error
P0404 - EGR Device (5)
Even if the EGR system is failing I don't understand how that could effect the performance if the EGR is blanked off. Confused
 
If you've blanked the EGR off, then the ECU can't get the EGR flow it requires - it measures the airflow and calculates EGR flow based on the reduction in intake airflow. If MAF is higher than expected with EGR valve open, it will cause this code. it shouldn't cause a problem though. is the new MAF sensor a genuine item or an ebay one ?. look at the MAF reading when you floor it in 4th.. it should rise quickly to maximum. also the requested and actual MAP (boost) with foot to floor in 4th.. from 1500rpm upwards.. they should match reasonably after approx 1800 rpm.. use the graph function to see whats happening. Also look at the timing.. again disconnect the exhaust after turbo and see if anything changes..
 
If you've blanked the EGR off, then the ECU can't get the EGR flow it requires - it measures the airflow and calculates EGR flow based on the reduction in intake airflow. If MAF is higher than expected with EGR valve open, it will cause this code. it shouldn't cause a problem though. is the new MAF sensor a genuine item or an ebay one ?. look at the MAF reading when you floor it in 4th.. it should rise quickly to maximum. also the requested and actual MAP (boost) with foot to floor in 4th.. from 1500rpm upwards.. they should match reasonably after approx 1800 rpm.. use the graph function to see whats happening. Also look at the timing.. again disconnect the exhaust after turbo and see if anything changes..
I got some interesting looks at the traffic lights as I'm glued to my laptop with wires coming out of the bonnet and through the window:)

The MAF is from a reputable local motor factor who I have used for years not ebay.
Response from MAF is as you describe.
Boost pressure (requested) remained resolutely at ZERO and did not change throughout the test. What could cause the zero?
Boost pressure (actual) rose slowly to approx 0.3bar at 1800rpm then quickly to a max recorded value of 1bar at 4400 rpm as I would have expected. But the car still feels like it has massive turbo lag, still no pull below 2000 rpm.

I'm afraid I don't follow your comment on timing. What should I be looking for.

Many thanks for ongoing help. I'm determined to beat this
 
I got some interesting looks at the traffic lights as I'm glued to my laptop with wires coming out of the bonnet and through the window:)

The MAF is from a reputable local motor factor who I have used for years not ebay.
Response from MAF is as you describe.
Boost pressure (requested) remained resolutely at ZERO and did not change throughout the test. What could cause the zero?
Boost pressure (actual) rose slowly to approx 0.3bar at 1800rpm then quickly to a max recorded value of 1bar at 4400 rpm as I would have expected. But the car still feels like it has massive turbo lag, still no pull below 2000 rpm.

I'm afraid I don't follow your comment on timing. What should I be looking for.

Many thanks for ongoing help. I'm determined to beat this

I think I would be giving you funny looks wondering why the wires from the bonnet when as far as Im aware the plug for the ecu is under where the fuses are in the car.
 
Not in the 1999 model. Its a 3 pin plug near the drivers side suspension turrett. No 16 pin socket in the cabin for me I'm afraid. Old school!
So whats next from the diagnostitians? Its like an episode of House. Its gotta be Lupus, its always Lupus!
Seriously the only thing I haven't tried is a suggestion to remove the exhaust to see if the cat is blocked. Must admit I'm not keen to go driving around with no exhaust. I would have thought that a blockage would effect high rev performance not low rev.
 
"I got some interesting looks at the traffic lights as I'm glued to my laptop with wires coming out of the bonnet and through the window" - well you can have the last laugh - while they happily leave their cars to garages who wouldn't have a clue or even be bothered to do something like this.
Not sure about the requested MAP being zero.. seems incorrect but maybe a software error.. but at least you have an actual MAP reading, which seems a bit low below the 2K rpm.. if there are no boost leaks then the only other things could be actuator on turbo, turbo itself or partially blocked exhaust. valve timing could also affect things..
 
x19fan, I have exactly the same problem with my 2.4 td ('98 model,28.000miles). Apart from cleaning the egr valve (no discernable difference) I haven't got around to doing anything about it yet, so am very grateful for your diagnosis by proxy! One thing I do as a temporary 'cure' which is also referred to elsewhere on the forum, is say in 3rd gear, dip the clutch (throttle off of course!) and let the revs drop below one thousand rpm, accelerator down and I have full (?!) power. It makes me wonder if the throttle potentiometer has any bearing on this issue? Can't do much at the moment as suffering from "labrynthitis" (don't ask, look it up!) But may resort to visiting an Alfa dealer near Shaftesbury who apparently has experience of the td 125. Will post any info. unless of course you come up with the miracle cure beforehand!

P.s. Mine has the big aluminium airflow sensor (debimeter) not the later tube type maf.
 
Back
Top