My low vacuum issue from a new perspective - still troubleshooting

Gremo87 · Jul 27, 2015

Been working on this issue for a couple weeks now. Car ran great when I bought it, aside from an unstable idle which I was told was a tuning issue. (has Link, and hadn't been tuned well)

*Speed density car*

Couple weeks after buying it, started to notice power loss, slower spooling (22 psi at 4500 rpm), less BOV noise. During a 2nd gear pull, experienced a 'floating' feeling where the RPM's stopped climbing and it felt sort of like losing traction, but like I said the RPM's didn't rise, nor fall - they just stopped and hovered where they were at while I was at WOT. This happened again in 2nd and then again when I shifted into 3rd, and I parked it in the driveway then until I can get it figured out.

Symptoms/Info:

- It has low vacuum at idle, and it's probably been like this since I bought it but the gauge was hooked up somewhere that didn't get vacuum at idle. Move it and gauge now reads about 15 in. HG and MAP sensor reads about 11-12.
I've done several boost leak tests and fixed every tiny leak I've found - none have made a difference. Can get to 30 psi no problem. During a BLT from the TB elbow, the drop from 25 psi to 18 psi takes just under 13 seconds, and from 18 to 11 takes an additional 24 seconds. I've blown cigar smoke into the vacuum system to the point of it coming out of the intake filter, but nowhere else. (aside from into the crank case)

- If I ground the timing pin to check timing, it has idle surge which gets progressively worse the longer the pin is grounded. If I then ground the diagnostic pin too, the car will die unless I first back the BISS screw way out - in which case it will stay running but with a horrendous idle surge. So the car can't stay running without the ECU constantly adjusting timing and air via the ISC, resulting in an idle that should be 850 but instead constantly fluctuates between 740ish and 1050ish.

- Cylinder 2 spark plug is always lighter (whitish) than the others indicating that cylinder 2 is getting more air than the others. (valve issue??) I've checked for vacuum leaks around cylinder 2 and found nothing. This has happened with 2 sets of spark plugs - one with at least a few hundred miles on them and another with less than 30.

- Hard cold starts (takes a while of cranking before it reluctantly comes to life) This has been the case since I bought it.

- Good compression (177, 165, 172.5, 172.5)

- No leakdown test yet (planning to make one very soon)

- I've checked mechanical timing at the cam gears and they're spot on. I didn't tear into everything to check the oil pump sprocket mark though.

- Base timing is at 5* but jumps just past the 1 T mark a lot (with the timing pin grounded)

- Seems to run pretty hot. Gets up to 210 (on gauge, 210-215 in Link) pretty easily after a decent amount of driving, and that's with a Mishimoto radiator, 2 aftermarket fans, ducting between FMIC and radiator, an air dam forcing air up in front of radiator...

- ISC and coolant temp sensor have been tested. ISC is a newer black model and all coils tested at 42.7-43 ohms.

- Turbo has noticeable shaft play in/out, up/down, side/side.

I think that's everything. Just wanted to get everything reframed and put together here. Thank you to everyone who has contributed to this troubleshooting process. Any ideas, I would love to hear them.

Sean

Edit to add: Here's a thread with pictures of spark plugs I pulled out with less than 40 miles on them - probably less than 30, and maybe even 20. http://www.dsmtuners.com/threads/is...gs-pictures-shiny-brown-on-insulators.495647/

pauleyman · Jul 27, 2015

You cannot check mechanical timing at cam gears alone. You must look at the crank also.
Turbo play is a problem.

lasershark · Jul 27, 2015

With the timing grounded it should stay stable at 5* before top dead center and should not bounce or jump anywhere until you un-ground it. Did you ground it manually or through link?

Gremo87 · Jul 27, 2015

Pauleyman - ah I meant I didn't check the oil pump sprocket mark. I lined the crank up so that piston 1 was at TDC on compression stroke and the cam gear marks were perfect.
I know the turbo play is a problem but that wouldn't be causing my whole issue would it? With just cylinder 2 being the odd one out?

lasershark I grounded it with Link. Is that unreliable? I know it shouldn't bounce though...what might that indicate? I'll do some searching in the meantime.

lasershark · Jul 27, 2015

No link should be the way to go for grounding, Do you hear the engine sound change when you ground it?

Gremo87 · Jul 27, 2015

I don't hear much of a change immediately, but it starts surging and gets progressively worse the longer the pin is left grounded

lasershark · Jul 27, 2015

I had a similar problem on my (now totaled) 1g gsx, PO had timing set to 10ish* atdc it didn't surge but vacuum was low and it ran pretty crappy and real hot. Manifold glowed after a short drive. When I ground the timing it started to surge but i adjusted it by ear till it stopped surging then busted out the timing light, got it 5* btdc then adjusted the biss and it actually stopped and started running good. I am not saying this is your problem but it sounded similar to a problem I had.

I found your other thread, that has got to be frustrating, I didn't realize you were having so many issues.

Gremo87 · Jul 28, 2015

Yeah it has been extremely frustrating....seems like I'm getting closer and closer though!

pauleyman · Jul 28, 2015

You have nine threads on nearly the same thing
Try grounding at the check connector. Set base timing. Set biss etc. You seem to be very much chasing your tail. Find one problem, fix that ONE problem. Move on.

Gremo87 · Jul 29, 2015

Do you not think they're all connected?
I lean towards thinking so - and I have been working on each of them individually and as a whole.

I've included in my threads that I've tried setting the BISS the proper way. It doesn't work because grounding both the timing and diagnostic pins causes the car to die unless I back the BISS out real far and then it has a horrendous idle surge.....yet BLT's check out fine, and I found no leaks using cigar smoke. Got the smoke coming out of the intake filter, but no where else.

I don't enjoy making a bunch of threads - it's just that as I make progress in my understanding of the issue(s), I feel it's helpful to present the issue from the new perspective. Right? Cause it definitely all seems connected to me.

This one was to consolidate all that into one, and hopefully the last.

pauleyman · Jul 29, 2015

If car dies it probably isnt getting enough air. You backed out biss....idle should raise. You have link correct? Are you logging to try and diagnose? First issue seems to be timing. When you ground connector timing doesnt stabilize. You need to find out why. Improper grounds? Problem inside ecu? Dud you try the actual check connector instead of link? What is isc count while car is idling? Did you rule out fiav? Thecidle circuit is very straight forward and simple. You sure the isc drivers in the ecu are good? Have you hadcecu damage previously? Have you looked lately?

Gremo87 · Jul 29, 2015

But idle surge is a symptom of getting too much air, and it surges pretty bad with those pins grounded. It seems that the ECU is able to hide/suppress the surging when they're ungrounded.

The idle does raise when I back out the BISS though. That's what saves it from dying when I ground the 2 pins - I have to back it out and raise the idle. If I leave the BISS where it's normally at with ISC position @ 30, the car dies when I ground those two pins.

Yep I have Link. I've logged, but I have very little experience so nothing jumps out to me in them. I see my MAP sensor showing low vacuum. A/F stuff is good. (Combined FT, A/F ratio) Airflowperrev, everything that I've learned about so far checks out in the logs.
97gsxIA has been assisting me with the logs in another thread: http://www.dsmtuners.com/threads/co...ds-hard-cold-starts-slow-spooling-etc.495371/
He suggested I reset everything and start from scratch, which I did. I tuned the idle and that's all fine, but it did nothing for this/these issue(s).

- I haven't tried manually grounding the connector(s), but when I do it with Link it's obvious that it's working, or at least having an effect, so I assumed that's working fine. It brings the timing down to around 5* - it just jumps a lot.
- Grounds look fine.
- ECU looks fine on the inside, including ISC drivers. Outside of ECU has labels on it that indicate caps were replaced/repaired when the ECU was socketed for Link.
- ISC count is 30 at idle.
- Have not ruled out the FIAV....I guess I just haven't suspected it very strongly. Perhaps I should start....but with cylinder 2 spark plug showing lean conditions in only that cylinder, I guess that's why I haven't really suspected it very strongly since that wouldn't effect just one cylinder. I dunno...I'm clueless at this point.

Edit to add: Something I keep forgetting to mention - there's a loud clacking noise that occurs when I shut the car off. Sounds like it's coming from under the valve cover or the fuel injector area, and sometimes is more quiet and mild and will happen maybe 2 times a second. Other times it's loud and much more pronounced and happens every 3 seconds or so. It goes on for 2-5 minutes. Only happens after car is turned off. Just doesn't sound like a normal cooling-down noise...so thought I'd mention it, though it could be nothing.

steve · Jul 29, 2015

Have you checked the valve timing lately?

Gremo87 · Jul 29, 2015

I'm not totally sure what valve timing refers to but my best guess is base timing. (I'm searching to confirm in the meantime)

I've checked base timing and it's jumpy - jumps from 5* to about 1/4" past the 1 T mark. (would it be better to say TDC?) It's constantly jumping back and forth.

Edit to add: I found this quote stating the valve timing of 91-94 manual turbo cars:

"intake opens 21 and closes at 51 Exhaust opens 57 and closes at 15 lift is 1.3974 intake and exhaust."

Not sure what to do with that information, but also - I have cams so...not sure if that changes anything.

steve · Jul 29, 2015

It means, check your timing belt and make sure the crank and cams still line up in the correct timing. You have low vacuum and one potential cause is jumping a tooth. Yes "bigger" cams can cause lower vacuum but this is all a process of elimination.

The car shouldn't be dieing when you try set the BISS, the timing should be rock solid @ 5* BTDC when you tell DSMLink to go into check timing mode.

Have you posted a log yet?

Gremo87 · Jul 30, 2015

Ah mechanical timing is dead on. (used a ruler at the cam gear bolts)

I'll post a fresh log when I get home later today.

steve · Jul 30, 2015

Gremo87 said:
Ah mechanical timing is dead on. (used a ruler at the cam gear bolts)

And you verified the crank position by making sure #1 piston was at TDC or some other method?

Gremo87 · Jul 30, 2015

I just used a tissue at the spark plug hole to identify exhaust and compression strokes of piston 1. It was definitely at the end of its compression stroke with the crank mark lined up but since I didn't use an extension in the spark plug hole I can't say for sure that it was at the highest point it could be.

thejollyrancher · Jul 30, 2015

Have you been messing with timing through Link at all? The floating RPMs youre describing very familiar. When i messed up my timing map a bit i felt the same float. It would sit at 3500 for a second and a half then shoot up. Is that what your experiencing?

Gremo87 · Jul 30, 2015

Nope, the idle is set in Link for 850 and it constantly wanders from 740ish to 1050ish.

Thanks for the idea though!

thejollyrancher · Jul 30, 2015

Gremo87 said:
Nope, the idle is set in Link for 850 and it constantly wanders from 740ish to 1050ish.

Thanks for the idea though!

What im suggesting has nothing to do with idle values in link. Take a look at your timing map and or sliders. I bet those are messed around with causing your float at 3000 rpm

pauleyman · Jul 30, 2015

A tissue? Seriously? No. Verify the crank position by removing the covers and lining it up.

thejollyrancher · Jul 30, 2015

pauleyman said:
A tissue? Seriously? No. Verify the crank position by removing the covers and lining it up.

Yes a timing tissue. I had the same symptoms when i messed up my timing. I probably have a log i can dig up for you proving it

Gremo87 · Jul 30, 2015

Pauleyman did you read my posts? I made sure that everything lined up except the oil pump sprocket with piston 1 at the end of its compression stroke. I just used a tissue to make sure I had piston 1 at the end of it's compression stroke and not exhaust. (watched for suction/blowing) Is that really so terrible? Not as accurate as putting an extension in the plug hole, and yeah I should have done that....but, next time.

I didn't have the time or the energy (nor the desire in 90* heat in the sun) to take off the lower cover

I shouldn't have said mechanical timing is dead on because I can't know that for sure - but it's got to be pretty dang close if not dead on. My bad there.

Gremo87 · Jul 30, 2015

Hey thejollyrancher, the floating happened before I'd changed anything at all in Link - and I haven't touched timing at all. So timing settings in Link don't seem too suspect to me, and I know the sliders are all zero but I'll take a look at the timing map and post a log tomorrow. Thanks for the idea.

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My low vacuum issue from a new perspective - still troubleshooting

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