It's a 2000 XKR that I just did the secondary tensioners on. I started it up for the first time since the tensioners were installed yesterday. Car started and ran great, had plenty of power, no odd noises or smells or fluids low(or mixed in with each other) and things were great throughout the 30 or so miles I drove it (put on maybe 10 at a time with just a few minutes(<10) off at each stop). On the last stop, 1 mile from my house at a gas station to pick up some milk it started to have problems.

It would start just as easy as usual, then it would idle extremely choppy, if at all, and then stall. You could repeat this cycle over and over, easy start, stumble and then stall. I did this maybe 5 times. The pedal to the floor method outlined in the manual for flooding issues didn't change anything. The car still had no fluid issues, no odd smells but now sounded like crap from the bad idle. The car had plenty of gas in the tank (about 40 miles in from a full fillup of BP Premium). The car wouldn't move under it's own power in gear when it would idle choppy and I tried to. Giving more pedal didn't seem to stabilize the idle, it would either stall immediately or do nothing.

I used my OBDII scanner and it gave me nothing on current MILs (there wasn't one), but there were codes pending for the oh so wonderful PO300 along with the codes for it's buddies for cylinders 1-4(301, 302, 303, 304; Pass or right hand Side). Pulled the plugs and they look good, as does the wiring to the coil packs(no chafing, slits or damage I can see). There isn't any visible corrosion on the connectors or the coil packs. Tonight I'm going to check for spark and then see about fuel delivery.

Does it sound like something is awry from my tensioner install? Does it sound like there may be something sensor related or fuel related? Any ideas?

 

Which tensioner install method did you use?

Are you sure the right hand side breather tube is firmly seated, did not pop off and is not damaged?

 

I did the zip tie.

I'll check the breather tube when I get home.

 

Sounds like your intake tube is loose, check it to be sure its not leaking air, starting at the throttle body clamp and working towards the MAF.

 

sounds like the manifold won't hold its internal pressure...check the oil dipstick (must be seated well), the oil cap, all breather hoses (as mentioned above by whitexkr, if there are any points for a leak, it will stumble very quickly. Valve cover should be double checked too...I hear it is easy to fold a corner or misalign the gaskets.

 

I checked the breather tubes, dipstick, oil cap and I checked the MAF, intake hose and all of that. I didn't check the valve cover gasket yet. I am going to check that tomorrow.

I did notice there is now a whirring noise coming from the throttle body actuator. If the connector is disconnected, it doesn't make the noise and it throws a message up inside on the odometer/information center. Reconnect it, the noise is back and the message is cleared.

Any ideas? This is really appreciated.

 

When you installed the tensioners, did you use the replacement shorter bolts? Did you pull the retaining pins in the new tensioners?

 

Yes and yes.

 

Today I pulled the cover. Everything is great. The gaskets were in perfect shape with no folds or issues.

I've got spark on the passenger side, and with the coils off the car, turning it over to check for spark actually started the car and it ran the same way as when the passenger side was hooked up.

I'm thinking that I need to test for fuel pressure for the passenger side. It seems that fuel delivery is the issue, any thoughts?

 

If you still have the RH cover off, it probably would not hurt to check the the cam flats are aligned. If that checks out I am ready to say that the fact you just did the tensioners is a red-herring and agree, to start looking elsewhere for the problem.

When the throttle body is whirring, can you see the butterfly 'hunting' or moving around?

 

The butterfly itself is not moving all about. It just makes a little noise.

 

Couple of more things to check:

Check the MAP (yes MAP, not MAF, which you already checked) sensor vacuum hose has not fallen off the sensor. The MAP is just under the windshield deck in the center, and is roughly an inch square black box.

Check that fuel pressure regulator vacuum hose has not fallen off of the fuel pressure regulator. The fuel pressure regulator is under the right charge cooler at the rear, accessible with the plastic intake pipe removed.

Both of these vacuum hoses are just pushed on and have releatively loose friction fits, and could conceivablly have been disturbed during the tensioner work you just did, or have deteriorated hoses.

If this does not turn anything up, I would clear the codes, reset the ECU (remove the + battery lead and touch it to ground). restart and see if that helps.

If that does not do anything, reread the fault codes. If they are still the same, then pull some run time data with your OBDII and post it. If you have a fuel pressure guage that data may help to.

 

maybe you the timing chain was louder pre-tensioner change, and you couldnt here the throttle body actuator noise over it...that was always there? Ours has the same electronic hum.

I'm going to recommend something drastic, but feel pretty confident that if you don't have leaks, you have fuel pressure at the rails, it may be either a faulty MAFS or could be an 02 sensor...an OBDII reader can confirm the latter.

My stumbling that occurred on startup was from, what I believe, the result of my MAFS sending out the wrong information upon getting initial startup voltage...making the car think my air volume was 3x-4x what it actually was ...at idle, and it added more fuel, causing the stumble, increase in RPM, then the MAFS readings slowly came back to normal.

Just replaced the MAFS today, so after a few days of cold starts after 12 hours of rest will tell me if the $60 remanufactured part was worth it.

 

I'm betting you have a bad fuel pump. You need to go back to the basics here and check fuel pressure. That car has 2 pumps, one is used to prime the rail on starting (and over 3000 RPMS), and the other to run the car under norma operating conditions. If the priming pump is working, but the other pump has failed, the symptoms you describe will occur. The car will start, then stumble and shut off. Check fuel pressure and report back. If you have no pressure after the initial startup, then check B+ and ground to the fuel pump. If power and ground are good, then you need a pump....and I highly rec. replacing BOTH, as well as the link lead in the tank, as they like to burn up.

HTH

 

ooooooh, I had forgotten about the dual fuel pumps on the Rs. That's another very plausible explanation.

 

Start and stumble sounds like a fuel pressure regulator.

 

I checked the connections on the MAP and Fuel Pressure Regulator. They were connected.

Checking the pressure at the rail it would prime it, it would hold it there and then when the car was started, pressure would fall off to nil and the car would stall. Looking at the ground and power to the pump tomorrow.

 

If I were a bettin' man.

 

...how's your b-ball bracket looking so far jagtec? I wouldn't bet against you on this one.

 

I don't like letting threads like these die, posting the conclusion makes it so that people who search and find this know the resolution.

Wiring all tested good outside the tank, and because the priming pump worked, I reversed the wiring at the connector outside the tank and it fired right up and ran great, so it's either the wiring to the main pump or the pump and I pulled the tank. When the tank was pulled and I tested the pumps, they were good. However, the link lead to the primary pump was not. I bought all new pumps and leads just because I don't want to go back soon; they're all installed now.

Car runs great now.

Thanks Jagtec and all others that posted. I'm glad to have this all resolved and the car back out now that Michigan has tolerable weather.