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Discussion Starter · #1 ·
Please excuse how long this description will be, as I feel like including all of the details will give a better picture of the car as a whole and where I'm coming from, so that you know I'm not a complete idiot. I've been trying to work on this with some help from fellow VWVortex poster Eur0tunE. (Corrie is also working on this beautiful mk4 build if you care to take a look):
http://forums.vwvortex.com/showthread.php?7032444-My-600hp-AWD-converted-GTI-build

I have an '88 16v GTI running CIS-E engine code PL. It has "mild street cams" (told by PO, but he didn't tell me what kind), TT headers, Borla Exhaust, Autotech Power Module, and numerous other suspension/interior/exterior mods, with 93k original miles.

When I got it, it was very apparent diving into the car that the PO didn't take care of the car whatsoever. I have two close friends who are mechanics and own a shop, and have been helping me since I got the car. We have replaced an absurd amount of parts in the 8 months I've owned the car. I replaced the entire suspension (H&R cup kit, full poly, new ball joints, inner tie rods, boots, axle seals and grease, etc.) when I bought it, along with the front brakes/calipers/rotors and rear brakes. The quad headlights and relays were a mess of spaghetti, so I bought a harness for them from someone on this forum (can't recall who), which was a godsend.

Just recently, the pedal went to the floor while driving, and turned out to be a worn push rod, broken push rod release lever (or whatever its called), and broken thrust plate. We ended up replaced the flywheel, clutch, thrust plate, push rod, PR bushing and seal, throwout bearing, release lever, rear main seal and gasket, axle seals, got the USRT linkage kit and USRT mushmeister (WOW, these mods are a must), and new clutch cable.

The car has had an idle problem the entire time I've had the car, which has been a struggle since CIS-E is strange to not only me but both mechanic friends.
Sometimes it starts strong, sometimes it needs a bit of gas, and sometimes it just stalls out right away and fires up on the second try. When it idles, it hunts for idle around 700-1050 rpms, sometimes hanging at 1000-1050 for an extended amount of time before dropping and loping slightly. When driving, warm or cold, sometimes the revs hang, sometimes they plummet, and sometimes they correctly slow when they hit 1900 and fall slowly to 950.

When we did the clutch job last week, I also tested and replaced a the Coolant temp sensor (white/clearish for the 16v), and the O2 sensor (was stuck reading lean), and the two temp senders on the side of the block. This made the gauge read higher (temp sender to gauge), and the car feels stronger with the new O2 sensor in there. We tested and cleaned the ISV, which hums and when removed but plugged in, it moves to open and close. We tested the throttle switch, which is also fine. We did a smoke test for vacuum leaks, which didn't show any. We replaced all the vacuum lines anyway with silicone, and threw a hose clamp on the PCV hose on the block which didn't have one and was slightly leaking oil. We also tried to check the timing but it seems that the searching idle is causing the timing to not be consistent, for whatever reason.

We removed the anti-tampering screw to set CO and idle and pulled up the famous Rubjonny thread for the 16v diagnostics. I keep seeing this "red/black" wire going to the ignition coil that has to be removed to put it into setup mode. However, my ignition coil doesn't have that wire. I have a solid yellow along with the red from the autotech on the 15 (+) terminal, and a green/black along with the solid green from the autotech on the 1 (-) terminal. We found that the autotech module wasn't plugged into the DPR, so we disconnected the stock harness, plugged the male end from the autotech into it, and the female into the DPR. We then seemed to get the car to idle properly last week, right at 950 steady. The revs would consistently drop to 1900 then slowly fall down to idle (but not too slowly). The car felt noticeably smoother and stronger (though I haven't really gotten on it due to the new clutch). This held for a couple days, but it seems to be getting worse upon start up and idle. It just started to hunt for idle again the other day, and I am absolutely out of time, energy, and overall just so F***ing frustrated with this car :banghead:

I am not sure which wire is correct for my coil, or if the PO really messed something up here. Also I'm not sure of the cams in the car, but they do look a bit beefier and quite a bit nicer than the stock cams, though when I had the valve cover off I didn't think to check for any markings :facepalm: Wouldn't it make sense for there to be a bit of lope in the idle when it's adjusted correctly? Just point me in the right direction for what to do next, please!
 

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Mk4 VR6, Mk2 16v, 05 CVPI, Accord DD
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These cars have wiring problems not only because of their age but also because of how much they've been worked on. Grounds are especially important to be clean, free from corrosion, and well connected, which they are likely not unless they have been specifically addressed within the last few years. All wiring, however is subject to chafing, being mis-routed during previous work and causing premature wear or damage, or corrosion. Corroded or pinched wires are a very serious problem for all types of circuits. Just a direction to go in. I've fixed so many wiring problems in my career and as a hobbyist, it's insane.
 

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"The car has had an idle problem the entire time I've had the car, which has been a struggle since CIS-E is strange to not only me but both mechanic friends.
Sometimes it starts strong, sometimes it needs a bit of gas, and sometimes it just stalls out right away and fires up on the second try. When it idles, it hunts for idle around 700-1050 rpms, sometimes hanging at 1000-1050 for an extended amount of time before dropping and loping slightly. When driving, warm or cold, sometimes the revs hang, sometimes they plummet, and sometimes they correctly slow when they hit 1900 and fall slowly to 950."

Did you check your throttle switches and isv? Its in the Bentley.
 

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You stated that you changed all the vacuum lines but you should consider other sources of vacuum leaks as well( intake manifold gaskets,injector o-rings, thottlebody the list goes on. Smoke test helps to find vacuum leaks when you have a huge a gaping obvious vacuum leak hence I've never relied on that crap. Get yourself a vacuum gauge and measure vacuum at idle that way. A motor with stock cams should see 17-20 in.Hg on the gauge, with aftermarket cams it will read lower vacuum at idle possibly at or around 15-16 in.Hg depending on how snotty those cams car in there. I have an 8v CIS-E with an aftermarket cam it's real Lopey at idle and on occasion when I throw the clutch in when braking at a light it'll hang at around 1500 before coming down to idle. Mine was a lot worse before I changed the the injector o rings though. It's totally drivable and runs great . I don't think I'll ever get the idle quality perfect with the cam I have in there and I've accepted that:D. I hope any of that can be helpful to ya!
 

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A set of aftermarket 16v "street" cams are usually Autotech's Sport Set or TT's Street cams and neither set should make the idle lope. I own both sets in different cars and they idle as smoothly as stock.

I see you're in Perkasie, I'm not that far away in Bechtelsville. I have some experience with CIS-E 16vs and I may be able to help you out if you wanted to swing by sometime. No promises, but I can try and check a few things.
 

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Discussion Starter · #6 ·
"The car has had an idle problem the entire time I've had the car, which has been a struggle since CIS-E is strange to not only me but both mechanic friends.
Sometimes it starts strong, sometimes it needs a bit of gas, and sometimes it just stalls out right away and fires up on the second try. When it idles, it hunts for idle around 700-1050 rpms, sometimes hanging at 1000-1050 for an extended amount of time before dropping and loping slightly. When driving, warm or cold, sometimes the revs hang, sometimes they plummet, and sometimes they correctly slow when they hit 1900 and fall slowly to 950."

Did you check your throttle switches and isv? Its in the Bentley.
Yes, I tested both and they are both in spec.

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Discussion Starter · #7 ·
You stated that you changed all the vacuum lines but you should consider other sources of vacuum leaks as well( intake manifold gaskets,injector o-rings, thottlebody the list goes on. Smoke test helps to find vacuum leaks when you have a huge a gaping obvious vacuum leak hence I've never relied on that crap. Get yourself a vacuum gauge and measure vacuum at idle that way. A motor with stock cams should see 17-20 in.Hg on the gauge, with aftermarket cams it will read lower vacuum at idle possibly at or around 15-16 in.Hg depending on how snotty those cams car in there. I have an 8v CIS-E with an aftermarket cam it's real Lopey at idle and on occasion when I throw the clutch in when braking at a light it'll hang at around 1500 before coming down to idle. Mine was a lot worse before I changed the the injector o rings though. It's totally drivable and runs great . I don't think I'll ever get the idle quality perfect with the cam I have in there and I've accepted that:D. I hope any of that can be helpful to ya!
Thank you! I'll definitely check this out next. I have yet to do the o rings, I'm sure they aren't an expensive fix.

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Discussion Starter · #8 ·
A set of aftermarket 16v "street" cams are usually Autotech's Sport Set or TT's Street cams and neither set should make the idle lope. I own both sets in different cars and they idle as smoothly as stock.

I see you're in Perkasie, I'm not that far away in Bechtelsville. I have some experience with CIS-E 16vs and I may be able to help you out if you wanted to swing by sometime. No promises, but I can try and check a few things.
Wow! I may have to take you up on that! I'm doing a lot of work with grad school applications at the moment and since the car still gets me from A to B at the moment, I can't put too much more time or money into it. Maybe in a couple weeks I'll be able to swing by, that would definitely be a huge help since I am not familiar with this car at all. With the amount of time and money I've put in, it's got to be something really dumb.

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