Well, got the body sorted, now on to getting it running better.
My car has a 1.8L with hydro cam, and stock d-jet, and a stick shift (The manual cars got a different decel system, right?). The idle is too high. it starts at 1200 when cold, then stumbles for a few minutes, surging between 500 and 1500, and once warm it goes to 1500. The idle bypass screw is all the way in. My TB dosent have a hole in the butterfly either. I replaced the manifold gaskets and injector seals, which helped a bit. I have been searching for this vac leak for ever. (I assume its a vac leak, otherwise how could the idle get too high with the screw all the way in?). I plugged off the aux. air reg, no difference. Plugged off the decel valve, no difference. All hoses are new, and clamped. I sprayed quickstart everywhere I saw a vac connection and all over the plenum etc. No difference. when i plug off the mps, sometimes the idle goes up, and sometimes it dies... it is the stock mps, with the epoxy still in the rear plug. I set the fuel pressure to 30 psi to compensate for the added displacement. Any ideas?! Could it be something other than a vac leak?
It sounds like you have tried blocking inputs to the plenum - AAR, decel valve. Did you plug them at the plenum? Did you plug the PCV input to the plenum? Is the PCV working?
Mine ran fast until I removed the PCV and replaced with a 2mm fixed orifice.
Is the plenum free of cracks/leaks?
Is the throttle body to plenum grommet free of leaks?
I replaced the pcv with a fixed orfice also. and yes, i plugged the lines at the plenum (except the mps hose, I just kinked it. I will try it at the plenum). When I completley plug off the pcv for a few seconds, the idle goes to about 900, but because the pcv is supposed to let some air in, I assume there is another leak. To test the mps I attached a hose and sucked, it seemed to hold vacuum well.
Thanks for the response Bill, I just wanted to be sure it had to be a vacuum leak, and not something else. I will continue the search.
Several things:
(1) You should not be using a hydraulic cam with D-jet at all. (a) the hydro cam's valve adjustment ability is nowhere near precise enough for D-jet. D-jet is extremely sensitive to valve adjustment settings because two of four injections are heavily out of phase with intake valve opening points and the other two are not quite perfect either. The injection is timed from the camshaft on this system. (b) D-jet cams are very specific in their intake valve timing points. Hydraulic cams are not generally set up to the same timing points.
These issues alone can change the vacuum signature enough to possibly insure that you never get the idle under control.
How big is the orifice/hole in your PCV line that you replaced the PCV valve with?
If this used to be an 1800, does it still have the 1800 TB? If so...have you replaced the upper and lower throttle shaft seal....and the o-ring on the adjusting screw?
In general...as you have figured out.... it can idle too high because you have too much air going into the mix....causing the adjusting screw to not be able to subtract enough to make any difference. A 3mm hole is a decent starting place for the PCV orifice.
If all other potential vacuum leaks are known to have been stopped....manifold runner boots, the cork gasket at the oil breather, dipstick tube boots, valve cover gaskets, decel valve lines, vacuum advance chambers
and....make very sure that your throttle cable is not too tight keeping the TB cocked open even a small amount.
If all of these are know to be good (it sounds good so far)....and your timing is correct.....it is very common that your actual problem is that the MPS adjustment is feeding you Too little fuel ...to go with what is a normal amount of intake air. This is why its acting like its getting too much air...because it is.
Also make sure that if you have a very late model ECU...the gray CO adjustment knob is dead center in the range....about 12 clicks in from either end.
How did you end up with a hydraulic cam on your car? Also, what is your compression? Ray
I know the hydro cam sucks for this injection, thats why i mentionned it. I was wondering if the cam was a possibility. the PO installed it. He also did not know the CR when I asked. I have set the timing with a light also. I did not replace the TB. as far as i know it is the 1700 unit. Can i get seals for the 1700 TB?
Also, since I just did the bodywork, the interior panels are all off. So I checked the CO knob and it is 9 clicks from the left! I moved it 3 more clicks (to the 12 position) and it seemed to help a bit with idle stability, but the idle is still too high. I have access to an exhaust analyzer so I will use that to check the CO later.
The PCV orfice is about 3mm.
bradey bunch wrote:I know the hydro cam sucks for this injection, thats why i mentionned it. I was wondering if the cam was a possibility. the PO installed it. He also did not know the CR when I asked. I have set the timing with a light also. I did not replace the TB. as far as i know it is the 1700 unit. Can i get seals for the 1700 TB?
Also, since I just did the bodywork, the interior panels are all off. So I checked the CO knob and it is 9 clicks from the left! I moved it 3 more clicks (to the 12 position) and it seemed to help a bit with idle stability, but the idle is still too high. I have access to an exhaust analyzer so I will use that to check the CO later.
The PCV orfice is about 3mm.
Thanks,
Braden
If you have the 1.7L TB...it does not have shaft seals. If you ever end up with the 2.0L TB with shaft seals....you can use clucth pushrod seals from a rabbit/golf. They have identical thickness, ID...and are slightly small on OD. I install them with a dab of high temp RTV or epoxy and they work perfectly. About $3 each.
The seals for 2.0, and vanagon work fine for TB to plenum o-ring. Don't worry about the analyzer right now. If you can't control the idle...the CO is way off anyway. Yes...agree.....you could use a 2mm oriifce as well.
Also...D-jet does not like low compression engines as well. Difficult to tune. Higher within reason...is better.
Well, it was the TB to plenum seal as Bill suggested. It was in good condition, but was still leaking, so I put a light smearing of sealant on there and it fixed it. Now the idle is steady at about 900. However, occasionally the idle will go up to 1500 for a sec, only to come back down again. And after acceleration or revving it takes about 5 full seconds to settle down. Is this normal? I will now proceed to check the exhaust on the scope and set the mixture and see if that helps.
Try a few more clicks clockwise on the ECU mixture adjustment knob with corresponding reduction in idle speed with the throttle bypass screw to smooth the "hunting" and a stronger throttle plate return spring to snap it closed when you lift your foot. It's a "little here and a little there" exercise to get it running smooth.
bradey bunch wrote:Well, it was the TB to plenum seal as Bill suggested. It was in good condition, but was still leaking, so I put a light smearing of sealant on there and it fixed it. Now the idle is steady at about 900. However, occasionally the idle will go up to 1500 for a sec, only to come back down again. And after acceleration or revving it takes about 5 full seconds to settle down. Is this normal? I will now proceed to check the exhaust on the scope and set the mixture and see if that helps.
Thanks guys!
Just replace that seal. The only ones available are for late bus and they work fine on all years. Use something like a VERY thin smear of peramtex ultra...and let it dry overnight before starting.
Bear in mind that the CO adjustment is only for during idle...it does not affect the rest of yoru fuel mixture.
Keep a careful eye on this. In general you should not be running hydros. In the long run it creates variable tuning situations with D-jet. In short...its hard to keep in tune as outside temps, barometric pressure and oil temps change. Ray
