05 Golf Hard Start

I've been trying to fix a hard start situation with my Golf for some time.

It started with a previous starter replacement. I replaced the org. starter but in doing so one of the mounting bolts started to come loose with did not allow the bendix to engage the fly. Did not realize this before I ordered a new one. The teeth on the original starter looked out but the leading edge had some grinding. Installed the new starter.

This brought on a new problem. Seemingly slow cranking speed. (not sure how to test this but what it sounded). Turned the key to starting position, engine turned out for 10 seconds with no start. Multiple attempts will start the car. Tested the battery and found it to be low voltage on starting. Tested with a carbon pile and found it weak.

Replaced the battery and with this instead of 20 attempts it brought it down to 10ish. Problem persisted with slow and inconsistent cranking speed.

https://forums.tdiclub.com/showthread.php?t=344364

I read through this link and tested this best of my ability with the equipment I have. (no back probe). I disconnected the harness from both ends and found no continuity between any of the three terminals. Tested the crank sensor and it was outside of specs. Replaced the sensor.

Now I'm down to 2-3 attempts but it remains with slow/inconsistent speed.

I'm out of ideas

Well let's narrow down the problem if possible.

It either cranks at sufficient (normal) cranking speed, or it doesn't. Which is it? Even if there is a "no start" condition, the starter (if healthy) spun via electricity from the battery (if healthy) should spin the engine about fairly quickly. I cannot describe what a slow crank is, but try and convey to us if the engine is slow cranking or not.

If you suspect a slow crank, check for voltage drops on both sides (power and ground) during cranking (you may need a helper for this if you do not have a remote start button). This is done with a good DVOM.

12.6V nominal at battery, generally 10.5V during cranking is considered acceptable. That is what to expect at the battery. If you have more than that 1.1V drop, then you need to determine is the battery itself dropping off or is there a voltage drop between the battery and the starter (again, remember, BOTH sides: so the ground is to the bellhousing bolt).

Also, if the starter is not a genuine OEM type starter (mostly Bosch, but Valeo and Hitachi were also used, but Bosch is best), then chances are the starter is suspect. Autozone/O'reilly's type stuff is junk.

Where did you get the starter from?

I would do a voltage drop test.
Measure the voltage from the positive center post (not the clamp) of the battery to the positive stud on the starter.
Have someone crank the car over.
I would not want to see more then a few tenths of a volt drop.

Same from the battery negative post to a clean part of the starter case.

Did get the correct group battery?
Not sure but I think it's group 94.

So this ended up not being a starter issue.
-No voltage drop
-Immediate improvement with CPS
-Now without changing anything starts fine

Well a new issue popped up. There is a massive power loss at 3200-3300 RPMs. If I feather the throttle it'll stay close but more I press the pedal it will bounce 500 RPMs. Now I'm getting code P0726 "Engine Speed" intermittent fault when I do the above. No CEL unless hitting the power loss. I am also getting the ESP light on. Ideas?

I would make friends with someone what has VCDS and do some boost/MAF logging then a full scan. Post the results of the boost/MAF/MAP graphing and the scan results.

Could those issues result in Engine speed code being thrown and not a code of their own?

Hard to know, interweb. Could be crank or cam sensor, or? Some generic code readers will give false code. The power loss sounds like limp mode (comes and goes). Help in my signature.
Some reading-

futbalfantic said:

Could those issues result in Engine speed code being thrown and not a code of their own?

Click to expand...

If you can get it scanned with VCDS that will help give us the actual source of the P0726. At that time you can also log boost (requested vs actual), MAF & MAP to better help us understand what's doing.

Welp MAF is bad. The internal test points shows an open circuit. Ordering a new one and hopefully all will be well