Hello! Looks like I'm never getting rid of the problems with my xj40, I have already posted about fuel hiccup and Loud fuelpump but not the car has got bad idle after standing still on idle for a while but can't say it's too good when just started to, it's backfiring and don't have any power sometimes? I drove about 20km with no problem until this started to happen and the car rolled to a stop and was then hard to start but eventually got it to start and took me a smal bit before it happens again. It just looses power and nothing happens but backfires? Think the fuel consumption is a little high to, was saying 1.2 L/km when driving in only 70 km/h??

I'm gonna sum it up allt the things I've done on the car trying to fix the other problem is.
New fuelpump, fuelfilter, intake gasket, IACV, coolant sensor, sparkplugs, cables, rotor, distributor cap, coil, fuel pressure regulator, new oil, new oil filter, changed coolant, cleaned the intake and throttlebody then set the TPS right and the set up the idle right. Also cleaned the fueltank.

After all these things I changed the pressure regulator last and that one seemed to make the pump go quiet but now I have this problem instead? Haven't been satisfied with the idle at all after I had the intake removed but I changed all the ignition parts at the same time so I don't know what did it. The idle got better after I set it up correctly but it still is not perfect and also all the other things and I suppose it have something with eachother to do.

I have checked the sparkplugs and they tell me the fuelmix is normal. I have been spraying startgas around the intake and there are no vacuumleaks.

When on idle the idle gets worse and worse and then the engine light comes up but I get now code and if I then got the gas it backfires and eventual dies?

Anyone have any ideas? Getting real tired of my new car already, haven't had one faultfree ride yet haha..

Edit. There is two videos of it.

 

No one?
Checked the sparkplugs again and they now it seems the cars is getting to much fuel som om guessing it maybe it's drowning itself? It's bad from first cold start now bet gets worse after being on idle a while. Did a compression test and all cylinders where ok.

Maybe a fuel injector has stuck in open? The idle is always rough and it all's all's became worse after I had the inlet and everythin of so maybe I could check the injectors

 

Maybe you have a blockage in the air intake system, check the air filter intake and housing. Also possible your air flow meter or connection has a problem.

Larry

 

New airfilter, tried removing it but no difference, tested cleaning the connection and if I pull it out the car dies

 

Have another look at the oxygen sensor and TPS harness connectors and make sure no pins are pushed back in the sockets..

Very occasionally the ECU harness connection can go high resistance due to corrosion, have you inspected and tried unplugging/replugging that component? I would give that a try too.

Larry

 

Have checked these connections more than twice with no luck, checked every connection I could find actually no corrosion what so ever

 

How is your crank position sensor - did you change that too?

Or - maybe your oxygen sensor isn't working and the car runs in way too rich

Larry

 

yes it's brand new

 

After I hade the intake of the car and so and the did a new setup of the iacv the adjustment screw is maxed out to get a low enough idle, it wasn't maxed out before I hade the intake of and cleaned

 

Hi Simon,

That is a very unhappy engine!

Since you have a Check Engine warning, you should have at least one diagnostic trouble code stored in memory. Have you tried checking the Vehicle Condition Monitor for codes?

To do so, turn the key to position II (ON) but do not crank the engine. Press and release the VCM button on the trip computer to the right of the steering wheel. Watch for a message in the small display window below the speedometer where the mileage counter/odometer usually appears. Codes appear in the form of Fuel Fault or FF and a single-digit number. Here is a list of the available codes:



Disconnecting the battery will clear the memory, so do not do that until you've checked for codes.

If your VCM doesn't display any codes, my recommendation would be to perform a compression test on all six cylinders and a smoke test on the intake, crankcase breathing system and evaporative emissions system. A serviceable smoke machine can be built at home in a paint can. See YouTube for DIY examples.

Cheers,

Don

 

My only suggestion left is that you have somehow blocked the crankcase breathing system and are choking the engine with back pressure.

Larry

 

Had a look at somethings today, made a smoketester and saw a leak after the MAF fixed that, then gapes the sparkplugs to 0.9mm. Also installed a fuel pressure gauge on the fuel line so that i Always can see if that's alright. After all this the car seemed to be running better on idle, the fuel pressure was good att first, but then I took it out for a spin an the car starter staling again, took a look at the gauge and saw that the fuel pressure had dropped 1BAR? That seems to be the problem then but why? The tank is cleaned, the pump and the filter is new?

Any ideas?

 

Defective pump?

Larry

 

I can hear it buzz and it's brand new, the last one worked to, just thought it buzzed too loud so I tested changing it and the new one is more quiet

 

Try removing the gas cap and take it for another spin,also try checking the current draw on the fuel pump circuit,to make sure a poor connection is not heating up and causing low fuel pressure.

hope this helps,Jim.

 

I may be the red herring here, but is the fuel pressure diaphragm working correctly. You say you replaced it but maybe it is stuck? Or if it is defective it may be the cause of too much fuel. Does the car run better with vacuum line unhooked from the diaphragm?
I feel your pain and hope it heals soon.

 

Tried removing the cap but no difference, will have a look at the connections but they didn't look very bad when I changed the pump, will test to connect some other cables directly to 12v.

I changed the pressure regulator and looked at the fuel pressure att idle and checked it with and without the vacuum line connected and everything was working correctly according to Haynes book. Wasn't untill I started driving it droped this time, but have droped after being on idle a long while also.

 

What about that check valve on the fuel line - have you changed that?

Larry

 

Which one? Didn't know there was a separate one? I have the fuelpump under the car and thought there was one built in the pump or am I wrong? Actually heard a slurping sound last from the tank so maybe it's broken, but shouldn't this just affect the car when it's turned off by loosing pressure then? While driving the pump should keep the pressure up and the check valve wouldn't make a difference?

 

Hi Simon,

On your '89, there is a fuel pressure check valve in the fuel line on the output side of the fuel pump.

Have you checked the VCM for stored fault codes?

I'm also wondering whether the "coolant sensor" you replaced was the single-terminal sender for the temperature gauge on the instrument cluster, or the two-terminal sensor that provides the signal to the ECM?

Also, if your coolant thermostat is stuck open, the engine may not be reaching full operating temperature, which causes the ECM to continue to apply cold-start fuel enrichment even after the engine has warmed up, so it will run rich. If the thermostat and coolant temperature sensor (CTS) are both inoperative, this can lead to excessively rich running.

Have you done a compression test on all six cylinders?

Cheers,

Don