Cascade Crew

DBL_TKE · Posted: Mon Apr 16, 2007 11:38 pm Post subject: Slower than normal

I can't seem to figure out why my car is so slow. It's and '85 LB9 and I constantly see people post times in the mid 15 second range with LB9/700r4 cars. My fastest ET to date reads 16.834 @ 83.07 and my best 60 ft was a 2.386

I'm going to check and replace the cap, coil, and rotor soon. As well as check the TPS voltage and injectors (previous owner said he replaced them). The engine has always had a sort of weird idle to it. Sounds like it is kind of cutting out after each revolution. I can keep a beat with it, it is that noticeable.

It's kind of a let down as my car already has 3.23 gears so I can't blame it on that. My buddy's stock TBI Firebird can post times over half a second quicker than my Camaro.

Any thoughts?

Xophertony · Posted: Tue Apr 17, 2007 12:05 am Post subject:

should have bought a bird...

Had too. Very Happy

sounds like you are on the right track, make sure you are getting optimum spark, i would pull your spark plugs and take a look at them. also may want to replace your fuel filter as well.
get under your car and hit your catalytic converter with a rubber mallet, does it rattle? if so it may be all busted up and in need of replacement.

DBL_TKE · Posted: Tue Apr 17, 2007 12:24 am Post subject:

I'm one step ahead of ya. I've recently replaced the spark plugs for the Bosch Platinum +4's (I'm now hearing bad things about them though) but I've checked them and they do seem to be getting a good bit of carbon build up. I replaced my fuel filter when I replaced my fuel pump (December). Also I went to check my cat one day because it wouldn't pass the sniffer test when I tested it at school and to my surprise, I found that it had been gutted. I'm also going to check my O2 sensor, maybe it's gone bad or has too much carbon build up.

I've already done some tests and compression is pretty darn good on all cylinders and vacuum is excellent as well. So that rules out any burned valves, blown head gaskets, or cracked cylinders/pistons. I did, however, run a full diagnostics test on the engine and found that cylinder #1 is low on spark and the rest of the cylinders were dancing around a little bit.

All this leads me to believe it's something in the ignition system. I have overheated the engine a couple times so I may need some new rings but not prior to those track runs.

aaron_sK · Posted: Tue Apr 17, 2007 5:29 am Post subject:

I'd say probably either a bad cap or rotor, or your timing is off.

Twilightoptics · Posted: Tue Apr 17, 2007 8:54 am Post subject:

Timing is something to check. Spark plugs to check.

And that 60ft time!

I actually had an '85 LB9 700R4. The best time I could EVER muster was a 15.2@ 89MPH. That's also with a 2.111 60ft.

I had: Flowmaster muffler, hi-flo cat, tuned up, hypertech chip (for what it's worth), rebuilt 700r4, K&N.

The 700R4 is a HORRIBLE drag racing trans. It never shifts consistant, and it shifts too late for the TPI setup. You should be shifting about 5000/5200 and I bet the 700 is spinning it farther than that.

BigDaddyVu · Posted: Tue Apr 17, 2007 9:48 am Post subject:

did your car gain any weight?

Sellmanb · Member Joined: 30 Nov 2004 Posts: 727 Location: Tigard, OR

just check tune-up stuff, it's more than likely in there Wink

Schultzy89GTA · Posted: Tue Apr 17, 2007 11:57 am Post subject:

Twilightoptics · Posted: Tue Apr 17, 2007 7:17 pm Post subject:

Schultzy89GTA · Posted: Tue Apr 17, 2007 7:28 pm Post subject:

ahh I thought that they retained heat and that keeps them cleaner and helps them to last. I also thought that the heat is also why they are not recommended with nitrous due to pre-ignition.

I am sure someone will straighten me out.

-Schultzy

izcain · Posted: Tue Apr 17, 2007 10:40 pm Post subject:

You can make that 700 shift perfect but there is to much of a drop in the power band on the 1st to 2nd shift. Thats there main downfall.

DBL_TKE · Posted: Tue Apr 17, 2007 10:41 pm Post subject:

Funny thing is that my tranny always shifts way too early. I've even adjusted the TV cable so that it shifts as late as possible and it still shifts at 3500 RPM @ WOT. However, when drag racing I always shift the trans manually because of this, so that's not a factor in my times.

aaron_sK · Posted: Tue Apr 17, 2007 10:51 pm Post subject:

izcain · Posted: Tue Apr 17, 2007 10:52 pm Post subject:

Sounds like the governor needs to be reworked. In the tail shaft of the trans there is a governor that controls shift timing also. different weights will change the timing of the shift.

Quasi-Traction · Posted: Tue Apr 17, 2007 11:05 pm Post subject:

700R4=

In all seriousness though, they aren't a good racing trans unless you make some modifications.

See, this is yet another reason to swap a 5 speed Razz

aaron_sK · Posted: Tue Apr 17, 2007 11:07 pm Post subject:

izcain · Posted: Tue Apr 17, 2007 11:10 pm Post subject:

You dont have to remove the trans at all for that. There is a little side cover near the tailshaft that comes off and that governor pops out of there and you can change the springs and weights to make it shift differently. I had a 700 before with 2400 holeshot and Hughes rebuilt kit with all the add ons and a reverse manual valve body, and the servo kits installed. It was a great trans and I ran many sub 11 second passes on it and thousands on street miles on it but it just wasn't that great for gear spacing.

DBL_TKE · Posted: Mon Apr 23, 2007 12:15 am Post subject:

So I finally got around to checking everything out. First I decided that I should check the rotor and contact points on the cap. After I get the thing off I noticed how dirty everything was so I scrubbed everything clean. Then I noticed that a screw had fallen out of the cap. Turns out it was the second screw for the rotor. I can't believe the car had been running like this. I tightened everything down and took it out for a test drive. The engine feels like it now pulls up to 4500 RPM now as where it used to just hit a wall after 3500 RPM before.

Next on the list was to check my timing. Turns out my timing was way advanced. so now I have it toned down to about 4/5*. I know thats not going to do much for performance. As I took it out for another test drive I ran across my friend at his house. We decide to do a bit of diagnosing at his house and we checked the TPS voltage, however we did it with the engine running Rolling Eyes

. So those stats are irrelevant.

Then we tried figuring out why my engine seems to be "chugging" at idle. We proceeded to disconnect each fuel injector connector individually just to see if each was functioning properly. each one seemed to be fine. When we would disconnect it, the engine would barely idle. However, when we disconnected the connector for the 5th cylinder, it did nothing to the idle. so we checked the voltage and it was reading "0". Apparently I'm running on 7 cylinders then? So the connector must be bad or there is a break in the wire somewhere in the wiring harness. Now that I found a (don't know if it's 'the') problem, I'm not so sure how to fix this. If it's the connector itself then I'm assuming i could get a new one and splice it on, but if it's a break in the wire then I'm going to have to tear into the wiring harness trying to find where it is.

Now one last (don't quote me here) question. If I rev the engine from idle there's this hesitation that I notice. It makes a rattling/knocking sound. Kind of like rod knock. But you only hear it when you get on the throttle from idle. Now that I've bumped down the timing it's more noticeable. It sure doesn't sound too healthy. Any idead as to what it is?

Xophertony · Posted: Mon Apr 23, 2007 11:02 am Post subject:

DBL_TKE · Posted: Tue Apr 24, 2007 7:46 pm Post subject:

Alright, I did that test today with swapping the injector connectors. I found that I am not only running on 7 cylinders but occasionally only on 6. I decided to swap fuel injector connector #5 with #7 and it didn't change anything. So I started fiddling with the wires leading to the connector #5. In the process I moved around #7's wires a bit accidentally and the idle got even worse. I kept messing with the wire to #5 and it finally idled better. Then I moved around #7's wire again and the idle got even better.

It seems like the wires are broken right where they meet the connectors. Now I had to hold the wires to keep the good idle for as soon as I let go, it would return to the previous state. I was able to carefully arrange the wires so the engine was idling nice and smooth and I took the car for a quick run up the block. It definitely pulled much harder. No question about it.

So it seems like I may have to get a new wire harness for the injectors. I tried following the wires to see where the harness lead to, but it was getting dark and I couldn't see anything. Where does the harness detach from? I'm assuming it's next the the firewall behind the engine block? Any tips on how I would be able to access it?

Thanks for the help guys. I've been trying to chase this problem for months.