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Intake refresh lessons: TPS install, fuel pump relay jumper, coolant, ISV harness

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Old 05-26-2017, 11:30 AM
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chart928s4
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Default Intake refresh lessons: TPS install, fuel pump relay jumper, coolant, ISV harness

Hi everyone. Thanks to all for the advice and time to noobs like myself on the forum. Based on several new threads, it is the season when 928 owners turn to their intakes. Sorry for the length but wanted to describe these things fully.

I learned four valuable lessons that I think all intake refresh rookies should heed. It was hard to find specifics on these, and at a minimum this thread will allow me to easily find these lessons next time, and hopefully help others also.

Background: I completed an intake refresh on my 1991 S4 auto last November. When started, it blew a lot of white smoke that eventually cleared and, while improved, the car still ran poorly, stalling at warm idle. Also it did not catch fire, so that was good. However I eventually had to remove the intake again to fix the main problem, which led to...

Lesson #1: TPS installation.

If you do not install the replacement TPS properly you will never have a good warm idle or correct WOT. The experienced guys gloss over this fact and so the noobs can get tripped up, apparently often. A lot of people seem to think the ISV is the problem, but in many cases I think it's the TPS. Here is a quote from michaelathome from a 2012 thread:

"At Frenzy 8 we tested several cars with a sharktuner and of the 8 or so tested there were 5 that couldn't hit WOT and 3 that could. All 5 of those that failed had done intake refreshes."

He goes on to say the TPS was incorrectly installed on all 5. That is an astounding statistic - 100% of the refreshed intakes had the TPS wrong (like mine). They probably had bad warm idle too?

Correct installation: Push the TPS onto the throttle shaft and put the 2 mounting screws in loosely. With the two screws loose and throttle closed, i.e. the default, turn the TPS until you hear a click. Test by pulling the throttle open and shut manually while holding the position, and listening for the on and off click. Then tighten the screws. This is dead easy when you work through it. Do it right the first time and save yourself a weekend.

Lesson #2: Fuel pump jumper test.

This is a fuel system leakage test that is highly recommended for safety after reattaching the fuel rails. I did it in November and during the TPS re-do I couldn't find the procedure I used - mentioned but not described in several places including the WSM. Again, the experienced guys mention it but don't describe it. So here it is ('91 S4 version):

- Make a Wally Plumley relay jumper by putting an SPST switch at one end of a lamp cord. Put spade connectors on the other end. Mine is 8' long and 16 ga.
- The EZK on the passenger right footwell blocks the XXVI fuel pump relay on the CE panel. Use a socket to remove the 10mm mounting nuts/washers for the EZK. Two nuts are above the EZK, two are below. They are small and easy to fumble. Let the EZK gently hang from its cable. (BTW - thanks Porsche for making this step necessary)
- Pull the fuel pump relay. I used two right angle picks. A relay puller would be better.
- There are four relay connections, one on each side of the square plug, oriented variously. You want connection 30 (left) and 87 (right) on the CE socket. Plug one of your spade connectors into each of these.
- Connect the battery if it's been disconnected
- Close the switch. You should hear a hum and then some flatulent noise from your fuel rails as the system pressurizes. Let it run (for about 5 min in my case). It will not hydrolock nor flood the cylinders.
- Check for leaks in all fuel connections, starting at the supply and working your way around. Use coffee filters under the joints to easily show drips. Feel under the connection for wet fuel.
- If you see leaks, tighten the offending joint a little and retest. If not you're good to go.

Lesson #3: Coolant in the crankcase

You are going to expose coolant in at least three places. The main one is at the water bridge, where you will be changing the thermostat and gaskets. Less obvious is when you loosen the hex bolts on the 2 rear blockoff plates (under the fuel damper and pressure thing near the firewall) to get at the intake mounting bolts.

In all three cases, take steps to ensure coolant doesn't get into the crankcase. You can do this by draining the coolant (then replacing it), by draining down to the top of the block (then topping it off), or simply letting it drain out when you remove the various components. On the big refresh I did the second by draining from the radiator hoses. On the re-do I did the third.

The coolant can easily get into the crankcase when you change out the oil filler neck. It is not a disaster at least from my experience, but you will have to change the oil. The coolant will separate and sit at the bottom of the oil pan so it should come out readily. You will see it in your drained oil and will probably be shocked and worried. But I have seen no ill effect after the oil change and I hope that continues.

If you aren't careful and haven't drained the system, as with my re-do, the blockoff plates will leak a small amount of coolant. Most goes on the ground, but some - maybe a jigger or so - can leak into cylinders 4 and 8. When I noticed this, I just used some paper towels and mopped it up. But better coolant control is the proper way to go. I didn't notice this on the first refresh but it might have happened, but on the second I saw it immediately. Just use a paper towel to get enough coolant out so it's lower than the block, or put a towel between the cylinder and the blockoff port so any runoff is absorbed.

Lesson #4: Extend the ISV electric connection. I saved aggravating hours by doing this on advice from an early thread. Make a 12" extender out of a male and female Bosch connector and some wire. Attach it to the ISV. The harness disconnect/reconnect will now be literally the easiest part of the job instead of one of the hardest. About $30 for the parts from Roger.

Result: A quick intake removal and reinstall, and a smooth-idling, non-flammable, no-white-smoke first start. I was amazed at the difference and it instantly flipped me to loving the car from a concern over how much work it would take to make the car run well.

Good luck to all those attempting a first time intake refresh. It is a great first project and makes a world of difference for the car. Hope the above helps, and thanks again to all the gurus who are so generous with their time and experience.
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Old 05-26-2017, 03:12 PM
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Well done, and good of you to post.
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Old 01-20-2018, 12:01 PM
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GREAT POST! I to have a 91 928 S4 midnight blue. 88,000 miles and runs great. I did some of the basics so far ie. timing belt/motor mounts/X pipe/ac R134 conversion and so on. Anyway....now I noticed that it blows white smoke/not blue on start up which then goes away as it warms up. May be a blown head gasket or maybe its just been so damn cold( I'm in northern NJ). Any thoughts on next steps? Also, you use a few acronyms that I don't know. ISV, EZK, TPS
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Old 01-20-2018, 12:24 PM
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This is an excellent post. I just happened this morning to re-read my thread on the subject from two years ago.

1. I tested my TPS in place, and ignored convention to change it regardless. I need a good reason to risk screwing things up, and I also regard new parts with suspicion.

2. I also failed to check for leaks the safe way, mainly because - as you say - the details are seldom provided. By the way, do the leads need male or female spade connectors?

3. Horrors! Coolant is running out of the rear towards the open intakes! And down the open wound near the water bridge into the sump! Good one.

4. Didn't do the ISV extension, which I may indeed regret.
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Old 01-20-2018, 12:41 PM
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Thanks for the kind words. I think white smoke from a cold engine on a cold day is normal - mostly H2O and inefficient startup fuel burning/cold catalytic converter effects. It should moderate quite a bit as the engine warms. Of course it could also be a head gasket.

ISV is "idle stabilization valve." It's a cylindrical device about the size of a tomato paste can under the throttle body and it opens and closes under certain conditions to modulate throttle behavior. EZK is the Bosch ignition system, controlled by a box on the right side of the passenger footwell. It is screwed to the LH (i.e. "brain" ) and together they stick out a few inches from the side panel (preventing access to the right side of the fuse/relay panel on the firewall in the passenger footwell). TPS is the throttle position switch, known by many names (throttle position sensor, throttle valve switch, etc). It's a gray plastic pentagon on the left side of the throttle.

Motor mounts and timing belt are both fairly serious jobs, especially the MMs. Intake work is a not heavy lifting. Use Dave Chamberland's intake disassembly guide, available multiple places, or use Dwayne's Garage very detailed tutorial. You should read the new visitor threads if you haven't yet.

And post some pics of your awesome color car!
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Old 01-20-2018, 12:46 PM
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Curt - Re, the relay bypass: The leads should male spade connectors that mimic the relay plugs. Crimp them on and save this valuable "locally fabricated tool". Like many things, it's a little opaque to read about, but when you actually do it the process is easy and obvious.
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Old 01-20-2018, 04:58 PM
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I'm curious about the TPS...for the ones not installed properly, what was different? Any idea? Can this be determined visually? I'm going to be doing an intake refresh soon, but I was not planning on replacing the TPS without some evidence that it was required.
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Old 01-21-2018, 06:43 AM
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Originally Posted by chart928s4 View Post
Hi everyone. Thanks to all for the advice and time to noobs like myself on the forum. Based on several new threads, it is the season when 928 owners turn to their intakes. Sorry for the length but wanted to describe these things fully.

I learned four valuable lessons that I think all intake refresh rookies should heed. It was hard to find specifics on these, and at a minimum this thread will allow me to easily find these lessons next time, and hopefully help others also.

Background: I completed an intake refresh on my 1991 S4 auto last November. When started, it blew a lot of white smoke that eventually cleared and, while improved, the car still ran poorly, stalling at warm idle. Also it did not catch fire, so that was good. However I eventually had to remove the intake again to fix the main problem, which led to...

Lesson #1: TPS installation.

If you do not install the replacement TPS properly you will never have a good warm idle or correct WOT. The experienced guys gloss over this fact and so the noobs can get tripped up, apparently often. A lot of people seem to think the ISV is the problem, but in many cases I think it's the TPS. Here is a quote from michaelathome from a 2012 thread:

"At Frenzy 8 we tested several cars with a sharktuner and of the 8 or so tested there were 5 that couldn't hit WOT and 3 that could. All 5 of those that failed had done intake refreshes."

He goes on to say the TPS was incorrectly installed on all 5. That is an astounding statistic - 100% of the refreshed intakes had the TPS wrong (like mine). They probably had bad warm idle too?

Correct installation: Push the TPS onto the throttle shaft and put the 2 mounting screws in loosely. With the two screws loose and throttle closed, i.e. the default, turn the TPS until you hear a click. Test by pulling the throttle open and shut manually while holding the position, and listening for the on and off click. Then tighten the screws. This is dead easy when you work through it. Do it right the first time and save yourself a weekend.

Lesson #2: Fuel pump jumper test.

This is a fuel system leakage test that is highly recommended for safety after reattaching the fuel rails. I did it in November and during the TPS re-do I couldn't find the procedure I used - mentioned but not described in several places including the WSM. Again, the experienced guys mention it but don't describe it. So here it is ('91 S4 version):

- Make a Wally Plumley relay jumper by putting an SPST switch at one end of a lamp cord. Put spade connectors on the other end. Mine is 8' long and 16 ga.
- The EZK on the passenger right footwell blocks the XXVI fuel pump relay on the CE panel. Use a socket to remove the 10mm mounting nuts/washers for the EZK. Two nuts are above the EZK, two are below. They are small and easy to fumble. Let the EZK gently hang from its cable. (BTW - thanks Porsche for making this step necessary)
- Pull the fuel pump relay. I used two right angle picks. A relay puller would be better.
- There are four relay connections, one on each side of the square plug, oriented variously. You want connection 30 (left) and 87 (right) on the CE socket. Plug one of your spade connectors into each of these.
- Connect the battery if it's been disconnected
- Close the switch. You should hear a hum and then some flatulent noise from your fuel rails as the system pressurizes. Let it run (for about 5 min in my case). It will not hydrolock nor flood the cylinders.
- Check for leaks in all fuel connections, starting at the supply and working your way around. Use coffee filters under the joints to easily show drips. Feel under the connection for wet fuel.
- If you see leaks, tighten the offending joint a little and retest. If not you're good to go.

Lesson #3: Coolant in the crankcase

You are going to expose coolant in at least three places. The main one is at the water bridge, where you will be changing the thermostat and gaskets. Less obvious is when you loosen the hex bolts on the 2 rear blockoff plates (under the fuel damper and pressure thing near the firewall) to get at the intake mounting bolts.

In all three cases, take steps to ensure coolant doesn't get into the crankcase. You can do this by draining the coolant (then replacing it), by draining down to the top of the block (then topping it off), or simply letting it drain out when you remove the various components. On the big refresh I did the second by draining from the radiator hoses. On the re-do I did the third.

The coolant can easily get into the crankcase when you change out the oil filler neck. It is not a disaster at least from my experience, but you will have to change the oil. The coolant will separate and sit at the bottom of the oil pan so it should come out readily. You will see it in your drained oil and will probably be shocked and worried. But I have seen no ill effect after the oil change and I hope that continues.

If you aren't careful and haven't drained the system, as with my re-do, the blockoff plates will leak a small amount of coolant. Most goes on the ground, but some - maybe a jigger or so - can leak into cylinders 4 and 8. When I noticed this, I just used some paper towels and mopped it up. But better coolant control is the proper way to go. I didn't notice this on the first refresh but it might have happened, but on the second I saw it immediately. Just use a paper towel to get enough coolant out so it's lower than the block, or put a towel between the cylinder and the blockoff port so any runoff is absorbed.

Lesson #4: Extend the ISV electric connection. I saved aggravating hours by doing this on advice from an early thread. Make a 12" extender out of a male and female Bosch connector and some wire. Attach it to the ISV. The harness disconnect/reconnect will now be literally the easiest part of the job instead of one of the hardest. About $30 for the parts from Roger.

Result: A quick intake removal and reinstall, and a smooth-idling, non-flammable, no-white-smoke first start. I was amazed at the difference and it instantly flipped me to loving the car from a concern over how much work it would take to make the car run well.

Good luck to all those attempting a first time intake refresh. It is a great first project and makes a world of difference for the car. Hope the above helps, and thanks again to all the gurus who are so generous with their time and experience.
Well done, thank you
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