Passat B5 starts and idles but no throttle

Could it be a restriction on the intake. Maybe some Rags or tape that forgot to be pulled off well you had the engine apart or something else that got in the engine?
PS. I had a piece of carbon in my EGR valve on my truck that caused it to only idli.

If the engine can rev up (at times), you are confirming that the compression, injectors, wiring (to the injectors) are good.

What's left is something else electrical (but not as likely as this type of fault would likely set a code), air, or fuel.

I would be looking very hard at air and fuel if this were my problem to solve.

Are you still using the accelerator pedal for a diesel car?

Yes. I'm still using the stock diesel accelerator pedal.
I'll be re-checking air intake and fuel supply next. I'm also curious about how the "specified MAF" is derived. It seems that when the specified MAF is 850 then the throttle doesn't work. I'm guessing that the 850 value is some kind of default setting but what causes it to go to that in the first place?

Here are a few links that may help:
http://tunertools.com/articles/Load-Control-101.asp
The correction factors paragraph is notable.

http://www.myo-p.com/Ford-EEC/EEC Help files/sensor and hardware/Mass Air Flow Sensor.htm
Operation

The 850 may be generated from the MAF table. A few other articles I've read(hotrod forums) indicated it is from being tuned or using a tuner.

Wasn't Whitbread in the area last month, offered help to get this sorted?

Something I'd be tempted to have a crack at. Brain teasers interest me.

would a faulty brake light switch apply to this car ?

Thanks all for your input. The MAF stuff looks interesting; I'll dig into later tonight to see if there's anything applicable. The ECU that I'm currently using is stock tuning with an Immobilizer delete so it hasn't been altered by a tuner.

I've been searching the web for info re: specified MAF higher than actual MAF but can't find anything. Most of the posts are the other way around. Also curious how coolant temp affects specified MAF as there seems to be a correlation between throttle response, coolant temp, and specified MAF dropping below 850 to approximate actual MAF. What conditions cause the specified MAF to be so much higher than actual MAF?

If Matt in Vallejo likes brain teasers and wants to get involved we should talk.

Next step for me as soon as the rain let's up is to check out the EGR and ASV. I checked out the full run of the intake and no rags, rats, or other obstructions. I ran the lift pump and in 30 seconds collected almost a quart of fuel from the line that goes from the filter to the tandem pump. I also checked flow through the tandem pump return line and collected less than an ounce in 30 seconds with the engine off and the lift pump running. Is that enough flow? I read somewhere that that the lift pump should pump about 2.5 quarts per minute.

Yes Matt Whitbread stopped by when he was in town. Ultimately, he stated that it was the "weirdest running (not running) car he'd ever seen" (which I think is saying a lot) and didn't have much to offer besides wishes for good luck.

Did you resolve this problem? I have car with a similar issue.

I wouldn't dwell on the maf thing at all. IMO it has nothing to do with what you are experiencing. If you have doubt just unplug it and eliminate it from the picture for troubleshooting purposes. You won't have full power available with it unplugged, and there will be a CEL, but the car will run just fine if the maf is bad, and you will know to look elsewhere. In any case Maf does not affect the throttle non-response that you are describing.

Do not spend one more second wondering about the MAF actual/requested value mismatch. The Sole purpose of those values is EGR control. Period. Having a higher value than actual is how the factory turns off egr under certain situations. Do not worry about it or obsess about it or even give it another thought, it is NOT your problem.

I would focus n the fuel supply. namelym the in-tank lift pump. It will act EXACTLY what you are seeing if it is bad. Then if that checks out, fuel filter and tandem pump.

What is the IQ value at idle? if it stays around 6-7 or higher after warmup, then the injectors are tired. And speaking of which, have you checked the cam!?!?

Also you can unplug your coolant temp sensor to troubleshoot. it will use a different starting map and if it acts differently then you have a better clue where to look.

Dynamic /running timing has a profound effect on starting and responsiveness. Unplug the fuel temp sensor and it will default to the coolant temp sensor value for timing. you would still have throttle response so probably not it.

hope this helps, trying to do a brain dump but got to get back to work

Due to weather and a high level of frustration I've been unable to work on this project and so the problem is still unresolved. Thanks KERMA for your recent input; I'll follow through on your suggestions. I have tested the lift pump and the flow seems up to specs. Would this be affected by temperature? Also, when I say NO throttle response I mean absolutely NOTHING; as if it's not even connected.

So this is the current situation when I try to start it:
The cold car starts immediately but starts at a low rough idle, around 450 rpm, which increases to around 950 rpm over a couple of seconds at which point the engine usually shuts down. After a few tries like this instead of shutting down completely it will catch itself and idle very roughly at 450-500 rpm. At this point there is no throttle response (VCDS shows the TPS operating properly), the timing is at 13-14 BTDC, the Specified MAF (SMAF) is 650-850 while the Actual MAF (AMAF) is around 450 and the IQ is 33.8.

It will idle in this condition and gradually warm up. As the coolant temp rises the rpm slowly increases and gets smoother. The throttle remains unresponsive and the timing and SMAF are unchanged. When the coolant temp reaches 56-58 C everything changes-
the idle is smooth and stable at 850 rpm, the throttle is responsive, the timing is within normal specs (1.6 BTDC), the SMAF and AMAF are approximately the same in the 250-450 range, and the IQ is 4.7. The engine revs normally to redline and if I shut it down and restart it, the car runs normally.

The only codes on a VCDS Autoscan are related to the missing TCM which should not effect whether the engine runs properly or not. I have tried 3 coolant temp sensors, the last one from the VW dealer with no change. I’m confident that this is not an ECU issue and I’ve tried a different MAF sensor from my friend’s Passat without any change.

Anyone?

I read the first and last page and see where the tcu was plugged back in to test and yielded no positive results; have you tried using vcds to recode the ecu for a manual tranny? At least then you can completely eliminate that from the list of variables. This is an extremely strange puzzle that you've presented. If nothing aside from allowing it to get up to temp fixes it, maybe install a frost heater and run it year round ha ha

Sent from my mobile look-at device

Many thanks for the input.
I do also have an ECU that has been recoded for the manual transmission. It doesn't make any difference other than not allowing the engine to idle roughly long enough to warm up.
The fueling problem sounds interesting and I'll try bypassing the T later next week and report back. I'm open to trying anything at this point.
I'm also planning on rechecking the timing belt as I have zero faith in the mechanic who replaced it when he did the BSM delete. The extremely advanced timing when cold seems pretty strange.

I finally got around to checking the fuel lines today per QuickTD's suggestion. No change. I also re-checked the timing belt and all is as it should be. It's very odd that the timing is so far advanced when it's cold and as soon as the coolant temp hits 57-58C the timing suddenly goes back to normal and the throttle works perfectly. Any other suggestions out there? Thanks

I'm betting there is a rag in the intercooler.

Or those injectors are torched. Ive had several no-start PD cars that sat for a long time prior to me getting involved. New set of nozzles and they'd fire right up.

Thanks for your suggestions. Can you explain to me how a rag in the intercooler or bad injectors would cause the problem and some of the abnormal findings, i.e. very advanced timing when cold, unresponsive throttle when cold, completely normal running when warmed up, high specified MAF when cold, etc? Is there something I could observe in a measuring block that would indicate injectors are toast?
The car ran perfectly before the manual transmission swap.

completely normal running when warmed up

Click to expand...

Man, I guess I missed that part.

I left a rag stuffed in the intercooler of a BHW once and it wouldn't rev. So that's where I was coming from. My other suggestion was based on my experience with a handful of PD cars that sat for a long time and had injector issues as a result. Both possibilities could have plausibly applied here.

What readings does the MAP sensor registe hot / cold?

Here's a log of MBs 002,003,004 with the MAF sensor UNPLUGGED. (I was asked to log this for a different forum).
The first group is when car is cold. The second group is at the point where the car suddenly runs "normally" and the throttle starts to function.

You mentioned that you had replaced the tandem pump gasket. After a camshaft replacement on our Passat, the tandem pump drive sheared off, which resulted in no vacuum assist for the brakes, and the car would hardly rev at all. You may want to check and make sure that you have vacuum coming from the tandem pump, if you do, then you know that it is spinning.