1.8 Rebuild Won't Idle Options

[jwilliamadams]

Greetings,

I have rebuilt my 1.8 and at the same time used new slip in pistons and cylinders that were slightly larger (93x66mm, which I believe works to 1.9+L). The place I purchased them from (West Coast Core in CA) assured me that my L-Jet FI would still work great. Well, I can't get the damn thing to idle. I do not have any vacuum leaks (sure of it.) Timing and dwell are right on. Fuel pressure is good. It runs great past idle with all kinds of power. I have the idle adj screw all the way maxed. At this setting it maybe idles at 700RPM. I have a second air flow meter from same year (1974) that I know works and tried it out with same results. Is it possible that with the new p/c size they are needing more air at idle, more than can be sent through the current idle air port in the throttle assembly?

Thanks for any help!

[srb7f]

Does it hunt when it idles? The 2.0 I just installed had similar problems with the idle for whatever reason. It wouldn't idle well at all, and would usually stall out any time I pushed in the clutch. The problem ended up being that it was running too lean (even with the adjustment screw all the way rich). The solution for me was to add 3 100 ohm resistors in series with the cyllinder head temperature sensor. This will richen the fuel mixture at idle and under acceleration. Such that you have increased the size of your pistons (in essence adding air) without changing your L-jet (fuel) seems like this might be a problem for you as well. I think the resistors cost me all of $4 at radioshack and another 30 minutes tinkering in the parking lot and I was good to go. Steve

[jwilliamadams]

It's not hunting. Still not sure what is going on. When I go to time it with a strobe it runs better when the timing is off and worse as I bring the timing mark into view. Very odd. I am going to purchase the compu-fire points/capacitor replacement module today to see if that helps.

Any other ideas anyone?

[drewvw]

When I go to time it with a strobe it runs better when the timing is off and worse as I bring the timing mark into view.

any chance the dizzy is off by a tooth or two?

[Cap'n Krusty]

93 mm is stock for a 1.8. Valve adjustment done right (.006"/.006")? Dwell OK, breaker plate ground strap intact? Timing set to 1.8 specs? (Careful, it's done WAY differently from the D-jet cars.) BOTH oil cap seals in good shape? ALL vacuum hoses intact and correctly hooked up? Fix the fundamentals before you throw money at it. Report back. The Cap'n

[bd1308]

L-jet senses the additional air and accounts for that....


I think its more big-engine friendly.

b

[jwilliamadams]

drewvw, good question. I guess I assumed that if the gear were off a tooth or two that timing would adjust for that? Should I try to reinstall the drive gear to see if I am off a tooth or two?

Now a new problem. I bought the compu-fire and have it installed but by the time I put the little spacer ring on the shaft, followed by the timing disk (making sure it is all the way seated per instructions) the rotor sits too high and the cap won't seat.

(IMG:style_emoticons/default/WTF.gif)

Thanks!

[bd1308]

I believe some material must be taken off OR you havent seated the magnetic collar down all the way....

b

[bd1308]

on mine the collar wasnt down all the way...it took some force to get it to snap into place...

b

[jwilliamadams]

I can't believe this. I just finally re-read every piece of literature I have on timing and am realizing that I have been trying to time to TDC rather than 7.5 BTDC. What a dip. Going out to try this again!

Got the compu-fire timing disk installed. Had to leave out the spacer ring and it worked.

[jwilliamadams]

Listed my bore wrong up above. It's 96, not 93. So my displacement is 1910cc.

Got it timed to 7.5 BTDC and it is still not idling right.

[srb7f]

Did you remember to remove and plug both the advance/retard hoses on the distributor before you timed it?

Did you check the alignment of your throttle position sensor at idle? That could also be giving you trouble.

[jwilliamadams]

I had both hoses plugged. I'll check the TPS. Have not tried that yet. Did verify that fuel pressure is OK. It is (between 30-40psi).

Thanks!

[jwilliamadams]

Help! I have the engine perfectly timed to 7.5 BTDC now, compu-fire is working great. Fuel pressure is right. The engine is very strong above idle and is fast as hell and drives beautifully. With the big bore p/c I have 1910cc. Is it possible that the idle port is simply not big enough for the extra draw at idle? I ask this because if I bypass the decel valve and just hook a hose directly from the intake air boot to the air distributor of course that gives it more air/fuel and makes it idle at like 2000. I can slip a hose clamp on this hose and tighten it, thereby restricting the airflow and get the idle down to where it should be and it idles fine. This is what makes me think the idle port is too small.

Or am I just out of my mind and the L-jet should be taking everything into consideration, including the extra draw and my problem is still somewhere else?

Thanks

[bd1308]

take the decel valve out...

[jwilliamadams]

I tried that too, when I bypassed it as I described above. So is my theory wrong do you think?

[bd1308]

yeah i think its a little off. The 912E used the 2.0 914 engine and used the L-jet system off of the 1.8. I've been told and it made sense to me that porsche built the 912E to get rid of the extra 914 engines they had.

Okay, so what I would look for is vacuum leaks. I had a leak in the boot and it caused a horribly LOW idle, which of course was also lean as well.

Your idle adjustment screw is on the throttle body.

I went to my FLAPS and bought a full container of plugs that covered up and sealed those ports in the plenum. I didnt need to complicate things just yet. K.I.S.S. method at work here (IMG:style_emoticons/default/smile.gif)

Anyway,I did get it to idle after some electrical issues and once it idled, I continued to look for leaks until it idled well (idled well at 1100 warm)

Then one by one i connected the tubes until I got everything to work.

Start simple and work your way up.

b

[Joe Bob]

Ummm, isn't this where ya check the oil cap gasket and go...DOH? (IMG:style_emoticons/default/blink.gif)

Oh yeah...LIGHTLY spray carb cleaner or ether/quickstart around known to leak areas.....when the idle changes...ya gots a leak....

[Cap'n Krusty]

Tell us HOW you set the timing. Did you follow the L-jet procedure? As I said earlier, it's very different from the D-jet procedure. The Cap'n

[srb7f]

Does adjusting the idle screw have any effect on idle speed? If not, have you looked closely at the throttle body to make sure that the idle ports are not clogged?